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Aspects of social organization and diurnal activity patterns of Californian bighorn sheep (Ovis Canadensis.. 1981

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ASPECTS OF SOCIAL ORGANIZATION AND DIURNAL ACTIVITY PATTERNS OF CALIFORNIAN BIGHORN SHEEP (OVIS CANADENSIS CALIFORNIANA DOUGLAS 1829) B . S c , The U n i v e r s i t y of B r i t i s h Columbia A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF ANIMAL SCIENCE We accept t h i s t h e s i s as conforming t o the requ i red standard THE UNIVERSITY OF BRITISH COLUMBIA November 1981 by THOMAS ROSS ECCLES © Thomas Ross E c c l e s , 1981 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head of my department o r by h i s o r her r e p r e s e n t a t i v e s . I t i s understood t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n ot be al l o w e d without my w r i t t e n p e r m i s s i o n . Department of /)/y / ? i * 5 6 J E A A I E _ - The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Abstract The soc ia l organizat ion and diurnal a c t i v i t y patterns of capt ive Ca l i f o rn i a bighorn ewes were invest igated from May 1977 to December 1978. Social in teract ions between ewes were br ie f in duration and infrequent, r e l a t i ve to bighorn rams. Aggressive interact ions (butts) were more common than horn d i sp lays . Although a dominance hierarchy was evident in the herd, i t was not strongly l i nea r . Age, horn length, and body weight were not shown to be strongly corre lated to dominance. The most dominant animals proved to be the most aggressive, i n i t i a t i n g more interact ions than subordinate animals. The presence of a lamb appeared to improve the soc ia l status of some ewes. Dominant status could not be shown to pos i t i ve l y a f fect an animal 's d ie t , a c t i v i t y budget or p roduc t i v i t y . The herd's d iurnal a c t i v i t y pattern changed considerably on a seasonal bas is . The a c t i v i t y pattern was characterized by successive feeding and bedding periods in spr ing and summer. Ac t i v i t y peaks general ly decl ined in number and increased in duration during the f a l l and winter per iods. The herd's d iurnal a c t i v i t y budget also varied seasonal ly. The proportion of the day devoted to feeding increased with decreasing daylength, although actual dayl ight grazing times were poorly corre lated to daylength. The proportion of the day devoted to bedding was highest in spr ing and summer, and to a lesser extent, in mid-winter. Actual bedding times were s i gn i f i c an t l y corre lated (r = 0.92) to daylength. Both the actual time and proportion of the day devoted to standing, t r a ve l l i ng and "other" a c t i v i t i e s showed only minor seasonal f l uc tua t i ons . It was shown that poor health in herd members i i i a f f e c t ed a c t i v i t y budgets s i g n i f i c a n t l y . Late s tages of pregnancy cou ld not be shown t o s i g n i f i c a n t l y a f f e c t a c t i v i t y budgets . Average basa l metabo l i c r a tes (BMR) and d i u r n a l a c t i v i t y c o s t s were es t ima ted f o r the he rd . Both BMR's and a c t i v i t y co s t s were h igher i n s p r i n g and e a r l y summer than at o ther t imes of the y e a r . i v Table of Contents Page Abs t rac t i i i L i s t of Tables v i i i L i s t of F igures x Acknowledgements x i INTRODUCTION 1 STUDY AREA 6 METHODS 7 F i e l d Procedures 7 Comparative Ana l y s i s - Methods and Ra t i ona le A. Soc i a l O rgan i za t i on 1. Dominance h ie ra r chy of the adu l t ewes 8 2. Determinants of dominance 10 B. Consequences of Dominance 1. D ie t comparisons 11 2. A c t i v i t y budget comparisons 12 3. P r o d u c t i v i t y comparisons 14 v Page C. Forage A v a i l a b i l i t y and Herd Behaviour 15 1. Seasonal d i u r na l pa t t e rns 15 2. Seasonal a c t i v i t y budgets 16 D. E f f e c t s of P h y s i o l o g i c a l Cond i t i on on A c t i v i t y Budgets 16 E. Energy Expendi ture Est imates f o r the Adu l t Ewes 17 RESULTS A. Soc i a l O rgan i za t i on 1. Dominance h i e ra r chy of the adu l t ewes 21 S t a b i l i t y of the adu l t ewes s o c i a l system 25 2. Determinants of dominance 26 B. Consequences of Dominance 1. D ie t Comparisons 29 2. A c t i v i t y budget comparisons 30 3. P r o d u c t i v i t y comparisons 33 C. Forage A v a i l a b i l i t y and Herd Behaviour 35 1. Seasonal d i u rna l pa t te rns 39 Nocturnal a c t i v i t y 47 2. Seasonal a c t i v i t y budgets 49 D. E f f e c t s o f Ph y s i o l o g i c a l Cond i t i on on A c t i v i t y Budgets 54 E. Energy Expendi ture Est imates f o r the Adu l t Ewes 56 v i Page DISCUSSION A. Soc i a l O rgan i za t i on 1. Dominance h i e ra r chy of the adu l t ewes 59 S t a b i l i t y o f the adu l t ewes s o c i a l system 64 2. Determinants of dominance 66 B. Consequences of Dominance 1. D ie t comparisons 70 2. A c t i v i t y budget comparisons 72 3. P r o d u c t i v i t y comparisons 75 C. Forage A v a i l a b i l i t y and Herd Behaviour 77 1. Seasonal d i u rna l pa t te rns 78 Nocturnal a c t i v i t y 88 2. Seasonal a c t i v i t y budgets 90 Da i l y v a r i a b i l i t y i n herd behaviour 95 D. E f f e c t s of Ph y s i o l o g i c a l Cond i t i on on A c t i v i t y Budgets 96 E. Energy Expendi ture Est imates f o r the Adu l t Ewes 98 SUMMARY 103 BIBLIOGRAPHY 107 v i i L i s t of Tables Table Page I Dominance va lues of c ap t i v e ewes, based on dyad ic i n t e r a c t i o n s ( fo r pe r iod June 1 - December 31, 1977) 23 II Dominance va lues of c ap t i v e ewes, based on dyadic i n t e r a c t i o n s ( f o r pe r i od January 1 - June 30, 1978) 24 I I I C o r r e l a t i o n between Dominance Values (D.V.) and p r ed i c t ed determinants of dominance: age ( A . ) , body weight (WT.), horn length (H .L . ) and aggress iveness (AG.) ( i . e . number of i n t e r a c t i o n s i n i t i a t e d ) (June t o December, 1977) 27 IV C o r r e l a t i o n between Dominance Values (D.V.) and p red i c t ed determinants of dominance (January t o June, 1978) 28 V D ie t comparisons between Dominants, Intermediates and Subordinates 31 VI Average d a y l i g h t feed ing and bedding t imes f o r Dominants, Intermediates and Subord inates (September 1977 t o March 1978) 32 VII Seasonal weight change comparisons of Dominants, Intermediates and Subord inates 34 V I I I Mean cover of the major unders tory p l an t spec ies over the 1977 sampl ing pe r iod (From Wikeem, i n p rep . ) 36 v i i i Table Page IX Average day l i g h t a c t i v i t y budgets of the adu l t ewes, by month 50 Xa Average day l i gh t g raz ing and bedding t imes of hea l thy and s i c k ewes (October t o December 1977) 55 b Average day l i g h t g raz ing and bedding t imes of pregnant and non-pregnant ewes (March, A p r i l 1978) 55 XI Average basal metabo l i c ra tes f o r the adu l t ewes, by month 57 XII Average day l i g h t energy expend i tures f o r the adu l t ewes, by month 58 i x L i s t o f F igures F igure Page Graphs of monthly d i u rna l pa t te rns of the cap t i ve herd (May 1977 t o A p r i l 1978) 40 x Acknowledgements F i n an c i a l support f o r t h i s study was prov ided by an NRC Scho la r sh ip t o the author and a Canadian W i l d l i f e Se rv i ce and NRC Operat ing Grant t o Dr. D.M. Shack leton of the U n i v e r s i t y o f B.C. Dr. Don Eastman, Research Coord inator of the B.C. F i s h and W i l d l i f e Branch, must a l s o be g r a t e f u l l y acknowledged f o r h i s support dur ing the f i e l d program. I t i s w i t h p leasure t ha t I thank Dr. D.M. Shack leton f o r h i s support and d i r e c t i o n dur ing t h i s s tudy, as we l l as my adv i so ry committee, Drs . M. P i t t , F. Bunnel l and D. Hebert f o r t h e i r suggest ions and t e chn i c a l a i d . A spec i a l note of thanks i s conveyed t o Br ian Wikeem f o r sha r i ng h i s bo tan i ca l e xpe r t i s e and t o a l l members of t h i s coopera t i ve study f o r t h e i r c on t r i b u t i o n s to my work. Other i n d i v i d u a l s t o whom I extend my app re c i a t i on i n c l ude Mr. E. Lacey and f am i l y o f the Okanagan Game Farm f o r the major r o l e they p layed i n p r o v i d i ng both the study s i t e and the study animals and f o r t h e i r f r i e n d s h i p du r i ng my f i e l d work, and Ms. C. Braun and Ms. P. Py le f o r t h e i r e x c e l l e n t t yp i ng and word p rocess ing s k i l l s , r e s p e c t i v e l y . My warmest thanks are extended to my parents f o r t h e i r support and encouragement throughout u n i v e r s i t y , and t o my w i f e , L i z and son, Aaron f o r t h e i r pa t i ence and f o r the weekends " s a c r i f i c e d " f o r the t h e s i s . x i INTRODUCTION In the pas t , research i n t o the s o c i a l behaviour of animals was l a r g e l y a " . . . study of behav iour pa t te rns shown between c o n s p e c i f i c i n d i v i d u a l s u sua l l y s tud i ed i n dyad ic i n t e r a c t i o n . . . " (Crook 1970). Recen t l y , s o c i a l behaviour has been l i n k e d t o the ecology and dynamics of animal popu la t i ons (E isenberg 1966, Crook 1970, Ge i s t 1971, Wi lson 1975, Crook et al_. 1976, Krebs and Davies 1978), prompting d i s cu s s i on on the e c o l o g i c a l imp l i c a t i o n s of such s o c i a l t r a i t s as group s i z e and cohes ion , s o c i a l o r gan i z a t i on and reproduc t i ve s t r a t e g i e s of va r ious spec i e s . Ungulates have rece i ved cons ide rab l e a t t e n t i o n from s o c i o - b i o l o g i s t s , l a r g e l y because of t h e i r o f ten obvious and spec t a cu l a r s o c i a l nature (Ge i s t 1971, Es tes 1967, 1974, Ge i s t 1971, Jarman 1974, K i t chen 1974, S i n c l a i r 1974). Whi le some ungulates such as the moose (A lces a l c e s ) and chev ro ta in (Chevrota in t r agu l u s ) are s o l i t a r y i n na tu re , gene ra l l y a s s o c i a t i n g w i th c on s pe c i f i c s on ly du r i ng maternal and rep roduc t i ve a c t i v i t i e s , the ma jo r i t y of spec ies demonstrate a s t rong tendency f o r he rd ing . F r equen t l y , a h i e r a r c h i a l system has evo lved t o enable c on spe c i f i c s t o c oex i s t i n s o c i a l u n i t s w i th a minimum of h o s t i l e i n t e r a c t i o n s between group members. Soc i a l behaviour s t ud i e s have shown tha t r e l a t i v e l y l i n e a r dominance orders e x i s t f o r many spec ies ( - ca t t l e (Bos t a u r u s ) , Syme et ^1_. 1979; re indeer (Rang i fe r t a r andus ) , Espmark 1964; mountain sheep (Ovis canadens i s , 0_. d a l l i ) , Ge i s t 1971)) and t ha t dominant s t a t u s i s p o s i t i v e l y c o r r e l a t e d t o body s i z e , an t l e r / ho rn s i z e , and age. However, such s tud i e s have concent ra ted on male s o c i e t i e s and t h e i r 1 rep roduc t i ve a c t i v i t i e s . Th is preoccupat ion w i th male behaviour i s not s u r p r i s i n g , c on s i de r i ng the o f ten spec tacu l a r nature of male i n t e r a c t i o n s , but i t has l a r g e l y ignored the s i g n i f i c a n c e of the i n f r a s t r u c t u r e of female-nursery groups. S ince the s o c i a l and behav ioura l development of animals of both sexes occurs i n the company of adu l t females , the female s o c i e t y , by modi fy ing the responses of young animals t o environmental s t i m u l i , i s o f fundamental importance t o popu la t i on s t a b i l i t y and p r o d u c t i v i t y . Some researchers have prov ided l i m i t e d in fo rmat ion on the s o c i a l behaviour of ungulate nursery groups (domestic l i v e s t o c k , Hafez 1969, A rno ld and Dudz insk i 1978; b l a c k - t a i l e d deer (Odocoi leus hemionus), M i l l e r 1974; pronghorn (An t i l o ca rpa amer i cana) , K i t chen 1974). But more research i s needed i n t h i s area t o complete the s o c i o - b i o l o g i c a l p i c t u r e of many other ungulate spec i e s . The concept of dominance i n h i e r a r c h i a l systems a l s o requ i res f u r t h e r c o n s i d e r a t i o n . Whi le i t has been suggested t ha t occupants of r i g i d l y defended t e r r i t o r i e s have d e f i n i t e r ep roduc t i ve , f o r ag i ng and/or s u r v i v a l advantages over t r a n s i e n t i n d i v i d u a l s (Wi lson 1975), l e s s re fe rence has been made t o the e c o l o g i c a l b ene f i t s of dominant s t a tus i n f r ee ranging groups of an ima ls . Wi lson (1975) summarizes tha t "wi th ra re ex cep t i on s , the agg re s s i ve l y supe r i o r animal d i s p l a c e s the subord inate from food, from mates and from nest s i t e s " . However, t h i s statement i s based l a r g e l y on i n fo rmat i on from s tud i e s which have again concent ra ted on aspects of male i n t e r a c t i o n s ( e . g . Ge i s t 1971). That h igh s o c i a l rank i n female h i e r a r c h i e s a c t u a l l y improves an i n d i v i d u a l ' s gene t i c f i t n e s s i s more specu l a t i v e and few s tud i e s have i n v e s t i g a t ed t h i s hypo thes i s . 2 The f i r s t objectives of this study were to investigate: A) the social organization, and B) the apparent consequences of dominance in a captive group of adult California bighorn ewes. Hypotheses formulated and tested in the investigation in their alternative (HA), form included: A. Social Organization 1. A relatively stable linear hierarchy would be established amongst the ewes. 2. Age, horn size and body size would be directly correlated to social status. B. Consequences of Dominance 1. Dominant animals would, during months of limited available forage, have access to higher quality foraging areas and would, as a result, remain on a higher plane of nutrition than subordinate animals. 2. Access to high quality foraging areas would increase intake and assimilation rates, reduce the daily grazing times and increase the daily bedding times of dominants over those of subordinates. 3. Dominant ewes, because of their higher plane of nutrition, would better survive the physiological stresses of winter and, as a result, would be in better physical condition and have a higher reproductive output than ewes of lower social rank. 3 The need f o r comparable data on the g raz i ng t imes of i n d i v i d u a l herd members prompted an i n v e s t i g a t i o n i n t o seasonal changes i n the d a i l y a c t i v i t y budgets of these animals as a second major research o b j e c t i v e . For severa l decades, researchers o f domest ic animals have conducted such s tud i e s t o determine the e f f e c t s o f environmental and p h y s i o l o g i c a l v a r i a b l e s on the feed ing behav iour and p r o d u c t i v i t y o f f r ee ranging l i v e s t o c k (Meyer et al_. 1957, Arno ld 1960a, 1960b, 1962, Squ i re 1974, Arno ld and Dudz insk i 1978). S tud ies on domestic sheep (Ovis a r i e s ) , f o r example, have shown tha t herd g raz ing t imes gene ra l l y i n c rease w i th seasonal de c l i n e s i n range q u a l i t y and quan t i t y (Arno ld 1960a). Conve rse l y , the degree of herd cohes ion i n f r e e - r ang i ng g raz ing animals o f ten decreases w i th d e c l i n i n g range cond i t i on s (Dudz insk i and Arno ld 1967, Dudz insk i et ajk 1969). Animal s c i e n t i s t s have a l s o repor ted tha t great d a i l y v a r i a t i o n i n behaviour e x i s t s between i n d i v i d u a l herd members sub jec ted t o the same environmental cond i t i ons because of d i f f e r en ce s i n age, sex, p h y s i o l o g i c a l c o n d i t i o n , gene t i c s , weight and forage s e l e c t i o n . Such i n fo rmat i on on herd and i n d i v i d u a l behav iour has, i n t u r n , been employed i n i n t e n s i v e range and animal management. S i m i l a r s tud i e s on many w i l d ungulates are d i f f i c u l t because of the poor v iewing cond i t i o n s a f fo rded by the an ima l s ' na tu ra l h a b i t a t . Few quanta t i ve data are a v a i l a b l e on the d a i l y a c t i v i t y pa t te rns and po t en t i a l energy expend i tu res o f mountain sheep f o r t h i s reason. Var ious researchers ( M i l l s 1937, Davis 1938, B lood 1963, Ge i s t 1971) have desc r i bed herd a c t i v i t y from r e l a t i v e l y few days of obse rva t i ons , g i v i n g the t ime of occurrence and du ra t i on of a c t i v e and non-ac t i ve per iods f o r severa l d i f f e r e n t herds . Van Dyke (1978) completed a more thorough study of t h i s k i n d , examining the a c t i v i t y pa t te rns of ewes, lambs, and rams, and comparing the a c t i v i t y budgets 4 of the d i f f e r e n t sex and age groups w i t h i n seasons. However, researchers of w i l d popu la t i ons are u sua l l y fo rced t o observe d i f f e r e n t animals on d i f f e r e n t days and even f l u c t u a t i n g numbers on the same day. Th is obscures i n d i v i d u a l animal behav iour , r e s u l t i n g in "average data" being c o l l e c t e d even f o r s p e c i f i c age and sex c l a s se s of an ima l s . To f u l l y understand and assess the a c t i v i t y budgets and po t en t i a l energy expend i tu res of herd members, i d e n t i f i a b l e i n d i v i d u a l s must remain under observa t ion throughout the study t o enable t h e i r d a i l y behaviour to be i n t e r p r e t ed w i th respect t o the environmental and ph y s i o l o g i c a l f a c t o r s mentioned above. The cap t i ve s t a t e and a c c e s s i b i l i t y of the animals i n t h i s study prov ided such research o p p o r t u n i t i e s . As a r e s u l t , the secondary research ob j e c t i v e s of t h i s study were: C. To determine the e f f e c t s o f forage c ond i t i o n and season on 1) the d i u rna l p a t t e r n s , 2) the a c t i v i t y budgets of a c ap t i v e popu la t i on of C a l i f o r n i a b ighorn ewes. D. To assess the e f f e c t s of p h y s i o l o g i c a l c ond i t i o n on the d a i l y a c t i v i t y budgets of the adu l t ewes. E. To es t imate the r e l a t i v e mean d a i l y energy expend i tures of the adu l t ewes on a monthly b a s i s . 5 STUDY AREA In A p r i l 1977, a 40 ha enc losure adjacent to the Okanagan Game Farm, P en t i c t o n , B .C . , was cons t ruc ted f o r i n t e n s i v e s t ud i e s on C a l i f o r n i a b ighorn sheep, a spec ies na t i v e t o the a rea . The enc l o su re , s i t u a t e d on s teep l y s l o p i n g g ra s s l and , f a l l s w i t h i n the Ponderosa P ine-Bunchgrass b i ogeoc l ima t i c zone (K r a j i n a 1969) and i s s i m i l a r i n both e l e v a t i o n and vegeta t ion to the rangeland occupied year round by maternal groups of the Vaseux Lake bighorn popu l a t i on . However, the study area has a predominant ly eas tern aspec t , d i f f e r i n g from the Vaseux range which faces p r i m a r i l y west-southwest . Before t h i s study commenced, the enc losure had rece ived only l i g h t , i n t e r m i t t e n t g raz i ng from horses and was cons idered t o be i n a near c l imax success iona l stage (Wikeem, pers . comm.), being dominated by bluebunch wheatgrass (Agropyron sp i ca tum) . Est imates of the c a r r y i n g capac i t y of the study s i t e ( P i t t , Wikeem, pe r s . comm.) d i c t a t e d the s i z e of the herd which was re leased i n t o the a rea . 6 METHODS F i e l d Procedures From January t o March, 1977, a drop net was used at the Vaseux Lake C a l i f o r n i a b ighorn range, 20 km south of P en t i c t on , t o capture animals f o r research at the study s i t e . A t o t a l of 16 ewes, th ree lambs, and one y e a r l i n g male were captured and t r anspo r t ed t o the Game Farm. Before be ing re leased i n t o the enc losure i n A p r i l , each animal was f i t t e d w i th an i d e n t i t y c o l l a r . Behav ioura l obse rva t i ons f o r t h i s study commenced i n May, 1977 and cont inued f o r 14 consecu t i ve months. Most observa t ions were made through a 20-40 x 60 zoom b i nocu l a r s po t t i n g scope from a po in t 200 m east o f the lower boundary of the enc losure where the ma jo r i t y of the study s i t e cou ld be viewed. Th is e l im i na t ed any obvious d i s tu rbance t o the animals du r i ng sampl ing pe r i od s . When the animals occupied the northwestern corner of the enc losu re , observa t ions were made from a l i g h t l y t imbered area approx imate ly 50 m north o f t h i s po r t i on of the study s i t e . A l though water and minera l b locks were prov ided a r t i f i c i a l l y i n the nor theast corner of the enc l o su re , the sheep were dependent on the bluebunch wheatgrass -b ig sage (Artemi s i a t r i d e n t a t a ) p lan t community w i t h i n the enc losure as a food source . As a r e s u l t , t h e i r d a i l y a c t i v i t y pa t te rns were cons idered t o be r ep re sen ta t i v e of f r ee ranging animals on b o t a n i c a l l y s i m i l a r ranges, p a r t i c u l a r l y those popu la t ions not e x h i b i t i n g seasona l , v e r t i c a l m i g r a t i on s . In l a t e December and throughout January , c rus ted snow cond i t i on s made f o r ag i ng d i f f i c u l t f o r the sheep and severa l m o r t a l i t i e s prompted the 7 d i s t r i b u t i o n of supplemental hay near the water and minera l supp ly . Approx imate ly 45 kg of hay was prov ided at dusk each day. Behav ioura l data c o l l e c t e d dur ing t h i s pe r iod were i n t e r p r e t e d w i th due cons i de r a t i on f o r the a r t i f i c i a l feed ing s i t u a t i o n . Comparative Ana l y s i s - Methods and Ra t i ona l e A. Soc i a l O rgan i za t i on 1. Dominance h i e ra r chy of the adu l t ewes To determine the s o c i a l r e l a t i o n s h i p s e x i s t i n g between the cap t i ve ewes, obse rva t i ons of dyad ic i n t e r a c t i o n s were c o l l e c t e d p r i m a r i l y by ad 1 ib i tum sampl ing (Altmann 1974). Two assumptions necessary f o r such a sampl ing scheme to y i e l d unbiased da ta , and cons idered f u l f i l l e d dur ing the study were, a) t ha t a l l behav ioura l pa t te rns used i n dominance i n t e r a c t i o n s had an equal l i k e l i h o o d of be ing observed and, b) t ha t the i n t e r a c t i o n s of ewes of each s o c i a l c l a s s had equal l i k e l i h o o d of being observed. Observat ions of i n t e r a c t i o n s from ad 1 ib i tum sampl ing were supplemented by those c o l l e c t e d i n c i d e n t a l l y du r i ng scan sampl ing p e r i o d s , a sampl ing method d i s cussed i n Sec t i on B2 of Methods and Ra t i ona l e . In format ion recorded f o r each i n t e r a c t i o n inc luded the i d e n t i t i e s of the i n i t i a t o r and r e c e i v e r , behaviour pa t te rns used by both as desc r ibed by Ge i s t (1971) and Shack leton (1973), and the nature of the i n t e r a c t i o n . I n t e r a c t i on s were c l a s s i f i e d i n t o one of f i v e c a t ego r i e s : bedding, f eed ing , p o s i t i o n a l , 8 p l a y f u l or u n c l a s s i f i e d (where i n t e r a c t i o n was a l ready i n p rogress , making c l a s s i f i c a t i o n impo s s i b l e ) . A "dominant" animal was de f ined as an i n d i v i d u a l which d i s p l a ced a f e l l ow herd member from a resource ( i . e . bedding s i t e , feed ing s i t e , e t c . ) , or as an i n d i v i d u a l t o which subord inate behaviour (Ge i s t 1971) was d i r e c t e d . Th is i n fo rmat i on was t abu l a ted i n two i n t e r a c t i o n mat r i ces of "Dominants" and "Subord ina tes " , the f i r s t c on ta i n i ng data c o l l e c t e d from June 1977 t o December 1977; the second cons t ruc ted from data gathered from January 1978 t o June 1978 a f t e r the s t r u c t u r e of the herd had been a l t e r e d by mid-w in te r m o r t a l i t i e s . The c e l l s o f each mat r i x conta ined the number and outcome of d i spu tes occur ing between every p a i r o f herd members f o r t ha t p a r t i c u l a r t ime pe r i od . Each animal was then ranked accord ing t o the number and i d e n t i t y o f f e l l ow herd members tha t i t had dominated and had been dominated by. Ne i ther the 18 lambs born on s i t e i n 1977 nor the th ree y e a r l i n g s were i n c l uded i n these ana lyses s i n ce the ma jo r i t y of t h e i r i n t e r a c t i o n s were p l a y - l i k e and d i f f i c u l t to i n t e r p r e t . A Dominance Value (D.V. = a r c s i n \/x> where x = p ropor t i on of opponents dominated (see Be i l h a r z et a K 1966)) was determined f o r each animal from the p ropo r t i on of opponents t ha t i t dominated. D .V . ' s have been employed t o s o c i a l l y rank i n d i v i d u a l s w i t h i n a group of animals i n s i t u a t i o n s where such a process i s not po s s i b l e from a quan ta t i ve a n a l y s i s o f dyad ic encounters a l one , e i t h e r because of dominance c i r c l e s or a lack of ac tua l s o c i a l i n t e r a c t i o n s between c e r t a i n pa i r s o f an ima l s . (Such a s i t u a t i o n arose f o r the cap t i v e herd; see R e s u l t s ) . P rov i d i ng each herd member i s i nvo l ved i n a s u f f i c i e n t and comparable number of i n t e r a c t i o n s , a D.V. can be ass igned t o each an ima l , r ega rd less of the i d e n t i t y of i t s opponents. In a d d i t i o n , these 9 va l ues , once converted by an a r c s i n t r an s f o rma t i on , become normal ly d i s t r i b u t e d , enab l i ng parametr ic c o r r e l a t i o n s between rank and b i o l o g i c a l parameters t o be made. Severa l d i f f e r e n t methods of e s t ima t i ng D .V . ' s have been developed (angular D . V . ' s , used i n t h i s s tudy , weighted angu lar D . V . ' s , l e a s t - s qua r e D . V . ' s ) . However, B e i l h a r z et <fL (1966) found tha t . . . " t h e th ree measures of s o c i a l dominance gave p r a c t i c a l l y i d e n t i c a l e va l ua t i ons of dominance". From ana l y s i s of the Dominance Va lues , th ree d i s t i n c t s o c i a l c l a s s e s were recognized among the adu l t ewes. A d e s c r i p t i o n of these th ree groups, l a b e l l e d Dominants, Intermediates and Subord ina tes , i s g iven i n Sec t i on A ( l ) o f R e su l t s . Landau's index of l i n e a r i t y was a l s o determined f o r each h i e r a r c h y , an index which prov ides a measure of the degree of l i n e a r i t y f o r any given h i e ra r chy (Wi lson 1975). In fo rmu la : h 12 x (Va - n - l ) ? n3-n 2 where h = Landau's index n = the number of animals i n the study group Va = the number of group members t ha t the a t n animal dominates Values range from 0 t o 1, w i th 1 i n d i c a t i n g a complete ly l i n e a r o rder . 2. Determinants of dominance To determine i f p r ed i c t ed morpholog ica l c r i t e r i a were important i n determin ing s o c i a l rank i n the adu l t ewes, ages (es t imated by horn annu l i (Ge i s t 1966)) , body weights and horn lengths were c o l l e c t e d from each animal four t imes 10 dur ing the course of the study (September and December, 1977, March and August , 1978). The degree of c o r r e l a t i o n between Dominance Values and age, mean weights and horn lengths was determined f o r the herd members i n each of the h i e r a r c h i e s . To i n v e s t i g a t e the importance of behav ioura l as we l l as morpholog ica l parameters t o dominance, the number of aggress i ve encounters i n i t i a t e d by each i n d i v i d u a l was t a l l i e d f o r both the 1977 and 1978 h i e r a r c h i e s . The degree of c o r r e l a t i o n between these t o t a l s and r e spec t i v e Dominance Values was then assessed . A l e v e l o f 5% probability was e s t ab l i s h ed a p r i o r i f o r t h i s and a l l subsequent s t a t i s t i c a l a n a l y s i s . B. Consequences of Dominance 1. D ie t comparisons Two separate approaches were taken t o compare d i e t s of the three s o c i a l c l a s s e s of ewes. In January , 1978, the herd demonstrated an apparent "p re fe rence" f o r the supplemental hay over the more abundant range fo rage , d ep l e t i n g the hay supply before s t a r t i n g t h e i r g raz i ng r ou t i n e . Fo l l ow ing a s i m i l a r approach t o tha t of Espmark's (1974a, 1974b) s tud ies on roe deer (Capreolus capreo lus) and re indee r , the mean d a i l y t ime spent by each s o c i a l c l a s s consuming hay was compared (method of data c o l l e c t i o n w i l l be d i scussed i n a l a t e r s e c t i o n ) . A S tuden t ' s t - t e s t was used t o t e s t the hypothes is t ha t dominant ewes would gain g rea te r access to the "p r e f e r r ed " feed than i n te rmed ia te or subord inate ewes. 11 Use of f e ca l n i t r ogen (N) l e v e l s was the second, more i n d i r e c t , approach to d i e t compar isons. Hebert (1973) found f e ca l N l e v e l s t o be p o s i t i v e l y c o r r e l a t e d t o crude p r o t e i n and energy l e v e l s o f forage consumed by bighorn sheep. Recogn iz ing t h i s f a c t , f e ca l samples were c o l l e c t e d from ewes of d i f f e r e n t s o c i a l s t a tu s dur ing recaptures i n December, 1977 and March, 1978. Mean N l e v e l s i n feces of dominants were then compared to those of i n te rmed ia te and subord inate ewes, again us ing S tuden t ' s t - t e s t . 2. A c t i v i t y budget comparisons Comparisons of the mean d a i l y g raz ing and bedding t imes of the th ree s o c i a l c l a s s e s of ewes were conducted based on the f i n d i ng s of domestic animal s t u d i e s . A rno ld (1960a) showed tha t the g raz ing t ime of domestic sheep inc reased and ruminat ing t ime decreased w i th dec reas ing pasture q u a l i t y . For t h i s s tudy , i t was pos tu l a ted tha t dominant ewes would, i n gene ra l , forage on h igher q u a l i t y vege ta t i on and, as a r e s u l t , would demonstrate reduced feed ing t imes and g rea te r bedding t imes than in te rmed ia te and subord inate ewes fo rced i n t o more marg ina l l y n u t r i t i o u s a reas . Scan sampl ing (Altmann 1974) was used to c o l l e c t data on the a c t i v i t y d u r a t i o n s , movements and l o c a t i o n s of i n d i v i d u a l ewes f o r t h i s comparat ive a n a l y s i s . Dur ing th ree t o seven sampl ing days per month, the study s i t e was scanned every 15 minutes from dawn to dusk and the a c t i v i t y o f each i n d i v i d u a l was noted, toge ther w i th i t s quadrat l o c a t i o n taken from a gr idded map of the a r ea . Al though each animal was observed f o r on ly f i v e seconds t o determine i t s a c t i v i t y , approx imate ly two t o ten minutes were requ i red f o r a complete scan of the herd, depending on the degree of herd d i s pe r s i o n and movement. A c t i v i t i e s were ca t ego r i z ed as f eed ing , bedding, t r a v e l l i n g wi thout f eed ing , 12 s tand ing and other ( p l a y , s o c i a l i n t e r a c t i o n s , grooming). The t ime devoted to these a c t i v i t i e s du r ing the da y l i g h t hours was c a l c u l a t e d each day f o r each an ima l . Only data c o l l e c t e d on feed ing and bedding t imes from September, 1977 t o March, 1978 were u t i l i z e d f o r t h i s p a r t i c u l a r a n a l y s i s , s ince i t was assumed tha t h igh q u a l i t y forage would on ly be l i m i t e d dur ing t h i s per iod and t ha t compet i t i on between c on spe c i f i c s would be ev ident only dur ing t h i s p e r i o d . The v a r i a t i o n i n the mean d a i l y feed ing and bedding t imes of the d i f f e r e n t s o c i a l c l a s se s of adu l t ewes was assessed each month by ana l y s i s of va r i ance , us ing a two f a c t o r a n a l y s i s w i th one i n t e r a c t i o n term and an unbalanced nested terms. In l i n e a r model form: Y i j k =r + G i + D J + ( G x D ) i J + N K ( i ) + L " ( G x D ) i j x N K ( i ) ] d a y l i g h t t ime devoted t o g raz ing (or bedding) herd mean s o c i a l g roup .e f f e c t ( three l e v e l s ) sampl ing day e f f e c t ( three t o e i gh t l e v e l s , depending on month group x day i n t e r a c t i o n term animal w i t h i n s o c i a l group e f f e c t (unbalanced nested te rm) . Leve l s o f the nested terms decreased s l i g h t l y as the study progressed because of m o r t a l i t i e s and herd r educ t i on . exper imenta l e r r o r term The LSM 76 computer program (Harvey, 1977) was used f o r the a n a l y s i s . where Y i j k Gi D j (GxD) i j V i ) (GxD) i j x N k ( i ) = 13 3. P r o d u c t i v i t y comparisons Severa l p roduct ion parameters were used t o compare the b i o l o g i c a l " f i t n e s s " of ewes of d i f f e r e n t s o c i a l s t a t u s . Seasonal weight change was one such parameter. I t was hypothes ized tha t dominant an ima l s , w i th access t o high q u a l i t y forage would ma inta in a more constant body weight than subord inate an ima l s . To t e s t t h i s hypo thes i s , the average October t o December, 1977 weight l o s s of dominant ewes was compared ( t - t e s t s ) t o t ha t of each of the remain ing two s o c i a l c l a s s e s . S i m i l a r l y , mean weight ga ins between March and August , 1978 were a l s o compared. In each case , weight changes were expressed as a p ropo r t i on of the o r i g i n a l weight ( i . e . October and March we i gh t s ) . Unexpected m o r t a l i t i e s i n the herd i n December, 1977 a l lowed an â  p o s t e r i o r i comparison of f i t n e s s between s o c i a l groups. Using a Chi'2 goodness of f i t t e s t , the observed f requenc ies of deaths from the th ree s o c i a l c l a s ses were compared t o expected va l ues . Expected va lues were c a l c u l a t e d from the t o t a l number of deaths and the p ropo r t i on of animals i n each s o c i a l c l a s s . Reproduct ive measures were used as a t h i r d compar ison. Research on n u t r i t i o n i n domest ic sheep has demonstrated the s i g n i f i c a n c e of pre-partum d i e t q u a l i t y o f dams on b i r t hwe igh t and s u r v i v a l of the neonate (Alexander 1961). The re fo re , one may expect a dominant ewe, by ma in ta i n i ng a h igher n u t r i t i o n a l p lane than subord inate an ima l s , t o be r ep roduc t i v e l y more success fu l than the 1 a t t e r . In 1978, when on ly f i v e of the ten p o t e n t i a l l y p roduc t i ve ewes produced lambs, the expected and observed f requenc ies of b i r t h s from the th ree s o c i a l c l a s se s 14 were compared by a Chi2 goodness of f i t t e s t . Expected f requenc ies were c a l c u l a t e d from the t o t a l number of lambs produced and the number o f ewes of each c l a s s compr i s ing the herd. Th is was not p o s s i b l e f o r 1977, s i nce every c ap t i v e ewe produced at l e a s t one lamb. B i r t h weights of the lambs were not a v a i l a b l e f o r compar ison. C. Forage A v a i l a b i l i t y and Herd Behaviour In format ion on forage a v a i l a b i l i t y and s e l e c t i o n by the sheep was a v a i l a b l e from the vege ta t i on study o c cu r r i ng s imu l taneous ly w i th t h i s behav ioura l work ( P i t t and Wikeem 1979, and unpubl i shed d a t a ) . Consequent ly , i t was po s s i b l e t o cons ide r the e f f e c t o f range phenology and animal d i e t on the a c t i v i t y pa t t e rns and budgets of the herd. 1. Seasonal d i u r na l pa t te rns As desc r i bed i n Sec t i on B2 of Methods, scan sampl ing was used to c o l l e c t i n fo rmat i on on the d i u r na l a c t i v i t y pa t te rns of herd members. For every sampl ing day i n a month, the p ropo r t i on of the herd a c t i v e ( a l l a c t i v i t i e s o ther than bedding) at each 15 minute sampl ing i n t e r v a l throughout the d a y l i g h t pe r iod was c a l c u l a t e d . These va lues were, i n t u r n , used t o determine the mean d a i l y number and d i s t r i b u t i o n of a c t i v i t y peaks f o r every month of the yea r . More than 50% of the herd had t o be a c t i v e f o r at l e a s t two consecu t i ve sampl ing i n t e r v a l s ( i . e . 30 minutes) t o c o n s t i t u t e an a c t i v i t y peak. S i m i l a r l y , a non-ac t i ve pe r i od was recognized on ly i f 50% or more of the herd remained bedded f o r at l e a s t two consecu t i ve sampl ing i n t e r v a l s . 15 2. Seasonal a c t i v i t y budgets The a c t i v i t y data c o l l e c t e d dur ing each 15 minute scan sampl ing i n t e r v a l enabled seasonal t rends i n the d a i l y a c t i v i t y budgets of the herd members t o be moni tored. Est imates of t o t a l d a y l i g h t t imes ( i n hours) devoted to f o r a g i n g , bedding, t r a v e l l i n g , s tand ing and "o ther " a c t i v i t i e s were determined each day by summing the number of 15 minute sampl ing i n t e r v a l s i n which an a c t i v i t y was observed and d i v i d i n g by f ou r . Mean d a i l y va lues were then c a l c u l a t e d f o r each ewe and f o r the herd as a whole on a monthly b a s i s . Us ing a high i n t e n s i t y spot lamp and the s po t t i n g scope, the herd was monitored on f ou r occas ions (May 5, June 20, November 14, December 17, 1978) t o determine the extent of n i gh t - t ime a c t i v i t y . However, i n d i v i d u a l animals cou ld not be i d e n t i f i e d dur ing such obse rva t i ons and n ight data were not i n c l uded i n monthly a c t i v i t y budget de te rm ina t i ons . D. E f f e c t s o f P h y s i o l o g i c a l Cond i t i on on A c t i v i t y Budgets A c t i v i t y budget comparisons were conducted from October to A p r i l between animals of d i f f e r e n t ph y s i o l o g i c a l c o n d i t i o n . Ana l y s i s of blood samples c o l l e c t e d from the ewes i n the September-October recapture program (Pete rson , pe r s . comm.) showed e l eva ted l e v e l s o f SGOT, an enzyme i n d i c a t i v e of body t i s s u e ca tabo l i sm , i n s i x ewes. With one ex cep t i on , a l l ewes demonstrat ing these high l e v e l s d ied dur ing December or January . Graz ing and bedding du ra t i ons of these moribund animals i n the th ree months p r i o r t o t h e i r death were compared t o those of hea l thy animals w i t h i n t h e i r r e spec t i ve s o c i a l c l a s s by S tuden t ' s t - t e s t . 16 Feeding and bedding t imes of pregnant and non-pregnant ewes were compared i n March and A p r i l , the two f i n a l months of pregnancy when f e t a l demands would be g r e a t e s t . S i m i l a r t o the f a l l compar isons, on ly data from ewes of the same s o c i a l c l a s s were compared t o prevent f a c t o r confounding. S tudent ' s t - t e s t was again the s t a t i s t i c a l method used. E. Energy Expend i ture Est imates f o r the Adu l t Ewes Us ing the b i oene rge t i c l i t e r a t u r e a v a i l a b l e on mountain sheep (Chappel 1978), domest ic sheep (Graham 1964, C lapper ton 1961, i n Moen 1973), re indeer (Hammel 1962, i n Moen 1973), and deer (Moen 1973), the mean d a i l y a c t i v i t y budgets of the herd were conver ted t o mean d a i l y energy expend i tu re es t imates f o r each month. Chappel (1978) developed a p r e d i c t i v e b i oene rge t i c model f o r b ighorn sheep which es t imates f a s t i n g and r e s t i n g metabo l i c ra te (FMR and RMR, r e s p e c t i v e l y ) , g iven the sex, we ight , n u t r i t i o n a l s t a tu s ( fed or fas ted) and gross energy i n take of the an ima l , date of the t r i a l , t r i a l temperature and mean ambient temperature th ree days p r i o r t o the t r i a l . With the except ion of gross energy i n t ake va l ue s , which had a r e l a t i v e l y low p r e d i c t i v e va lue i n the o v e r a l l model, i n fo rmat i on on a l l of the above f a c t o r s was a v a i l a b l e f o r t h i s s tudy . Monthly mean ewe weights were taken from i n t e r p o l a t e d po in t s on a graph of weights obta ined dur ing f i v e capture programs. Weather data from the Pen t i c t on a i r p o r t , f i v e km from the study s i t e , prov ided the necessary temperatures . The mean temperature on sampl ing days was used as the t r i a l temperature , wh i l e the monthly mean temperature was used as the ambient temperature . To determine the d a i l y energy expended by an animal on a g iven a c t i v i t y , va r i ous convers ion f a c t o r s have been developed which are gene ra l l y app l i ed t o 17 t ha t an ima l ' s basal metabo l i c r a t e . Basal metabol ism, de f ined as "the minimal energy cos t when an animal i s a t r e s t i n a thermoneutra l environment and i n a post abso rp t i ve c o n d i t i o n " (Brody 1945, i n Moen 1973), i s a d i f f i c u l t c ond i t i o n t o ach ieve i n ruminants dur ing metabo l i c research because of long r e t en t i on t imes of food i n the ruminant stomach and the tendency of study animals t o stand ra the r than l i e i n metabo l i c chambers. As a r e s u l t , FMR's measured from f a s t ed animals (36 - 72 hrs) gene ra l l y i n a s tand ing p o s i t i o n , have been more r e cen t l y used as an app rop r i a te equ i va l en t ( B l a x t e r , 1962). In t h i s s tudy , average d a i l y FMR values minus the added cos t s of s tand ing (based on Chappe l ' s f i n d i ng s ) were used as es t imates of BMR va lues in the c a l c u l a t i o n o f d a i l y energy expend i tu res . Energy convers ion f a c t o r s f o r a c t i v i t i e s were taken from var ious sources . The a d d i t i o n a l energy cos t s of both s tand ing and feed ing f o r ewes (0.22 Kcal Kg-1 hr -1 and 0.43 Kcal Kg-1 h r - 1 , r e s pe c t i v e l y ) were taken from Chappe l ' s work (Chappel 1978) wh i l e ruminat ing increments (0.24 K c a l . Kg-1 hr -1) app l i ed to bedding t imes and running increments (8 x BMR Kcal Kg-1 hr -1) above BMR were taken from the research of Graham (1964) and Hammel (1962, i n Moen 1973), r e s p e c t i v e l y . C l apper ton ' s (1961, i n Moen 1973) es t imate of wa lk ing cos t s (0.59 K c a l . Kg-1 Km-1) was used i n t h i s s tudy . It was assumed tha t a l l t r a v e l l i n g was done a long contours (an assumption f u l f i l l e d the ma j o r i t y o f the t ime) and tha t the animals walked at the ra te of 5 km h r _ l . Th is negated the need f o r es t imates of the d i s t ance t r a v e l l e d by the an ima l s , va lues not c on f i d en t l y obta ined from the data c o l l e c t e d , and converted the energy cos ts of wa lk ing t o Kcal Kg-1 h r _ l . Costs of a c t i v i t i e s l a b e l l e d "o ther " ( i n t e r a c t i n g , p l a y i ng ) were es t imated from Moen's (1973) convers ion f a c t o r f o r p lay (3xBMR Kcal Kg-1 h r _ l ) . Pregnancy and l a c t a t i o n demands were a l s o 18 cons ide red , us ing approximate energy expend i tu res presented i n Moen (1973) f o r such l e v e l s of p roduc t i on . Moen es t imates t ha t a 60 kg dee r ' s maintenance requirements (normal d a i l y a c t i v i t y cos t s ) are approx imate ly 1.42 x BMR. Th is m u l t i p l e i nc reases t o 1.52 (1.08 x a c t i v i t y cos t s ) by the end of ges ta t i on and t o 1.86 (1.31 x a c t i v i t y cos t s ) du r ing peak l a c t a t i o n w i th one fawn. The m u l t i p l e s i n b rackets were app l i ed t o d a i l y energy expend i tures i n app rop r i a te months ( Ap r i l f o r pregnancy, May f o r peak l a c t a t i o n ) i n t h i s s tudy . The average t o t a l energy expended dur ing the d a y l i g h t hours was determined f o r each month and converted t o an hour ly ra te o f consumption. Th is va lue was then expressed as a m u l t i p l e of the he rd ' s mean FMR f o r tha t month. The p ropo r t i on of energy expended on each a c t i v i t y dur ing the day was a l s o c a l c u l a t e d each month. The general c a l c u l a t i o n procedures f o r the energy expend i ture es t imates were as f o l l ow s : A c t i v i t y Equat ion Graz ing Bedd ing- ruminat ing Walk ing (5 km/hr) Running Stand ing "Other" A c t i v i t i e s QGi = [BMR-j + 0.43 (Wt i ) ] T G i V i = C B M R i + ° * 2 4 ( W t i ) ] T B /R i QWi = [BMRi + 0.59 (Wtj)V] Twi QRi = [BMRi + 8.0 (BMRi)] TR-j QSi = [BMRi + 0.22 (Wt i ) ] T S i QOi = [BMRi + 3 (BMRi)] T Q i 19 where QQI , Q B / R i , QWi, QR1, QS i , QOi = average day l i g h t energy expended on g r a z i ng , bedd ing/ ruminat ing , wa l k i ng , runn ing , s tand ing and "o ther " a c t i v i t i e s , r e s p e c t i v e l y , du r ing the i t h m o n t h ( K c a l ) . BMR-j = average d a y l i g h t energy expended on basal metabol ism dur ing the i t h month (Kcal h r - 1 ) . Wti = average weight of adu l t ewes dur ing the i t h month (kg) V = v e l o c i t y o f t r a v e l (5 km h r - l ) . T G i , T B / R i ' TWi» T R i , T S i , Toi = average d a y l i g h t t ime devoted t o g r a z i ng , bedd ing/ ruminat ing , wa l k i ng , runn ing , s tand ing and "o ther " a c t i v i t i e s , r e s p e c t i v e l y , du r ing the i t h month ( h r s ) . N.B. - Convers ion f a c t o r s f o r g r a z i ng , bed . / rum. , and s tand ing have un i t s o f Kcal kg-1 h r - 1 . - Convers ion f a c t o r s f o r running and "o ther " a c t i v i t i e s are u n i t l e s s . - Convers ion f a c t o r s f o r wa lk ing has un i t s o f Kcal k g - 1 km-1. 20 RESULTS A. Soc i a l O rgan i za t i on 1. Dominance h i e ra r chy of the adu l t ewes A t o t a l o f 180 i n t e r a c t i o n s between adu l t ewes were observed dur ing the s tudy . These i n t e r a c t i o n s were t y p i c a l l y sudden, b r i e f encounters (< 10 s ) . Ewes demonstrated a very l i m i t e d behav ioura l r e p e r t o i r e , performing only two or th ree d i f f e r e n t pa t te rns i n the ma jo r i t y of i n t e r a c t i o n s . Bu t t i ng was the most common pa t te rn used by dominants to d i s p l a c e subord inate an ima l s , f o l l owed i n frequency by the horn t h r e a t . The subo rd i na te ' s response was u sua l l y t o squat , u r i n a t e and then move from the a rea , or t o s imply f l e e . However, m i l d c l a s he s , f o l l owed by severa l seconds of horn w r e s t l i n g i n which i n t e r a c t o r s would lock horns and push or t w i s t heads, o f ten r e su l t ed from the i n i t i a l b u t t , r ega rd less of the d i f f e r e n c e i n s o c i a l rank of the i n t e r a c t o r s . Almost i n v a r i a b l y (> 90%), the i n i t i a t o r o f such an encounter was the eventual dominant. Other pa t te rns used i n f r equen t l y by dominant ewes towards subord inates inc luded the low s t r e t c h and k i c k . Subord inate animals o c c a s i o n a l l y d i s p l a yed head shakes or t h r ea t jumps a f t e r be ing d i sp l a ced by dominants and, on two occas i ons , were observed nu z z l i n g more dominant an ima ls . Of the f i v e ca t ego r i e s of i n t e r a c t i o n s , encounters at bedding s i t e s were those most f r equen t l y observed throughout the y ea r , compr i s ing 60 (33.3%) of the 180 i n t e r a c t i o n s recorded. F i f t y - o ne i n t e r a c t i o n s (28.3% of the t o t a l ) occurred at feed ing s i t e s , i n c l u d i n g the supplemental m i ne r a l , water and feed sources . P o s i t i o n a l i n t e r a c t i o n s arose p r i m a r i l y when subord inate animals appeared t o 21 v i o l a t e the " i n d i v i d u a l d i s t ance " (Hediger 1950, d i s cussed i n Syme and Syme 1979) of more dominant ewes, or when animals u n i n t e n t i o n a l l y b locked e s t a b l i s h ed t r a i l s du r i ng herd movements and were d i s p l a c ed , u sua l l y by more dominant an ima l s . F o r t y - s i x (25.6%) o f a l l i n t e r a c t i o n s c l a s s i f i e d were of t h i s t ype . P l a y f u l i n t e r a c t i o n s were cons idered t o be those encounters not a s so c i a t ed w i th resources or p o s i t i o n i n g . P lay was c ha r a c t e r i z ed by e r r a t i c behav iour pa t te rns (jumps, burs t s of runn ing , exaggerated horn t h r ea t s ) not normal ly observed i n d a i l y maintenance behav iour . Such i n t e r a c t i o n s between adu l t ewes, u sua l l y i n i t i a t e d by the p l a y f u l behav iour of y e a r l i n g s and lambs, were most p reva len t i n the sp r i ng ( l a t e March t o June ) , t ape r i ng o f f i n f requency as the summer progressed and becoming rare t o non-ex i s t an t dur ing the f a l l and w i n t e r . Because of t h i s seasonal t r e nd , p l a y f u l i n t e r a c t i o n s comprised only 7.2% (13) of a l l adu l t encounters f o r the e n t i r e yea r . The remain ing 10 i n t e r a c t i o n s (5.5%) were u n c l a s s i f i e d . R i t u a l i z e d dominance d i spu tes t y p i c a l of b ighorn rams (Ge i s t 1971, Shack leton 1973) were not observed dur ing the 14-month s tudy . In a dd i t i o n t o be ing o f b r i e f d u r a t i o n , i n t e r a c t i o n s between adu l t ewes were a l s o so i n f requen t t ha t encounters between some pa i r s o f animals were never observed. As a r e s u l t , severa l c e l l s of each i n t e r a c t i o n mat r i x (Tables I and I I ) con ta in no i n fo rmat ion on the s o c i a l r e l a t i o n s h i p s between p a r t i c u l a r p a i r s o f ewes. However, computat ion of Dominance Values enabled a s o c i a l rank t o be ass igned t o each i n d i v i d u a l . An eva l ua t i on of the Dominance Va lues , i n t u r n , showed the ex i s t ence of th ree r e l a t i v e l y d i s t i n c t s o c i a l groups f o r both t ime p e r i o d s . For the June t o December, 1977, sampl ing pe r i od (Table I ) , f ou r ewes (WWW, W, RWB, WW) were dominant over much of the herd and had high Dominance Va lues , rang ing from 65.9 t o 90 .0 . Three ewes (WBW, NCA, W/R) were 22 Table I. Dominance Values of captive ewes, based on dyadic interactions Xl- (for period June 1 - December 31, 1977) Prop, of Animal Identification Codes opponents Dominance dominated Value = WWW W RWB WW BIBI RB BW W/B NCT PBC R/B RBR W/R NCA WBW by i ARCSIN v^i" 1 WWW *+(2) (0) (0) (0) (0) + (1) (0) + (2) + (2) + (D + (D -$(4) + (D + (D (0) 1.00 90.0 2 W -(2) + (3) (0) (0) + (3) + (D + (D (0) + (1) + (3) + (1) + (1)' + (1) 0.89 70.3 3 RWB (0) -(3) **±(2) + (D + (D (0) (0) + (4) (0) (0) + (D + (2) + (D + (2) 0.83 65.9 4 WW (0) (0) + (2) -(1) (0) (0) + (2) + (1) + (1) + (1) (0) + (1) + (3) + (1) 0.83 65.9 5 BIBI (0) (0) -(1) + (D -(1) + (D (0) (0) + (2) + (1) (0) (0) (0) (0) 0.67 54.7 6 RB (0) -(3) -(1) (0) + (D (0) + (2) (0) + (2) + (D + (2) (0) (0) + (3) 0.63 52.2 7 BW -(1) -(1) (0) -(2) -(1) (0) (0) (0) + (2) (0) (0) (0) + (D + (D 0.50 45.0 8 W/B (0) -(1) (0) -(1) (0) + (2) (0) (0) + (5) (0) + (2) (0) (0) (0) 0.50 45.0 9 NCT -(2) (0) -(4) -(1) (0) (0) (0) (0) (0) -(1) (0) + (2) + (2) + (D 0.43 40.9 10 PBC -(2) -(1) (0) -(1) -(2) + (2) -(2) -(5) (0) (0) + (D + (1) + (D + (3) 0.41 39.8 11 R/B -(1) -(3) (0) -(1) -(1) -(1) (0) (0) + (D (0) -(1) + (D + (1) + (2) 0.40 39.2 12 RBR -(1) E+(4) -(1) (0) (0) -(2) (0) -(2) (0) -(1) + (D + (1) + (2) (0) 0.36 36.9 13 W/R -(1) -(1) -(2) -(1) (0) (0) (0) (0) -(2) -(1) -(1) -(1) + (2) + (2) 0.15 22.8 14 NCA -(1) -(1) -(1) -(3) (0) (0) -(1) (0) -(2) -(1) -(1) -(2) ±(2) + (3) 0.14 21.7 15 WBW (0) -(1) -(2) -(1) (0) -(3) -(1) (0) -(1) -(3) -(2) (0) -(2) -(3) 0.00 0.0 Linearity of hierarchy, based on Landau's Index: 0.59 *When reading across Tables I and II, plus signs indicate dominance, minus signs subordination. When reading down, reverse is true. The number of interaction between each pair of ewes is given in parentheses. **+ indicates dominance reversal in successive interactions. Table I I . Dominance Values of c ap t i ve ewes, based on dyad ic i n t e r a c t i o n s ( f o r per iod January 1 - June 30, 1978) Prop, o f opponents Dominance dominated Value = i R/B W WW RWB NCT RB RBR W/R NCA WBW by 1 ARCSIN 1 R/B *(0) (0) + (1) + (5) + (1) (0) + (1) + (1) + (D 1.00 90.0 2 W (0) **+(2) + (3) + (2) + (4) (0) + (4) (0) (0) 0.90 71.6 3 WW (0) + (2) - (4) + (2) + (1) + (1) + (5) + (2) (0) 0.79 62.4 4 RWB - (1 ) - (3 ) + (4) + (5) + (2) + (3) + (D + (3) + (2) 0.78 61.9 5 NCT - (5 ) - (2) - (2) - (5) + (D + (2) + (2) + (D + (1) 0.56 48.2 6 RB - (1 ) - ( 4 ) - (1 ) - (2 ) - ( 1 ) + (2) t ( 2 ) + (D + (2) 0.39 38.6 7 RBR (0) (0) - (1) - (3) - (2 ) - (2 ) (0) + (1) + (1) 0.33 35.3 8 W/R - (1 ) - ( 4 ) - (5 ) - (1 ) - ( 2 ) 1 (2 ) (0) (0) + (3) 0.21 27.6 9 NCA - (1 ) (0) - (2) - (3) - (1 ) - (1 ) - (1) (0) + (D 0.14 22.2 10 WBW - (1 ) (0) (0) - (2 ) - ( 1 ) -(2) - ( 1 ) - ( 3 ) - ( 1 ) 0.00 0.0 L i n e a r i t y of h i e r a r chy , based on Landou's Index: 0.46 *When read ing across Tables I and I I , p lus s i gns i n d i c a t e dominance, minus s i gns s ubo r d i n a t i o n . When read ing down, reverse i s t r u e . The number of i n t e r a c t i o n between each p a i r o f ewes i s g iven i n parentheses . **+ i n d i c a t e s dominance reve rsa l i n succes s i ve i n t e r a c t i o n s . subord inate t o the ma j o r i t y o f herd members and had r e l a t i v e l y smal l va lues (22.8 t o 0 . 0 ) . The remaining animals o f i n te rmed ia te s t a tu s were dominant over approx imate ly the same number of animals as they were subord inate t o . As a r e s u l t , Dominance Values f o r these animals c l u s t e r ed around the mid-po int of 45 .0 , ranging from 36.9 t o 54 .7 . For the January t o June, 1978, sampl ing pe r i od (Table I I ) , the th ree groups were again ev ident but of s l i g h t l y d i f f e r e n t compos i t i on . Four dominant (R/B, W, WW, RWB) and three subord inate animals (W/R, NCA, WBW) were again c l e a r l y d e f i n ab l e from t h e i r h igh (61.9 t o 90.0) and low (27.6 t o 0.0) Dominance Values r e s p e c t i v e l y . Intermediate animals (NCT, RB, RBR), g r ea t l y reduced in numbers because of w in te r m o r t a l i t i e s , had va lues ranging from 35.3 t o only 48 .2 . I t was hypothes ized tha t a s t r ong l y l i n e a r h i e ra r chy would develop w i t h i n the c ap t i v e herd . However, f i n d i ng s presented below fo rced the r e j e c t i o n of t h i s hypo thes i s . A l though the animals cou ld be ranked l i n e a r l y from t h e i r Dominance Va lues , the h i e r a r c h i e s showed poor l i n e a r i t y , based on Landau's index (0.59 and 0 .46, r e s pe c t i v e l y f o r the 1977 and 1978 h i e r a r c h i e s ) . A h i e r a r chy w i th a score of 0.9 or g rea te r i s gene ra l l y judged t o be s t r ong l y l i n e a r (Wi lson 1975). I t would appear t ha t the low index values l a r g e l y r e s u l t e d from the lack of i n t e r a c t i o n s between many p a i r s of herd members and the abundance of dominance r e v e r s a l s . There were no e s t ab l i s h ed dominance c i r c l e s ev ident i n e i t h e r h i e ra r chy t o c on t r i b u t e t o t h e i r n o n - l i n e a r i t y . S t a b i l i t y o f the adu l t ewes' s o c i a l system The a n a l y s i s o f herd i n t e r a c t i o n s f o r two d i f f e r e n t t ime per iods enabled the s t a b i l i t y o f the he rd ' s s o c i a l system to be eva lua ted over a one year pe r i od . Winter m o r t a l i t i e s r e su l t ed i n the l o s s of f i v e adu l t ewes from the herd (one 25 dominant - WWW; fou r in te rmed ia tes - PBC, W/B, BLBL, BW). Al though most animals r e ta i ned r e l a t i v e l y constant Dominance Values and s o c i a l p o s i t i o n s a f t e r t h i s r edu c t i on , some rank changes were ev i den t . R/B moved from a low in te rmed ia te s t a tu s (D.V. = 39.1) t o a very h igh rank ing p o s i t i o n (D.V. 9 0 . 0 ) , r e v ea l i n g her inc reased dominance f i r s t i n l a t e A p r i l , 1978 and then more c on c l u s i v e l y i n May and June. NCT made a more moderate c l imb , r eve r s i ng p o s i t i o n s w i th RB w i t h i n the in te rmed ia te s o c i a l c l a s s . Her inc reased dominance was f i r s t noted i n mid-May, 1978. RB showed a cons ide rab le decrease i n her Dominance Va lue , dropping from 52.2 i n 1977 t o 38.3 i n 1978. In J u l y , 1977, a ewe from the Game Farm paddocks jumped i n t o the study enc losu re and j o i n ed the cap t i v e herd . Th is occurrence caused no apparent i n c rease i n the number of aggress i ve i n t e r a c t i o n s w i t h i n the herd nor d i d i t d i s r u p t the e s t ab l i s h ed h i e r a r chy . The ewe appeared t o be a r e l a t i v e l y dominant an ima l , a l though her s tay was too l i m i t e d t o a c cu ra te l y assess her s t a t u s . 2. Determinants of dominance The p red i c t ed determinants of dominance (age, horn l e ng t h , body weight) were not c l e a r l y r e l a t ed t o s o c i a l s t a tus i n the herd. Age est imates d id demonstrate t ha t the th ree most subord inate ewes i n each h i e ra r chy were the youngest adu l t s ( th ree years of age) i n the herd. However, a fou r yea r o l d ewe was one of the fou r most dominant ewes i n each h i e r a r chy . S ince age es t imates by horn annu l i were only cons idered accura te up t o s i x y e a r s , ages cou ld not be mean ing fu l l y c o r r e l a t e d t o s o c i a l rank f o r the ma jo r i t y of the ewes. 26 Table I I I C o r r e l a t i o n between Dominance Values (D.V.) and p red i c t ed determinants of dominance: age (A . ) , body weight (WT.), horn length (H .L . ) and aggress iveness (AG.) ( i . e . number of i n t e r a c t i o n s i n i t i a t e d ) June t o December, 1977 So c i a l Animal Mean 1977 Mean 1977 C l a s s I .D. D.V. Age Weight (kg) Horn Length (mm) Aggress iveness Dominants WWW 90.00 6+ 50.5 302.5 9 w 70.3 6+ 50.5 275.0 15 RWB 65.9 4 56.5 271.0 11 WW 65.9 6+ 60.5 277.5 8 I n t e r - BIBI 54.7 6+ 46.5 280.0 3 mediates RB 52.2 6+ 53.0 270.0 9 BW 45.0 6+ 52.5 280.0 3 W/B 45.0 6+ 50.0 305.0 6 NCT 40.9 6+ 50.5 264.5 4 PBC 39.8 6+ 49.5 230.0 6 R/B 39.2 6+ 55.0 262.0 4 RBR 36.9 6+ 56.5 287.5 4 Sub- W/R 22.8 3 o rd ina tes NCA 21.7 3 WBW 0.0 3 C o r r e l a t i o n c o e f f i c i e n t s : r/\# rWT. r H . L . r AG . 52.0 244.5 2 52.0 230.0 4 44.5 253.0 0 not ob ta i nab l e w i th ag ing techniques used = 0.33 (NS) = 0.61 (p < 0.05) = 0.79 (p < 0.05) 27 Table IV C o r r e l a t i o n between Dominance Values (D.V.) and po s s i b l e determinants of dominance January t o June, 1978 So c i a l C l a s s Animal I .D. D.V. Age Mean 1978 Weight (kg) Mean 1978 Horn Length (mm) Aggress iveness) Dominants R/B 90.00 6+ 55.0 261.5 10 W 71.6 6+ 51.0 277.0 13 WW 62.4 6+ 55.0 280.5 12 RWB 61.9 5 57.0 271.0 17 I n t e r - NCT 48.2 6+ 51.0 269.5 7 mediates RB 38.6 6+ 51.5 270.0 5 RBR 35.3 6+ 55.0 291.0 1 Sub- W/R 27.6 4 50.5 250.0 4 o rd i na te s NCA 22.2 4 52.5 233.0 0 WBW 0.0 4 45.0 261.0 0 C o r r e l a t i o n c o e f f i c i e n t s : TA . = not ob ta inab l e w i th ag ing techn iques used rWT. = ° - 6 7 (P < ° - 0 5 ) r u . = 0.36 r A G < = 0.81 (p < 0.05) 28 In 1977, weights and Dominance Values were poor ly c o r r e l a t e d (r = 0.33) but s i g n i f i c a n t l y c o r r e l a t e d i n 1978 (r = 0 .55; p < 0.05) (Tables I I I and IV ) . The reverse was t r ue f o r horn l eng th s , w i th the horn l ength - D.V. c o r r e l a t i o n c o e f f i c i e n t s i n 1977 and 1978 being 0.61 (p < 0.05) and 0.35 (not s i g . ) , r e s p e c t i v e l y . A l though no morpho log ica l c r i t e r i a were s t r ong l y c o r r e l a t e d t o dominance i n both 1977 and 1978, aggress iveness appeared t o be a c o n s i s t e n t l y s i g n i f i c a n t requirement f o r h igh s o c i a l s t a t u s . In both h i e r a r c h i e s , the number of aggress i ve i n t e r a c t i o n s i n i t i a t e d by an i n d i v i d u a l showed a h i gh , p o s i t i v e c o r r e l a t i o n t o Dominance Value ( r i g j j = °- 76; r^gyg = 0 .81; p < 0 . 05 ) . A l t e r n a t i v e l y , aggress iveness may have been a r e s u l t , ra ther than a determinant of dominance, and dominance may have been a t t r i b u t e d t o some o the r , more sub t l e f a c t o r ( s ) . Based on these r e s u l t s , the hypothes is t ha t age, horn length and body weight were s t rong determinants of s o c i a l s t a tus had t o be r e j e c t ed . B. Consequences of Dominance 1. D ie t comparisons I t was p red i c t ed tha t dominant animals would, du r ing months of l i m i t e d a v a i l a b l e f o rage , have g rea te r access t o h igh q u a l i t y feed ing s i t e s and would remain on a h igher plane of n u t r i t i o n than more subord inate an ima l s . However, r e s u l t s o f the d i e t comparisons conducted between s o c i a l groups fo rced the 29 r e j e c t i o n of t h i s hypo thes i s . Ne i the r the t imes spent at h igh q u a l i t y , supplemental feed i n January (Table Va ) , nor the f e ca l N l e v e l s found i n December, 1977 and March, 1978 samples (Table Vb) were s i g n i f i c a n t l y d i f f e r e n t between s o c i a l groups. 2. A c t i v i t y budget comparisons The hypothes i s tha t dominant animals would show sho r t e r g raz ing t imes and longer bedding t imes than more subord inate animals du r i ng po t en t i a l months of shortages i n h igh q u a l i t y forage was a l s o r e j e c t e d . The g raz ing t imes of the th ree s o c i a l c l a s s e s d i d not d i f f e r i n the months used f o r comparisons (September t o March) . Some d i f f e r en ce s d i d a r i s e i n bedding t imes , a l though not i n the manner p r ed i c t e d . In October, the mean bedding t ime o f Dominants was s t a t i s t i c a l l y s i m i l a r t o tha t of both Intermediates and Subord inates . Intermediate ewes, however, bedded s i g n i f i c a n t l y l e s s than Subord inates . In January , the mean bedding t ime of Dominants was aga in s i m i l a r t o tha t of the others w h i l e , u n l i k e October, Intermediates bedded s i g n i f i c a n t l y longer than Subord inates (see Table V I ) . A l though between-c lass d i f f e r en ce s were min ima l , there were cons ide rab le d i f f e r en c e s between the a c t i v i t y budgets of animals w i t h i n a g iven s o c i a l c l a s s . Th is was p a r t i c u l a r l y t r ue f o r ewes of i n te rmed ia te s ta tus whose d i s s i m i l a r g raz i ng or bedding t imes con t r i bu t ed s i g n i f i c a n t l y t o the var iance o f the s t a t i s t i c a l model i n a l l months t e s t ed except February and March. Dominant animals showed s i g n i f i c a n t l y v a r i a b l e bedding t imes i n September and February and s i g n i f i c a n t l y v a r i a b l e g raz ing t imes i n November and February . Subord inate animals d i f f e r e d l i t t l e i n t h e i r a c t i v i t y p a t t e r n s , demonstrat ing only v a r i a b l e g raz i ng t imes i n November and February . 30 TABLE V D ie t comparisons between Dominants, Intermediates and Subord inates a) Average d a i l y hours spent at supplemental feed - January , 1978. Soc i a l C lass Mean hours feed ing Dominants 1.65 (S .D . I = l . 20 ) Intermediates 1.85 (S.D. = 1.68) Subord inates 1.28 (S.D. = 1.11) b) Fecal N l e v e l s - December, 1977 and March, 1978 No. o f December Average % No. of March Average % Soc i a l C lass Samples Fecal N Samples Fecal N Dominants 8 1.60 5 1.77 (S.D.=0.21) (S.D.=0.12) Intermediates 10 1.76 3 1.62 (S.D.=0.39) (S.D.=0.06) Subord inates 14 1.64 5 1.63 (S.D.=0.11) (S.D.=0.08) IS .D . = standard d e v i a t i o n 31 Table VI. Average dayl ight feeding and bedding times for Dominants, Intermediates and Subordinates (September 1977 to March 1978). Month Sept. Oct. Nov. Dec. Jan. Feb. Mar. Social Feed. Bed. Feed. Bed. Feed. Bed. Feed. Bed. Feed. Bed. Feed. Bed. Feed. Bed. Class (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) Dominants 9.26 1.85 7.93 1.45ab2 7.69 0.64 5.48 1.40 5.27 2.14ab 7.34 1.43 8.52 1.81 (1.53)1 (0.96) (0.78) (0.69) (0.72) (0.53) (1.27) (1.15) (1.16) (0.92) (1.74) (1.06) (0.89) (1.24) Intermediates 9.26 1.83 8.11 1.24a 7.68 0.29 5.25 1.85 5.0 2.58a 7.02 1.37 8.25 2.42 (1.43) (0.98) (1.09) (0.67) (0.96) (0.75) (1.46) (1.40) (1.62) (1.24) (1.53) (0.65) (0.85) (0.86) Subordinates 9.07 1.92 7.93 1.64b 7.55 0.87 5.29 1.37 5.61 1.78b 7.00 1.65 8.15 2.17 (1.20) (0.66) (0.92) (0.64) (0.68) (0.59) (1.49) (1.11) (0.90) (0.82) (1.62) (1.07) (0.61) (0.89) 1 values in parenthesis are standard deviations 2 within a given column, values with different small case letters are significantly different (p < 0.05) 3. P r o d u c t i v i t y comparisons A l l hypotheses of t h i s study p r e d i c t i n g the improved p r o d u c t i v i t y o f dominant animals were r e j e c t e d . Seasonal weight changes i n the th ree s o c i a l c l a s se s d i d not d i f f e r s i g n i f i c a n t l y . From October t o December, 1977, a l l c l a s ses showed a weight l o s s of between f i v e and s i x percent of t h e i r October body weights (Table V I I ) . A l though Subord inates appeared t o demonstrate h igher average weight ga in from March t o August than Dominants and Intermediates (32.5% vs . 18.6% and 17.3% of March body weights r e s p e c t i v e l y ) , the d i f f e r en c e s were not s t a t i s t i c a l l y s i g n i f i c a n t . A t o t a l o f f i v e animals d i ed dur ing the 1977-78 w i n t e r . Without excep t i on , a l l animals were over s i x years of age and seve re l y emaciated. Of the fou r animals autops ied i n d e t a i l , a l l showed advanced stages of gum nec ros i s and l o s s of premolars and mo lars . A l though fou r o f the f i v e deaths occurred w i t h i n the in te rmed ia te s o c i a l c l a s s , the frequency of death w i t h i n each c l a s s d i d not vary s i g n i f i c a n t l y from expected va l ue s . (Ch i? = 1.70, df = 2 ) . The hypotheses t ha t dominant ewes would be r ep roduc t i v e l y more success fu l than ewes of lower s o c i a l rank was r e j e c t ed on the bas i s of lamb product ion i n 1978. Of the ten remaining adu l t ewes compr i s ing the herd i n 1978, fou r were cons idered Dominant, th ree In te rmed ia te , and th ree Subord inate in s t a t u s . Of these ewes, th ree Dominants, one Intermediate and one Subord inate produced lambs, w i th one lamb of the dominant group dy ing at or s ho r t l y a f t e r b i r t h . Whi le these f i g u r e s g ive the impress ion of a preponderance of r ep roduc t i ve l y success fu l dominant ewes, the frequency o f lambs from each group d i d not vary s i g n i f i c a n t l y from expected va lues (Chi2 = 0.84, df = 2 ) . 33 TABLE VII Seasonal weight change comparisons of Dominants, In te rmed ia tes , and Subord inates Soc i a l C lass Domi nants Intermediates Subord inates Average weight l o s s - Oct-Dec, 1977 (% of Oct . body wt . ) 5.27 (S .D . I = 3.04) 5.04 (S .D. = 3.31) 5.63 (S.D. = 4.63) Average weight gain - March-Aug, 1978 (% of March wt . ) 18.57 (S.D. = 2.93) 17.27 (S.D. = 8.3) 32.50 (S.D. = 19.16) 1 S.D. = standard d e v i a t i o n 34 c. Forage A v a i l a b i l i t y and Herd Behaviour Ninety p l an t spec ies were i d e n t i f i e d i n the study s i t e enc losure dur ing the 1977 sampl ing pe r i od (Wikeem & P i t t pe r s . comm.). As p r ev i ou s l y desc r i bed , the area i s dominated by a bluebunch wheatgrass (Agropyron spicatum) - b i g sage (Artemi s i a t r i d e n t a t a ) community w i th grasses c o n t r i b u t i n g more than 40% of the ground cover . Table V I I I l i s t s the mean cover va lues of the major unders tory p l an t spec ies determined from 1977 data (from Wikeem, unpub. d a t a ) . I t should be emphasized tha t these are mean va lues f o r the yea r and may vary s i g n i f i c a n t l y from es t imates determined at any p a r t i c u l a r po in t i n t ime . Many f o r b s , f o r example, are senescent f o r much of the yea r , but con t r i bu te s i g n i f i c a n t l y t o the ground cover dur ing the sp r i ng growing season. Of the 90 p l an t spec ies p resen t , 67 were u t i l i z e d by the sheep at some per iod throughout the year at va r ious degrees of i n t e n s i t y (Wikeem, pe r s . comm.). D ie t compos i t ion was not always s i m i l a r t o the bo tan i ca l composi t ion of the area as the sheep demonstrated a high degree of s e l e c t i v i t y not only f o r p a r t i c u l a r p l an t spec ies but f o r p l an t pa r t s as we l l ( P i t t and Wikeem 1979, Wikeem, pe r s . comm.). The seasonal growth c y c l e f o r the study area commenced i n March w i th the produc t ion of new growth by severa l p l an t s pe c i e s . Of the more common grass s pe c i e s , Agropyron sp icatum, Bromus tec torum, Koe l e r i a c r i s t a t a and Poa secunda were i n f i r s t or second l e a f stages w i th at l e a s t 3 cm of 35 Table V I I I Mean cover of the major unders tory p l an t spec ies over the 1977 sampl ing per iod (From Wikeem, i n p rep . ) P l an t Spec ies % Cover ( spec ies names from Hi tchcock and Cronqu i s t 1973) Grasses Agropyron spicatum 20.53 Bromus tectorum 10.24 Koe l e r i a c r i s t a t a 3.63 S t i pa comata 3.32 Poa secunda 2.79 Festuca s c a b r e l l a t r a ce Forbs Ba lsamorhiza s a g i t t a t a 2.16 Eriogonum niveum 1.36 Eriogonum herac l eo ides 0.94 A c h i l l e a m i l l e f o l i u m 0.89 Antennar ia dimorpha 0.34 Antennar ia p a r v i f l o r a 0.26 Lupinus se r i c eus 0.24 C a s t i l l e j a thompsoni i 0.22 Shrubs A r t em i s i a t r i d e n t a t a 8.07 Symphoricarpos a lbus 0.65 Chrysothamnus nauseosus 0.57 Others (g rasses , f o r b s , shrubs) 5.89 Tota l cover 62.36 So i l and rock 17.64 L i t t e r 17.18 97.18 36 v i s i b l e growth by mid-March. New leaves were a l s o ev iden t on such fo rbs as Ba lsamorh iza s a g i t t a t a and A c h i l l e a m i l l e f o l i u m wh i l e buds were bu r s t i ng on browse spec ies i n c l u d i n g Amelanchier a l n i f o l i a and Symphoricarpos al bus A l though es t imates of d i e t compos i t ion had not been completed f o r t h i s per iod of i n i t i a l growth at the t ime of t h i s s t udy ' s comp le t ion , a p rogress i ve pre fe rence towards new growth by the sheep was obvious from ocu l a r reconna issance of the a r e a ' s vegeta t ion (Wikeem, pe r s . comm.). From l a t e May t o l a t e J u l y , 1977, the study area supported i t s g rea tes t vege ta t i v e biomass f o r the yea r w i th the ma j o r i t y o f g ras s , f o rb and shrub spec ies pass ing through t h e i r rap id growth phase and p rogress ing i n t o the f l owe r i ng or f r u i t i n g s tages . With the a v a i l a b i l i t y o f a wide range of very pa l a t ab l e and n u t r i t i o u s p l a n t s , the sheep demonstrated a high degree of s e l e c t i v i t y , gene ra l l y p r e f e r r i n g forbs (Balsamorhiza s a g i t t a t a , Lupinus s e r i c eus ) and shrubs (Amelanchier a l n i f o l i a ) and s e l e c t i n g aga ins t the more common grasses (Bromus tec torum, Agropyron spicatum) ( P i t t and Wikeem, 1979). From mid-June t o mid-September, the study s i t e exper ienced the seasona l l y h igh temperatures and dry cond i t i on s common to t h i s reg ion and the ma jo r i t y of p l an t spec ies had cured by l a t e August. Al though l i m i t e d amounts of green f o l i a g e were s t i l l observed i n such common grasses as Agropyron spicatum and Koe l e r i a c r i s t a t a and such fo rbs as Eriogonum niveum, Eriogonum herac leo ides and Achi11ea m i l l e f o l i u m , most fo rbs d r i e d and wi thered i n t o an unusable f o r ag i ng c o n d i t i o n . With the except ion of A r t em i s i a t r i d e n t a t a and Chrysothamnus nauseosus which showed only i n i t i a l f l ower development i n August , the common shrubs on the study s i t e (Symphoricarpos a l bu s , Amelanchier a l n i f o l i a ) had formed and dropped t h e i r f r u i t and o f f e r ed no new l e a f development. With the d e c l i n i n g a v a i l a b i l i t y of fo rbs and shrubs , the sheep 37 exer ted g rea te r f o rag ing pressure on the common g rasses , showing l e s s s e l e c t i v i t y f o r p a r t i c u l a r spec ies but being h igh l y s e l e c t i v e f o r any remain ing green growth of Festuca s c a b r e l l a , Agropyron spicatum and Koe l e r i a c r i s t a t a , i n t ha t order (Wikeem, pe r s . comm.; pe r s . o b s e r v a t i o n s ) . From mid-September t o mid-November some regrowth occurred f o r a l l of the major perenn ia l bunch g rasses , annual grasses (Bromus tectorum, Bromis m o l l i s ) and remain ing f o r b s . By l a t e October, most shrubs had dropped t h e i r l e a ve s , a l though A r t em i s i a t r i d e n t a t a and Chrysothamnus nauseosus were s t i l l i n the f l owe r i ng or seed produc t ion s tage . Dur ing t h i s p e r i o d , the regrowth of the grass spec ies formed the bulk of the sheep 's d i e t , a l though use of some fo rbs (Eriogonum niveum, JE. he rac l eo ides ) a l s o cont inued (Wikeem, pe r s . comm.). From December to February , no s i g n i f i c a n t growth i n the vegeta t ion was apparent and the bo tan i ca l compos i t ion of the study area changed l i t t l e . Green f o l i a g e was present throughout t h i s pe r iod on many of the common grasses and fo rbs but was not r e a d i l y a v a i l a b l e once the area rece ived a 15 t o 30 cm. snow cover by l a t e December. The animals exer ted t h e i r g rea tes t f o rag ing pressure on Agropyron spicatum and Koe l e r i a c r i s t a t a , c r a t e r i n g f o r the most recent growth of the p l an t s where p o s s i b l e but u t i l i z i n g p r i m a r i l y emergent vege ta t i on dur ing the deep snow (> 20 cm) pe r iod ( e . g . E_. he r a c l eo i de s , A r t em i s i a t r i d e n t a t a , A. f r i g i d a ) . Th is d i e t remained r e l a t i v e l y constant u n t i l s p r i ng growth of grasses and fo rbs commenced i n e a r l y March. At tha t t ime, the sheep were h i gh l y s e l e c t i v e f o r t h i s new growth. 38 1. Seasonal d i u r na l pa t te rns Monthly a c t i v i t y graphs ( F i g . 1) demonstrate the seasonal c y c l e of the herd ' s d i u r na l p a t t e r n . Each graph conta ins data from one day cons idered t o be r ep r e sen t a t i v e f o r tha t month. Two days are presented f o r December to demonstrate the e f f e c t s o f w i n t e r storms and snow cover on herd behav iour . The average number of d a i l y a c t i v i t y peaks observed i n each month appears on the app rop r i a t e graph. In May and June, the herd members f o l l owed a c y c l i c a l and synchronous pa t te rn w i th moderate d a i l y v a r i a t i o n s . In gene ra l , major a c t i v i t y peaks occurred at dawn, mid-morning (8:00 - 10:00 h r s ) , noon and l a t e a f te rnoon . The f i n a l a c t i v e per iod was the most e x t en s i v e , s t r e t c h i n g over four hours from approx imate ly 16:00 hrs t o a f t e r dark . A l though s h o r t - l i v e d c loud burs t s would o c c a s i o n a l l y prompt a b r i e f , unscheduled bedding per iod by the herd du r i ng May, weather, i n gene ra l , had l i t t l e v i s i b l e e f f e c t on the t ime of onse t , du ra t i on or p e r i o d i c i t y o f a c t i v i t y peaks. In June, a f i f t h peak of shor t du ra t i on o f ten occurred at approx imate ly 14:00 hrs and the l a t e a f ternoon pe r iod was b i s e c t ed by a shor t bedding s e s s i on . As a r e s u l t , a d a i l y average of 5.3 a c t i v i t y peaks was observed i n June, compared t o only 4.3 i n May. In J u l y , an average of 5.0 peaks occurred each day, but d a i l y v a r i a t i o n i n d i u r na l pa t te rns was g rea te r than the prev ious two months. A c t i v e per iods were c o n s i s t e n t l y observed at dawn and from l a t e evening t o dusk. However, peaks dur ing the i n t e r im da y l i g h t hours showed a v a r i e t y of du ra t i ons and d i s t r i b u t i o n s from day t o day. 39 FIGURE 1 Graphs of monthly d i u rna l pa t te rns of the c ap t i v e herd (May 1977 t o A p r i l 1978) T = mean temperature (°C) f o r t ha t sampl ing day. Range of temperatures are g iven i n brackets x = mean number of d a i l y a c t i v i t y peaks demonstrated f o r tha t month. S = range of snow accumulat ion on the study s i t e . y = percent of the t o t a l herd a c t i v e at each 15 minute sampl ing i n t e r v a l PST = P a c i f i c Standard Time, i n hours . No. o f sampl ing days/month: 3 ( J a n . , Ap r . ) 4 ( J u l y , Aug . , Dec . , Mar .) 5 ( Sep t . , Feb.) 6 (June, Oc t . ) 7 (May, Nov.) 1004 UJ > o < z UJ O CC UJ 0. 1 27 May § T=15.1° (7.8-22.2) I U=4.3so.6 HI 13June ' I T=17.7° | (10.0-25.4) 1 X=5.3so.6 23 September 1=12.6° (9.5-15.5) X= 1.3*0.0 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 TlME[hours-PST] 41 " i — I 1 1 1 1 1 1 1 1 r—r—i 1 1 r 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 TIME 42 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 T I M E 43 August data were the f i r s t t o show a breakdown i n the c y c l i c a l d i u rna l pa t te rn p r e v i ou s l y observed. An average of 4.5 peaks occur red each day but many of those observed from mid-morning t o mid-af ternoon were of shor t du ra t i ons and i nvo l ved only s l i g h t l y more than 50% of the herd. Peaks at dawn and l a t e evening were again always present but va r i ed i n length from day t o day. Weather dur ing much of June, J u l y and August was c o n s i s t e n t l y hot and d ry . Consequent ly , no r e l a t i o n s h i p between weather and d i u r na l pa t te rns cou ld be recogn ized on a d a i l y b a s i s . From September t o November, the ma jo r i t y o f the herd was a c t i v e at any g iven t ime f o r much of the day. In September, there was no cons i s t en t bedding pe r i od demonstrated by the herd and, r e s u l t a n t l y , the average number of d i s t i n c t a c t i v i t y peaks dropped t o 1.3 per day. In October, an obvious bedding sess ion re turned at midday, d i v i d i n g the da y l i g h t a c t i v e pe r iod i n t o two d i s t i n c t peaks. November da ta , however, showed a reduced midday i n a c t i v e pe r i od and h igh a c t i v i t y l e v e l s throughout the day. For the f i r s t t ime , i t became apparent t ha t some animals were a c t i v e con t inuous ly throughout the d a y l i g h t hours . The average number of peaks observed per day was 1.67. A l though , w i t h i n each month, weather was v a r i a b l e , the re was again no obvious r e l a t i o n s h i p between weather and the an ima l s ' d i u r na l p a t t e r n . In December, the herd demonstrated two e n t i r e l y d i f f e r e n t d i u rna l pa t te rns at d i f f e r e n t t imes of the month. The f i r s t f ou r days of December were r e l a t i v e l y m i l d (above f r e e z i ng ) w i th only t r a c e accumulat ions of snow on the study s i t e . From December 12 t o 31, ground accumulat ions of snow were again minimal w i th mean d a i l y temperatures d ipp ing s l i g h t l y below f r e e z i n g on ly i n l a t e December. In the i n t e r im pe r i od , however, the study s i t e exper ienced sub-zero temperatures and a 15 t o 20 cm snow cover . The herd reacted t o each ambient 44 cond i t i on i n a d i f f e r e n t manner. Dur ing the m i ld and/or snow-free pe r i od s , herd a c t i v i t y pa t te rns resembled those of November, w i th the ma jo r i t y of the herd being a c t i v e throughout the day. The midday bedding pe r iod was even l e s s ex tens i ve than November. Dur ing the seven days of snow accumulat ions and co l d temperatures , a morning and af ternoon a c t i v i t y peak were p resent , w i th a midday bedding pe r iod i n v o l v i n g almost the e n t i r e herd separa t ing the two. For the f i r s t t ime i n the s tudy , the animals showed s i g n i f i c a n t l y reduced a c t i v i t y i n the e a r l y morning and l a t e evening hours . For December, an average of 1.3 a c t i v i t y peaks were observed per day. In January , a c rus ted snow cover of up t o 30 cm on h igher po r t i ons of the study s i t e and s l i g h t l y sub-zero temperatures (monthly mean of -2 .1°C) were present f o r much of the month. As p r ev i ou s l y mentioned, a l i m i t e d supply of supplemental feed (45 kg of hay per day) was prov ided f o r t h i s per iod i n the nor theast corner of the study a rea . In gene ra l , the herd would feed at the hay f o r much of the morning and upon i t s d e p l e t i o n , move t o the lower s lopes of the enc losure t o forage on the na t i ve vege ta t i on f o r the remainder of the day. Ea r l y morning a c t i v i t y was minimal but herd a c t i v i t y remained high throughout the day once f o rag ing was i n i t i a t e d , u sua l l y by l a t e morning (11:00 h r s ) . Data from only one observa t ion day showed a s i g n i f i c a n t degree of mid-morning f o r ag i ng and a synchronous bedding pe r iod before the normal l a t e morning t o dusk a c t i v i t y peak (x = 1.3 peaks/day) . In February , snow accumulat ion r a p i d l y de c l i n ed on lower s lopes and the herd was again dependent s o l e l y on the mature vege ta t i on of the study s i t e . An avoidance of e a r l y morning hours by the animals was no longer pronounced and the herd showed l i t t l e d i f f e r en ce i n i t s d i u r na l pa t te rn from January . The ma jo r i t y of the animals began f o r ag i ng at or s l i g h t l y before 8:00 hrs and, 45 i n gene ra l , remained a c t i v e throughout the day from tha t t ime on. As i n January , an average of 1.3 a c t i v i t y peaks per day was observed. March data showed the re tu rn of m u l t i p l e a c t i v e and bedding per iods dur ing the d a y l i g h t hours . An a c t i v i t y peak was once again c o n s i s t e n t l y observed at dawn and a second, more ex tens i ve one s t r e t ched from l a t e morning to dusk. A l though the on ly major bedding sess ion occur red at mid t o l a t e morning, a second i n a c t i v e pe r i od , va ry ing in du ra t i on and degree of herd member p a r t i c i p a t i o n , was f r equen t l y observed at mid a f ternoon (13:00 - 15:00 h r s ) . The average number of a c t i v i t y peaks observed per day increased from Feb rua ry ' s va lue of 1.3 t o 2.3 i n March. In A p r i l , the herd members were extremely synchronous and c y c l i c i n t h e i r a c t i v i t y p a t t e r n s , s i m i l a r t o t ha t observed i n May and June of the prev ious yea r . The herd would f r equen t l y t r a n s f e r from an a c t i v e , f o rag ing s t a t e t o one of complete i n a c t i v i t y i n the i n t e r v a l between two consecut ive scan sampl ing obse rva t i ons (15 m i n . ) . Cons i s t en t peaks occur red a t dawn, l a t e a f ternoon (16:00 hrs) and evening to dusk wh i l e i n t e r im a c t i v i t y per iods va r i ed d a i l y i n d i s t r i b u t i o n and du r a t i o n . An average of 5.3 peaks were observed per sampl ing day. A l though i n t e n s i v e f i e l d observa t ions f o r t h i s study ended on June 30, 1978, a d d i t i o n a l herd a c t i v i t y data were c o l l e c t e d on November 14, 1978 and December 17, 1978 dur ing b r i e f v i s i t s t o the study s i t e ( F i g . 1 ) . Th is enabled the he rd ' s d i u rna l pa t te rn t o be determined a f t e r a growing season in which g ra z i ng pressure had been reduced cons ide rab l y from the prev ious yea r . On November 14, weather c ond i t i on s were seasona l , w i t h c l e a r s k i e s and day- 46 l i g h t temperatures rang ing from -3°C t o 0°C. The study area had not rece ived snow t o t ha t da te . Four a c t i v i t y peaks were observed, the two most ex tens ive o c cu r r i ng from dawn t o e a r l y morning (9:00 hrs) and from l a t e af ternoon (18:00 h rs ) t o dusk. Two a d d i t i o n a l peaks were observed a t 9:45 hrs and 12:30 h r s . Th i s pa t te rn va r i ed cons ide rab l y from that demonstrated i n November, 1977, where the ma jo r i t y of the herd was a c t i v e at any given t ime f o r most of the day. On December 13, 1978, a 5 cm snow cover and s l i g h t l y sub-zero temperatures made ambient c ond i t i on s s i m i l a r t o those present dur ing the stormy per iod of December, 1977. However, the he rd ' s d i u r n a l pa t t e rn resembled tha t observed on m i l d e r , snow-free days of the prev ious December. A c t i v i t y was reduced only s l i g h t l y i n the e a r l y morning and l a t e even ing , and the ma jo r i t y of the herd was a c t i v e at any g iven t ime throughout the e n t i r e day. Some i n a c t i v i t y was obv ious at midday but i nvo l ved on ly 45% of the herd at i t s peak pe r i od . Nocturnal a c t i v i t y The degree of nocturna l a c t i v i t y of the herd va r i ed cons ide rab l y w i th the t ime o f y ea r . On May 5 and June 20, 1978, the herd was observed from dusk t o 24:00 hrs P a c i f i c Standard Time (PST) under c l e a r s k i e s and moonl i t c ond i t i o n s . L i g h t i n g was cons idered t o be at a minimal l e v e l (animals were no longer v i s i b l e w i thout the spot lamp) by 19:30 and 21:15 hrs PST, r e s p e c t i v e l y . On both o c cas i ons , the he rd semed to cont inue the c y c l i c graz ing/bedd ing pa t te rn e s t a b l i s h ed du r i ng the d a y l i g h t hours o f these months, a l though a c t i v e per iods were l e s s ex tens i ve and i nvo l ved fewer an ima l s . The e n t i r e herd on May 5 was bedded by 20:08 h r s , approx imate ly 38 minutes a f t e r complete darkness . With the except ion o f minor s h u f f l i n g o f bedding s i t e s , the re was no a c t i v i t y from 47 t h i s t ime t o 22:10 h r s , when fou r animals began f o r ag i ng . A l i m i t e d a c t i v i t y peak i n v o l v i n g only fou r to s i x animals at a t ime cont inued f o r the remainder of the obse rva t i on p e r i o d . Dur ing t h i s t ime , f o r ag i ng was r e s t r i c t e d t o the immediate v i c i n i t y o f the bedding a rea . On June 20, the herd was complete ly bedded by 21:00 h r s , 15 minutes before the area was cons idered to be i n complete darkness , and the herd remained i n a c t i v e u n t i l 22:35 h r s . At tha t t ime , a f o rag ing bout was i n i t i a t e d by th ree an ima l s , cu lm ina t ing i n an a c t i v i t y peak which i nvo l ved a l l but f i v e herd members. S i m i l a r t o May 5 obse r va t i on s , the g raz ing animals remained w i t h i n 50 m of the bedding a r ea . By 23:19 h r s , a l l animals had rebedded and cont inued t o do so f o r the re s t of the obse rva t i on pe r i od . On November 14, 1978 du r i ng the r u t t i n g p e r i o d , the herd was monitored from dusk t o 21:00 hrs P a c i f i c Standard Time (PST) i n c l e a r moonl i t c ond i t i on s and s l i g h t l y sub-zero temperatures . A l though i n i t i a l s igns of bedding were observed at 17:02 h r s , 15 minutes before the area exper ienced i t s minimum l i g h t l e v e l s f o r the n i gh t , bedding was not ex tens i ve f o r almost an hour because of the cont inued harassment of ewes by c ou r t i n g rams. By 17:55 h r s , 13 of the 26 herd members were s t i l l a c t i v e and remained so u n t i l 18:30 hrs when a l l but seven animals bedded. The e n t i r e herd f i n a l l y became i n a c t i v e at 19:05 hrs and no f o r ag i ng or cou r t sh i p behaviour was observed f o r the re s t of the mon i to r ing p e r i o d . At dawn the f o l l o w i n g morning, only e i gh t of the herd members had moved a s i g n i f i c a n t d i s t ance (> 100 m) dur ing the n i gh t , i n d i c a t i n g l i m i t e d nocturna l movement. On December 17, n igh t observa t ions were recorded from dusk t o 20:00 hrs under a low overcas t sky and -3°C temperatures . The study area was b lanketed by approx imate ly 15 cm of f r e sh snow. Bedding a c t i v i t y was i n i t i a t e d by the 48 animals at 16:05 h r s , approx imate ly 40 minutes before t o t a l darkness and progressed g radua l l y u n t i l the e n t i r e herd was bedded by 17:45 h r s . With the except ion of occas iona l s h i f t s i n bedding s i t e s , the herd remained s t a t i o na r y throughout the du ra t i on of the obse rva t i on pe r i od . Dur ing scan sampl ing in December, 1977 and January , 1978, observat ions c o l l e c t e d at dusk and dawn of success i ve sampl ing days showed, w i th ra re ex cep t i on s , no movement i n the animals ove rn i gh t . Th i s may suggest t ha t movement dur ing the n igh t s of co l de r months i s more r e s t r i c t e d than dur ing n igh t s of more temperate seasons. 2. Seasonal a c t i v i t y budgets Average d a y l i g h t hours devoted t o feed ing by the herd members ranged from 5.32 hrs/sample day and 5.27 hrs/sample day f o r December and January , r e s pe c t i v e l y t o 9.22 h r s . i n September (see Table I X ) . However, means f o r the remaining months showed no con s i s t en t t r end and were a l l w i t h i n one hour of the y e a r l y mean o f 7.43 hrs/sample day, r e s u l t i n g i n an i n s i g n i f i c a n t c o r r e l a t i o n between feed ing t ime and day length (r = 0 . 51 ) . Regard less of a m id-w in te r i n c rease i n d a i l y bedding t ime , the average number of d a y l i g h t hours devoted t o bedding proved t o be s i g n i f i c a n t l y c o r r e l a t e d t o day length (r = 0 . 92 ) , peaking at 5.75 hrs/sample day i n June and decreas ing monthly t o 0.77 hrs/sample day i n November. A l though December and January va lues inc reased i r r e g u l a r l y t o 1.6 and 2.2 hrs/sample day, r e s p e c t i v e l y , the bedding t imes began an o rde r l y monthly c l imb from 1.47 hrs/sample day i n February t o 5.51 hrs/sample day i n May. The y e a r l y average was 3.0 hrs/sample day. 49 Table IX. Average dayl ight ac t i v i t y budgets of the adult ewes, by month. Month # days/ month Mean length of sampling days Feeding Time % o f Daylength Bedding Time % Of Daylength Travel time % o f Daylength Standing Time % Of Daylength "Other" Time % of Daylength (hrs) (hrs) (hrs) (hrs) (hrs) (hrs) May 7 15.00 % (0.0)( 1) 7.40 (0.87) 49.3 5.51 (0.60) 36.7 0.97 (0.41) 6.5 0.67 (0.49) 4.5 0.46 (0.37) 3.1 June 6 16.04 (0.70) 7.90 (1.13) 49.3 5.75 (1.03) 35.8 0.64 (0.36) 4.0 1.09 (0.80) 6.8 0.65 (0.41) 4.1 July-Aug. 8 16.21 (0.59) 8.38 (1.05) 51.7 5.39 (0.97) 33.2 1.03 (0.51) 6.4 0.99 (0.65) 6.1 0.42 (0.33) 2.6 September 5 12.70 (0.48) 9.22 (1.40) 72.6 1.85 (0.89) 14.6 0.72 (0.48) 5.7 0.58 (0.39) 4.6 0.33 (0.30) 2.6 October 6 10.75 (0.42) 8.03 (0.98) 74.7 1.37 (0.67) 12.7 0.60 (0.48) 5.6 0.58 (0.48) 5.4 0.17 (0.25) 1.6 November 7 9.39 (0.49) . 7.65 - (0.84) 81.5 0.77 (0.69) 8.2 0.40 (0.29) 4.3 0.42 (0.34) 4.5 0.13 (0.20) 1.4 December 4 8.56 (0.24) 5.32 (1.39) 62.1 1.60 (1.30) 18.7 0.81 (0.47) 9.4 0.73 (0.56) 8.5 0.13 (0.20) 1.5 January 3 9.5 (0.00) 5.27 (1.28) 55.5 2.20 (1.04) 23.2 0.71 (0.37) 7.5 1.22 (0.61) 12.8 0.11 (0.20) 1.2 February 5 10.25 (0.40) 7.14 (1.62) 69.7 1.47 (0.95) 14.3 0.46 (0.36) 4.5 1.07 (0.84) 10.4 0.10 (0.16) 1.0 March 4 11.44 (0.59) 8.33 (0.80) 72.8 2.10 (1.04) 18.4 0.36 (0.27) 3.1 0.49 (0.28) 4.3 0.14 (0.26) 1.2 Ap r i l 3 14.52 (0.14) 7.13 (0.94) 49.1 4.61 (0.83) 31.7. 1.69 (0.85) 11.6 0.91 (0.47) 6.3 0.19 (0.24) 1.3 x = 12.21 x = 7.43 r = 0.5l( 2) x = 3.0 r = 0.92* r x = 0.76 = 0.51 r x = 0.80 = 0.24 x = 0.26 r = 0.85* Nov. '78 (1 day) x = 9.75 x = 5.42 (0.76) 55.6 x = 3.04 (0.57) 31.1 x = 0.44 (0.25) 4.52 x = 0.75 (0.41) 7.70 7 = 0.10 (0.13) 1.14 Dec. '78 (1 day) x = 9.0 x = 6.33 (0.55) 70.3 x = 1.23 (0.60) 13.7 x = 0.55 (0.50) 6.1 x = 0.96 (0.58) 9.6 x = 0.03 (0.09) 0.3 (1) = values i n parenthesis are standard deviations (2) = c o r r e l a t i o n c o e f f i c i e n t (with daylength) *'s indicate s i g n i f i c a n t correlation (p= < 0.05) Da i l y t r a v e l t ime showed no obvious seasonal pa t te rn dur ing the yea r . Values ranged from 1.69 ( A p r i l ) to 0.36 hrs/sample day in March and were not s i g n i f i c a n t l y c o r r e l a t e d t o day length (r = 0 . 51 ) . R e l a t i v e l y h igh values a l s o occurred i n May (0.97 hrs/sample day) and J u l y - August (1.03 hrs/sample day ) . Da i l y s tand ing t ime , a l s o not s i g n i f i c a n t l y c o r r e l a t e d t o day length (r = 0 . 24 ) , showed two peaks dur ing the study yea r , w i th the h ighest values o c cu r r i n g i n the ho t t e s t and co l de s t months of the year (June t o August, January t o February r e s p e c t i v e l y ) . Dur ing these per iods s tand ing t imes remained at or s l i g h t l y above 1 hr/sample day. For the remaining months, va lues f l u c t u a t ed i r r e g u l a r l y between 0.42 hrs/sample day (Nov.) and 0.91 hrs/sample day ( A p r i l ) . Time devoted t o "o the r " a c t i v i t i e s ( p l a y i n g , i n t e r a c t i n g , maternal behaviour) du r i ng the d a y l i g h t hours proved t o be s i gn i f i c an t l y c o r r e l a t e d t o day length (r = 0 . 85 ) , peaking i n May, June and J u l y (0 .46 , 0.65 and 0.42 hrs/sample day, r e s p e c t i v e l y ) and then dropping g radua l l y t o a low of 0.10 hrs/sample day i n February . Values began i n c r ea s i ng i n the s p r i n g , reach ing 0.19 hrs/sample day by A p r i l 1978. Because day lengths va r i ed cons ide rab l y on a seasonal b a s i s , ac tua l d ay l i g h t a c t i v i t y t imes prov ided marg ina l l y use fu l and sometimes decept i ve in fo rmat ion on the seasonal t rends of these a c t i v i t i e s . Consequent ly , the p ropor t ions of sampl ing days devoted t o va r ious a c t i v i t i e s were c a l c u l a t e d t o prov ide a more s tandard i zed set o f va l ue s . It i s these p ropo r t i ons which are dea l t w i th i n Sec t i on C2 of D i s c u s s i on . 51 Un l i k e ac tua l f eed ing t imes , the p ropo r t i on o f d a y l i g h t hours spent f o rag ing va r i ed d r ama t i c a l l y between seasons. Values inc reased i n an o rde r l y fash ion from A p r i l (49.1%) t o November (81.5%), dropped t o 62.1 and 55.5% i n December and January , r e s p e c t i v e l y , and then c l imbed i n February and March to 69.7 and 77.8%, r e s p e c t i v e l y . Bedding p ropor t i ons gene ra l l y f o l l owed a reversed t rend t o tha t o f f eed ing , d e c l i n i n g from peak sp r i ng va lues (31.7% i n A p r i l , 36.7% i n May) t o on ly 8.2% i n November. Winter bedding p ropo r t i ons inc reased t o 18.7 and 23.2% i n December and January , r e s p e c t i v e l y , and then dropped t o 14.3 and 18.4% i n February and March, r e s p e c t i v e l y . The p ropo r t i on of day length devoted t o t r a v e l , s i m i l a r t o ac tua l d a i l y t imes , showed no seasonal t r e nd , ranging between va lues of 3.1% to 7.5% f o r the months of May t o November i n c l u s i v e , January , February and March. Travel t ime p ropo r t i ons peaked i n A p r i l (11.6%) w i th r e l a t i v e l y h igh va lues a l s o o c cu r r i ng i n December (9.4%). Stand ing t ime p ropo r t i ons a l s o showed no seasonal t r e nd . R e l a t i v e l y h igh va lues occurred i n January (12.8%), December (8.5%) and February (10.4%), w i th va lues f o r the remain ing months f l u c t u a t i n g i r r e g u l a r l y between 4.3% (March) and 6.8% ( June) . Un l i ke ac tua l s tand ing t imes/sample day, s tand ing t ime p ropo r t i ons d i d not demonstrate a secondary peak i n summer. The p ropo r t i on o f day length devoted t o "o the r " a c t i v i t i e s fo l l owed a s i m i l a r pa t t e rn as ac tua l t imes . Peak va lues occur red i n May (3.1%) and June (4.1%), de c l i n ed i n a gradual f a sh ion t o 1.0% i n February , and then inc reased to 1.2 and 1.3% i n March and A p r i l , r e s p e c t i v e l y . 52 The he rd ' s d i u rna l budget va r i ed cons ide rab l y on sampl ing days i n November and December 1978 from tha t demonstrated dur ing a comparable pe r iod i n 1977. A l though t imes devoted t o t r a v e l l i n g , s tand ing and "o ther" a c t i v i t i e s on November 14, 1978 were not un l i k e the mean d a i l y va lues f o r November, 1977, the herd reduced t h e i r g raz ing t ime and inc reased t h e i r bedding t ime by more than two hours from 1977 va l ues . Times devoted t o s t and ing , t r a v e l l i n g , and "o the r " a c t i v i t i e s a l s o va r i ed on ly s l i g h t l y between December 1977 and 1978 sampl ing days. However, dur ing inc lement weather on December 13, 1978, t ime spent g raz ing inc reased by more than one hour over the December 1977 mean d a i l y va lue , wh i l e bedding t ime decreased by approx imate ly 0.4 hours . Of the t o t a l average g raz i ng t ime demonstrated by the herd i n 1978, 0.8 hrs was devoted t o c r a t e r i n g f o r fo rage . Th is va r i ed cons ide rab l y from 1977, when c r a t e r i n g t imes averaged 0.2 hrs/sample day dur ing snow accumulat ions of December, d e c l i n i n g t o 0 hrs/sample day once m i l d temperatures removed much of the snow cover i n l a t e December. In add i t i o n t o these seasonal changes i n the he rd ' s a c t i v i t y budget, d a i l y f l u c t u a t i o n s were a l s o ev i den t . As desc r i bed i n Sec t i on B2 of Methods, the l i n e a r model used t o s t a t i s t i c a l l y assess between group d i f f e r en ce s i n g raz ing and bedding t imes a l s o assessed the e f f e c t s of sampl ing day and the sampl ing day - s o c i a l group i n t e r a c t i o n term. Al though the i n t e r a c t i o n term con t r i bu t ed no s i g n i f i c a n t var iance t o the s t a t i s t i c a l model, there was s i g n i f i c a n t day t o day v a r i a t i o n i n the he rd ' s a c t i v i t y budget f o r most months of the yea r . May to September i n c l u s i v e , December and February were months i n which s i g n i f i c a n t day t o day f l u c t u a t i o n s were present i n the t imes devoted t o a l l f i v e a c t i v i t y c a t e go r i e s . In October, November and A p r i l , a l l but one a c t i v i t y ( s tand ing , s tand ing and "o the r " , r e s pe c t i v e l y ) showed s i g n i f i c a n t d a i l y v a r i a t i o n i n d u r a t i o n , wh i l e i n March, bedding a lone va r i ed 53 d a i l y . January was the only month i n which the he rd ' s a c t i v i t y budget was c on s i s t en t from day t o day. D. E f f e c t s o f P h y s i o l o g i c a l Cond i t i on on Da i l y A c t i v i t y Budgets As p r ev i ou s l y desc r i bed i n Sec t i on B3 of R e s u l t s , on ly ewes of dominant and i n te rmed ia te s t a tu s d i ed dur ing the w i n t e r . There fo re , comparisons of g raz ing and bedding t imes of hea l thy and s i c k animals i n October, November and December were po s s i b l e only w i t h i n these two s o c i a l c l a s s e s . Among the dominant an ima l s , no s i g n i f i c a n t d i f f e r en c e s e x i s t ed between the g raz i ng or bedding t imes of s i c k and hea l thy animals f o r any of the th ree months t e s t e d . However, d i f f e r en ce s were ev ident w i t h i n the in te rmed ia te c l a s s of animals (Table Xa ) . In October, s i c k animals grazed s i g n i f i c a n t l y (p < 0.05) longer than hea l thy an ima l s , a l though bedding t imes were s i m i l a r f o r the two groups. In December, j u s t p r i o r t o the ma jo r i t y o f deaths , g raz ing t imes were s i m i l a r but s i c k animals bedded s i g n i f i c a n t l y longer than hea l thy an ima l s . In March and A p r i l , ewes from each of the th ree s o c i a l c l a s s e s were suppor t ing l a t e stages of f e t a l development, enab l i ng g raz ing and bedding t imes of pregnant and non-pregnant ewes t o be compared w i t h i n each c l a s s (Table Xb) . Pregnancy demands d i d not appear t o a l t e r a c t i v i t y budgets app r e c i ab l y , and no s i g n i f i c a n t d i f f e r en c e s were detected between the s o c i a l groups. However, w i t h i n every c l a s s , pregnant ewes i n A p r i l d i d demonstrate longer g raz ing t imes than non-pregnant ewes, but not s i g n i f i c a n t l y so . 54 Table Xa - Average g raz ing and bedding t imes of hea l thy and s i c k ewes (October t o December 1977), i n hours Dominants Intermediates Feed, t imes Bed. t imes Feed, t imes Bed. t imes Oct . Nov. Dec. Oct. Nov. Dec. Oct. Nov. Dec. Oct. Nov. Dec. Heal thy 8.10 7.82 5.28 1.48 0.55 1.38 7 .78a l 7.29 5.48 1.11 0.66 1.2 ia S i ck 7.75 7.56 5.69 1.42 0.73 1.44 8.32° 7.67 5.08 1.32 0.87 2.28b 1 w i t h i n any given column, va lues w i th d i f f e r e n t smal l case l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t (p < 0.5) Table Xb - Average graz ing and bedding t imes o f pregnant and non-pregnant ewes (March, A p r i l 1978), i n hours Domi nants Intermediates Subord inates Feed, t imes Bed, t imes Feed, t imes Bed, t imes Feed, t imes Bed, t imes Mar. Apr . Mar. Apr . Mar. Apr . Mar. Apr . Mar. Apr . Mar. Apr. Pregnant 8.42 7.49 1.73 4.42 8.00 7.58 2.13 5.00 8.71 7.33 1.94 4.58 Non-pregnant 8.81 7.08 2.06 4.50 8.37 6.87 2.56 4.83 8.06 6.50 2.28 4.54 E. Energy Expendi ture Est imates f o r the Adu l t Ewes The es t imated mean basal metabo l i c ra te f o r the adu l t ewes demonstrated no c l e a r seasonal t r e nd s , o the r than an e l e va ted l e v e l i n the sp r i ng r e l a t i v e t o o ther per iods of the year (Table X I ) . BMR's reached 1.53 and 1.60 Kcal Kg-1 hr-1 i n May and June, r e s p e c t i v e l y , dropping to a y e a r l y low of 0.93 Kcal kg-1 h r _ l i n the J u l y - August and September pe r i od s . Values ranged i r r e g u l a r l y between 1.18 and 1.06 Kcal kg-1 h r _ l from October t o February , before demonstrat ing inc reased ea r l y sp r i ng l e v e l s of 1.50 and 1.49 Kcal kg-1 h r _ l i n March and A p r i l , r e s p e c t i v e l y . Es t imates of the average hour ly energy expended by the herd members dur ing a t y p i c a l d a y l i g h t r ou t i ne fo l l owed a s i m i l a r pa t t e rn t o BMR's (Table X I I ) . Values peaked i n A p r i l , May and June (2 .29 , 2.39, 2.29 Kcal kg-1 h r - 1 , r e s p e c t i v e l y ) , dropped t o y e a r l y lows of 1.52 and 1.54 Kcal kg-1 h r _ l i n the J u l y - August and September pe r i od s , r e s pe c t i v e l y and then ranged i r r e g u l a r l y between 1.83 and 1.61 Kcal kg-1 h r _ l from October t o February . In March, the a c t i v i t y cost i nc reased cons ide rab l y t o 2.04 Kcal kg-1 h r - l . With the i n c l u s i o n of pregnancy c o s t s , A p r i l ' s value c l imbed t o 2.47 Kcal kg-1 h r - l . L a c t a t i o n cos t s inc reased May's va lue t o 3.13 Kcal kg-1 h r - l . When expressed as mu l t i p l e s of BMR, average d a i l y a c t i v i t y cos t s demonstrated i r r e g u l a r but l i m i t e d monthly f l u c t u a t i o n s (Table X I I ) . Normal d ay l i gh t behav iour proved t o be s l i g h t l y more expens ive r e l a t i v e t o BMR i n J u l y - August (1.63 x BMR), September (1.67 x BMR) and December (1.63 x BMR) and l e a s t expens ive i n June (1.43 x BMR) and March (1.36 x BMR). Mu l t i p l e s ranged between 1.52 and 1.56 i n the remaining months. 56 +-> O 3 CD 3 -a ro CD 4-> S- o to CD +-> ro S- O .a rO 4-> CD E ro c/i ro -Q CD cn ro S- <D > X rO E c a) cr cr. T5 OJ 5 l l C K i r - l O f l " CO t£> (M lO C O' Z CT4 m *c a- o- — c — c c m «J Jol t» — co cr f» cr p- «r — in ft o I e o ^ j ^ e ^ c r i — t n j ^ i n ^ j ^ i« r c| »̂ IC in r-~ m CO *T a\ n Cr- « i — — d cc ID *o m m m C •© E[ ro " CN) fsj C\J CVJ t\j CM CM • PJ i! | f j g s 5 5 c s s s s l l p eil i ! II «! i l §1 i i i ! gf i i i l s P is inni $ ?nnnn j H?l *| i : | ii ii s| ii mn 11 f 1 Ifc R S ft R R R R R R R ft j S B | |S| a s R 5 5 s 5 5 5 5 s " = I : | | 2 i Mi M ? ? M M M !!!!!!!! t f . . . . iliU!I! " ; 511j | H i S £ £ £ £ £ £ £ £ £ £ ! 2 H ! I 5 ! i 5 5 5 3 5 5 5 S S S I J *i J | i 11 i i i i i i i i I E 57 c o -a CO O) S- +J •a c <D cu X OJ l < cu c CU •o cu rO S- cu > X CD o »* I - is-g I cr cr co in o- O T3 e O CO Oi >, OJ re S ~- « ro m «7 ^ I >> -a I -3 fc. C - ui m co C Q.— "O ID c CTi CT> O ro Dl E D> (_ 58 DISCUSSION A. Soc i a l O rgan i za t i on 1. Dominance h i e ra r chy of the adu l t ewes The s o c i a l behav ioura l r e p e r t o i r e of the adu l t ewes was cons ide rab l y reduced from tha t recogn ized i n prev ious s t ud i e s f o r b ighorn rams. Of the 17 behav ioura l pa t te rns of rams desc r ibed by Ge i s t (1971), only e igh t were performed by females i n t h i s s tudy , w i th pa t te rns i n v o l v i n g horn d i s p l a y s be ing consp icuous ly absent . That b ighorn ewes would have r e l a t i v e l y few horn d i s p l a y s i s not s u r p r i s i n g , cons i de r i ng the l i m i t e d v a r i a b i l i t y i n horn s i z e of a d u l t s . Ge i s t (1971, p. 179) suggests t ha t rams can assess a st range ram's s o c i a l s t a t u s by the l a t t e r ' s horn s i z e and, as a r e s u l t , horn d i s p l a y s have evo lved as a non -v i o l en t means of e x h i b i t i n g s o c i a l s t a t u s . However, amongst ewes, such d i s p l a y s would have l i t t l e va lue because of the o f ten i n d i s t i n g u i s h a b l e d i f f e r en c e s i n t h e i r horn s i z e s . In most ungulate s o c i e t i e s where horn or a n t l e r s i z e s of adu l t s show only sub t l e d i f f e r e n c e s , behaviour pa t te rns which exaggerate body ra ther than horn development are more pronounced (mountain goat (Oreamnos amer i canus) , Ge i s t 1964; East A f r i c a n bu f f a l o (Syncerus c a f f e r ) , S i n c l a i r 1974). I t i s a l s o po s s i b l e t h a t , i n r e l a t i v e l y s m a l l , c on s i s t en t groups o f an imals such as the cap t i v e herd, i n d i v i d u a l r e cogn i t i on develops between herd members (Shack leton 1973), thus e l i m i n a t i n g the need f o r many s o c i a l d i s p l a y s once a h ie ra rchy has been e s t a b l i s h e d . 59 Two add i t i o n a l pa t te rns (horn w r e s t l i n g , from Shack leton 1973, and squat- u r i n a t i o n by subo rd ina tes , s i m i l a r t o the u r i n a t i o n response of oest rus and anoestrus females t o aggress i ve males, desc r ibed by Ge i s t 1971) were a l s o observed f o r the ewes. Horn w r e s t l i n g appeared t o be an ex tens ion of the c l a s h , imposs ib l e i n l a r ge rams where basal horn d iameters would prevent i n t e r l o c k i n g . The u r i n a t i o n response of subord inate ewes was d i r e c t ed both at dominant ewes and rams a f t e r aggress ive approaches by these an ima ls . Dominant ewes, once conf ronted by t h i s pos tu re , would show no f u r t h e r aggress ion towards the subord ina te . The in f requent occurrence of s o c i a l i n t e r a c t i o n s between the cap t i ve ewes i s a behav ioura l q u a l i t y not uncommon f o r female ungulate s o c i e t i e s . Such a s o c i a l s t r a t egy i s b i o l o g i c a l l y sound, c on s i de r i ng a fema le ' s b i oene rge t i c c o n s t r a i n t s . To maximize her rep roduc t i ve success , a ewe must minimize energy expend i tures on a c t i v i t i e s not v i t a l t o maintenance or t o her reproduc t i ve e f f o r t (Ge i s t 1971). S ince i n t e r a c t i o n s , p a r t i c u l a r l y prolonged dominance d i spu tes and p l a y , are e n e r g e t i c a l l y very c o s t l y and o c c a s i o na l l y damaging, these a c t i v i t i e s w i t h i n the female s o c i e t y should be g r ea t l y reduced i n number and du r a t i o n , compared w i th those of males. Such a r eac t i on was c l e a r l y ev ident among the c ap t i v e an ima l s . The two-year o l d ram i n the herd i n i t i a t e d 67% more aggress i ve i n t e r a c t i o n s w i th the s i n g l e y e a r l i n g ma le .he rd member from June t o December 1977 than the most aggress i ve adu l t ewe i n i t i a t e d w i th 14 po t en t i a l adu l t ewe opponents dur ing the same pe r i od of t ime . In a d d i t i o n , ewes d i d not e x h i b i t any r i t u a l i z e d dominance f i g h t s , as d i d the rams, and r e s t r i c t e d t h e i r p l a y l i k e a c t i v i t i e s t o l a t e sp r i ng and summer months when t h e i r p h y s i o l o g i c a l and f o r ag i ng cond i t i on s were at an optimum annual l e v e l . Reduced aggress ion amongst females i n comparison t o males has been repor ted 60 f o r severa l ungulate s pe c i e s , i n c l u d i n g roan ante lope (Hippotragus equ inus, Jouber t 1974) and oryx (Oryx b e i s a , Walther 1978). The r a r i t y o f ac tua l dominance f i g h t s between female mountain sheep has a l s o been reported by Ge i s t (1971) and Blood (1963). That the cap t i v e ewes cou ld s u c c e s s f u l l y c oe x i s t w i t h such a qu iescent s o c i a l s t r u c t u r e was probably the r e s u l t o f resource a v a i l a b i l i t y . H i e r a r ch i e s o f ten f un c t i on as a r e l a t i v e l y e f f i c i e n t means of resource a l l o c a t i o n but vary i n t h e i r r i g i d i t y depending on the supply and d i s t r i b u t i o n of resources . R i g i d h i e r a r c h i e s would be expected w i th l i m i t e d , l o c a l i z e d resources . Forage and rams were the two most s i g n i f i c a n t resources which the ewes requ i red f o r maintenance and rep roduc t i ve success , r e s p e c t i v e l y . However, ewes were bred rega rd l e s s of t h e i r s o c i a l s t a t u s , negat ing the need f o r dominance d i spu tes amongst the ewes t o a t t a i n breeding p r i v i l e g e s . Forage, i n t u r n , was d i s t r i b u t e d r e l a t i v e l y homogeneously over the study area f o r much of the f a l l , w i n t e r and ea r l y s p r i ng pe r i od s . Ge i s t (1974) suggests tha t "d i spersed and d i f f u s e d food of low dens i t y per un i t area w i l l l ead t o a s e l e c t i o n aga ins t food compet i t i on by over t a g g r e s s i o n . . . " . Consequent ly , i t can be specu la ted t ha t the cap t i v e sheep, by e x p l o i t i n g a r e l a t i v e l y d i spe rsed food resource , were ab le t o c oex i s t w i t h a minimum of forage d i s pu t e s . Th is was p a r t i c u l a r l y t r ue a f t e r the range p l an t s had cured t o a low n u t r i t i v e s t a t e and the animals were d i spe rsed t o t h e i r g rea tes t degree du r i ng f o r ag i ng bouts . Converse ly , f eed ing d i spu tes became more f requent when the animals were dependent upon "po i n t " or l o c a l i z e d resources , such as the water t rough and supplemental hay. The preponderance o f bedding d i spu tes l i k e l y r e s u l t e d from the repeated use by the herd members of one of s e v e r a l , apparent ly p re f e r r ed bed s i t e s dur ing 61 major r e s t i n g pe r i o d s . Th is behaviour concent ra ted animals i n t o l o c a l i z e d a reas , c r e a t i n g a s i t u a t i o n conducive t o s o c i a l c on f r on ta t i on s and eventual i n t e r a c t i o n s . I t i s doubt fu l tha t an ac tua l shortage of bedding s i t e s i n i t i a t e d these bedding d i s pu t e s . The r e l a t i v e abundance of p o s i t i o n a l d i spu tes appeared to r e s u l t from crowding by the herd, a r t i f i c i a l l y enhanced by t h e i r c ap t i ve s t a t e , ra the r than a lack of space. I n v a r i a b l y , a f o r ag i ng d r i v e would be i n t e r r up t ed by the per imeter fence of the enc l o su re , caus ing the animals t o c l u s t e r momentari ly before r e d i r e c t i n g t h e i r f eed ing e f f o r t . Th is crowding would f r equen t l y i n i t i a t e a burs t of s o c i a l i n t e r a c t i o n s as i n d i v i d u a l d i s tances were being v i o l a t e d . In a l l p r o b a b i l i t y , the absence of a b i o l o g i c a l requirement f o r a r i g i d h i e ra r chy ( i . e . l o c a l i z e d , l i m i t e d resource) was l a r g e l y r e spons ib l e f o r the non - l i n e a r and somewhat d i so rgan i zed h i e ra r chy of the c ap t i v e herd. En fo rc ing a r i g i d h i e ra r chy wi thout d e f i n i t e resource gains would have been e n e r g e t i c a l l y wa s t e f u l . However, a dd i t i o n a l f a c t o r s may a l s o have con t r i bu ted t o the h i e r a r c h y ' s n o n - l i n e a r i t y . Dominance r e ve r s a l s and t r i a n g l e s are o f ten a temporary i n s t a b i l i t y common t o a new assemblage of animals (Wilson 1975). When f i r s t t rapped , the cap t i v e herd was comprised of animals of at l e a s t two and po s s i b l y severa l d i f f e r e n t maternal groups which p r ev i ou s l y may not have mutua l l y i n t e r a c t e d . There fo re , con f ined t o a common a rea , many of these animals had no r e l a t i v e s ta tus t o each o the r and the h i e ra r chy was i n i t i a l l y unc l ea r . In December and January , w in te r m o r t a l i t i e s fo rced even more dominance r e - o r g a n i z a t i o n , po s s i b l y e x p l a i n i n g the cont inued low l i n e a r i t y of the h i e ra r chy i n 1978. S i ze of the herd i s an equa l l y p l a u s i b l e exp l ana t i on f o r the h i e r a r c h y ' s 62 n o n - l i n e a r i t y . Ce r t a i n animal s o c i e t i e s have an inherent c r i t i c a l herd or f l o c k s i z e , above which t h e i r h i e r a r c h i e s demonstrate non - l i n ea r tendenc ies (Schje lderup-Ebbe 1922, A l l e e 1952, i n Wi lson 1975). It i s p o s s i b l e tha t the o r i g i n a l s i z e of the c ap t i v e herd (16 adu l t s ) was too l a rge f o r a s t r a i g h t l i n e h i e ra r chy t o deve lop . B l ood ' s (1963) and Shack l e ton ' s (1973) da ta , which showed the average maternal group s i z e of b ighorns i n c l u d i n g lambs and y e a r l i n g s t o be s u b s t a n t i a l l y l e s s than 16 animals f o r much of the yea r , adds support t o the suggest ion t h a t , s o c i a l l y , the c ap t i v e group was unusua l l y 1arge. Behav ioura l s tud i e s on o ther ungulate s o c i e t i e s have r e su l t e d i n a v a r i e t y of f i n d i n g s on s o c i a l h i e r a r c h i e s . Bighorn rams have a s t r ong l y l i n e a r h i e ra r chy (Ge i s t 1971), but spend the ma jo r i t y o f the yea r i n r e l a t i v e l y sma l l , cohes ive bands of l e s s than ten animals (Blood 1963, Shack leton 1973, personal o b s e r v a t i o n s ) . It i s not known i f s i m i l a r s t r a i g h t l i n e h i e r a r c h i e s develop i n l a r g e r bands of males which can e x i s t t empo r a r i l y . L i n e a r i t y has a l s o been repor ted f o r the h i e r a r c h i e s of domest ic c a t t l e (Schein and Fohrman 1955), adu l t cow and b u l l Rooseve l t e lk ((Cervus canadensis r o o s e v e l t i ) L ieb 1968, i n F r a n k l i n et al_. 1975) , mixed herds of roan ante lope (Joubert 1974), pronghorns (K i tchen 1974), and adu l t b u l l East A f r i c a n bu f f a l o ( S i n c l a i r 1974). Un fo r t una te l y , the s t reng th of the l i n e a r i t y i s not expressed ( e . g . Landau's index of l i n e a r i t y , from Wi lson 1975) i n many of these s t u d i e s , making assessment of t h e i r f i n d i ng s d i f f i c u l t . The ma jo r i t y of ungulate s t ud i e s show v a r i a b l e degrees of l i n e a r i t y i n the h i e r a r c h i e s w i th prominent dominance t r i a n g l e s and dominance r e ve r s a l s (domest ic c a t t l e , Wagnon et al_. 1966; r e i ndee r , Espmark 1974; roe deer , Espmark 1974; American b ison (Bison b i s o n ) , Lo t t 1974; adu l t cow East A f r i c a n b u f f a l o , Gr imsde l l 1969, i n S i n c l a i r 1974), s i m i l a r t o the f i n d i ng s of t h i s s tudy . 63 Given f r ee ranging cond i t i on s and a more na tu ra l group s i z e and age compos i t i on , i t i s p o s s i b l e t ha t cohes ive maternal bands of b ighorn sheep develop a l i n e a r h i e r a r chy . However, cons i de r i ng tha t these animals t r a d i t i o n a l l y e x p l o i t a r e l a t i v e l y d i spe r sed resource and must govern themselves behav i ou ra l l y because of ene rge t i c c o n s t r a i n t s , i t can be pos tu l a t ed tha t dominance i n the group would not be any more r i g i d l y enforced or ev ident than i t was w i t h i n the cap t i v e an ima l s . S t a b i l i t y o f the adu l t ewes s o c i a l system R e l a t i v e s t a b i l i t y i s a requ i red c h a r a c t e r i s t i c of a h ie ra rchy i f such a s o c i a l system i s to be e n e r g e t i c a l l y b e n e f i c i a l to i t s p a r t i c i p a n t s . H i e r a r ch i e s presumably enable c on s pe c i f i c s t o c o e x i s t as a s o c i a l un i t w i th a minimum of c o s t l y aggress i ve i n t e r a c t i o n s over resource a l l o tment (Ge i s t 1971, Wi lson 1975). An unstab le dominance system would r e s u l t i n dominance d i spu tes and f requent f i g h t s , thus l o s i n g i t s energy conserv ing q u a l i t i e s . Not s u r p r i s i n g l y , the c ap t i v e herd demonstrated on ly minor dominance s h u f f l i n g dur ing the 14 month s tudy , i n s p i t e of the herd reduc t ion i n December and January . The two animals which showed inc reases i n t h e i r dominance values and r e l a t i v e p o s i t i o n s i n the h ie ra r chy d i d so j u s t p r i o r t o or a f t e r the b i r t h of t h e i r lambs. Cons ide r i ng tha t only f i v e lambs were produced tha t year (two of them to p r ev i ou s l y e s t a b l i s h ed dominants) , i t would appear t ha t the presence of lambs may have been a c o n t r i b u t i n g f a c t o r t o the ewes' r i s e i n s t a t u s . H ie ra rchy s t a b i l i t y has been w ide ly documented f o r many ungulate s pe c i e s , i n c l u d i n g da i r y h e i f e r s (Be i1harz e t al_. 1963), domest ic goats ((Capra hi reus) Ross and Berg, 1956), Rooseve l t e l k ca l ves (L i eb 1968, i n F r a n k l i n et a K 1975) and roan ante lope (Joubert 1974). Sco t t (1958, c i t e d i n Joubert 1974) 64 suggests tha t l i n e a r h i e r a r c h i e s are r e l a t i v e l y s t ab l e and permanent, presumably "due t o the d r a s t i c and long l a s t i n g emotional responses connected w i th f i g h t i n g and a v o i d a n c e . . . " . However, s i m i l a r t o t h i s s tudy , dominance s h u f f l i n g has been reported where members of a h i e ra r chy exper ience morpho log ica l or p h y s i o l o g i c a l changes. Espmark (1964) showed tha t the s o c i a l s t a t u s of re indeer dec l i ned upon the l o s s of t h e i r a n t l e r s . He a l s o suggested t ha t pregnant cows or cows w i th ca l ves w i l l have a r e l a t i v e l y high s o c i a l rank and w i l l a t t a i n the feed ing p r i v i l e g e s of dominants needed i n t imes of food shortages t o meet rep roduc t i ve demands. S i m i l a r l y , M i l l e r (1971, 1974) found t ha t pregnant does become more aggress i ve once t h e i r fawns were born, o f ten dominat ing p r ev i ous l y dominant an ima l s . E s t ab l i s hed h i e r a r c h i e s w i l l o f ten show temporary i n s t a b i l i t y and inc reased i n t e r n a l aggress ion w i th the i n t r o du c t i o n of " s t range" animals t o the herd, as these animals a t t a i n t h e i r r e spec t i ve s o c i a l ranks (Wilson 1975). Such xenophobic tendenc ies were not expressed by the cap t i v e herd when a ewe from the Game Farm paddock entered the study area unexpected ly . Consequent ly , i t would appear t ha t the herd ' s h i e r a r chy , i n add i t i o n to being l oose l y ma in ta ined , was a r e l a t i v e l y open system enab l i ng the uneventfu l passage of animals i n t o or out of the group. Such a system i s h i gh l y d e s i r a b l e i n animals wh ich , l i k e sheep, o f ten concent ra te w i th u n f a m i l i a r c on spe c i f i c s on l o c a l i z e d w in te r ranges f o r severa l months of the yea r . Aggress ion at t h i s t ime would mean a c o s t l y energy expend i tu re at a t ime of l i m i t e d forage a v a i 1 a b i 1 i t y . Xenophobic tendenc ies are u sua l l y pronounced i n t i g h t - k n i t , r i g i d l y s t r u c tu r ed groups t y p i c a l of many spec ies of b i r d s (domest ic ch i c kens , Wi lson 1975), pr imates (rhesus monkeys (Macacca mu l a t t a ) , Southwick 1969, i n 65 Wilson 1975), and can ids (wol f (Canis l u pu s ) , Mech 1970). They have a l s o been repor ted f o r some ungulate spec ies i n c l u d i n g roan ante lope (Joubert 1974) and male oryx (Walther 1978). However, i n most f r ee ranging ungulate s o c i e t i e s , the s o c i a l systems are r e l a t i v e l y open, s i m i l a r t o the cap t i v e bighorn herd, and new animals are permi t ted t o j o i n e s t a b l i s h ed herds w i th l i t t l e aggress ion a r i s i n g ( e . g . c a r i b o u , Bergerud 1974). 2. Determinants o f dominance Most behav ioura l s t ud i e s which have attempted t o e l u c i d a t e the determinants or consequences of dominance have been faced w i th c on s t r u c t i n g h i e r a r c h i e s from incomplete i n t e r a c t i o n mat r i ces ( i . e . , where i n t e r a c t i o n s between a l l p o s s i b l e p a i r s o f herd members were not observed) . Consequent ly , dominance values have gene ra l l y been determined f o r study animals from the p ropor t i on of opponents each animal dominates. The herd members are then ranked accord ing t o these va l ues . The r e l a t i o n s h i p of rank t o va r ious parameters has been assessed non -pa ramet r i c a l l y by rank c o r r e l a t i o n methods (Kruska l and Wall i s method, i n Wagnon et ^1_. 1966). More commonly, the dominance values are t ransformed i n t o angles which are normal ly d i s t r i b u t e d and which enable c o r r e l a t i o n c o e f f i c i e n t s between dominance va lues and va r i ous parameters to be determined pa r ame t r i c a l l y ( Be i l h a r z and Myl rea 1963, B e i l h a r z et. _al_. 1966, C o l l i s 1976). K a i s e r ' s l e a s t squares method has a l s o been used ( Be i l h a r z et al_. 1966, Dickson e t a]_. 1966). Regard less o f the method o f a n a l y s i s , these va lues do have inherent f a u l t s and can g ive decept i ve r e s u l t s . For example, an animal i n vo l ved i n r e l a t i v e l y few i n t e r a c t i o n s (< 5) may be g iven a decep t i v e l y h igh o r low s o c i a l rank because i t i n t e r a c t ed w i th a b iased sample of opponents, a h i gh l y probable occurrence w i th such a smal l sample s i z e . There fo re , care must be taken when i n t e r p r e t i n g h i e r a r c h i e s which have been cons t ruc ted from 66 such va lues . In t h i s s tudy , the use of D .V . ' s i n c on s t r u c t i n g a h i e ra r chy was a necess i t y because of the l i m i t e d number of p a i r combinat ions which were observed i n t e r a c t i n g . B e i l h a r z ' s method of angu lar t r ans fo rmat i on was employed because o f i t s r e l a t i v e ease and comparable performance t o o ther methods ( Be i l h a r z et a l . 1966). The major p o t en t i a l weakness of the rank ing system was the f a c t t ha t the dominant-subord inate r e l a t i o n s h i p s between pa i r s of animals were o f ten concluded from only one or two i n t e r a c t i o n s . I t may be po s s i b l e t ha t repeated i n t e r a c t i o n s would have i n d i c a t e d a reversed r e l a t i v e rank i n some cases . In a d d i t i o n , some animals from both h i e r a r c h i e s faced r e l a t i v e l y few d i f f e r e n t opponents, making t h e i r es t imated D .V . ' s somewhat ques t i onab l e . However, there i s evidence to suggest tha t these weaknesses were not s i g n i f i c a n t . For example, B e i l h a r z and Mylrea (1963) found great s i m i l a r i t i e s between h i e r a r c h i e s cons t ruc ted from s i n g l e and m u l t i p l e days data and showed tha t dominance r e ve r s a l s occurred i n f r e quen t l y enough t o enable h i e r a r c h i e s t o be c on f i d en t l y determined from r e l a t i v e l y few i n t e r a c t i o n s . Second ly , the ewes w i th ques t i onab le D .V . ' s i n t h i s study d i d not occupy unreasonable p o s i t i o n s i n the h i e r a r c h y , cons i de r i ng t h e i r opponents. There fore , s i n ce the two h i e r a r c h i e s i n t h i s study r e f l e c t e d the dyadic dominant-subord inate r e l a t i o n s h i p s which had been observed, the c o r r e l a t i o n between var ious parameters t o dominance cou ld be assessed w i th some degree of con f idence . Younger herd members (< 2 years ) were not monitored as i n t e n s i v e l y as the adu l t ewes and were exc luded from the a n a l y s i s o f i n t e r a c t i o n data f o r t h i s s tudy . However, i t d i d appear t ha t from b i r t h t o e a r l y adu l t y e a r s , age and s i z e (almost complete ly confounded f a c t o r s dur ing the growth per iod) were the 67 predominant determinants of s o c i a l s t a tu s f o r female. In the study a rea , lambs were the most subord inate group of animals and appeared i n t e r n a l l y ranked by s i z e , w i th the l a r g e r lambs u sua l l y i n i t i a t i n g and dominanting most encounters . Lambs d i d not assume the s t a tu s of t h e i r dams at any t ime , a phenomenon observed i n re indeer (Espmark 1964). The two female y e a r l i n g s were the next most subord ina te group, again c l e a r l y ranked r e l a t i v e t o each other by s i z e . As mentioned i n R e su l t s , the th ree youngest adu l t ewes occupied the th ree lowest p o s i t i o n s of the adu l t female h i e r a r c h y . Had s u i t a b l e age es t imates of the o l de r ewes been a v a i l a b l e , a h igh c o r r e l a t i o n between age and dominance may have been ev i den t . The f a c t tha t weights and horn lengths were not c o n s i s t e n t l y c o r r e l a t e d t o dominance dur ing the study per iod l i k e l y r e su l t ed from c e r t a i n s t a t i s t i c a l l y confounding f a c t o r s . Animals i n the 1977 herd which even tua l l y d ied were i n v a r i a b l y o l de r ewes w i th longer than average adu l t horn lengths but w i th s l i g h t l y reduced average weights because of t h e i r emaciated cond i t i on by e a r l y w i n t e r . S ince t h e i r dominance p o s i t i o n had been est imated p r i m a r i l y from the summer and ea r l y f a l l i n t e r a c t i o n s before t h e i r p h y s i o l o g i c a l c ond i t i on had d e t e r i o r a t e d , the re was l i t t l e c o r r e l a t i o n between average weight and s ta tus by l a t e f a l l and e a r l y w i n t e r , when weights were c o l l e c t e d . Consequent ly , a low c o r r e l a t i o n c o e f f i c i e n t between weight and dominance va lue r e su l t ed f o r the 1977 h i e r a r chy . In 1978, w i th the absence of these moribund an ima l s , weight proved t o be s i g n i f i c a n t l y c o r r e l a t e d w i th dominance. The decreas ing s i g n i f i c a n c e of horn length t o dominance from 1977 t o 1978 was more pe r p l e x i ng . Cons ide r i ng tha t severa l " long horned" animals of only i n te rmed ia te s t a tu s were removed from the herd i n December, one would have expected the degree of c o r r e l a t i o n between horn l ength to dominance t o show an 68 i n c rease from 1977 t o 1978, and not the r eve r se . However, the promotion of two r e l a t i v e l y shor t -horned i n d i v i d u a l s w i t h i n the h i e ra r chy in 1978 was s u f f i c i e n t t o cause the c o r r e l a t i o n c o e f f i c i e n t t o drop t o an i n s i g n i f i c a n t l e v e l . Th is occurrence a lone was po s s i b l y i n d i c a t i v e of the bo rde r l i n e importance of horn length as a determinant of dominance i n the cap t i ve ewes. That aggress iveness and not phys i ca l a t t r i b u t e s showed the g rea tes t c o r r e l a t i o n t o dominance i s not s u r p r i s i n g , c ons i de r i ng the in f requency of phy s i c a l i n t e r a c t i o n s amongst ewes. Ge i s t (1971) suggests tha t c lashes between rams occur f r equen t l y enough t o enable these animals t o a s so c i a t e c l a s h fo r ce w i th horn s i z e . In such a system, l a rge horns are an obvious dominance symbol. Among ewes, however, i n t e r a c t i o n s are too in f requent and horn s i z e d i f f e r en c e s are too sub t l e t o a l l ow an a s s o c i a t i o n between horn s i z e and dominance s t a tu s t o deve lop . Consequent ly , p a r t i c u l a r l y aggress ive ra the r than l a rge i n d i v i d u a l s cou ld a t t a i n r e l a t i v e l y high s o c i a l ranks s imply through i n t i m i d a t i o n . It was apparent t ha t some ewes w i th new young became p a r t i c u l a r l y agg re s s i ve , pos s i b l y e x p l a i n i n g the r i s e i n s ta tus of the two p roduc t i ve ewes. Dur ing ac tua l c l ashes and horn w r e s t l i n g , weight becomes somewhat advantageous, which may e xp l a i n t h i s parameter ' s s i g n i f i c a n c e i n the 1978 h i e r a r chy . However, horn s i z e , because of i t s l i m i t e d v a r i a b i l i t y i n adu l t ewes, has l i t t l e bear ing on the outcome of such d i sputes and, consequent l y , i s l i k e l y o f l i t t l e importance t o rank. A l though these conc lus i ons are based on l i m i t e d da ta , they do appear s i m i l a r t o those from o ther s o c i a l behaviour s t ud i e s of female ungulate s o c i e t i e s , where phys i ca l a t t r i b u t e s show only minor d i f f e r en ce s between an ima ls . B e i l h a r z jet aj_. (1966) and C o l l i s (1976) both suggested tha t aggress iveness was the s t ronges t p r e d i c t o r o f dominance i n c a t t l e . Only B e i l h a r z et aj_. 69 showed weight t o be an a dd i t i o n a l s t rong p r e d i c t o r wh i l e both authors reported i n s i g n i f i c a n t and negat i ve c o r r e l a t i o n s r e s p e c t i v e l y f o r he ight at w i the rs and dominance. Schein and Fohrman (1955) showed age and weight t o be s i g n i f i c a n t i n d i c a t o r s of dominance i n c a t t l e but f u r t h e r demonstrated tha t s e n i o r i t y i n the herd , a f a c t o r confounded by age and we igh t , was the u l t ima te determinant o f s o c i a l rank. Dixon et _al_. (1966) found on ly weight t o be s i g n i f i c a n t l y c o r r e l a t e d t o dominance. Espmark (1964) repor ted t ha t age was of g rea tes t importance i n re indeer w i t h i n a sex, wh i l e s i z e and s t rength determined dominance between the sexes . Chase (1973, 1974, i n Wi lson 1975) o f f e r s a "magn i f i c a t i on process" hypothes is t o e xp l a i n the reason f o r the high c o r r e l a t i o n between dominance and aggress i veness . He suggests tha t aggress i ve i n d i v i d u a l s , by f r equen t l y i n i t i a t i n g i n t e r a c t i o n s w i th t i m i d , submiss ive opponents, develop improved i n t i m i d a t i n g and f i g h t i n g s k i l l s and become i n c r e a s i n g l y con f iden t w i th each success fu l encounter . Th is inc reases the p r o b a b i l i t y o f success i n l a t e r encounters , l i f t i n g the animal upward i n the h ie ra r chy u n t i l a s o c i a l e q u i l i b r i u m i s reached. Converse ly , submiss ive animals e ven tua l l y occupy low p o s i t i o n s i n the dominance o rder . "Acc iden ta l events , such as f a t i g ue on a c e r t a i n day or a chance blow" are suggested by Chase as reasons f o r the occas iona l dominance r e ve r s a l s which are observed i n h i e r a r c h i e s . B. Consequences of Dominance 1. D ie t comparisons The absence of d i f f e r e n c e s i n d i e t q u a l i t y between the th ree s o c i a l c l a s se s of ewes may s imply have been a f unc t i on of the d i s t r i b u t i o n of t h e i r forage 70 supp ly . Dur ing the w in te r months, the an ima ls ' d i e t was p r ima r i l y f a l l regrowth from the study s i t e ' s dominant g rasses , a resource which was homogeneously d i s t r i b u t e d over the area (wikeen pe r s . comm.). Even when supplemental hay was p rov ided , the herd s t i l l u t i l i z e d na t i ve forage f o r much o f the day. With such a d i spersed food resource , there was l i t t l e need f o r dominant animals t o i n i t i a t e c o s t l y aggress i ve d i spu tes over f eed ing s i t e s when equa l l y good s i t e s were r e ad i l y a v a i l a b l e . Increased aggress ion d i d occur at the hay supply but most encounters were b r i e f , enab l i ng the i n i t i a t o r only t o e s t a b l i s h a feed ing p o s i t i o n . It i s probable tha t the a c t i v e e x c l u s i on of subord inates from the s i t e would have been a needless and waste fu l energy expend i ture once the dominant animal had secured a feed ing p o s i t i o n . Consequent ly , t ime spent at the supplemental feed d i d not vary between s o c i a l c l a s se s of an ima l s . Had the hay been conta ined w i t h i n a feeder w i th a l i m i t e d number of feed ing spaces ( e . g . 2 or 3 ) , then dominance would l i k e l y have p layed a much g rea te r r o l e i n resource a l l o c a t i o n . There i s some i n d i c a t i o n tha t dominance i n a group of animals competing f o r a l i m i t e d po in t resource ensures an improved food supply to the high rank ing i n d i v i d u a l . Wi lson (1975) repor t s tha t the s e l e c t i o n of a n t e r i o r t e a t s by p i g l e t s o f f e r s c e r t a i n feed ing advantages and tha t t ea t a l l o tment may be dominance r e l a t e d . Espmark (1964) found tha t h igh s o c i a l s t a tus i n re indeer meant ready access t o e s t ab l i s h ed feed ing c r a t e r s , but reported c o n f l i c t i n g r e s u l t s on the advantages of dominant roe deer a t supplemental feed ing s t a t i o n s (1974a, 1974b). Some authors have even used a l i m i t e d food supply t o e s t a b l i s h dominance r e l a t i o n s between pa i r s of animals (Ross and Berg, 1956). An ex tens i ve l i t e r a t u r e search uncovered no repor t s which showed tha t dominance o f f e r s feed ing advantages to animals e x p l o i t i n g a d i spersed 71 resource , s i m i l a r t o t ha t found on the study s i t e . A hypothes i s presented i n Ge i s t (1974) suggests t ha t the defense of such a t h i n l y s c a t t e r ed resource by dominants i n cu r s c o s t l y aggress i ve encounters w i thout r e s u l t i n g i n s i g n i f i c a n t ga in of resources . G e i s t , p resen t ing Kruuk 's (1972) sugges t i on , f u r t h e r reasons tha t defense of superabundant, l o c a l i z e d resources such as supplemental hay i s a l s o e n e r g e t i c a l l y i n e f f i c i e n t s i n ce e f f o r t would be be t t e r spent " feed ing ( i n c r ea s i ng ra te of food in take) ra ther than wast ing t ime and resources f i g h t i n g " . Dominance dur ing feed ing i s perhaps only b e n e f i c i a l t o an animal when both feed and feed ing spaces are l i m i t e d . 2. A c t i v i t y budget comparisons In any d e t a i l e d a c t i v i t y budget compar ison, the method of data c o l l e c t i o n i s o f obvious importance t o the accuracy of the eventual a n a l y s i s . Scan sampl ing was the on ly a v a i l a b l e procedure s u i t a b l e f o r such a l a rge study s i t e . It enabled data on a l a rge number of group members t o be c o l l e c t e d s imu l taneous ly and r e ad i l y prov ided data "appropr i a te t o e s t ima t i ng percent of t ime spent i n va r i ous a c t i v i t i e s " (Altmann 1974). The s e l e c t i o n of a sampl ing i n t e r v a l was p r i m a r i l y d i c t a t e d by the t ime requ i red t o c o l l e c t i n fo rmat ion on the e n t i r e adu l t herd . A 15 minute i n t e r v a l , wh i l e o c c a s i o n a l l y e x ce s s i v e , was necessary f o r a complete scan when the animals were mob i l e , w ide l y d i spe rsed or bo th . With such a lengthy t ime between scans , the percentage of i n t e r v a l s devoted t o an a c t i v i t y can vary cons ide rab l y from the a c tua l percentage o f t ime spent i n t ha t a c t i v i t y . However, t h i s margin of e r r o r i s most pronounced f o r shor t term a c t i v i t i e s such as p l a y i n g , nu r s i ng , e t c . and was not cons idered s i g n i f i c a n t f o r those o f longer du ra t i on such as g r a z i ng and bedding. Data c o l l e c t e d i n t h i s manner were s e n s i t i v e enough t o show s i g n i f i c a n t day to day v a r i a t i o n s i n the du ra t i ons of the he rd ' s major a c t i v i t y c l a s s e s (g ra z i ng , 72 bedd ing) . The re fo re , they were a l s o cons idered v a l i d f o r between-group comparisons of such a c t i v i t i e s . A v a r i e t y of scan sampl ing i n t e r v a l s have been used i n the research of g raz ing behaviour but , un f o r t una t e l y , no eva l ua t i on of the e f f e c t s o f i n t e r v a l s i z e w i t h i n a g iven study has been made. Hancock (1954) used 1, 2.5 and 5 minute i n t e r v a l s at va r ious t imes dur ing h i s research on the g raz ing hab i t s of d a i r y c a t t l e . Van Dyke (1978) mainta ined a f i v e minute i n t e r v a l throughout h i s study on the a c t i v i t y budgets of b ighorns i n Oregon. The ma jo r i t y o f s tud ies d ea l i n g w i th l a rge areas and group s i z e s have used a 15 minute sampl ing per iod f o r data c o l l e c t i o n ( r e i ndee r , Thompson 1971; c a r i b o u , Roby 1978). The hypothes is proposed f o r t h i s s e c t i on p red i c t ed tha t dominant an ima l s , by having access t o h igher q u a l i t y f o r ag i ng a reas , would have reduced feed ing t imes from subord inate herd members. However, the study animals were e x p l o i t i n g a r e l a t i v e l y d i spersed food resource where s o c i a l s ta tus meant l i t t l e t o the a c q u i s i t i o n of food (see prev ious s e c t i on on d i e t compar isons) . S ince the animals were ab le t o express t h e i r own f o r ag i ng s e l e c t i v i t y w i th a minimum of i n t e r f e r en ce of o ther herd members, i t would l o g i c a l l y f o l l ow tha t the average g raz ing t imes of the three s o c i a l c l a s ses would not vary s i g n i f i c a n t l y . Th is proved t o be the case . The degree of w i t h i n - c l a s s v a r i a b i l i t y i n the g raz i ng and bedding t imes of the th ree s o c i a l c l a s s e s suggests the e f f e c t s o f va r i ous b i o l o g i c a l f a c t o r s on the f o r ag i ng behaviour of an ima l s . Throughout the f a l l and w in te r months, the subord ina te animals d i f f e r e d s i g n i f i c a n t l y from each other i n t h e i r a c t i v i t y pa t t e rns i n on ly two of the seven months t e s t e d . From September t o December, 73 the d i s s i m i l a r g raz ing or bedding t imes of i n te rmed ia te animals added s i g n i f i c a n t va r i ance t o the s t a t i s t i c a l model i n every month. However, a f t e r the w in te r deaths , t h e i r a c t i v i t y budgets showed s i g n i f i c a n t w i t h i n - c l a s s v a r i a t i o n on ly i n January . Dominant animals showed s i g n i f i c a n t w i t h i n - c l a s s v a r i a b i l i t y i n more months than the subord inates but i n fewer months than i n t e rmed i a t e s . The group s i z e and the degree of w i t h i n - c l a s s v a r i a t i o n appeared t o vary d i r e c t l y . However, c e r t a i n b i o l o g i c a l l y i n f l uenced t rends a l s o become ev ident when the compos i t ion of each group i s cons ide red . The subord inate group was comprised of an age cohort and conta ined no members w i th a de t e c t ab l e , aber rant p h y s i o l o g i c a l c o n d i t i o n . The dominant group l i k e l y had a wide age range and, from October t o December, conta ined one s i c k animal (h igh SGOT) which even tua l l y d i ed . The in te rmed ia te group a l s o l i k e l y conta ined a wide age range and, from October t o December, f i v e animals w i th e l eva ted SGOT l e v e l s , f ou r of which d ied i n w i n t e r . There fo re , i t i s po s s i b l e tha t age and ph y s i o l o g i c a l c ond i t i o n were at l e a s t p a r t i a l l y r e spons ib l e f o r the v a r i a b l e behaviour of herd members. A more d e t a i l e d d i s cu s s i on on the e f f e c t s of p h y s i o l o g i c a l c ond i t i on on g raz ing behaviour i s presented i n Sec t i on D. S tud ies on domestic herb ivo res have shown the e f f e c t s of age on graz ing behav iour . Hancock (1954) found l i t t l e v a r i a b i l i t y i n the behaviour of twin h e i f e r s under i d e n t i c a l environmental c o n d i t i o n s , i n d i c a t i n g the poss i b l e importance of genet i c as we l l as age f a c t o r s on the behaviour of an ima ls . A l though he d i d f i n d v a r i a b l e behaviour between un re l a ted sets of s i m i l a r aged tw i n s , he a t t r i b u t e d these d i f f e r en ce s t o d i f f e r e n t l e v e l s o f mi lk p roduct ion amongst the s e t s . Arno ld and Ma i l e r (1977) found tha t animals w i th g rea te r per iods of f o r ag i ng exper ience i n a g iven environment take longer t o adapt t o new g raz ing regimes than animals o f l i m i t e d prev ious exper i ence . This o f f e r s a p l a u s i b l e exp l ana t i on of why age can a f f e c t g raz i ng behav iour . In l i g h t o f 74 cap t i v e animals i n t h i s s tudy , the dominant and in te rmed ia te ewes, having v a r i a b l e ages as we l l as v a r i a b l e f o rag ing expe r i ence , each adopted a s l i g h t l y d i f f e r e n t f o r ag i ng pa t t e rn wh i l e a d j u s t i n g t o the new vege t a t i on , r e s u l t i n g i n s i g n i f i c a n t behav ioura l d i f f e r e n c e s . The subo rd ina tes , because of young age and l i m i t e d prev ious exper i ence , were quick t o develop a common approp r i a te f o r ag i ng s t r a tegy f o r the study s i t e . Th is argument gains some support when behav ioura l data on lambs born on the study s i t e and y e a r l i n g s are assessed. The th ree y e a r l i n g s i n the herd, w i th l e s s than one year of prev ious f o rag ing exper ience on na t i v e range, showed no s i g n i f i c a n t w i th in -g roup behav ioura l v a r i a t i o n i n any of the months t e s t e d . S i m i l a r l y , lambs born and weaned on the study s i t e , demonstrated remarkably low w i th in -g roup v a r i a b i l i t y i n a c t i v i t y budgets once separated by sex. 3. P r o d u c t i v i t y comparisons The lack of between-c lass product ion d i f f e r en c e s can l o g i c a l l y be a t t r i b u t e d t o the s i m i l a r d i e t s o f the th ree s o c i a l c l a s s e s . Without ob t a i n i ng a h igher q u a l i t y forage supply than o ther an ima l s , dominant ewes would not be expected t o demonstrate g rea te r p r o d u c t i v i t y . Ce r t a i n between-c lass t rends in p roduc t i on , a l though s t a t i s t i c a l l y i n s i g n i f i c a n t , d i d seem apparent but most cou ld be i n t e r p r e t e d i n terms of f a c t o r s o ther than s o c i a l s t a t u s . For example, the average weight gain of Subord inates from March t o August which appeared h igh compared t o t ha t o f Intermediates and Dominants was l i k e l y the r e s u l t of growth as we l l as seasonal weight f l u c t u a t i o n s . A review by Shack leton and Shank ( i n press) showed both Rocky Mountain and C a l i f o r n i a b ighorn ewes cont inue t o grow a f t e r th ree years of age. S i m i l a r l y , Ge i s t (1971) suggested tha t b ighorn rams approach t h e i r maximum weight at 5 - 8 yea r s of age. There fo re , i t i s probable t ha t the subord inate ewes of t h i s 75 s tudy , a l l th ree years of age, were s t i l l demonstrat ing some phys i ca l maturat ion which c on t r i bu t ed t o t h e i r March t o August weight i n c r ea se . Th i s , o f course , was not the case f o r the o l de r an imals o f the remain ing two s o c i a l c l a s s e s . The f a c t t ha t a l l th ree subord inates were, on average, 5.0 kg heav ie r i n August 1978 than i n September 1977 supports t h i s sugges t ion . The apparent , a l though s t a t i s t i c a l l y i n s i g n i f i c a n t , preponderance of w in te r m o r t a l i t i e s w i t h i n the in te rmed ia te s o c i a l c l a s s can pos s i b l y be a t t r i b u t e d t o age ra the r than s o c i a l s t a t u s . As desc r ibed i n R e s u l t s , animals which d i ed were i n v a r i a b l y o l de r i n d i v i d u a l s (6+) w i th cons i de rab l e gum nec ros i s and too th l o s s , a c ond i t i o n which a f f e c t s the prehens ion , mas t i c a t i on and even d i g e s t i o n of f o rage . Age alone enabled these animals t o dominate the young Subord inates i n the herd . However, because of t h e i r r e l a t i v e l y poor phys i ca l c ond i t i o n f o r much of the yea r , these an ima l s , w i th the except ion of the dominant ewe WWW, were l i k e l y unable t o express the aggress iveness necessary t o ach ieve h igh rank ing s t a t u s . (Even WWW, a l though dominant, was r e l a t i v e l y d o c i l e , i n i t i a t i n g on ly a moderate number of i n t e r a c t i o n s compared t o other dominant an ima l s ) . Consequent ly , the ma jo r i t y o f deaths occurred w i t h i n the i n te rmed ia te s o c i a l c l a s s . Few s tud i e s of female ungulate s o c i e t i e s have f u l l y i n ve s t i g a t ed the r e l a t i o n s h i p between dominance and p r o d u c t i v i t y . An ex tens i ve l i t e r a t u r e review found no research which assessed the e f f e c t s of dominance on o f f s p r i n g p roduc t i on , even though a p o s i t i v e c o r r e l a t i o n between these two f a c t o r s has been suggested f o r the males of many ungulate spec ies (mountain sheep, Ge i s t 1971, pronghorn, K i t chen 1974). S i m i l a r l y , attempts t o compare o ther measures of the p r o d u c t i v i t y o f dominant and subord inate animals such as 76 t h e i r seasonal weight f l u c t u a t i o n s and t h e i r o f f s p r i n g s ' growth and behaviour have not been repo r ted . S ince such product ion comparisons requ i r e long term observa t ions of animals i n a c ap t i v e s t a t e , i t i s not s u r p r i s i n g tha t such research has concentrated on domest ic an ima l s . In research on da i r y cows, Schein and Fohrman (1955), B e i l h a r z e t al_. (1966) and C o l l i s (1976) a l l found no r e l a t i o n s h i p between dominance and mi lk p roduc t i on . In a d d i t i o n , C o l l i s (1976) found tha t l e v e l s o f c e r t a i n b lood c o n s t i t u e n t s , cons idered i n d i c a t i v e of n u t r i t i o n a l s t a t u s , were not c o r r e l a t e d t o dominance. He suggested tha t " i t was u n l i k e l y t ha t dominant animals had a g rea te r ra te of p roduct ion than subord inate animals " , p r i m a r i l y because of " the system of management on the farm, which n u l l i f i e d any po s s i b l e n u t r i t i o n a l advantage f o r dominant i n d i v i d u a l s . . . . " . In a s i m i l a r f a s h i o n , the homogeneously d i spe r sed nature of the forage on the study s i t e prevented dominant animals from ob ta i n i ng any n u t r i t i o n a l advantages and, consequent ly , from demonstrat ing grea te r p r o d u c t i v i t y than subord inate an ima l s . C. Forage A v a i l a b i l i t y and Herd Behaviour Un l i k e the i n v e s t i g a t i o n of the cap t i ve he rd ' s s o c i a l o r g an i z a t i o n , which enabled c e r t a i n hypothes i s t o be accepted or r e j e c t ed based on s t a t i s t i c a l p rocedures , research on the he rd ' s seasonal d i u r na l behaviour was not o r i en ted towards s t a t i s t i c a l a n a l y s i s , hypothes is t e s t i n g , and i nduc t i v e reason ing. Ins tead , causa l f a c t o r s f o r behav ioura l t rends cou ld only be hypothes ized ( i . e . r e t r o d u c t i o n , Romesburg 1981). A l though a l t e r n a t i v e hypotheses cou ld have been generated from the same i n fo rmat i on c o l l e c t e d dur ing t h i s s tudy , i t i s f e l t t ha t those presented below o f f e r the s t ronges t i n t e r p r e t a t i o n of 77 the an ima l s ' behav iour . 1. Seasonal d i u r na l pa t te rns Seasonal changes i n the d i u r na l pa t te rn of the c ap t i v e herd l i k e l y r e su l t ed from a complex i n t e r a c t i o n of a b i o t i c and b i o t i c environmental v a r i a b l e s , a concept expressed by most researchers of herb ivore behaviour (see Arno ld and Dudz insk i 1978). A b i o t i c f a c t o r s can e a s i l y be r e l a t ed t o c e r t a i n changes i n the he rd ' s behav iour . For example, a l though these animals showed some nocturna l t endenc i e s , the onset and t e rm ina t i on of t h e i r d i u rna l rou t i ne gene ra l l y centered around dawn and dusk, r e s p e c t i v e l y . Consequent ly , the t ime of sun r i s e and sunset ( i . e . day length) i n f l uenced the t im ing of two of the an ima l s ' major a c t i v e pe r iods ( i . e . e a r l y morning and l a t e even ing ) . S i m i l a r f i n d i n g s have been repor ted i n o ther b ighorn s t ud i e s ( M i l l s 1937, Davis 1938, Davis and Tay lo r 1939, Blood 1963, Ge i s t 1971, Van Dyke 1979) and from s tud i e s o f domest ic l i v e s t o c k (Hughes and Re id 1951, Hancock 1954, Sheppard et ^1_. 1957, Arno ld and Dudz insk i 1978). Al though not s t a t i s t i c a l l y assessed, day length a l s o proved t o be i n ve r s e l y r e l a t e d t o the number of a c t i v e and non -ac t i ve per iods demonstrated by the herd du r i ng the da y l i g h t hours , a t rend a l s o repor ted from other re l evan t s t u d i e s . A rno ld and Dudz insk i (1978) s t a t ed tha t " . . . i n l a t i t u d e s g rea te r than 35° the breaks between g raz ing decrease, as the days get s ho r t e r , u n t i l i n m id-w in te r some animals w i l l always be found g raz i ng dur ing d a y l i g h t " . A l though d e t a i l e d weather i n fo rmat ion was not a v a i l a b l e f o r the study s i t e , i t appeared, from d i r e c t ob se r va t i on , t ha t d a i l y weather pa t te rns had only minor temporary e f f e c t s on the he rd ' s behav iour . For example, co l d inc lement cond i t i on s i n December were l i k e l y r e spons i b l e f o r the he rd ' s reduced ea r l y 78 morning a c t i v i t y , a behav ioura l pa t te rn a l s o repor ted f o r S tone ' s sheep (Ge i s t 1971). Domestic l i v e s t o c k (Arno ld and Dudz insk i 1978) and deer (Severinghaus and Cheatum 1956, i n Moen 1973) a l s o demonstrate reduced a c t i v i t y dur ing p a r t i c u l a r l y c o l d days or co l d po r t i on s of a day. Severe r a i n storms i n the summer a l s o appeared t o a f f e c t the he rd ' s behaviour t empo r a r i l y , f r equen t l y e l i c i t i n g a b r i e f but o f ten premature bedding pe r i od by the herd. S i m i l a r behav iour has a l s o been repor ted i n domest ic l i v e s t o c k (Arno ld and Dudz insk i 1978). In s p i t e of t h e i r apparent i n f l u ence on behav iour , the combined e f f e c t s o f both weather and day length cou ld not f u l l y e xp l a i n the broad seasonal changes i n herd behav iour . For example, data from A p r i l and September, months of comparable temperatures , p r e c i p i t a t i o n and day l eng th , demonstrated va s t l y d i f f e r e n t average a c t i v i t y pa t te rns and budgets f o r the herd. Th is would suggest tha t o ther f a c t o r s must p lay a major r o l e i n i n f l u e n c i n g herd behav iour . Based on in fo rmat ion prov ided from Wikeem's research and from other re levant g raz i ng s t u d i e s , i t i s pos tu l a ted tha t forage cond i t i on ( i . e . forage a v a i l a b i l i t y and phenology) was l i k e l y the f a c t o r most i n f l u e n t i a l i n shaping the seasonal d i u rna l pa t te rns of the herd. Al though i t was a d i r e c t consequence of both day length and general weather pa t t e r n s , forage cond i t i on , i n a l l p r o b a b i l i t y , more d i r e c t l y d i c t a t e d the requ i red f o rag ing e f f o r t and subsequent behaviour of the herd. Ce r t a i n recogn ized r e l a t i o n s h i p s e x i s t between an an ima l ' s f o rag ing behaviour and forage q u a l i t y and q u a n t i t y . It i s w ide l y repor ted tha t g raz ing animals are h i gh l y s e l e c t i v e f o r both s p e c i f i c p l an t s and s p e c i f i c p lan t p a r t s . A rno ld and Dudz insk i (1978) summarized tha t "from the s i n g l e p l a n t , sheep and 79 c a t t l e eat l e a f i n p re fe rence t o stem (Cook and H a r r i s , 1950; Reppert , 1960; A rno l d , 1960b, 1964a), green (or young) ma te r i a l i n pre ference t o dry (or o ld ) ( S t ap l e t on , 1934; M i t t o n , 1953; Cook et al_. 1950; Co l i shaw and A l de r , 1960; Reppert , 1960; and A rno l d , 1964a)" . The degree of s e l e c t i v i t y expressed by an animal i s o f ten c l o s e l y r e l a t ed t o i n t ake r a t e s . Arno ld and Dudz insk i (1978) s t a t ed t ha t f o r sheep, i n take ra tes were r e l a t e d t o " . . . y i e l d s per un i t area of green and dry pas tu re , l ength of pas tu re , number of leaves per un i t area and d i e t d i g e s t i b i l i t y " . Gene ra l l y , as forage matures, herb ivores are p a r t i c u l a r l y s e l e c t i v e f o r new ra the r than o l d growth (Meyer e t a]_. 1957, A rno ld 1960b), but t h i s s e l e c t i v i t y i s o f ten t o the detr iment of i n take ra tes (Arno ld and Dudz insk i 1978). In s l i g h t l y more d e t a i l , White and T rude l l (1980) summarized the e x t r i n s i c f a c t o r s l i m i t i n g forage i n take ra tes i n ca r ibou and re indeer as be ing: a) food a v a i l a b i l i t y - biomass - p r o t e c t i on by snow - p r o t e c t i on by dead p l an t ma te r i a l b) food q u a l i t y - low dry matter d i g e s t i b i l i t y due to f i b rousness - low dry matter d i g e s t i b i l i t i e s due to d i g e s t i v e i n - h i b i t o r s ( e . g . t ann ins ) - t o x i c p l an t compounds c) harassment - by i n s e c t s and p reda t ion d) behav ioura l i n t e r a c t i o n s dur ing - c a l v i n g - r u t t i n g - resource compet i t i on 80 That g raz ing t imes gene ra l l y i nc rease w i th decreas ing pasture q u a l i t y and dec reas ing in take ra tes has been documented by a much l a r g e r number of r e sea r che r s . A l l den et a K (1970) s t a t ed tha t "when a c c e s s i b i l i t y of herbage imposed l i m i t a t i o n s on the ra te at which the animal was ab le t o prehend i t s f eed , i t was shown tha t the sheep was ab le p a r t i a l l y t o compensate f o r the reduced amount of herbage present by an inc rease i n g raz ing t ime (from 6 t o 13 h r s / d a y ) " . S i m i l a r l y , A rno ld (1960; sheep) , Hancock (1954; da i r y c a t t l e ) , Sheppard e t a]_. (1957; beef c a t t l e ) , and Waite e t a]_. (1951; d a i r y c a t t l e ) a l l repor ted an inc rease i n g raz ing t ime f o r animals w i th decreas ing forage q u a n t i t y , q u a l i t y and/or p a l a t a b i l i t y . Such t rends gene ra l l y meant longer but l e s s f requent f o r ag i ng bouts w i th d e c l i n i n g pasture c o n d i t i o n s . As p r ev i ous l y d i s cu s sed , Arno ld and Dudz insk i repor ted on the i n c r e a s i ng du ra t i on of g raz ing bouts w i th decreas ing day leng th , a t r end l i k e l y a s soc i a ted w i th d e c l i n i n g pasture cond i t i on s more so than day leng th . Some s tud i e s on l e s s domestic spec ies have shown s i m i l a r seasonal d i u rna l t r e nd s . For example, Thompson (1970) showed tha t a c t i v i t y per iods of w i l d r e indee r decreased i n l ength and inc reased i n frequency from w in te r t o sp r i ng months, a l though he presents no i n t e r p r e t a t i o n f o r t h i s t r end . Repor t ing s i m i l a r r e s u l t s f o r the cen t r a l A r c t i c ca r ibou herd, Roby (1978) suggested tha t i nc reased forage a v a i l a b i l i t y i n the summer months " . . . r e du ce s the t ime requ i red t o f i l l the rumen and inc reased q u a l i t y would be expected t o reduce rumen tu rnover t ime s " . Based on the above r e l a t i o n s h i p s , a d e t a i l e d i n t e r p r e t a t i o n of changes i n the he rd ' s seasonal d i u r na l pa t te rns has been deve loped. It i s pos tu l a ted tha t the change from the c y c l i c nature ( i . e . success i ve i n t e r v a l s of feed ing and bedding) of the he rd ' s a c t i v i t y pa t te rn i n s p r i ng and summer t o the more 81 cont inuous f o r ag i ng behaviour of the f a l l was c l o s e l y r e l a t e d t o d e c l i n i n g forage c o n d i t i o n s . As d i scussed i n Sec t i on C of R e su l t s , many p re fe r r ed d i e t a r y spec ies of g ras ses , shrubs , and fo rbs were abundant i n the sp r i ng and summer and i n a r ap i d growth phase. In a d d i t i o n , the leaves of many p re fe r r ed spec ies of fo rbs ( e . g . Ba lsamor iza s a g i t t a t a and Lupinus se r i c eus ) were r e l a t i v e l y l a r ge and succu len t and the t i l l e r l engths of u t i l i z e d grasses were r e l a t i v e l y l ong , a c ond i t i on conducive t o l a rge b i t e s i z e s i n the g raz ing animal (A l l den and Whi t taker 1970). S ince forage i n t h i s pheno log i ca l s t a t e has been shown to be high i n crude p r o t e i n and h igh l y d i g e s t i b l e (Hebert 1973), the c ap t i v e animals l i k e l y had rap id i n t ake and a s s i m i l a t i o n r a t e s , i n s p i t e o f the h igh degree o f spec ies s e l e c t i v i t y which they demonstrated du r i ng the pe r i od ( P i t t and Wikeem 1979). Cons ide r i ng t ha t the ra te of passage of i nges ta va r i e s d i r e c t l y w i t h i t s i n take ra te and d i g e s t i b i l i t y (B l a x t e r et a l . 1961), the tu rnover ra te f o r the inges ted forage was, t h e r e f o r e , probably h i g h . Th i s r ap id tu rnover ra te would have enabled the sheep t o f i l l t h e i r rumens and then ruminate, severa l t imes dur ing d a y l i g h t i n the c y c l i c f ash ion demonstrated. The change from t h i s c y c l i c pa t te rn of success i ve feed ing and bedd ing- ruminat ing per iods t o the more cont inuous f o rag ing behaviour i n the f a l l p a r t i a l l y r e su l t ed from the i n c r e a s i n g l y d i spe r sed d i s t r i b u t i o n of the c ap t i v e herd and the asynchrony of separate subgroups. That i s , d i f f e r e n t subgroups f r equen t l y out o f v i s u a l range o f each o the r , began t o bed and forage at s l i g h t l y d i f f e r e n t t imes , caus ing a c t i v i t y graphs f o r the herd as a whole t o f l u c t u a t e l e s s d r a s t i c a l l y , and t o i n d i c a t e a r e l a t i v e l y cons tan t , h igh l e v e l o f a c t i v i t y throughout the day. However, a n a l y s i s of i n d i v i d u a l animal a c t i v i t y pa t te rns demonstrated tha t animals were, i n f a c t , f o rag ing more con t inuous l y as the f a l l months progressed and tha t the herd a c t i v i t y 82 graphs were not m i s rep resen t i ng the herd ' s t r ue behav iour . Th is gradual convers ion t o cont inuous d a y l i g h t a c t i v i t y seemed to c o i n c i d e w i th the l a t e season maturat ion and f a l l regrowth of the study s i t e ' s vege ta t i on . The d e c l i n i n g a v a i l a b i l i t y o f forage from shrubs and ephemeral fo rbs p re fe r r ed by the herd dur ing the sp r i ng and summer appeared t o f o r ce the animals t o u t i l i z e the more common grass spec ies o f the study s i t e (Wikeem pe r s . comm.). While the animals demonstrated reduced spec ies s e l e c t i v i t y from prev ious months, they were s e l e c t i v e f o r p l an t p a r t s , showing a s t rong preference f o r f a l l regrowth on the grasses u t i l i z e d (Wikeem, pe r s . comm.) However, t h i s regrowth, o f ten shrouded by l e s s p a l a t a b l e , ap i c a l p l an t p a r t s , was not as a c c e s s i b l e or as abundant as p r e f e r r ed forage i n prev ious months and l i k e l y requ i red a cons ide rab l e degree of f o r ag i ng e f f o r t to procure i t . I t i s pos tu l a ted tha t the t ime requ i red t o express t h i s s e l e c t i v i t y and a reduc t ion i n b i t e s i z e reduced i n t ake r a t e s , enab l i ng the animals t o forage throughout most of the day w i thout repeated ly f i l l i n g t h e i r rumens and wi thout f requent bedd ing- ruminat ing pe r i o d s . Is i s f u r t h e r suggested tha t t h i s t rend became i n c r e a s i n g l y more pronounced dur ing the f a l l months because regrowth became l e s s a v a i l a b l e and i n take ra tes f u r t h e r d e c l i n e d . The absence of high l e v e l s of a c t i v i t y throughout the day dur ing the inc lement pe r i od of December appeared, i n p a r t , to be the consequence of low temperatures , as p r ev i ous l y d i s cus sed . However, the bedding per iod at mid-day, when temperatures approached the d a i l y maximum, may have r e f l e c t e d a need t o ruminate. I t i s u n l i k e l y t ha t an i nc rease i n i n take ra tes prompted the ruminat ion pe r i od , cons i de r i ng the snow accumulat ion at tha t t ime. However, i t i s p o s s i b l e tha t a decrease i n the d i g e s t i b i l i t y of the forage consumed by the herd may have been a f a c t o r . The deep snow covered any remain ing regrowth and the sheep, a l though c r a t e r i n g t o some ex t en t , seemed 83 content t o feed l a r g e l y on stems and seed heads of bluebunch wheatgrass and on browse spec ies which were above the snow. Th is h igh f i b r e fo rage , being l e s s d i g e s t i b l e and s low ly processed, would have fo rced the herd to bed and ruminate a f t e r shor t f o rag ing pe r i od s . Hoefs (1974) o f f e r ed a s i m i l a r exp l ana t i on f o r the mid-day " s i e s t a " observed i n h i s c ap t i v e D a l l ' s sheep herd . Once the snow cover d isappeared from study s i t e , the sheep rever ted back t o a more cont inuous f o r ag i ng behav iour . The animals were observed feed ing low t o the ground, po s s i b l y s e l e c t i n g the most recent growth of the p l an t s once aga i n . I t i s pos tu l a ted t h a t , s i m i l a r t o l a t e f a l l f o rag ing c o n d i t i o n s , i n t akes rates were s u f f i c i e n t l y low to enable the animals to forage con t inuous l y throughout the day l i gh t hours w i thout r e s t i n g t o ruminate. The a c t i v i t y pa t te rns demonstrated by the herd i n January were n a t u r a l l y i n f l uenced by the presence of supplemental f eed . From dawn t o l a t e morning, most, i f not a l l , o f the cap t i ve animals were concent ra ted i n the v i c i n i t y o f t h i s f eed . By f o r ag i ng at such an e a s i l y e x p l o i t e d , po in t food resource , each animal cou ld f i l l i t s rumen and process the i nges ta r e l a t i v e l y q u i c k l y , enab l i ng the animal t o feed and ruminate two or th ree t imes before the hay was dep le ted . Because the herd members were not synchronous in t h e i r a c t i v i t i e s around the feed supplement, l i k e l y because of the l i m i t e d fo rag ing space, the a c t i v i t y graph ( F i g . 1) i n d i c a t e s an avoidance of the ea r l y morning hours by the animals f o r January . Such behaviour was not apparent , as i t was du r i ng the inc lement c o l d weather pe r i od of December, probably because of the easy and e n e r g e t i c a l l y e f f i c i e n t f o r ag i ng cond i t i on s a f fo rded by the hay p i l e . 84 Since hay was provided at a rate of only 45 kg/day, this supplemental food source was depleted by late morning. Consequently, the animals were forced to u t i l i z e the study areas native vegetation during the afternoon. Clumps of vegetation on the lower half of the enclosure were snow free for much of January's latter half and the animals restricted their foraging to these areas. By primarily selecting the f a l l regrowth at the base of the more common grass species (Agropyron spicatum, Koeleria cristata) (pers. obs.; Wikeem, pers. comm.), i t i s postulated that the animals again had sufficiently low intake rates to reduce the rate of rumen f i l l and, consequently, eliminate the need for inactive ruminating periods. As a result, the majority of the animals did not bed until nightfall, when temperatures again began to drop. In February, warmer mean-daily temperatures and the loss of snow from the study site's lower elevations provided the animals with similar foraging conditions to those experienced in November and the mild periods in December. S t i l l selecting the f a l l regrowth of the study site's common grasses (pers. obs.; Wikeem, pers. comm.), the herd not surprisingly demonstrated similar daily activity patterns to those months. During March, the new growth of spring offered a highly nutritious food source to the animals. However, in i t s i n i t i a l development, this growth was not abundant, being homogeneously but lightly dispersed over the lower half of the study site. In the grasses and forbs, growth occurred low to the ground and, similar to f a l l regrowth, was often shrouded by less palatable, cured plant parts or l i t t e r . As previously discussed, the animals selected this new growth (Wikeem, pers. comm.) and demonstrated a more cyclic and synchronous pattern of feeding and bedding-ruminating periods than in previous f a l l and winter months. It is postulated that the new growth enabled the animals to 85 i n c rease t h e i r forage i n t ake and a s s i m i l a t i o n r a t e s , r e s u l t i n g i n the re turn of the he rd ' s c y c l i c a c t i v i t y pa t te rn which predominated i n the sp r i ng and summer. A c t i v i t y peaks were, however, longer and l e s s f requent than i n the s p r i ng and summer months, sugges t ing t h a t the low den s i t y s p r i n g growth was s u f f i c i e n t l y d i spe r sed or i n a c c e s s i b l e t o keep i n take ra tes below maximum l e v e l s . The add i t i o n a l a c t i v i t y data c o l l e c t e d i n November and December, 1978, a l though l i m i t e d in q u an t i t y , f u r t h e r demonstrated the e f f e c t s of forage q u a l i t y and quan t i t y on the he rd ' s d i u r na l behav iour . On November 14, 1978, the herd, under seasonable weather c o n d i t i o n s , demonstrated a c y c l i c , synchronous a c t i v i t y pa t te rn of success i ve feed ing and bedd ing-ruminat ing pe r i od s . Other researchers observ ing the herd dur ing November reported s i m i l a r behaviour f o r the herd (D. Eastman, A. B o t t r e l l , pe r s . comm.). Th is pa t te rn was complete ly u n l i k e the more cont inuous a c t i v i t y l e v e l s observed i n November 1977 and appeared t o be r e l a t ed t o forage cond i t i on on the study s i t e . The summer and f a l l months of 1978 were r e l a t i v e l y wet f o r the Okanagan reg ion and, consequent l y , many of the en c l o su r e ' s major p l an t spec ies remained i n a h igh q u a l i t y , vege ta t i ve s t a t e u n t i l the c o l d e r , d r i e r weather of October (Wikeem, pe r s . comm.). It i s pos tu l a ted tha t t h i s unusua l l y p roduct i ve growing season, coupled w i th a v a s t l y reduced herd s i z e i n 1978 (40% r edu c t i o n ) , r e su l t ed i n l a rge q u a n t i t i e s of h i gh l y n u t r i t i o u s , r e ad i l y a c c e s s i b l e forage be ing a v a i l a b l e even i n November (Wikeem, pe r s . comm.), a l l ow i ng the animals t o repeated ly f i l l t h e i r rumens and ruminate i n a c y c l i c f a sh i on more t y p i c a l o f s p r i n g and summer p e r i o d s . On December 13, 1978, green f a l l regrowth was s t i l l a v a i l a b l e t o the animals but was covered by a 15 cm cover of powder snow. Un l i ke t h e i r behaviour 86 dur ing s i m i l a r f o r ag i ng cond i t i on s i n e a r l y December, 1977, the sheep d i d not appear t o u t i l i z e seed heads and browse spec ies p ro t rud i ng above the snow but chose i ns tead t o c r a t e r t o the regrowth. The i r s e l e c t i o n of t h i s e n e r g e t i c a l l y more c o s t l y f o r ag i ng s t ra tegy was po s s i b l y a r e f l e c t i o n of t h e i r improved ph y s i o l o g i c a l c ond i t i on over tha t o f December 1977 or the grea te r abundance of f a l l regrowth or both . I t i s pos tu l a ted tha t t h e i r c r a t e r i n g e f f o r t s slowed i n t ake ra tes s u f f i c i e n t l y t o a l l ow the animals to forage in a cont inuous fash ion throughout the day, un l i k e the comparable per iod in December 1977 when a mid-day bedd ing-ruminat ion pe r iod was r equ i r ed . Severa l s tud i e s have presented data on the a c t i v i t y pa t te rns of mountain sheep but few make d e t a i l e d seasonal comparisons or i n t e r p r e t a t i o n s . Dur ing the sp r i ng and summer months, most s tud ied bighorn popu la t ions showed fewer a c t i v i t y peaks than our c ap t i v e herd, a l though a c t i v e per iods at dawn and l a t e a f t e rnoon , as p r ev i ou s l y d i s cu s sed , were i n v a r i a b l y p resent . M i l l s (1937) and Davis (1938) both found th ree peaks of a c t i v i t y f o r a Ye l lowstone Nat iona l Park popu l a t i on , o c cu r r i ng at dawn, mid-day and i n the l a t e a f te rnoon . Davis and Tay lo r (1939) found a bimodal a c t i v i t y pa t te rn i n Texas b ighorns w i th f o r ag i ng peaks ex tend ing throughout the morning and l a t e a f te rnoon . A s i n g l e r e s t pe r iod occur red at mid-day. Van Dyke (1978) found ea r l y morning and l a t e a f ternoon t o be the only c ons i s t en t per iods of a c t i v i t y f o r Oregon b ighorns . Reports on the f a l l a c t i v i t y pa t te rns of w i l d sheep more c l o s e l y resemble 1978 ra the r than 1977 data f o r the cap t i ve herd . Ge i s t (1971) found an average of f ou r a c t i v i t y peaks f o r S tone ' s sheep rams i n October, w i th one major bedding pe r iod at mid-day which i nvo l ved almost a l l v i s i b l e an ima l s . Hoefs (1974) found tha t a c ap t i v e D a l l ' s sheep ram a l s o demonstrated a mid-day bedding pe r i od dur ing the f a l l (except du r ing the r u t ) , w i th th ree or four a c t i v e 87 per iods dur ing d a y l i g h t . Van Dyke (1978) again no t i c ed on ly e a r l y morning and l a t e evening a c t i v i t y peaks, w i th an ex tens i ve mid-day r e s t i n g pe r i od . Researchers have repor ted v a r i a b l e a c t i v i t y pa t te rn f o r w i l d sheep herds dur ing w in t e r months. S i m i l a r t o the inc lement weather pe r iod of t h i s s tudy , Ge i s t (1971) noted tha t S tone ' s sheep fed l i t t l e i n the morning, w i th an a c t i v i t y peak o c cu r r i ng a t noon and again i n l a t e a f te rnoon . Blood (1963) presented s i m i l a r r e s u l t s f o r C a l i f o r n i a b ighorns but showed a t h i r d a c t i v i t y peak a t dusk. However, Hoefs (1974) and Van Dyke (1978) found no avoidance o f the morning hours by mountain sheep i n t h e i r s t u d i e s . Ins tead, sheep showed a major a c t i v i t y peak i n e a r l y morning and l a t e a f t e rnoon , w i th an ex tens i ve mid-day re s t p e r i o d . S ince r e s u l t s from t h i s study have i n d i c a t e d the importance range cond i t i on s t o the d i u rna l behav iour of sheep, the between-s i te d i s c r epanc i e s d i scussed above are d i f f i c u l t t o i n t e r p r e t w i thout more d e t a i l e d range in fo rmat ion on each s i t e . The r e l a t i v e l y l a rge number of a c t i v i t y peaks demonstrated by the cap t i v e herd i n sp r i ng and summer, f o r example, may s imply r e f l e c t a more concen t ra ted , r e a d i l y a v a i l a b l e food resource on the study s i t e than on o the r , na tu ra l ranges, a l l ow i ng f o r more rap id rumen f i l l . D i f f e rences i n the s i z e of study areas may have a l s o caused the d i s c r epanc i e s between t h i s and other s t u d i e s . Animals occupy ing a l a r g e r , more rugged na tu ra l range l i k e l y showed l e s s synchrony w i t h i n a herd than d i d our c ap t i v e sheep. Th is asynchrony would have obscured the more mu l t i -peaked a c t i v i t y pa t te rn of i n d i v i d u a l s , p a r t i c u l a r l y w i thout animals equipped w i th i d e n t i t y c o l l a r s . Nocturnal a c t i v i t y A l though l i m i t e d a c t i v i t y data were c o l l e c t e d dur ing the hours of darkness , 88 c e r t a i n c h a r a c t e r i s t i c s o f t h i s nocturna l behav iour were apparent and seemed t o be of p r a c t i c a l and b i oene rge t i c s i g n i f i c a n c e . As p r ev i ou s l y d i scussed i n R e s u l t s , n ight f o r ag i ng bouts were not as f requent nor as lengthy as those dur ing d a y l i g h t hours . They u sua l l y i n vo l ved l e s s than 50% of the herd at any one t ime and were r e s t r i c t e d t o the immediate v i c i n i t y o f the bedding a rea . Th is behaviour may have some s u r v i v i a l va lue . A l though sheep obv ious ly possess r e l a t i v e l y good n igh t v i s i o n , i t i s l i k e l y not as developed as tha t of some nocturna l p r eda to r s . By l i m i t i n g t h e i r f o r ag i ng bouts t o areas near o ther feed ing or bedding an ima l s , sheep reduced the r i s k of being s i ng l ed out and a t tacked by a p o t en t i a l p r eda t i on . It would appear tha t sheep have a l s o mod i f i ed t h e i r d i u r na l pa t te rns to ensure tha t t h e i r n ight a c t i v i t y i s minimized i f p o s s i b l e . Almost i n v a r i a b l y , sheep demonstrate t h e i r most ex tens i ve f o r ag i ng pe r i od l a t e i n the day, i n the sp r i ng t o f a l l pe r iod of the y ea r . Th is may f unc t i on t o f i l l t h e i r rumens t o t h e i r g rea tes t capac i t y of the d a y l i g h t p e r i o d , w i thout the thermal d i s comfor t t ha t would occur dur ing the ho t t e r po r t i on s of the day. Such a s t r a tegy would, i n t u r n , reduce the s t imu lus t o forage dur ing the n i gh t . The apparent decrease i n nocturna l a c t i v i t y by the sheep dur ing the co l de r w in te r months was l i k e l y an energy conserv ing s t r a t e g y , c on s i s t en t w i th t h e i r avoidance of e a r l y morning hours. Forag ing in the rma l l y and v i s u a l l y suboptimal cond i t i on s probably r e s u l t s i n a g rea te r negat ive energy balance than s imply bedding and conserv ing heat , p a r t i c u l a r l y i f good v i s i b i l t y i s r equ i r ed by sheep f o r e f f i c i e n t forage s e l e c t i o n . Other authors have repor ted on the nocturna l behaviour of mountain sheep but i n l i t t l e d e t a i l . Ge i s t (1971) repor ted tha t sheep are a c t i v e and w ide ly d i spe r sed at n i g h t f a l l , w i th s u f f i c i e n t l y developed n ight v i s i o n to enable 89 them t o r e t i r e t o rugged c l i f f t e r r a i n dur ing darkness . Woolf et al_. (1970) no t i c ed feed ing at i n t e r v a l s throughout the n igh t but suggested tha t movements were " l i m i t e d t o the immediate v i c i n i t y o f the bedground". Van Dyke a l s o repor ted some n igh t movements i n b ighorns . A f u r t h e r d i s cu s s i on on the po s s i b l e seasonal t rends in the nocturna l behav iour of the c ap t i v e herd appears i n Sec t i on C2. 2. Seasonal a c t i v i t y budgets As p r ev i ou s l y d i s cu s sed , r e sea r ch , on domest ic an imals has shown an i nve r se r e l a t i o n s h i p between pasture q u a l i t y and g raz i ng t imes (Sheppard et ail_. 1957, A rno ld 1960a). Such a t rend was not obvious f o r the cap t i ve herd from t h e i r d a i l y a c t i v i t y budgets. Although the animals devoted a g rea te r p ropor t i on of the day t o f o r ag i ng as pasture cond i t i on s d e c l i n e d , they were s imply unable t o s u b s t a n t i a l l y i n c rease t h e i r d a y l i g h t f o r ag i ng t imes because of shor ten ing day leng ths . Research has shown t ha t b ighorns ma in ta in r e l a t i v e l y high t o t a l i n t ake l e v e l s over a 24 hr pe r i od dur ing the e a r l y f a l l months (Hebert 1973, Chappel 1978), at l e a s t u n t i l crude p r o t e i n l e v e l s drop below 7 t o 8% (Hebert 1973). Cons ide r i ng tha t Wikeem (pe rs . comm.) found crude p ro t e i n l e v e l s of the f a l l regrowth of u t i l i z e d grasses t o e a s i l y exceed t h i s va lue , i t can be assumed tha t the cap t i v e herd was a t tempt ing t o ma inta in r e l a t i v e l y high nu t r i e n t i n take l e v e l s , l i k e l y as a p rew in te r i ng f a t t e n i n g requirement. However, w i th the proposed reduced i n t ake ra tes f o r t h i s pe r iod of the yea r (see Sec t i on C I ) , i t i s doubt fu l t ha t the d i u r na l g raz i ng t imes of the herd were s u f f i c i e n t t o p rov ide adequate n u t r i t i o n a l l e v e l s . Consequent ly , i t i s hypothes ized tha t the herd inc reased i t s nocturna l g raz ing t imes as day length decreased, and tha t t o t a l g raz i ng t ime f o r the herd over a 24 hr per iod peaked 90 i n the e a r l y f a l l (September, October) months. A secondary peak may a l s o have occur red i n s p r i n g (March) w i th the onset o f body growth and, t o a secondary degree, r ep roduc t i ve demands. Arno ld and Dudz insk i (1978) noted such a t rend o f i n c r e a s i ng nocturna l a c t i v i t y f o r c a t t l e and suggested tha t . . " t h e p ropo r t i on of n igh t g raz ing was s i g n i f i c a n t l y r e l a t e d t o t o t a l g raz ing t ime (+ ve ) , day length (- ve) and l a t i t u d e (- v e ) , w i th day length being the most impor tan t " . A s i m i l a r r e l a t i o n s h i p appears to e x i s t f o r domest ic sheep (Arno ld and Dudz insk i 1978, F i g . 1.2) Based on the d i u r na l and l i m i t e d nocturna l data c o l l e c t e d on the study animals du r ing December and January , i t was apparent t ha t t h i s t rend of i n c r ea s i ng f o r ag i ng t imes f o r the complete 24 hr pe r iod w i th decreas ing day l i gh t was d i s r up t ed du r i ng the w in t e r months, when the herd reduced t h e i r f o r ag i ng t imes and e f f o r t s ( i . e . p ropo r t i on of day) c on s i d e r ab l y . Such reduced w in te r a c t i v i t y i n b i gho rns , r epo r ted l y an energy conserv ing s t r a t e g y , has been suggested by Ge i s t (1971) and Chappel (1978) and i s a s soc i a t ed w i th reduced metabo l i c and i n t ake ra tes (Chappel 1978). S ince A rno ld and Dudz insk i (1978) repor ted tha t supplemental feed gene ra l l y reduced the g raz ing t ime of pasture an ima l s , i t i s probable t ha t January ' s low f o r ag i ng va lue was the r e s u l t of both the supplement food source and the reduced w in t e r a c t i v i t y suggested above. Reduced nocturna l a c t i v i t y du r ing the w in te r has a l s o been documented, a l though not s p e c i f i c a l l y f o r b ighorns . Ozoga and Verme (1970), i n s tud ies on penned w h i t e - t a i l e d deer , reported two nocturna l a c t i v i t y peaks in ea r l y w i n t e r , but a d e c l i n e i n n igh t a c t i v i t y as the w in t e r progressed. Craighead et _al_. (1973) found t ha t e lk " a c t u a l l y fed l e s s per hour of darkness dur ing the w in t e r than summer", w i t h animals spending . . . "mos t o f the hours o f the long w in t e r n igh t b edded . . . " . 91 Both observed and suggested t rends f o r the he rd ' s d a i l y g raz ing e f f o r t s and t imes have been repor ted by o the r researchers o f w i l d ungu la tes . Van Dyke (1978) found b ighorn d a y l i g h t f o rag ing e f f o r t ( i . e . p ropo r t i on of day length) t o i n c rease from summer t o w i n t e r . He a t t r i b u t e d t h i s t r end t o : a) l e s s d a y l i g h t hours a v a i l a b l e i n which t o be a c t i v e i n w i n t e r ; b) poorer forage q u a l i t y i n w i n t e r ; c) l e s s a v a i l a b l e forage i n w i n t e r ; d) c o l de r temperatures i n w in te r which causes an i nc rease i n energy demands. (In l i g h t of Chappe l ' s (1978) f i n d i ng s on the thermal neut ra l zone of b i gho rns , t h i s l a s t p o s t u l a t i o n seems somewhat que s t i o nab l e ) . Cra ighead et a]_. (1973) , i n t h e i r study of r a d i o - c o l l a r e d e lk i n Ye l lowstone Nat iona l Park , found t o t a l feed ing t imes over 24 hr per iods peaked i n f a l l and s p r i n g , w i th cons ide rab l y reduced t imes being ev ident i n summer and p a r t i c u l a r l y i n w i n t e r . Wi th in the reduced w in t e r a c t i v i t y regime of the study an ima l s , the degree of w i n t e r f o rag ing t imes on a d a i l y bas i s seemed l a r g e l y dependent on the a c c e s s i b i l i t y o f f o rage . The cap t i v e herd , as p r e v i o u s l y d i s cu s sed , devoted cons i de rab l y more d a y l i g h t t ime t o f o r ag i ng du r i ng the m i l d , snow-free pe r iod o f l a t e December 1977 than dur ing the more d i f f i c u l t fo rag ing , pe r iod of e a r l y December 1977, when ground accumulat ions o f snow reached 30 cm. S i m i l a r l y , Cra ighead e t a]_. (1973) a t t r i b u t e d low fo rag ing t imes in w in te r to a 92 " s c a r c i t y o f p a l a t ab l e food , t r a v e l r e s t r i c t i o n s imposed by deep snow, and the need t o conserve energy" . Roby (1978) o f f e r ed an opposing view on the impacts of snow cover , sugges t ing tha t f o r ag i ng e f f o r t s were g rea tes t when snow depths and c r a t e r i n g requirements were g r ea t e s t . S ince the cap t i v e sheep gene ra l l y ruminated i n a prone p o s i t i o n , bedding t imes f o r the herd were l a r g e l y a f unc t i on of the he rd ' s ruminat ion requ i rements . Consequent ly , bedding t imes were s i g n i f i c a n t l y c o r r e l a t e d t o day length (r = 0 . 92 ) , peaking i n the sp r i ng and ea r l y summer when forage i n take ra tes were presumably h igh and dropping i n the e a r l y s p r i ng and f a l l when i n take ra tes were presumably lower and f o r ag i ng e f f o r t h i gh . The mid-w inter peak, l e s s pronounced than i n s p r i ng and summer, was l i k e l y the r e s u l t of the herd ' s reduced a c t i v i t y l e v e l s , ra the r than h igher i n take r a t e s . It can be specu la ted t h a t , over a 24 hr p e r i o d , t o t a l bedding t imes would l i k e l y have been h igher i n w i n t e r than at any o ther t ime of the year because of the l i m i t e d nocturna l a c t i v i t y du r ing the long w in t e r n i g h t . S i m i l a r t o t h i s study Van Dyke (1978) gene ra l l y found d i u rna l bedding e f f o r t t o be the r e c i p r o c a l of feed ing e f f o r t . Cra ighead et al_. (1973), found bedding t imes over a 24 hr pe r iod t o be r e l a t i v e l y cons i s t en t i n s p r i n g , summer and f a l l , and high i n w i n t e r . A d e t a i l e d i n t e r p r e t a t i o n of the seasonal f l u c t u a t i o n s i n t imes devoted to the o ther behav ioura l ca tego r i e s i s of l i m i t e d va lue . A 15 minute sampling i n t e r v a l proved t o be too long t o prov ide accura te a c t i v i t y budget data on such shor t term events as s tand ing , t r a v e l l i n g (wa lk ing , running) and "o ther" a c t i v i t i e s ( nu r s i ng , i n t e r a c t i n g , p l a y i n g ) . However c e r t a i n seasonal t rends i n such behav ioura l c a t ego r i e s were apparent and can be d i s cussed . For example, the r e l a t i v e l y h igh p ropo r t i on of t ime devoted t o s tand ing dur ing the 93 co l de s t months appeared t o r e f l e c t a behav ioura l adapta t ion of the animals t o low temperatures . Both Ge i s t (1971) and Chappel (1978) repor ted tha t b ighorns f r equen t l y stood i n a " c l osed s tand ing pos tu re" (Chappel 1978) t o combat co l d temperatures , r a the r than bed. It can be specu la ted tha t such a posture o f f e r s equ i va l en t or g rea te r energy conse rva t i on than bedding, i n c e r t a i n c i r cumstances . Gene r a l l y , p r e f e r r ed w in te r bed s i t e s f o r the cap t i ve herd occur red under l a rge Ponderosa pines (P inus ponderosa) , where accumulated l i t t e r was a v a i l a b l e as an i n s u l a t i v e bedding mate r i a l and where the t r e e canopy l i k e l y reduced heat l o s ses to long wave r a d i a t i o n . However, i n December, January and February , f o rag ing was l a r g e l y conf ined to the supplemental feed or the lower t h i r d of the study s i t e , where only three p re f e r r ed bed s i t e s occur red . Consequent ly , on many occas i ons , animals r e q u i r i n g a pe r iod of ruminat ion were a cons ide rab l e d i s t ance from one of these s i t e s . Rather than t r a v e l t o such a s i t e or bed on un insu la ted ground dur ing the a c t i v e pe r i od of the day, animals f r equen t l y chose t o s tand . (Major t r e k s t o and from the p re f e r r ed bed s i t e s d i d occur at dawn, dusk and o c c a s i o n a l l y at m id -day) . It i s p o s s i b l e tha t convec t i ve heat l o sses i n such a p o s i t i o n c on s t i t u t e d l e s s of an energy d r a i n f o r shor t per iods than wa lk ing t o p r e f e r r ed s i t e s or bedding on un insu l a ted ground. The r e l a t i v e l y h igh p ropo r t i on of t ime devoted t o t r a v e l i n A p r i l r e f l e c t e d a general h igh l e v e l o f " f l i g h t y " behaviour f o r the herd i n tha t month. The herd f r equen t l y made long t r e k s between f o r ag i ng bouts and "pan i c " f l i g h t s f o r no apparent reason. Th is behaviour cont inued i n t o May, a l though at reduced l e v e l s , dur ing the ea r l y development of tha t y e a r ' s lambs. D i f f i c u l t to i n t e r p r e t , such f l i g h t y behaviour seemed to occur s imu l taneous ly w i th the re tu rn of opt imal f o r ag i ng c o n d i t i o n s , i n d i c a t i n g a po s s i b l e r e l a t i o n s h i p t o 94 i n c r e a s i ng a v a i l a b l e energy. The presence of lambs w i th t h e i r h i gh l y energ i zed p lay bouts seemed t o prompt such behaviour t o cont inue throughout May. The h igh t r a v e l p ropor t i ons i n December appeared t o r e s u l t from the opposing d i s t r i b u t i o n s of feed ing and bedding s i t e s . Animals almost i n v a r i a b l y chose areas adjacent t o the water paddock f o r major bedding p e r i o d s , wh i l e p r e f e r r ed feed ing s i t e s of reduced snow accumulat ions occurred more than 0.5 km t o the sou th . Th is r e su l t e d i n r e l a t i v e l y f requent obse rva t i ons of t r a v e l l i n g an ima l s , p a r t i c u l a r l y i n the morning and l a t e even ing . The r e l a t i v e l y h igh p ropo r t i on of d a y l i g h t t imes devoted t o "o ther " a c t i v i t i e s by the herd appeared r e l a t ed t o the maternal i n t e r a c t i o n s between ewes and t h e i r lambs. Nurs ing , which peaked i n May and ea r l y June, was the predominant c o n t r i b u t o r t o t h i s a c t i v i t y ca tegory . I n t e r a c t i o n s and p lay bouts amongst the ewes, but gene ra l l y i n i t i a t e d by the lambs, consumed the remaining t ime devoted t o t h i s ca tegory . That r u t t i n g a c t i v i t i e s d i d not produce a secondary "o ther " a c t i v i t y peak i n November a c cu ra t e l y r e f l e c t e d the qu iescent r u t t i n g pe r i od o f the he rd . I t appeared tha t few ewes became sexua l l y r e cep t i ve i n 1977, e i t h e r because of t h e i r poor p h y s i o l o g i c a l c ond i t i o n or the inexper ience o f the young rams in t roduced f o r the r u t . Other s t ud i e s us ing s i m i l a r scan sampl ing techn iques t o t h i s one have repor ted on a f a l l peak i n "o ther" a c t i v i t i e s , gene ra l l y r e l a t ed t o the rut (Roby 1978, Van Dyke 1978). Da i l y v a r i a b i l i t y i n herd behaviour The day t o day v a r i a b i l i t y i n the he rd ' s behav iour was a s i g n i f i c a n t source of v a r i a t i o n i n the l i n e a r model used t o ana lyze herd behaviour i n a l l months but 95 January . With the except ion of data c o l l e c t e d i n December, there was no ev idence to suggest t ha t such v a r i a b i l i t y was the r e s u l t o f gross weather pa t te rns ( i . e . mean d a i l y temperatures , d a i l y maximum and minimum temperatures , p r e c i p i t a t i o n ) . However, more sub t l e weather f a c t o r s such as changes i n barometr i c p ressu re , wind speed and r e l a t i v e humidi ty have been l i n k e d t o changes i n animal behaviour (Arno ld and Dudz insk i 1978) and, i n a l l p r o b a b i l i t y , were at l e a s t p a r t i a l l y r e spons ib l e f o r d a i l y behav ioura l v a r i a t i o n i n the cap t i v e herd . Fu r the r work i n t h i s area i s requ i red t o v a l i d a t e such a sugges t i on . Day t o day changes i n behaviour have been documented f o r domestic g r a ze r s . Hancock (1954) repor ted tha t day t o day d i f f e r en c e s i n the g raz ing and ruminat ing t imes of da i r y c a t t l e accounted f o r 50 and 60% of the t o t a l v a r i a t i o n i n t imes devoted to these a c t i v i t i e s . Hancock a t t r i b u t e d these d a i l y v a r i a t i o n s t o f l u c t u a t i o n s i n weather and range c o n d i t i o n . Sheppard et a l . (1957) a l s o found g raz ing t imes between days t o vary s i g n i f i c a n t l y f o r c a t t l e , but much l e s s so f o r consecut i ve days. They suggested tha t " c l i m a t i c or l i g h t f a c t o r s " and "pastures and other b i o t i c f a c t o r s " , a l l o f which i n f l u en ce g raz ing behav iour , "are more near l y a l i k e on consecut i ve than on non-consecut ive d a y s . . . " . January ' s data from t h i s study supports Sheppard's sugges t i on . Janua ry ' s sampl ing days, u n l i k e those of o ther months, were consecu t i ve and behav ioura l da t a , as p r e v i ou s l y mentioned, showed no day t o day v a r i a t i o n . D. E f f e c t s of P h y s i o l o g i c a l Cond i t i on on Da i l y A c t i v i t y Budgets An aberrant p h y s i o l o g i c a l c ond i t i o n such as ma l n u t r i t i o n appeared to more g ro s s l y a f f e c t the c ap t i v e he rd ' s d i u r na l pa t t e rn than normal pregnancy. The 96 i nc reased g raz ing t imes of s i ck animals i n October over tha t of hea l thy i n d i v i d u a l s may have been an e a r l y attempt t o improve t h e i r c ond i t i o n before w i n t e r . In December, w i th d e c l i n i n g hea l th and low f a t r e se rves , these animals appeared to convert t o an energy conserv ing s t ra tegy even more pronounced than the remainder of the herd . Whi le ma in ta in ing a f o rag ing e f f o r t equ i va l en t t o o ther herd members, the a i l i n g animals bedded longer and reduced e n e r g e t i c a l l y c o s t l y a c t i v i t i e s such as t r a v e l and s o c i a l i n t e r a c t i o n s . Th is observed behav ioura l t r end seemed con s i s t en t w i th the l i m i t e d l i t e r a t u r e a v a i l a b l e . Arno ld and Dudz insk i (1978) gene ra l i z ed tha t " t h i n sheep eat more than f a t sheep under a l l pasture c ond i t i o n s " by g raz ing longer and u sua l l y ea t i ng f a s t e r than f a t sheep. However, under extreme weather cond i t i on s ( i . e . c o l d ) , a reversed t rend was noted, w i th sheep i n poor cond i t i on reduc ing g raz i ng t imes (Arno ld and Dudz insk i 1978). S i m i l a r l y , Roby (1979) found tha t a ca r ibou herd from a poor w in te r range i n Greenland and s u f f e r i n g from high w in t e r s t a r v a t i o n ra tes demonstrated h igher bedding t imes than a be t t e r nour ished ca r ibou herd i n A l a s ka . Moen (1973) suggested tha t a deer employing severa l energy conserv ing s t r a t e g i e s , i n c l u d i n g bedding w i th i t s head down, cou ld reduce energy l o s se s t o 2 x BMR even i n -40°C weather. Such a s t ra tegy would be of obvious importance t o an a i l i n g animal dur ing d i f f i c u l t f o rag ing c o n d i t i o n s . The f a c t t ha t pregnant ewes i n the herd demonstrated no g rea te r f o rag ing t imes l a t e i n pregnancy than d i d barren ewes i s a l s o c on s i s t en t w i th the l i t e r a t u r e (Arno ld 1962, Arno ld and Dudz insk i 1978). Whi le i t i s gene ra l l y accepted tha t pregnant ewes have inc reased n u t r i t i o n a l demands du r i ng f i n a l stages of f e t a l development, i t appears tha t these inc reased demands are not ex tens ive 97 ( B l a x t e r 1962) and are po s s i b l y met by an i n c rease i n r a te of e a t i n g , r a the r than an i nc rease i n g raz ing t ime (Arno ld 1962). Such a response i s p a r t i c u l a r l y p o s s i b l e dur ing l a t e stages of pregnancy when forage q u a l i t y and quan t i t y i s gene ra l l y h igh and the forage i s e a s i l y ha rves ted . E. Energy Expendi ture Est imates f o r the Herd The average BMR's es t imated f o r the herd members us ing Chappe l ' s p r e d i c t i v e - 0 73 model ranged from 2.75 Kcal KgW * h r - * in Ju l y - August to 4.79 -0 73 Kcal kgW * h r - * i n June. These values were gene ra l l y h igher than -0 73 B rody ' s average f i g u r e f o r mammals o f 2.94 Kcal kgW~ ' h r - l ( B l a x t e r 1962). It would appear t ha t the es t imated b ighorn BMR's were a l s o h igher than tha t f o r domest ic sheep. Both Marston (1948, i n B l a x t e r 1962) and Ritzman and Benedict (1930, i n B l a x t e r 1962) found FMR's of only 2.46 Kcal -0 73 kgW~ ' h r - l f o r adu l t merino ewes. However, ne i t he r the e leva ted va lues of our c ap t i v e b ighorns nor the monthly v a r i a b i l i t y of these values seem unreasonable, s i n ce BMR's (and FMR's) have been demonstrated by other researchers t o be both spec ies s p e c i f i c and h i gh l y v a r i a b l e w i t h i n s pe c i e s . For example, B l a x t e r (1962, Table 17) showed tha t the FMR's of s tee rs -0 73 es t imated from var ious s tud ies ranged from 3.33 to 4.01 Kcal kg h r - l p e r i od . In a d d i t i o n , Ritzman and Benedict (1938, i n B l a x t e r 1962) . . . . " f o u n d metabol ism t o vary i n the same i n d i v i d u a l by 40% or more, and they showed tha t much of t h i s v a r i a t i o n appeared t o be a s soc i a t ed w i th the t ime of y ea r , maximum va lues be ing obta ined i n the sp r i ng and ea r l y summer". The i r r e g u l a r seasonal f l u c t u a t i o n s i n the BMR's developed f o r the cap t i ve herd on ly s l i g h t l y resembled t rends repor ted by o ther resea rche rs . Chappel (1978) found s p r i ng and p a r t i c u l a r l y f a l l FMR va lues t o be no t i c eab l y h igher 98 than w in te r va l ues . Chappel a l s o found forage i n take ra tes of h i s study animals t o be h igher i n sp r i ng and f a l l than i n w i n t e r , as d id Hebert (1973, b i gho rn s ) . A s i m i l a r seasonal t r end has been recognized f o r severa l w i l d , high l a t i t u d e c e r v i d s ( w h i t e - t a i l e d deer , S i l v e r et a K 1969, 1970; ca r ibou and re i ndee r , McEwan and Whitehead 1970). It has been suggested tha t the reduced w in t e r ra tes r e f l e c t a w in te r "growth dormancy" pe r iod (Reimer 1979) which enables the animals t o best cope w i th low w in t e r temperatures and food shor tages . The gene ra l l y h igher s p r i ng t o f a l l r a t e s , i n t u r n , c o i n c i de w i th " . . . t h e inc reased energy requirements i n t h i s season due t o r ap id growth, l a c t a t i o n , mou l t i ng , a n t l e r growth and inc reased a c t i v i t y " (Reimer 1979). A l though the t y p i c a l s p r i ng - ea r l y summer peak and l a t e w in te r low i n BMR va lues were es t imated f o r the cap t i ve herd, l a t e summer-fal l BMR's were unusua l l y low, compared t o t rends d i s cussed above. The i r low va lue may have been an a r t i f a c t o f Chappe l ' s p r e d i c t i v e model, s i nce seasonal c o r r e c t i o n f a c t o r s f o r the June t o September pe r i od were ex t r apo l a t ed values and not based on ac tua l FMR readings from h i s study an ima l s . However, Chappe l ' s data do i n d i c a t e t ha t h igh ambient temperatures (> 10°C) have a depress ive e f f e c t on metabol ism. From t h i s i n f o rma t i on , one cou ld specu la te tha t b ighorns may lower t h e i r metabo l i c ra tes f o l l o w i n g peak rep roduc t i ve and growth demands and p r i o r t o r u t t i n g and p r e -w i n t e r i ng per iods t o combat excess i ve heat l oad ing du r i ng the hot summer pe r i od . B l a x t e r (1962) d i s cussed the po t en t i a l f o r such heat l o ad i ng , i n poor ly i n su l a t ed domestic animals exposed t o ex tens i ve , d i r e c t s o l a r r a d i a t i o n . However, b ighorn researchers have not reported on a l a t e summer reduc t ion i n forage i n take by these animals (Hebert 1973), a c ond i t i o n which would l i k e l y a r i s e w i th reduced metabo l i c r a t e s . S i m i l a r l y , behav ioura l s t ud i e s (Kornet 1978, Van Dyke 1978, t h i s study) have shown l i t t l e or no avoidance o f the ho t t e s t po r t i on of the day by b ighorns , a behav ioura l 99 pat te rn which should have been ev ident i f heat l oad ing was a problem. Un t i l f u r t h e r work on l a t e summer bighorn metabol ism i s completed, l i t t l e can be sa i d on t h i s aspect o f t h e i r b i o l o g y . A c t i v i t y cos t s es t imated f o r the herd on a monthly bas i s were s i g n i f i c a n t l y c o r r e l a t e d t o monthly BMR's (r2 = .93 , p < 0 . 05 ) , i n s p i t e of a c t i v i t y budget changes over the yea r . One might conc lude from t h i s i n fo rmat ion tha t the cap t i v e herd d i d not r e l y on seasonal behav ioura l adapt ions t o modify t h e i r energy expend i tu res , s ince the expend i tures of the animals were predominant ly c o n t r o l l e d by ph y s i o l o g i c a l adjustments t o BMR. While t h i s may l a r g e l y be t r u e , i t can be demonstrated tha t behav ioura l adapt ions may have been important i n determin ing the he rd ' s net energy ba lance. In gene ra l , r e l a t i v e l y "expens ive" a c t i v i t i e s (wa lk ing , runn ing , "o the r " ) which o f f e r ed no d i r e c t ene rge t i c re tu rns comprised a decreas ing p ropor t i on of the herd ' s energy expend i tures from sp r i ng ( A p r i l ) t o l a t e w in te r (March), w i th p ropor t i ons d e c l i n i n g from 29.8 to 11.5%, r e s p e c t i v e l y . (Because of high t r a v e l t imes i n December, i n t e r p r e t ed i n the prev ious s e c t i o n , t h i s t rend was d i s r up t ed s l i g h t l y i n m i d -w i n t e r ) . Converse l y , r e l a t i v e l y " inexpens i ve" ye t e s s e n t i a l a c t i v i t i e s ( g ra z i ng , bedd ing-ruminat ing) which y i e l d e d gross ene rge t i c re tu rns ( i . e . a s s im i l a t e d forage) comprised a gene ra l l y i n c r ea s i ng p ropo r t i on of the he rd ' s energy expend i tures from A p r i l to March (with the except ion of December and January , where g raz i ng t imes were unusua l l y l ow) , w i th p ropo r t i ons r i s i n g from 67.7% i n A p r i l t o 84.9% i n March. It can be specu la ted tha t t h i s s h i f t i n a c t i v i t y emphasis improved the net energy balance of the an ima l s , at l e a s t dur ing the da y l i g h t hours , by l a r g e l y e l i m i n a t i n g those per iods of high negat ive energy f low and i n c r ea s i ng per iods of p o s i t i v e or neu t ra l energy f l ow . 100 The extent to which the herd ' s a c t i v i t y cos ts exceeded BMR's appeared con s i s t en t w i th the l i t e r a t u r e . Moen (1973) found mu l t i p l e s of BMR, c a l c u l a t e d from the cos t s of f i v e d i f f e r e n t a c t i v i t y regimes of a 60 kg w h i t e - t a i l e d deer , t o vary from 1.23 t o 1.98 x BMR. S i m i l a r l y , a c t i v i t y cos ts of a 60 kg pronghorn were equ i va l en t t o 1.45 x BMR. Un l i ke t h i s s tudy , Moen (1973) demonstrated d e c l i n i n g mu l t i p l e s of BMR from summer t o f a l l t o w i n t e r . However, t h i s d e c l i n e was l a r g e l y the r e s u l t o f Moen's use o f a standard BMR va lue throughout the yea r . Consequent ly , when l e s s "expens ive" a c t i v i t i e s ( i . e . bedding, ruminat ing) began t o comprise a l a r g e r p ropor t i on of the an ima l s ' day, the d a i l y a c t i v i t y cos t s became l e s s expens ive , r e l a t i v e t o BMR. Had Moen inc luded expected seasonal v a r i a t i o n s i n BMR, a l e s s obvious t rend would l i k e l y have a r i s e n . That the peak l a c t a t i o n pe r i od of the c ap t i v e herd was the most expens ive t ime of yea r , even more so than pregnancy, i s c on s i s t en t w i th the f i n d i ng s of researchers of animal b i o ene r ge t i c s . Overman and Gaines (1933 i n B l a x t e r 1962) developed a general formula f o r the energy content of m i l k , where c a l o r i c va lue (Kcal kg-1) = 304.8 + 114.1 f (f = % f a t c on t en t ) . S ince the f a t content of mi lk of a C a l i f o r n i a b ighorn ewe dur ing the f i r s t 44 days of l a c t a t i o n has been measured at 5% (Atk inson 1980), the c a l o r i c va lue of t h i s mi lk would be approx imate ly 875 Kca l k g - * o f mi lk produced. Assuming tha t sheep are 60% e f f i c i e n t at conve r t i ng me t abo l i z i b l e energy i n t o mi lk (est imated e f f i c i e n c y f o r d a i r y c a t t l e , from Mo l lgaard 1929, i n B l a x t e r 1962), and tha t they produce mi lk at a ra te of 1.6 kg day-1 (minimum va lue es t imated f o r domest ic sheep du r i ng peak l a c t a t i o n , from Munroe 1962), mi lk p roduct ion f o r a b ighorn ewe would requ i r e at l e a s t 2300 Kcal o f energy above tha t used f o r maintenance on a d a i l y b a s i s . Th is would r e s u l t i n an 101 energy expend i ture 1.7 t imes tha t es t imated f o r May a c t i v i t y c o s t s , a mu l t i p l e even h igher than p r ed i c t ed by Moen (1973) f o r deer . Pregnancy, even i n i t s f i n a l s tages , i s r e l a t i v e l y i nexpens i ve , a f a c t which has l a r g e l y been a t t r i b u t e d i n domest ic sheep t o the r e l a t i v e l y low metabo l i c ra te of the lamb i n u t e ro , est imated t o be s i m i l a r per kg of weight t o t ha t o f the adu l t ewe (B l a x t e r 1962). Consequent ly , . . . " i n p r a c t i c a l t r i a l s , i t has been d i f f i c u l t t o measure any i nc rease i n the energy needs o f the pregnant animal per kg of her t o t a l we igh t " . ( B l a x t e r 1962). 102 SUMMARY A. Social Organization 1) Agonist ic interact ions between adult ewes were br ief . encounters, pr imar i ly comprised of butts or horn threats. It is postulated that the conspicuous absence of horn displays, charac ter i s t i c of bighorn rams, was the resul t of l imited v a r i a b i l i t y in horn s ize of the adult ewes. 2) Interactions between ewes were infrequent, re l a t i ve to that reported for rams. It is postulated that th is reduced socia l a c t i v i t y is a general behavioural strategy adopted by ewes to minimize energy expenditures on a c t i v i t i e s not v i t a l to maintenance or to reproductive success. 3) A dominance hierarchy developed among adult ewes. However, because of several dominance reversa ls , the hierarchy was not l inear . It was postulated that the homogeneously d is t r ibuted food resources of the ewes reduced food competition, thus el iminat ing the need for a r i g i d l y maintained and orderly hierarchy. 4) The hierarchy, although neither r i g i d nor l inear , remained r e l a t i v e l y stable over the study period. A r i se in status of two r e l a t i v e l y low ranking ewes appeared related to the i r reproductive success. 5) Neither horn lengths nor body weights were shown to be strongly and cons is tent ly correlated to socia l status. Because aging techniques were 103 cons idered accurate on ly to s i x years of age, the r e l a t i o n s h i p between age and dominance could not be adequately i n v e s t i g a t ed . Aggress iveness ( i . e . number of i n t e r a c t i o n s i n i t i a t e d ) was the on ly v a r i a b l e found to be s i g n i f i c a n t l y and c o n s i s t e n t l y c o r r e l a t ed to s o c i a l s ta tus .^ B. Consequences of Dominance 1) Dominant animals were not shown to have higher q u a l i t y d i e t s than subord inate an imals , based on comparison of f e c a l N and time spent at supplemental f eed . I t was pos tu la ted that dominance dur ing feed ing i s b e n e f i c i a l to an animal on ly when both feed and feed ing spaces are l i m i t e d . 2) Dominant animals d id not have reduced feed ing t imes or increased bedding times compared to subord inate an imals . I t was pos tu la ted that s i m i l a r d i e t s r e su l t ed in s i m i l a r a c t i v i t y budgets. 3) Dominant animals were not shown to be more product ive than subord inate animals , in terms of seasonal weight f l u c t u a t i o n s , winter m o r t a l i t y ra tes or lamb p roduc t i on . I t was pos tu la ted that s i m i l a r d i e t s of the s o c i a l c l a s ses r e su l t ed in s i m i l a r l e ve l s of p r o d u c t i v i t y . C. Forage A v a i l a b i l i t y and Herd Behaviour 1) The herd ' s d i u rna l a c t i v i t y pa t te rn was cha ra c t e r i z ed by success i ve feed ing and bedding per iods in spr ing and summer. A c t i v i t y peaks gene ra l l y dec l i ned in number and increased in du ra t i on dur ing f a l l and winter pe r i od s . Al though daylength and weather cond i t i ons were shown to e f f e c t 104 a c t i v i t y pat terns to a minor degree, i t was pos tu la ted that reduced intake ra tes in the f a l l and winter r e s u l t i n g from de c l i n i n g forage a v a i l a b i l i t y were more d i r e c t l y r e spons i b l e f o r the increase in dura t i on of a c t i v i t y bouts dur ing t h i s per iod of the year . 2) Although day l i gh t g raz ing t imes were r e l a t i v e l y constant throughout the year , with the except ion of December and January va l ues , the propor t ion of day l i gh t devoted to feed ing gene ra l l y increaed from ea r l y spr ing ( A p r i l ) to l a t e winter (March). I t was pos tu la ted that animals compensated fo r reduced intake rates dur ing the f a l l and l a t e winter months by i nc reas ing nocturnal g raz ing pe r i ods . The reduced graz ing t imes in December and January co inc ided with the most inclement weather of the winter and a supplemental food supp ly , r e s p e c t i v e l y . D. E f f e c t s of P h y s i o l o g i c a l Cond i t i on on Da i l y A c t i v i t y Budgets 1) P r i o r to t h e i r w in ter deaths, most moribund animals demonstrated increased graz ing t imes r e l a t i v e to hea l thy an imals . Immediately p r i o r to death, moribund animals gene ra l l y had s i m i l a r g raz ing times but increased bedding t imes r e l a t i v e to hea l thy animals . 2) The feed ing and bedding t imes of pregnant ewes d id not d i f f e r s i g n i f i - c a n t l y from non-pregnant an imals . E. Energy Expendi ture Est imates f o r the Herd 1) Both average BMR's and day l i gh t a c t i v i t y cos ts f o r the ewes were higher in sp r ing ( Ap r i l to June) than in summer, f a l l and w in t e r . 105 2) I t was demonstrated t ha t , wi th the except ion of December and January va lues , the p ropo r t i on of day l i gh t energy devoted to those a c t i v i t i e s p rov id ing gross ene rge t i c re tu rns ( i . e . f eed i ng , bedd ing-ruminat ing) gene ra l l y increased from spr ing ( A p r i l ) to l a t e winter (March). 106 BIBLIOGRAPHY A lexander , G. 1961a. Energy expend i tu re and m o r t a l i t y i n new-born lambs. Proc. 4th I n t e r n a t l . Cong. Anim. Reprod . , 3:630-37. A l l d e n , W.G. and J . A . McD. Wh i t take r . 1970. The determinants of herbage in take by g raz i ng sheep: the i n t e r r e l a t i o n s h i p of f a c t o r s i n f l u en c i n g herbage i n take and a v a i l a b i l i t y . Aus t . J . A g r i c . Res . , 21:755-766. Altmann, J . 1974. Observat iona l study of behav iour: sampl ing methods. Behav iour , 49:227-267. A rno l d , G.W. 1960a. The e f f e c t o f the quan t i t y and q u a l i t y of pasture a v a i l a b l e t o sheep on t h e i r g raz i ng behav iour . Aus t . J . A g r i c . Res . , 11:1034-1043. . 1960b. S e l e c t i v e g raz i ng by sheep of two forage spec ies at d i f f e r e n t stages of growth. Aus t . J . A g r i c . Res . , 11:1026-1033. . 1962. The i n f l u ence of severa l f a c t o r s i n determin ing the g raz ing behav iour of Border L e i c e s t e r x Merino sheep. J . Br . G r a s s l . Soc. , 17:41-51. . and M.L. Dudz i n s k i . 1978. Etho logy of f r ee - r ang i ng domestic an ima l s . E l s e v i e r S c i e n t i f i c Pub l i s h i ng Co. Amsterdam, Oxford , New York. 198 pp. and R.A. M a i l e r . 1977. E f f e c t s o f n u t r i t i o n a l exper ience i n e a r l y and adu l t l i f e on the performance and d i e t a r y hab i t s of sheep. App l . Anim. E t h o l . , 3:5-26. A t k i n son , J . K . 1980. S tud ies on b ighorn sheep: I-Gross compos i t ion of mi lk over e a r l y l a c t a t i o n . I I -Determinants of e s t r u s c y c l e d u r a t i o n . B.Sc. t h e s i s , U n i v e r s i t y o f B .C . , Vancouver, B.C. B e i l h a r z , R.G. and P . J . My l r ea . 1963. Soc i a l p o s i t i o n and behaviour of d a i r y h e i f e r s i n y a r d s . Anim. Behav. ,11:523-533. , D.F. Butcher and A . E . Freeman. 1966. Soc i a l dominance and mi lk p roduc t ion i n H o l s t e i n s . J . Da i ry S c i . , 49:887-892. Bergerud, A .T . 1974. Ru t t i ng behaviour of Newfoundland c a r i b ou . In V. Ge i s t and F. Wal ther , e d s . , The behaviour of ungulates and i t s r e l a t i o n t o management, pp. 395-435. IUCN Pub. 24, Morges, Sw i t z e r l and . 941 pp. 107 B l a x t e r , K . L . , F.W. Wainman and R.S. W i l son . 1961. The r egu l a t i on of food i n take by sheep. Anim. P r o d . , 3:51-61. . 1962. The energy metabol ism of ruminants . Hutchinson and Co. ( Pub l i she r s ) L t d . , 178-202 Great Po r t l and S t r e e t , London. 329 pp. B lood , D. 1963. Some aspects of behaviour of a b ighorn herd. Can. F i e l d - N a t . , 77:79-94. Chappel,*R.W. 1978. B i oene rge t i c s o f Rocky Mountain b ighorn sheep Ovis canadensis canadensis Shaw. M. Sc. t h e s i s , U n i v e r s i t y of A l b e r t a , Edmonton. C o l l i s , K.A. 1966. An i n v e s t i g a t i o n of f a c t o r s r e l a t e d t o the dominance order of a herd of d a i r y cows of s i m i l a r age and breed. App l . Anim. E t h o l . , 2:167-173. Cra ighead, J . J . , F .C. Cra ighead, R.L. Ruf f and B.W. O'Gara. 1973. Home ranges and a c t i v i t y pa t te rns of nonmigratory e l k of the Madison Drainage Herd as determined by b i o t e l eme t r y . W i l d l i f e Monograph No. 33. 50 pp. Crook, J . H . 1970. Soc i a l o r gan i z a t i on and the environment: aspects of contemporary s o c i a l e tho logy . Anim. Behav. , 18:197-209. , J . E . E l l i s and J .D . Goss-Custard . 1976. Mammalian s o c i a l systems: s t r u c t u r e and f u n c t i o n . Anim. Behav. , 24:261-274. Dav i s , W.B. 1938. Summer a c t i v i t y of mountain sheep on Mt. Washburn, Ye l lowstone Nat iona l Park . J . Mammal., 19:88-94. and W.P. Tay l o r . 1939. The b ighorn of sheep of Texas. J . Mammal., 20:440-445. D i ckson , D.P. , G.R. Bar r and D.A. Wiecker t . 1966. Soc i a l r e l a t i o n s h i p of d a i r y cows i n a feed l o t . Behav iour , 29:295-203. Dudz i n s k i , M.L. and G.W. A rno l d . 1967. A e r i a l photography and s t a t i s t i c a l a n a l y s i s f o r s tudy ing behaviour pa t te rns of g raz i ng an ima ls . J . Range Manage., 29:77-83. , P . J . Pahl and G.W. A rno l d . 1969. Quantat ive assessment of g raz i ng behaviour of sheep i n a r i d a reas . J . Range. Manage., 22:230-235. 108 E i senberg , J . F . 1966. The s o c i a l o r gan i z a t i on of mammals. Handb. Z o o l . , 10:1-92. Espmark, Y. 1964. S tud ies on dominance-subord inat ion r e l a t i o n s h i p i n a group of semi-domest ic re indeer (Rang i fe r tarandus L . ) . Anim. Behav., 12:420-426. . 1974a. Soc i a l behaviour of roe deer at w in te r feed ing s t a t i o n s . App l . Anim. E t h o l . , 1:35-47. . 1974b. Dominance r e l a t i o n s h i p s as a p o s s i b l e r egu l a t i n g f a c t o r i n roe deer and re indeer popu l a t i on s . In V. Ge i s t and F. Wal ther , e d s . , The behaviour of ungulates and i t s r e l a t i o n t o management, pp. 787-796. IUCN Pub. No. 24, Morges, Sw i t z e r l a nd . 941 pp. E s t e s , R.D. 1967. The comparat ive behaviour of G ran t ' s and Thomson's g a z e l l e s . J . Mammal., 48:189-209. . 1974. Soc i a l o r gan i z a t i on of the A f r i c a n Bov idae. In V. Ge i s t and F. Wal ther , e d s . , The behaviour o f ungulates and i t s r e l a t i o n t o management, pp. 166-20l>7. IUCN Pub. No. 24, Morges, Sw i t z e r l and . 94~1 pp. F r a n k l i n , W.L . , A . S . Mossman and M. Do le . 1975. S o c i a l o r gan i z a t i on and home range of Roosevel t e l k . J . Mammal., 56:102-118. G e i s t , V. 1964. On the r u t t i n g behaviour of the mountain goat . J . Mammal., 45:551-568. . 1966. V a l i d i t y o f horn segment counts i n ag ing bighorn sheep. J . WiTd l . Manage., 30:634-46. . 1971. Mountain sheep: a study i n behaviour and e v o l u t i o n . The Un i v e r s i t y of Chicago P re s s , Ch icago. 383 pp. . 1974. On the r e l a t i o n s h i p of s o c i a l e vo l u t i o n and ecology i n ungu la tes . Amer. Z o o l . , 14:205-220. Graham, N. McC. 1964. Energy cos t s of f eed ing a c t i v i t i e s and energy expend i tu res of g raz ing sheep. Au s t r . J . Agr . Res . ,15:969-973. Hafez , E . S . E . , ed. 1969. The behaviour of domest ic an ima l s . 2nd ed. W i l l i ams and W i l k i n s Co . , Ba l t imo re . 647 pp. 109 Hancock, J . 1954. S tud ies of g raz ing behaviour i n r e l a t i o n t o g rass land management. I . V a r i a t i o n s i n g raz i ng hab i t s o f d a i r y c a t t l e . J . A g r i c . S c i . , Camb., 44:80-95. Harvey, W.R. 1977. Use r ' s guide f o r LSML 76: mixed model l eas t - squa res and maximum l i k e l i h o o d computer program. Ohio S ta te U n i v e r s i t y . Hebert , D.M. 1973. A l t i t u d i n a l m ig ra t i on as a f a c t o r i n the n u t r i t i o n of b ighorn sheep. Ph.D. t h e s i s , U n i v e r s i t y of B .C . , Vancouver, B.C. H i t chcock , C .L . and A. C ronqu i s t . 1973. F l o r a of the P a c i f i c Northwest: an i l l u s t r a t e d manual. U n i v e r s i t y o f Washington P re s s , S ea t t l e and London. 730 pp. Hoefs , V. 1974. Food s e l e c t i o n by D a l l ' s sheep (Ovis d a l l i d a l l i ) In V. Ge i s t and F. Wal ther , e d s . , The behaviour of ungulates and i t s r e l a t i o n to management, pp 759-786. IUCN Pub. No. 24, Morges, Sw i t z e r l and . 941 pp. Hughes, G.P. and D. Re i d . 1951. S tud ies on the behaviour of c a t t l e and sheep i n r e l a t i o n t o the u t i l i z a t i o n of g ra s s . J . Agr . S c i . , 41:350-366. Jarman, P . J . 1974. The s o c i a l o r gan i z a t i on o f ante lope i n r e l a t i o n t o t h e i r eco logy . Behav iour , 58:215-267. Joube r t , C . J . 1974. The s o c i a l o r gan i z a t i on of the roan ante lope Hippotragus equinus and i t s i n f l u en ce on the s p a t i a l d i s t r i b u t i o n of herds i n the Krager Nat iona l Park . In V. Ge i s t and F. Wal ther , e d s . , The behaviour of ungulates and i t s r e l a t i o n t o management, pp. 661-675. IUCN Pub. No. 24, Morges, Sw i t z e r l and . 941 pp. K i t chen , D.W. 1974. Soc i a l behaviour and ecology of the pronghorn. W i l d l i f e Monograph No. 38. 96 pp. K r a j i n a , V . J . and R.C. Brooke. 1969/1970. e d s . , Ecology of western North Amer ica . Pub l i shed by the Dept. of Botany, U n i v e r s i t y o f B .C . , Vancouver, B.C. 349 pp. Krebs , J . B . and N.B. Dav ies . 1978. Behav ioura l eco logy: an evo l u t i ona r y approach, pp. 1-18. Ed i ted by J . B . Krebs and N.B. Dav i s . Blackwel1 S c i e n t i f . P u b l i c a t i o n s . Oxford, London, Ed inburgh, Melbourne. 494 pp. L o t t , D.F. 1974. Sexual and aggress i ve behav iour o f adu l t male American b ison (B ison b i s o n ) . In V. Ge i s t and F. Wal ther , e d s . , The behaviour of ungulates and i t s r e l a t i o n t o management, pp. 382-394. IUCN Pub. No. 24, Morges, Sw i t z e r l a nd . 491 pp. 110 McEwan, E.H. and P .E . Whitehead. 1970. Seasonal changes i n the energy and n i t rogen i n t a ke i n re indeer and c a r i b o u . Can. J . Z o o l . , 48:905-913. Mech, L.D. 1970. The wo l f : the eco logy and behaviour of an endangered spec i e s . Natura l H i s t o r y P re s s , Garden C i t y , N.Y. 384 pp. Meyer, J . H . , G.P. Lofgreen and J . L . H a l l . 1957. S e l e c t i v e g raz ing by sheep and c a t t l e . J . Anim. S c i . , 16:766-780. M i l l e r , F .L . 1971. Behaviour of maternal b l a c k - t a i l e d deer (Odocoi leus hemionus columbiana) a s soc i a t ed w i th the death of fawns. Z. T i e r p s y c h o l . , 28:257-533. . 1974. Four types of t e r r i t o r a l i t y observed i n a herd of b l a c k - t a i l e d deer . In V. Ge i s t and F. Wal ther , e d s . , The behaviour of ungulates and i t s r e l a t i o n t o management. IUCN Pub. No. 24, Morges, Sw i t z e r l a nd . 941 pp. M i l l s , H.B. 1937. A p r e l im i na r y study of the b ighorn of Ye l lowstone Nat iona l Park. J . Mammal., 18:205-12. Moen, A .N . 1973. W i l d l i f e eco logy: an a n a l y t i c a l approach. W.H. Freeman and Co . , San F r anc i s co . 458 pp. Munro, J . 1962. A study of the mi lk y i e l d of th ree s t r a i n s of S c o t t i s h B lack face ewes i n two environments. Anim. P r o d . , 4:203-213. Ozoga, J . and L . J . Verme. 1970. Winter feed ing pa t te rns o f penned w h i t e - t a i l e d deer . J . W i l d l . Manage., 34:431-439. P i t t , M. and B.M. Wikeem. 1979. D ie t p re fe rence of C a l i f o r n i a b ighorn sheep on na t i v e rangeland i n sou th - cen t ra l B r i t i s h Columbia. Proceedings of the 1978 Northern Wi ld Sheep and Goat Conference. P en t i c t on , B.C. pp. 331 - 349. Re imers, E. 1980. A c t i v i t y pa t t e r n : the major determinant f o r growth and f a t t e n i n g i n Rang i fe r? In E. Reimers, E. Gaare, and S. Sk jenn ibe rg , e d s . , Proceedings of the Second I n t e r na t i ona l Re indeer/Car ibou Symposium. 17-21 Sep t . , 1979. Roros, Norway, pp 466-474. I l l Romesburg, H.C. 1981. W i l d l i f e s c i ence : ga i n i ng r e l i a b l e knowledge. J . W i l d l . Manage., 45:293-313. Ross, S. and J . Berg. 1956. S t a b i l i t y o f food dominance r e l a t i o n s h i p s i n a f l o c k of goats . J . Mammal., 37:130-131. Sche in , M.W. and M.H. Fohrman. 1955. Soc i a l dominance r e l a t i o n s h i p s i n a herd of da i r y c a t t l e . B r i t . J . Anim. Behav. , 3:45-55. Shack le ton , D.M. 1973. Popu la t ion q u a l i t y and b ighorn sheep (Ovis canadensis canadensis Shaw). Ph.D. t h e s i s , Un i v e r s i t y o f Ca lga ry , Ca lga ry , A l b e r t a . and C. C. Shank, i n p res s . Natura l h i s t o r y of Rocky Mountain and C a l i f o r n i a b ighorn sheep. Chapter 3. In Va ldez , R. e d . , The w i l d sheep of North Amer ica. Foundat ion f o r North American Wi ld Sheep. Sheppard, A . J . , R.E. B l a se r and C M . K i n c a i d . 1957. The g raz ing hab i t s of beef c a t t l e on pas tu re . J . Anim. S c i . , 16:681-687. S i l v e r , H . , N.F. Co lovos , J . B . Ho l t e r and H.H. Hayes. 1969. Fa s t i ng metabol ism of w h i t e - t a i l e d deer . J . W i l d l . Manage., 33:490-498. , , and . 1971. E f f e c t of f a l l i n g temperature on heat p roduc t ion i n f a s t i n g w h i t e - t a i l e d deer . J . W i l d l . Manage., 35:39-46. S i n c l a i r , A .R . E . 1974. The s o c i a l o r gan i z a t i on of the East A f r i c a n bu f f a l o . In V. Ge i s t and F. Wal ther , e d s . , The behaviour of ungulates and i t s r e l a t i o n t o management, pp. 676-689^ IUCN Pub. No. 24, Morges, Sw i t z e r l a nd . 941 pp. Syme, G . I . and L.A. Syme. 1979. So c i a l s t r u c t u r e i n farm an ima l s . Developments i n Animal and Ve te r i na r y Sc iences 4. E l s e v i e r S c i e n t i f i c P ub l i s h i ng Co . , Amsterdam, Oxford , New York. 200 pp. Thomson, B.R. 1971. Wi ld re indeer a c t i v i t y , Hardangerv idda, July-December 1970. Report o f Norwegian I . B . P . Statens v i l t u n d e r s o k e l s e r , Trandheim. pp. 1-83. Van Dyke, W.A. 1978. Popu la t ion c h a r a c t e r i s t i c s and hab i t a t u t i l i z a t i o n of b ighorn sheep, Steens Mounta in, Oregon. M. Sc. t h e s i s , Oregon State U n i v e r s i t y . 112 Waite, R., W.B. MacDonald and W. Holmes. 1951. S tud ies i n g raz ing management. I l l The behaviour of d a i r y cows grazed under the c l o s e - f o l d i n g and r o t a t i o n a l systems of management. J . Agr . S c i . , 41:163-173. Wagnon, K.A. , R.G. Loy, w.C. R o l l i n s and F.D. C a r r o l l . 1966. Soc i a l dominance i n a herd of Angus, Here fo rd , and Shorthorn cows. Anim. Behav. , 14:474-479. Wal ther , F.R. 1978. Behaviour observa t ions on oryx ante lope (Oryx be isa) i nvad ing Serenget i Nat iona l Park, Tanzan ia . J . of Mammal., 59:243-260. Whi te, R.G. and J . T r u d e l l . 1980. Pa t te rns of he rb i vo ry and nu t r i e n t i n take of re indeer g raz i ng tundra vege t a t i on . In E. Reimers, E. Gaare, and S. Skjenneberg, e d s . , Proceedings o f the Second I n t e rna t i ona l Re indeer/Car ibou Symposium. 17-21, Sep t . , 1979. Roros, Norway, pp. 180-195. W i l son , E.O. 1975. Soc i ob i o l ogy : the new s yn t h e s i s . The Belkap Press of Harvard U n i v e r s i t y P re s s , Cambridge, Massachusetts and London, England. 696 pp. Woolf , A . , T. O'Shea and D.L. G i l b e r t . 1970. Movements and behaviour of b ighorn sheep on summer ranges i n Ye l lowstone Nat iona l Park. J . W i l d l . Manage., 34:446-450. t 113

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