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Sexual segregation and group sizes of California bighorn sheep Ashcroft, Gregory Edward William 1986

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SEXUAL  SEGREGATION  AND  GROUP  SIZES  OF  CALIFORNIA  SHEEP  By GREGORY B.Sc.,  EDWARD  The  WILLIAM  University  of  Berkeley,  A  THESIS THE  SUBMITTED  IN  REQUIREMENTS MASTER  ASHCROFT  California  at  1983  PARTIAL  FULFILLMENT  FOR  DEGREE  OF  THE  OF  SCIENCE  in THE  FACULTY  OF  GRADUATE  (Department  We  accept to  THE  this  the  of  thesis  required  UNIVERSITY  OF  October, ®  Gregory  Edward  STUDIES  Forestry)  as  conforming  standard  BRITISH  COLUMBIA  1986  William  Ashcroft,  1986  OF  BIGHORN  In p r e s e n t i n g  this thesis  i n partial  f u l f i l m e n t of the  r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y of B r i t i s h it  Columbia,  freely available  I agree that f o r reference  agree that p e r m i s s i o n  the Library  shall  make  and study.  I further  f o rextensive copying o f t h i s  thesis  f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e h e a d o f my department o r by h i s o r h e r r e p r e s e n t a t i v e s . understood for  that  copying or p u b l i c a t i o n  f i n a n c i a l gain  forestry  Department o f The  University Main  fi/ft'-n  Canada  1Y3  Date  DF-6  of British  Mall  Vancouver, V6T  6  O c t o b e r  >  1  9  8  thesis  s h a l l n o t be a l l o w e d w i t h o u t my  permission.  1956  of this  It is  6  Columbia  written  Abstract  I  investigated  canadensis revealed  californiana  that  male  during  the  three  period  (or  rut). O f  78  percent  found  crude  protein  between and  but  in  differed not  males  maternal two  suggests group  group  among that  sizes.  males  that  groups  spring  during  or  females,  the  with  Food  males percent  the  not  differ  and  bedding  (P<0.05).  group  size  is  (P>0.05).  Comparisons a  and  misleading  percent  consumed  group  of  the  and  table  in  of  two  summary  fecal  winter differed  maternal size  statistic  shrubs  time  analysis. or  rut,  the  percent same  group  the  of  also  season,  and  spatially  mating  size, behaviour,  within Male  78  Results  percent  females  in w i n t e r  contingency  significantly  outside  72  grasses, during  of  fall  segregated,  habits  having  interaction  non-parametric  did  comprised  males  the  females  rut. W h i l e  between  of  (Ovis  Columbia.  temporally  outside with  sheep  British  segregated  rams  summer.  ate 80  using  seasons  were  mature  bighorn  south-central  associated  significantly  foraging  mean  sheep  yet  concerning  sizes  in  California  (winter.spring.summer)  females  tested  behaviours,  differed  in  and  Hypotheses were  the  of  1829)  female  immature,  trees, while  season  and  mixed  segregation  Douglas  seasons  were  males  (P<0.05),  sexual  period.  sex  and  Male  and  between group  sizes  measures for  reporting  Table  of  Contents  iii  Abstract  ii  List of Figures  iv  List of Tables  v  Acknowledgements  vi  CHAPTER ONE -  GENERAL  INTRODUCTION  STUDY AREA  1 3  CHAPTER TWO - SEXUAL SEGREGATION  7  INTRODUCTION  7  METHODS  9  RESULTS  13  Plant Phenology  13  Sexual Segregation  15  Crude Protein  17  Food Habits  20  DISCUSSION  20  CHAPTER THREE - GROUP SIZE  29  INTRODUCTION  29  METHODS  32  RESULTS  34  DISCUSSION  .42  LITERATURE  CITED  52  iv  List  Figure  1.1. M a p  Figure  2.1. P h e n o l o g y  Figure  of  the  study  of  of  Figures  area  three  5  grass  species  on  the J u n c t i o n  2.2. P e r c e n t a g e d i s t r i b u t i o n o f m a l e s b y horn i n c l u d e d at l e a s t o n e a d u l t f e m a l e ; c o n t r a s t i n g males)  Figure  2.3a. Locations  of  male  and  maternal  groups  sheep  range  c l a s s , in groups w h i c h four seasons (n=422 16 outside  of  the  fall  mating  period Figure  Figure  18  2.3b. L o c a t i o n s mating  14  of  male,  mixed,  and  maternal  groups  during  the  fall  period  3.1. Frequency d i s t r i b u t i o n population (n=544 groups)  19 of  all group  sizes  for  the  Junction  sheep 33  Figure  3.2. P e r c e n t c u m u l a t i v e f r e q u e n c y d i s t r i b u t i o n o f all g r o u p s i z e s , f o r the J u n c t i o n sheep population. The frequencies of groups and individuals are contrasted 35  Figure  3 . 3 a . R e l a t i v e p e r c e n t f r e q u e n c y o f g r o u p s in e a c h g r o u p s i z e c a t e g o r y , for the J u n c t i o n bighorn sheep p o p u l a t i o n b e t w e e n M a y , 1984 and J u l y , 1985 38  Figure  3.3b. R e l a t i v e p e r c e n t n u m b e r o f s h e e p in e a c h g r o u p s i z e c a t e g o r y , the J u n c t i o n bighorn s h e e p p o p u l a t i o n b e t w e e n M a y , 1984 and J u l y , 1985  Figure  3.4. P e r c e n t c u m u l a t i v e f r e q u e n c y d i s t r i b u t i o n o f d e s e r t g r o u p s i z e s (data are f r o m H a n s e n 1980). T h e f r e q u e n c y groups and individuals are contrasted  for 38  bighorn sheep distributions of .43  V  List  Table  2.1.  Mean  percent  fecal  crude  of  Tables  protein  for  the  Junction  sheep  population,  1984-1985  21  Table  2.2. F o o d h a b i t s o f the J u n c t i o n s h e e p p o p u l a t i o n , d e t e r m i n e d b y f e c a l f r a g m e n t s a n a l y s i s . S e a s o n a l mean percentages for m a l e s and females a r e p r e s e n t e d w i t h s t a n d a r d d e v i a t i o n s in p a r e n t h e s e s . D a t a w e r e c o l l e c t e d in 1985 22  Table  3.1. M e a n g r o u p s i z e ( x ) a n d t y p i c a l g r o u p s i z e ( g ) s u m m a r y the J u n c t i o n bighorn s h e e p p o p u l a t i o n . Data w e r e c o l l e c t e d b e t w e e n 1984 a n d J u l y , 1985  Table  3.2.  Results  of  2X4  G-tests  comparing  group  sizes  among  seasons  for May, 36 39  vi  Acknowledgements  First,  I thank  opportunity, project.  To  and Dr.  indispensable of  working  expended  my  for  his  D.M.  the  time  hypotheses;  he  provided  suggestions  on  the  drafts two  many  of  the  year  Gillingham Creek,  B.C.  assisted all my help  and  of  the  sincere of  Ministry  graduate some  of  project  and  can  Dr.  of  S.  the  the  the  for  privilege  Shackleton  helpful  product. and  Dr.  on  D.R.  M.  Grieg,  Walker  sheep  over  Dr.  of  M.P.  and  assistance. to  successfully  a  Riske  herd  field  Seip  earlier  interactions  contributed  completed  of  workable  valuable  who  research  grateful  for  D.M.  through  provided  be  and  stages  advice.  knowledge  most  many  ideas.  this stages  am  Dr.  final  planning  unmentioned,  I in  his  the  the  all  formulate  students,  J . Brooke and  live Area.  me  statistical  considerable  no  the  during  to  improved  during  provided  logistics.  for  cabin  helping  providing  Branch,  Management  greatly  stimulate  mentioned  Wildlife  encouragement,  fellow  for  the  To  project,  without  the  people.  Council  Scholarship student.  winter  project  of  his  Bunnell  suggestions  splendid  effort  much  Hovey  thanks,  good  The Research  F.W.  F.L.  B.C.  Wildlife  and  My  helped  people  a  comments  thesis.  imparted  with  the  manuscript  useful  period,  of  Junction  Dr.  pertinent  support,  substantial  provided  many  Hebert  logistic on  supervisor  was of  Canada  Environment. provided  funded  A  by  under  the a  Canadian  personal  support  Natural grant  to  Forestry  Sciences Dr.  F.L.  Service  throughout  my  and  Engineering  Bunnell,  and  by  the  Post-Graduate tenure  as  a  graduate  B.C.  1 CHAPTER  It  is  American First, the  unclear  ungulates.  males  future  without  maximize  rut  to  are  the  breeding  separate  by  segregation of  males'  Second,  most  North  have  been  from  female  ranges,  offspring  access  to  males  males  are  in  explanation  different  Third,  which  INTRODUCTION  moving  onto  satisfied.  predators  sexual  classes  competition.  best  avoid  general fitness  requirements,  requirements  GENERAL  their  of  male-female  -  encourages  Three  mothers  nutritional  the  what  ONE  and  females,  ranges  where  move  attracted  from  by  in  allowing  better  forage,  having  disparate  these  female  males  tendered.  ranges  their  after  weakened  state.  Geist  and  canadensis) separated  on  Petocz the  different  forage.  They  male  offspring  would  Such  a  further the  of  be  also  reasoned  would that  hierarchy rank.  range  males  ranges.  to  reduce  females'  bighorn  sheep  females  were  and  They  hypothesized  competition  competition  the  (1979) .working  separation  dominance  winter  that  Mountain  with  ability  with  females  to  rear  that  c_  males  females  would  the  (O,  lead  for to  males'  enhanced.  with  social  Rocky  found  reduced  because  competition  postulated  the  that  fitness  studying  Range,  common  parts  McCullough virginianus')  on  presumed  increased  reduce  Palliser  spatially  utilized  (1977),  This  them lead  for  by  that  with  males, and to  males  white-tailed by  thus  enhance  increased to  breed  associating with  competition  moving  would  deer away  the  fitness  (Odocoileus from  survival of  the  males  discourage  to  of  their  breeding  s u c c e s s f u l l y , they  other  females,  reach  must a  non-breeders  should offspring.  males. work  higher from  He up  2  remaining  with  Lenarz associated  not  (1979)  with  Segregation was  females  females  occurred  seasonal  and  males  energetic  requirements  potential  for  natural  of  males  compete  for  per  body  of  Larger  weight  groups  were  (1982) w o r k that  the on  different  females  were  greatest  during  higher Bowyer that  quality  result red  deer  nutritional major  forage  than  (1984) w o r k i n g in  on  water  that  1982;  Darwin  ones,  with  (Hudson  (1977),  and to  better  (Cervus  elaphus)  males  and  southern  in  areas mule  requirements,  a  use  such  metabolic  requirements  studied  deer  the  in  of  of  them of  areas.  same  diet maternal  Clutton-Brock  led  sheep,  to  consequence  (1982)  of  Via  bighorn  ability  behaviour of  nutritional  1982).  as  their  areas.  females  where  the  consequence  members  Scotland,  and  a  in  and  foraging  the  lessened  differences  of  differential  shortage, in  use  He  reduced  that  range,  differential  food  Shank  concluded  Breeding  periods.  Shank  possible  1985).  their  to  species  a  and  is  1871;  lower  smaller  long  differences  ai.  requirements  of  for  s e g r e g a t i o n ; _ L e . it  can  lambed.  fitness.  engender  contributors  periods  differences  et  access  of  increasing  nelson])  continuously.  harassment,  is  c,  parturition,  enhance  Petocz had  reduced  at  which  Geist  which  ranges  characteristics  range  rams,  females  mammal  requirements  between  the  (0,  females  polygynous  nutritional and  most  not  to  bodies  than  when  thus  sheep  although  segregate  leads  resources.  bighorn  year,  female  via  sexes  different as  the  competition,  sexual  mates.  the  females  sexes  desert  period  left  why  limited  accompanied  (Clutton-Brock  secondary  unit  of  between  selection,  develop  males  having  view  selection  the  for  male  throughout  intraspecific  requirements  that  during  that  Another  competing  reported  reasoned  sexual  and  to  et  aj.'s  suggest  males  and  Segregation  was  may  have  obtained  were  more  concentrated.  deer  (Qdocoileus  form  of  hemionus).  nutritional  difference  proposed  3  between  males  A moved when  third away  view, from  the males  insufficient The  and females  these  and  habitats after  within  and Hudson  those  ranges.  t h e rut t o r e d u c e  behaviour  outside  The Junction respect  major  Wildlife t o their  presented Chapter  Management  Area,  study  is located  in w i n t e r ,  51°45'N  bounded  on t w o sides  of  biology.  focus to find  the predator  males  predation  sheep  be unable  Rocky  of  hypothesis  would  males  avoidance  deer.  Mountain  although  that  expenditure  research Area  they  leave  male-male  w a s h o w bighorn  were  chapter.  area, c o m m o n l y  latitudes  that  suggested  3 compares  approximately  would  of  in w h i t e - t a i l e d  observed  distributed  bighorn  ram  used  different  female  groups  agonistic  Sexual  known  between  o n the  and space  Specific  segregation  sizes  with  hypotheses  is treated  are  in  sexes.  AREA  as the Junction Wildlife  16 k m s o u t h  a n d 51°54'N, a n d l o n g i t u d e s by the Chilcotin  sheep  in t i m e  environment.  group  STUDY  The  predators  this  males  period.  in each  Chapter  aspects  considered  c o n s p e c i f i c s a n d t o their  and evaluated  2, while  my  that  the risk  considered  other  predators  ranges  They  the mating  of  of  segregation  the energy  focus  state. They  (1979)  (1981)  the s a m e  (1977), w a s that  the rut t o m i n i m i z e  a n d that  to explain  used  and Petocz  in v i e w  McCullough  inadequate  e w e groups  after  segregation.  o n the premise  groups,  groups.  Morgantini  Geist  segregation  w a s based  that  sexual  in a w e a k e n e d  to explain  on female  hypothesis  by  the f e m a l e s  primarily left  proposed  were  hypothesis  caused  of  Riske  Creek  122°22'W  and Fraser  Management  B.C. between  a n d 122°35-W.  It i s  Rivers. The confluence  of  4  the of  two the  rivers sheep  did  not  the  entire  The  females larger  all  range  Fraser  River  basaltic  lava  undulating  the  two  the by  flat  top  of  rivers  at  Junction  grasslands  rain  by  facing  shadow,  annual  facing  plant  population at  Fish  from  as  sub-arid by  the  (about  of  the  by  320  to  Douglas-fir Mitchell  m  elevation sea  Sharp  terrain  Mountains  for  to  annually).  the  used  a  are  level  cliffs  the  are  in  sheep.  typically  (Valentine  the  (Artemisia  tridentata)  a  et  west, vegetation  provided  (at  rise  The  fPseudotsuga  (1973)  on  gently  above  plain).  sage  of  Rivers  a  climate  big  Most  Chilcotin  sub-humid  mm  Gulch  flat-lying,  which  Coast  land  boundaries.  chernozemics to  and  370  2  males, which  sharply  escape  brown  communities  and  top  serve  s l o p e s , and  about  km )  because  Ross  River.  and  menzieziH  is  on  detailed  communities.  survey  305 and  a  rise  85  by  past  underlain and  or  Chilcotin plateau. The  the  dark  created  slopes. Demarchi of  and  are and  (at  (about  foot  while  Fraser  which  on  area  is  area  population  Chilcotin  study  the  the  ranges  precipitation  grassland  south  B.C.  terraces  both  population the  silt  above  the  Here,  and  m  the  study  area  rivers,  round  Basin, which  1976).  1070  characterized  A  (Holland  year  outside  both the  the  sheep  efficiently  on  of  study  entire  along  area  Fraser  about  low  description  the  The  the  Canyon  ranged  found  with  on  in  by  survey  study  boundary  1.1).  upstream  were  to  to  Farwell the  the  sheep  1978). A  produces  within  on  rivers)  associated  past  (Figure used  ranges  gravel  plain  Soils  north  large  lies  by  where  stands  too  flows  immediately  ai.  was  females,  area  characterized  areas  range  remained  The  range  the  and  than  southernmost  of  population  area  the  population's  cover  vehicle. the  constitutes  in  March  1984  estimated  sheep  (females,  lambs,  and  Wildlife  Branch  estimated  the  the  maternal  yearlings). population  Aerial  segment  of  censuses  including  males,  Figure Fraser  1.1. M a p of the study area. The R i v e r s d e m a r c a t e the b o u n d a r i e s .  dashed  line  and  the  Chilcotin  and  6  at  400  in  North  yrs-old  to  500  sheep,  which  A m e r i c a . Currently, or  full  curl  makes hunting  minimum)  and  it  the  largest  permits five  are  females  California limited each  to  year.  bighorn nine  sheep  males  (>6  herd  CHAPTER  TWO  -  SEXUAL  SEGREGATION  INTRODUCTION  Limitations sheep  populations  (1985a)  about  Stelfox 15  Weight  Hudson  spring  than  spring.  The  (Oftedal  compete (Geist  1971).  growth with  mates  associated  competition when  small  relative  maximize  If caused  much  less  when  food  energy  for  Males late  for  the  (1978) and  high  and  and  are  intake  for  via  limited,  by  if  is  much  and  at  (Chappel  lactation costly  size  to  and  be  meet  the  fitness horn probably  limited,  apparent  would  are  better  are  when  during  of  their  weather,  during  greater  latitude, ram  spring  to  available  also  resources  females  of  libitum  of  most  dalli  sheep.  increase  60°N  be  opportunities  and  to  (O,  bighorn  more  horn  spring  early  seasonally  are  Bunnell  losses  be  demands  forage  should  and  should  Geist  with  during  males  foraging  segregation  conducted  Thus,  least, and Both  even  ad  may  forage  ultimately  that  females  Mountain  and  sheep  weight  available  the  Seip  Stone's  forage  body  correlated  production.  males  and  and  reported was  was  north-temperate  spring.  for  Rocky  lactation  fall,  and  quality  increase  for  overwinter  quality  pregnancy  must  in  demand.  segregation,  of  high  females,  primary  competition  studies  demands  resources to  reported female  more  food  winter  for  April  between  winter  sheep  in  during  (1970)  of  winter  weight  Bunnell  began  quality  during  limitation  trimester  1985).  for  likely  Although  costly  and  fall  winter,  third  energetically two  were  in  most  McGillis  of  1978).  quantity  food  and  percent  losses  the  are  documented  stonei):  and  to  during  resources expected  these  to  demands.  variable  vegetative  resources  outside  the  times.  relax Petocz  (1977)  and  critical Shank  are  The  (1979;1982),  8 focussed  only  temporal  pattern  range  on  the  winter  range  of  of  dispersion  of  male  an  annual  throughout  during  the  relaxed  critical  outside  Three sexual  these  types  or  do  male  Second,  if  groups  are  single-sex  groups  used  completely  period, the  they  same  were  were  space  not  segregation  Locations individuals  of  not  and  males  population. same and  I  groups. females  overlap,  different  during  and  Using  of  early  and  groups? it  If  was  measured  the  and  the  Junction  segregation  spring,  they  spatial  occurred if  2)  survey  these  rules,  working occur  a  contained  group  use  a  the  sexes  time  segregation  same  during  period,  but  the  if  for  same  at  least  one  group. units?  If  considered if  a  not  hypotheses  in  spatial  were  Conversely,  definitions  mixed-sex  component,  s p a c e , but  same  the  females  units,  a  same  in  considered  segregated.  classified sexes  females  first  used so,  ranges  overlapped,  times?  Each  in  the  these  space  same the they three  were and  used  time.  male-only  and  different  survey  single-sex  groups  simultaneously,  concerning  of  areas,  or  not  sheep or  to  The  independently  whether  locations  was did  groups  occurred  evaluated  Second,  of  if  on  I  used they  sexual  tested.  both  if  the  the  sheep  1)  included  invoking  considered  were  and  males  female,  used  segregated.  were  adult  Third,  groups  female  determine:  s i n g l e - s e x e d , do  segregated.  maternal-only  and  population.  times.  separate  adult  migratory  winter  separation  form  one  to  late  First, do  they  and  of  critical  of  segregation.  groups adult  times  cycle  a  tests  of  one  males  were  different  determine  and  used  use  same  the  possibilities  areas  was  another females  e. if  did  male  simultaneously,  evaluated  in  whether  for  the  of or  the  occurred  determine  a r e a s ±,  significant? Third,  dispersion  determined  to  overlap  the  their and or fall  if  in  the  males ranges female  at  different  rutting  9  period,  and  To and  detect  females,  well et  outside  wild  1985),  fecal  rumen rate.  and  protein  does  used  not  as  an  ingested  content  index  to  to  the  Fecal  of  the  Shank  test  significantly  forage  measured.  directly, would  samples  differ  was  1985b;  more  fecal  in  energy  Bunnell  values  collected  protein  digestible  been  (Seip  nitrogen I  rut.  differences  crude  with  has  sheep  the  potential  correlated  aj..  of  quality  crude  forage  of  1979).  Killing  induce  much  between  males  1973;  forage sheep too  that  and  males  protein, which  (Hebert  quality  hypothesis  between  Wofford  ingested  to  by  obtain  high  a  percent  females  is  mortality crude  within  seasons.  Seasons this  study,  more  are  plant  often  defined  phenology  meaningful,  arbitrarily,  was  definition  for  measured  from  to  a  cultural  provide  an  point  of  view.  ecological,  and  In  thus  season.  METHODS  The 8-10  h  study  area  was  divided  to  search  completely  during  the  limited  daylight  hours  major  topographic  features  such  boundaries.  Survey  within  after  1  h  sunrise  traversed.  Five  the  area. For  study  routes  survey  and  were and  days  each  days)  thus  beginning  ensured  that  end  all  as  five  blocks,  small  enough  winter. large  constant  block,  The  procedure  in  (one  surveys. the  was  continued  successive was  into  the  circuit) were I  alternated for  each  for  that  block  in  a  and  throughout until  block  to  blocks  draws  point  areas  The  each  in  were  the  beginning in  the  were  one next  completely  cliffs,  study.  to  for  using  as  Surveys that  began day  was  completely  search  and  points  ending  survey survey  surveyed  required  demarcated  route  required  block  which  survey  steep  entire  the  of  at  week week.  different  (5 This times  in  in 108  successive sheep  August  circuits.  surveys  1984,  completed,  Sheep  between  recording  circuits  and  binoculars  and/or  minimize  disturbing  routes  females  males  of to  into  consistently  group  type,  immature  the  horn  were  as  only,  development because  least  one  except  immature  was  very  50  6  circuits  with  km,  to  were  scope.  Distances  of  Care  was  8x30  often  composition  disturbance  May  completed.  eye,  2  conducted  I  From  necessary.  to  Maternal  and  groups  females,  requiring  groups was  high  was  taken  unavoidable  I  (Geist  1968).  defined  sensu  (Geist  1968).  long  distances between  and  one  The  groups  fourth of  it the  other  this  consisted  lambs,  were  males.  were  as  spotting  Class  male  winter,  naked  which  at  rare;  and  m  1985  to because  used.  distinguish  adult  the  30,  observations.  fall  class  recognized.  identified  accurately  males,  sheep  males  sheep  scope  Occasional  yearling  class,  with  the  June  circuits  from  by  areas  males  7  age-sex  aided  sheep.  types  1985,  ranged  and  During  spotting  l o c a t e d , the  adult  and  at  20-45X  observer  were  one  contained  scanning  yrs-old),  males  according  by  intersected  (>2  composed  located  usually  group  Immature  July  Once  recorded,  Four  to  a  1984  individual  April  and  carefully  5196  15,  successive.  with  subject  May  were  from  were  magnification.  survey  Between  as I  groups  class  II,  grouped  III,  and III  was  impossible  to  two.  Mixed from  type, type  males.  were  class  group  adult  immature  Male  sheep  last  and  of  IV and  IV  groups the  maternal  exclusively  were  excluded  from  analysis.  To 95  percent  evaluate  confidence  Presence/absence proportions  the  of  of  proportions intervals  males  mixed-sex  and groups  of  were  mixed  calculated  females and  groups  in  each  single-sex  for  and  of  each  group groups,  single-sex  groups,  proportion.  were were  tabulated,  and  contrasted  for  the  the  fail  rutting  intervals  followed  To  of  The  utilizing sheep  the  1-km ,  Pielou  knowledge  of  Sokal  Rohlf  and  'model level  I'  in  for  the  all  number  of  circuit,  by  were  the  of  area  Fecal  by  them  get  to  individuals. compare protein  of  up Shank  sex  and  values.  to  be  are  not  was  tested  is  The  using  was the  G-test  Fienberg  with  no  1980;  prior  recommended  G-test  fixed. The  by  contained  type  1949;  test  the  analyzed  cells  group  (Cole  sheep,  topographic  performed  taken.  regime  73  each  was  was  of  groups  maps;  of  a  for  priori  by  their significance  a =0.05.  and  females  were  estimated  c l a s s i f i c a t i o n (males  blocks  surveyed.  Each  mean  densities  for  and  circuit  by  dividing  maternal)  provided  the  seen  per  a  male  and  maternal  ranges  males  and  females  during  samples.  collected (1984),  then  measured  classes  variation  both  (1984)  and  winter  (1985).  watching  and  waiting  (from  collecting  the  fecal  during was  from  fall  sheep,  defecate,  age  This  was  bedded  (1979)  confidence  1:50,000  correction  Sampling  totals  sex/age  the  on  females  sampling  males  summer  and  the  distribution  topographic  Williams  samples  this  of  were  locating  for  maternal-only  and  1981).  marginal  the  samples  males  tests  marked  presence/absence  the  overall  from  (1984,1985),  obtained  of  of  each  sample;  calculated  spring  the  densities  sheep  standardized  cell,  for  statistical  Relative  cells  Rohlf  (1981)  first  on  number  which  were  grid  incorporating and  spatial-temporal  and  each  Sokal  it. C a l c u l a t i o n s  male-only  association  tables, 1977;  of  For  of  (1977).  sighted  UTM  J  then  outside  spatial, and  sheep  locations.  2x2  the  dispersion  tabulated, for  all  and  Cochran  evaluate  locations maps.  period,  crude  winter  probably  feces  protein,  because due  to  of  of but  Samples a  were  distance)  for  classified was  wide  collecting  unable  variation few  to in  samples  crude on  each of  collection  wide  variation  quality,  within  were  ground  large  attributable  minimal  Samples  associated  collected  I  Variability be  day, and spreading  mill  using  Kelowna  B.C. A n a l y s i s  was time  used  and then  with  a  results  protein  by  to compare  sample  fecal  changing  sizes  multiplying  by  crude  protein  then  nitrogen  for 24-36  Branch  were  h,  f o r total  laboratory  then  1984).  to  frozen.  and analyzed  Studies  between  intervals.  w a s expected  at 6 0 ° C  6.25 ( W i l l i a m s  forage  time  air dried  screen  at t h e T e r r e s t r i a l  short  quality,  oven  mesh  problems  and changing  were  in a c o n v e c t i o n  fecal  T o reduce  within  forage  The samples  in percent  time.  samples  1 - m m wire  percent  same  pellet  were  fecal  taken  composite  sample.  Analysis  Laboratory  Plant sampled  using  in  converted  Student's  to  £-test  the sexes, within  a  each  slides  of  used  were  sampled,  stations.  To avoid  trampling  during  different  direction  was followed  pellets  each  to define  each with each  outward  were  were  per  located  were  successive  time  for  period  at  60°C,  Microscopic  sample.  boundaries at v a r i o u s  (about  were elevations  marked. 2  sampling  the marking  used  Composition  permanently  t w o strides  from  fecal  dried  screen.  season  transect  from  groups  University  20 fields  The transects of  State  assembled  to a separate  1-mm wire-mesh  b y the Colorado 5  Fecal  were  analysis. Three  1 2 - 2 3 pellet  corresponded  samples.  with  the beginning  per transect  8  analysis  nitrogen  group;  sample  transects  per month.  habits  for fecal  pellet  of  mill  performed  aspects, with  stations  a total  phenology  twice  each Each  in a W i l e y  were  for food  obtained  from  sex, comprising ground  samples  groups  analyses  and  dried  over  period.  pellets each  of  periods.  an a u t o - a n a l y z e r  Composite .the  numbers  subsequently  crude  small  to seasonally  nitrogen  percent  with  collection  in a W i l e y  collections  m)  separating  period,  post.  Twenty  I  a recorded  recognizable stages  recorded  initiation, 1973;  growth  4)  five  stations  season  were:  full  Kamstra  stages  flower,  1973). per  bluebunch  macrantha)  were  simplicity,  only all  5)  For  The  any  three  three  species  (1973)  found  during  the  later  during  the  summer  that  stages of  (Apropyron  had  plant  6)  plant  station. The  growing,  seeds  3)  the  disseminated  species  was  spicatumV  were  cast  used  their  growth.  to  little  For  (Demarchi  define by  used grass  season  reason  to  least define  (Xoeleria For  boundaries.  mid-August. in  at  (Stipa  grasses.  difference  this  in  junegrass  occurring  seeds  was  and  growth  floral  species, representation  commonly  y e a r s , there  of  each  species, needle-and-thread  species  between  at  leaves  before  widespread,  three  forbs  and  required grass  these  1984  ripe,  particular  was  most  and  i n i t i a t i o n , 2)  seeds  wheatgrass  the  During  grasses  growth  transect  boundaries.  comata).  1)  of  Hebert  phenology  I did  not  sample  1985.  RESULTS  Plant  Results temperature and  the  late  of  growth late  prior  was to  June-early  April, July  events,  initiation Floral  in  disseminating  in  to  with  floral  initiation  three  species.  all  such  2.1), as  provided  combined lambing  an  was  early  in  July. The  needle-and-thread in  late  with  (April,May)  empirically-based  needle-and-thread  initiation  similar  for  (Figure  (October,November),  1985.  began  very  sampling  specific animal  Growth  April,  and  phenology  period  seasons.  ripened  wheatgrass  and  mating  March-early  seeds  plant  regimes  fall  definition  from  Phenology  grass  occurred  May-early trend  for  grass. Junegrass  early-mid  May.  Seeds  in  June; bluebunch initiated ripened  in  14  SPRING so  SUMMER  AQrppyron spicatum  SR  FF  FI  GR  GI  SD  UJ CD  ftoeteria macrentha  6—0—0-  SR  -o—o  o CD  GR  o—o—o  GI  SD  Sf/r>a comafe  SR  •  FF  /  ID—•  •  FI GR GI  • 5/4 T985 — •  J9/4  2/5  18JS  2/6  17/6  2/7  9/7  2l/7  »/8 t2/8  7984 — •  DATE  Figure 2.1. P h e n o l o g y o f three grass s p e c i e s o n t h e J u n c t i o n G I = g r o w t h i n i t i a t i o n ; G R = l e a v e s g r o w i n g ; FI = f ( o r a l i n i t i a t i o n ; FF=full flower; SR=seeds ripe; S D = s e e d s disseminated  sheep  range.  15  Spring early  April.  ceased  to  October  began Summer  grow  and  period  when began  (July).  (December), long  summary,  spring  September; January,  Onset  and  to  included was  February,  initiated  spring  of  and  ended  winter  April,  of  markedly None of  of  males  Few and  the  with  adult the  groups  110  male  rut  groups  males  >2  percent  found  in  differed small  and  (219)  groups widely  percentage  period  the  plants  in  post-rutting of  1984-1985  ended  in  early  summer  was  July,  included  mixed  only  5.4  there  groups  which  ±2  reflecting at  was  March.  August  In  and  December,  the  with  of  large  groups  males  outside of  much  differed  rest  of  the  significant these  year.  associations  three  seasons.  of  the  rutting  period,  groups  >2  sheep,  mixed  of  groups).  552  47  larger  percent  In  ±8  numbers  contrast,  percent  of  (of  adult  time.  found at  the  among  was  that  groups  statistically  groups  males  of  and  (30  of  that  rut,  percent  outside  from  or  small;  seen  included  same  females  mixed  females  groups the  of  the  differences  was  percent  proportion  in  showed  associated with  of  of  and  to  Segregation  period,  were  encountered),  all  rutting  set  winter  which  winter  corresponds  were  as  March. The  females  seasons  nor  associating with  Among 78  sheep  the  fall  defined  November;  mating  non-rut  proportion  the  fall  females,  comprised  during  males  the  three  seeds  the  June;  which  March.  of  between  was  and  Sexual  Occurrences  when  1983-1984  May,  and  growth,  until  through  that  October  new  continued  continued  compared  fall  and  Summer  November.  relatively  grasses  least  the  rut,  immature  females.  one  formed  female during  associated with  The  males  distribution  outside the  comprised  rut  females  of  the  (Figure  outside  of  males  rut, 2.2).  of  the  A  very rut.  100  [Z2  winter  ESS s p r i n g  II  KI3  summer  O  fall/rut  lll+IV  H o r n C l a s s of Males  Figure  2.2.  Percentage  distribution  of  males  by  horn  class,  in  groups  which  included  at  least  one  adult  female;  contrasting  four  seasons  (n = 4 2 2  males).  0>  During possible  19  1387  females  in  enclosing  male  groups,  at  least  males  and  55  male, the  rut  (35  of  same  grid  sheep  of  (Figure 55)  mixed  2.3b).  included  Of both  females  during  females  ( P < 0 . 0 5 ; d f = 1).  Although groups  seen  during  the  found  in  outside  a  segregation During round.  on  the  the  the  appears maternal  rut  were as  period.  cell  during  to  A  met  association for  the  were  test the  rut  of  The  same  moved  maternal  cells  revealed  the  rut  showed  that  of  period, for All  with  the  into  areas  males  between  the three  of  percent and  males  and  (Figure  2.3a), the  male  of  maternal  group  a  males  was  of  outside  l o c a t i o n s , 64  for  that  ( P > 0 . 0 5 ; d f = 1).  from  1 km  or  contained  differed  within  ( P < 0 . 0 5 ; d f = 1).  grid  dispersion  overlap  test  and  the  either  during  association  time  all  a  locations. The  association  year,  rut  sheep  range  Of  the  independence  not  same  entire  expected, males  for  some  range  the  of  males  association  conducted  significant  be  of  of  containing  test  a  ( P > 0 . 0 5 ; d f = 1).  significant  rut,  revealed  time  same  the  rut,  there  same  of  revealed  the  cells  of  384  of  contained  test  the  found  2.3a).  (25)  sheep  during  sexes. A  (359)  outside  circuits  I  occurrence  percent  enclosed  55  rut,  (Figure  sexes. A  areas  groups  the  6.5  both  cells  The  percent  Only  complete  219  the  infrequent  separate  three  and  of  of  sheep.  was  together.  possible  maternal,  cell  used  from  a  contained  member  females  outside  l o c a t i o n s , 93.5  both  adult  Results that  cells  not  one  circuits  1-km*  the  cells  complete  and  females  not  significant  rutting  period,  criteria  exception females  of  for the  sexual rut.  occupied  year  18  Figure 2.3a. period.  Locations  of  male  and  maternal  groups  outside  of  the  fall  mating  Figure 2.3b. Locations mating period.  of  male,  mixed  and  maternal  groups  during  the  fal  Crude  The between only (  null  males  during  x  hypothesis and  period crude data  (  x  that  forage  secondary  was  significantly There  being  suggest  fecal  either  than  compounds  no  during  males,  females,  Fecal  higher  was  lower  crude  rejected;  (P<0.05;n =43).  =6.8%).  protein  quality  females  winter  =8.2%) w a s  that  Protein  different  habits  forage  contained  80  types  percent  shrub/tree  fragments.  fragments  in  males'  it  than  for  consistent  time  during  the  winter  fecal in  protein the  revealed  forage  that  selected  males  feces  Artemisia  comprised  (Table  1984-85,  same  time  female 2.1).  fecal These  ingested  inflated by  winter  higher  because  of  males.  Habits  grasses, while  feces  or  (Table  were  in  the  male  significantly  significantly  males  periods of  differ  during  of  values  January-February,  spp.  for  females trend  not  differed  protein  other  or  during  although  the  (phenolics)  analysis  did  crude  Food  Food  protein  and  females  1985.  Feces  from  males 61  ingested from  contained  percent  of  widely  female 78  the  sheep  percent  shrub/tree  2.2).  DISCUSSION  Studies on  the  Shank  of  winter 1982).  period  spring  to  males  et  variables with  spring,  segregation  (Geist  Shannon  environmental contrast  sexual  aj. over  females.  males  and  and  Petocz  (1975) a In  in  wild 1977;  related  complete my  females  bighorn  sheep  Morgantini  sheep  'annual  have  and  distribution cycle',  study  area,  over  were  spatially  a  and  but one  concentrated  Hudson to  they  1981;  eleven did  year  temporally  not  period  from  separated  Table  2.1.  Mean  percent  fecal  crude  protein  (  x  )  for  the  Junction  bighorn  sheep  %Crude  population,  1984-1985.  Protein  Females  Seasons  Spring  N  » a b c  b  _ x  c  _ x  S x  _  N  0.229  12.1  12.7  0.239  63  1984  30  0.397  10.6  10.9  0.381  34  25  0.236  8.3  8.1  0.462  15  24  0.112  6.8  8.2  0.189  19  1985*  P<0.05 Sample Standard Mean  _ x  55  1984  Winter  S  1984-85  Summer  Fall  a  Males  Size Error  of  the  Mean  Table  2.2.  females  Food  are  habits  presented  of  the  with  Junction  standard  Winter  Forage  Items  sheep  deviations  in  population,  determined  parentheses.  Data  Males  4.1(3.8)  6.2(2.5)  fecal  fragments  collected  Early  (Jan-Feb)  Females  by  were  in  Spring  analysis.  Seasonal  mean  percentages  for  males  1985.  (April)  Mid-Late  Spring  (May-June)  Females  Males  Females  Males  6.6(4.2)  0.5(1.1)  Grasses  Agropyron  16.4(3.5)  9.6(3.9)  Bromus  2.9(2.2)  1.5(2.0)  Festuca  0.6(1.4)  Oryzopsis  0.6(1.3)  Poa  0.6(1.2) 8.5(4.9)  Sporobolus  29.8(1  Stipa  54.1(7.6)  80  Total  Grasses  0.5(1.1)  15.1(4.0)  12.1(8.2)  16.1(4.6)  0.5(1.1)  0.6(1.2)  0.8(1.8)  28.3(6.4)  32.7(5.7)  6.3(4.2)  49.9(8.0)  40.1(1  38.8(4.4)  14.6(4.5)  21  86  64  90  48  1.9(1.7)  43.6(8.6)  1.3)  1.1)  Shrubs/Trees  Artemesia A,  frigida  tridentata  Pseudotsuga  44.2(8.8)  1.1(1.5)  12.1(6.3)  4.3(2.7)  16.3(6.2)  8.7(3.7)  16.7(5.1)  3.9(4.5)  1.6(2.4)  15.9(5.6)  1.6(2.2)  0.6(1.4)  Shepherdia  Total  Others  Shrubs/Trees  1.8(1.6)  1.6(2.3)  6  78  10  30  0.6  0.6  5 4  5.2  2.0(2.0)  46  8.9  2.0  and  outside and  of  the  females  been  mating  effectively  male  red  months.  They  used a  obtained  eliminated  of  have  obtained  but  any  and  temporal  potential  no  consistent  the  study  obtained  distribution  competition  if  communities  than  of  in  winter.  Rhum  than  during  the  summer  winter  (Clutton-Brock  Shank Palliser  of  males  resources  did  females.  lightly-grazed groups  used  Koeleria. consumed during  food a[.  had  on  higher  with  more  summer,  was of male  it  high  greater  that  quality  the  one,  quality  1982).  the  (Calluna  of  food  However,  was  winter.  high,  in  one  females  The  utilized  different  particularly  the  densely  and  was  more  winter  than  heather  the  areas  in  areas  this  of a  females.  chamois  during  sites  plant  when  food  populated  less  abundant,  winter,  and  higher  biomass  considered than  aj.  the  heavily-used  segregation,  relatively  found  obtained  heavily-grazed  Festuca  was  in  during  that  pronounced  than  during  the  1982).  however,  They  area  sexual  more  density  populated  populated  less  et  during  in  et  were  forage  was  the  found  reported  grassland  grazed  population  promoting  less  deer  (Clutton-Brock  densely  females  with  was  Segregation  when  (1982),  Range  the  females,  red  difference  deer  mainland,  substantially  Rhum,  quality  in  than  areas  used  area, where  males  Scottish  forage  used  On  females  higher  the  quality  males  shrub.  and  on  males  and  quality  quantity-limited  portion  reported  males  scarce  poorer  females,  low  by  portion  than  spatial  al. (1982) w o r k i n g  also  by  grasslands,  may  et  deer  vulgaris!  was  This  limited.  Staines  area  period.  ingested  quality  characterized low  higher In  fRupicapra  male  by  quality  winter  study, in  by  a  high forage  Shank  the diet  a  Maternal percentage and  (1985)  Germany  on  quality  using  Festuca.  with  rupricapra)  higher  forage  biomass  another  a  bighorns  of  males found  used  that  habitats  with  less  forage  superior  in  than  quality  habitats  on  occupied  by  female-occupied  females.  ranges  Summer  compared  forage  to  was  male-occupied  ranges.  Results findings  on  protein  during  sheep  may  have  Phenolics  large  these  and  Robbins  1981).  High  crude  protein  content  of  sage  obtained  further.  phenolics  better  Females Based  round 2  pattern  with  low  with  higher  Scotland.  In  quality  on on  (male  sheepAm ),  rugged  in  the  with  pasture  The  by  seen  most  terrain  inflated  digestibility, and sagebrush  fecal  (Welch  than  Junction round x  density =1.6  was  in  lower of  males  sexes  accounts  birth;  spp.  high  I cannot  aj.  1983)  values  1981),  of  may  overwinter  Pederson  effects  females  their  et  nitrogen  the  males in  Kelsey  on  by  from  big  confound  sage  claim  heavily-grazed  estimates, 2  similar the  the  occupied  sheep/km ;  Junction, and  1982;  and  winter  that  and males  females.  range  resulting  in  results  fecal  crude  obtained  relatively  sheep,  cases  give  a_[.  nitrogen  published to  giving  et  on  biomass  both  (Kelsey  in  Artemisia  on  the  biomass,  plants  that  (1982)  fecal  sheep  nitrogen of  Shank's  between  than  information  density  at  quality fecal  with  male  component  proteins,  food  year  by  Without  presumably  forage  In  the  higher  However,  agree  relationship  obtained  of  period.  analyses  the  diet  appeared  time  relationship  winter.  the  complexed  (Mould  year  range  nitrogen  Assuming  quality,  confounded  diet.  foliar  fecal  quality.  same  been  winter  my  forage  the  have  the  plant  and  Junction  from  to  grazing  possibly  to  at  intensity  exhibited  during  lower  density  relatively  pattern  bighorn  were  occupying  occupying  remained  on  maternal  females  the  males  areas  x  on  the  densities  =7.1  the  male  ranges.  heavily-grazed  areas  lightly-grazed  areas  by  red  deer  in  separate.  sheep,  reduce  females  thermal  ventured  stress  on  the  into neonate  (Geist  1971;  Bunnell  measure  (Geist  of  females  time  thermal by  time  enabling groups  it  to  during  Curio ungulates (Canis  of  comm.;  and  in  were in  were  are  1986).  generalizations predators  Particularly to  occupy,  use  thereby  near  escape  they  occupied  decrease  the  in  about  have  in  the  in  spring.  winter  forage  kill  two  of  females  also  that  of  length for  developed, maternal presumably  maternal  groups  sheep  to  and  and  groups  present  and  cause  their  the  with  were  lambs  young  to  on  the  pressure  the  study  may Males  study  be  so  speculative.  cannot  terrain)  the  restricted  areas  not  pers.  mortality.  escape  induce  All  offspring.  offspring  in  (Felis  area.  populations,  juvenile  do  were  (J. Caldwell  would  same  coyotes  Cougars  ungulate  forage  young  Junction,  lambing.  vulnerable (less  that  chry_saetos)  among  high  areas  quantity.  the  and/or  mortality  occupied  grazing  At  during  variable  lamb  remarked  (Aquila  during  is  vulnerable  quality  eagles  lambs  females  ethology,  ungulates  mortality  Heavy  Larger  the  controlled  spring,  groups  frequently  potential  Maternal  the  security  expected  probably  I found  predation.  golden  most  to  more  compelling  predation  causes  spring,  same,  terrain.  of  rufus) were  Lamb  and  that  than  sufficiently  predators.  Lambs,  is  a  terrain.  areas,  killing  longer  during  as  proposed  isolation  terrain  from  and  known  usually  threatened.  susceptible to  (Lynx  observed  Ashcroft  afford  review  area, and/or  (1985)  become  when  period.  ubiquitous  bobcats  to  escape  escape  lambing  predators  However,  time  is  post-partum  protection  a  sheltered  Haywood  neonate  near  particularly  regularly  Coyotes  broad  (1976),  latrans)  these  the  from  a  post-partum  predators  same far  were  concolor^  for  required  venture  and  Therefore,  from  this  choosing  isolated  concentrated  lambs  not  seen  are  run  by  Shackleton  required  were  because  did  1971).  requirements.  the  found  1980)  a  in  males  areas  winter  that  subsequent suffer  the  lambing  constraint,  It  is  between the  probable  sexes  selective  driving  the  throughout  forage  quality  explain fully  et  to  the  rut;  the  sexes  the  e,g.  have  studies  1982), the obtained for  results higher  sexes  to  Among young,  males  maximize  their  and  not  it of  segregation  did  Nutritional  is  conditions  periods  to  red  it  has  is  been  used  could  females  relatively  when  deer  forage  and  were  expected  during  for  a  uniform  differences  males  were  I  more  in  while  segregation  Also,  though  requirement of  segregation,  of  appear  groups.  differences  competition  relax  sheep,  separation  foraging  of  competition  in  quality  spring.  forage  did  maternal  pronounced  early-mid when  avoidance  of  expected  though  diet  consequence  avoidance I  than  to  not  outside  uniform,  of  yet  separate.  stated,  another  an  as  "Behavior  function  yet  competition  discussed  If  widely  suggested,  a  Segregation  uniform,  summer  acquire  intraspecific  are  summer  complete  (1974)  for  any,  the  more  (1982)  winter  sexual  nearly  during  evolved  of  elsewhere.  remained  may  if  Clearly,  explain  Alexander effect  aj).  segregation  explain  Shank'  range.  more  range  segregation,  during  the  was  (Clutton-Brock inadequate  periods  to  equivocal.  sexual  relax  quality  as  winter,  behind  to  them  remains  critical  segregation  that,  during  force  force  during  enabling  of  of  et  segregation  quality  forage,  losing  reason,  differential  (Clutton-Brock  initially  without  unknown  and  that  aj.  were  with  the the  foraging  1982;  there  is  because  first."  consequence  1979;1982; in a  terms more  of  Segregation  opportunities.  Shank  inconsistent  suggesting  evolves  of  of  usually genetic  in  which  mate  with  fitness  only  females  several (Trivers  contribute  Among  Staines  et  which  sex  compelling  females, 1972).  thereby  Bighorn  to  caring  for  attempting  sheep  fall  into  may  reduced the al.  reason  segregate.  species  one  their to this  category. and  Male  the  1984).  dominant  Hogg  hierarchy, males  sheep  males  (1984)  Dewsbury  that  with  copulated  social  with  requisites  conclusive  study  on  dominance  yet  reported.  be  effects  of  success, by  dominance,  we  those  must  they  be  best  areas  which  sexes  are  maximize  the  second  expected  able  top  most  of  often, If  and  body  (Geist  of  the  but  that  1971;Hogg  subordinate outlined  reproductive  success,  success  bighorn  suggested  survival  in  that  upon of  size,  dominance  criteria  copulations  and  horn  breeding  third  females.  (1982)  parentage  supplied  implication  of  if  implication,  it is  quantity  deliberately  or  is  forage  for  to  in a sheep  evaluate  has  the  reproductive  the  for  for  offspring  otherwise,  to  be  or  conceived  that  best  seems  male the  in  of  quality  food  selection at  to  high  favour  which  to  low  it  that  sheep,  to use.  quality forage. is  A  available  males  quality the  where  range  quality if  use  needs  female  forage  if  producing  their  unreasonable,  quality  resultant  cases  use  higher  or sheep,  have  supply  will  male  horns,  propose  obtain,  It  threshold  and  would  males  high  expect a  that  of  possible;  independent  use  low  case  males  which  find,  use.  use  I would might  is  individual,  bodies  I  mates,  will  efficient  the as  These  areas  strategy  males  In  larger  mates.  inefficient  that  There  into  use  each  efficiently  requirements.  compete  this  for  possible.  as  transmit  males  available.  efficiently.  advantageous  their  the to  forage  be  compete  ability  sufficiently  feeding  the  reproductive  resources  to  would  to  best  their  sufficient  would  best  segregated,  One  was  would  maximization  animals  in  it  secure  would  abundant  the  upon  copulations.  to  energy  and  proportion  the  of  interpreting  Dewsbury  and  know  Presumably, female,  Briefly,  in  estrus  for  based  most  females  tended  are  do  males  estrus  (1982)  to  hierarchies  apparently  found  copulated  also  form  food  animal  particularly  males,  may  efficient.  change  The  foraging  energy  intake  Males  feeding  high  quality  females  by  are  on  sheep,  Blood  et  forage  Differences sufficient food  is  easily  in to  than  forage  different switch  north  percent  1976;  Seip  reported  Bunnell  male  size  male  and  confers  quality  forage  low  1984).  For  when  between  male  and  males  greater that  potentially  poor  food,  will  choose  a  males  should  feed  problem  arises  when  of  both.  occurs et  (scarcity)  of  and  at  understand  the  lower  can  this must  extreme effects  Junction  sheep  population  because  males  and  under  intersexual showed  females  no  occupied  to  and  than  could  ever  males,  be  many  illustrated  upon  to  areas.  high  quality  on  more food  utilize lead  is  the to  higher  to  utilize  by  foraging  behaviour  forage  more  feeding  competition  be  resource  different  abundance,  intersexual  may  be  able  of  lower  fitness.  may  be  53  1983).  must  tested. The  competition  separate  as  on  ultimately  may  and  quality  their  conditions  under  extreme  high  females  Females  bighorn  females  if  a].  kg  sheep,  females  for  extreme  Harvey  maximize  sexes  than  observed to  it  et  88  choice. When  better  threshold  hypothesis be  do  males  densities  scarcity  of  on  competition.  Only  food  of  feeding  bighorn  it. C o n v e r s e l y ,  between  foraging  preventing  females  from  The  a l . (1982).  limitation  conditions,  Competition  female  (Blood  California  weights  and  when  populations,  weight  size  males  sheep  body  body  larger  gain  to  female  of  will  availability.  advantages  flexibility  animal  less  and/or  temperate  of  and  an  becomes  quality  Clutton-Brock  possibly  Clutton-Brock  75  body  resource.  which  to  In  which  1974;  fitness  males  60  abundant,  males,  may  at  strategy  Jarman  Obviously,  reduced  food  one  1971;  allow  limited  quality  Olsen  obtainable  same  point  of  scarce.  when  (Bell  scarce,  sufficiently  the  food  becomes  Larger  is  to  al. (1970)  respectively.  quality  high  and  strategy  threshold  generally  Bunnell  feeding  switching  food  1970;  kg  their  clearly  strategy.  for  forage,  The  CHAPTER  THREE  -  GROUP  SIZE  INTRODUCTION  Six  studies  sheep  (Blood  1979;  Shackleton  except  the  was  not  my  study  sex,  of  upon  1963;  clear  Chilelli  was  document  and  in  size food  quality,  d i s c u s s e d the  group  size  in  environment  and  and  low  quality  closed  habitat groups  maximum  group  size  Seasonal  growth  influence found  by  the  1981;  Geist  1975). in  All  Chilelli  latter  one  group  group  1971;  were and  was  size  migratory  Krausman  migratory.  sheep  effects  population  of  for  bighorn  Leslie  sizes, according  bighorn the  of  and  Douglas  populations,  (1981), The  and  it  objective  of  to  behaviour  in  south-central  sex, behaviour  food with  and  limited  by  c h a r a c t e r i s t i c s of  sheep  group  Jarrnan  predator  that  the  interaction  living  in  quality, as  the food  form  clumped an  and  season  larger food  plants in  on group  and the  due  avoidance the  feeding  and  with  upon  predator  uniformly  groups  types.  than  animals  Jarrnan  mechanism,  (1974) while  availability" of Junction  size  trends  to  Jarrnan  of  habitat  anti-predator  "dispersion  sizes, resulting  (1974).  different open  be  season.  and  resources, should  primarily  to  may  style  argued  animals,  high  population  distribution, related  foraging He  sheep  characteristics induced  form is  Junction  food  antelope.  species  that  those  in  effects  African  suggested  may  ai.  seasonal  strategies. Grazing  distributed in  this  evaluate  changes  (1974)  avoidance  et  California  to  in  Krausman  reported  not  changes  size.  Group  living  or  non-migratory  group  and  population  to  seasonal  Shannon  whether  Columbia;  changes  treated  1973;  desert  a  British  have  sheep similar  the  forage. range, to  The slopes, same  and  they  broken  differ  shown  spring,  because  and  lambing  produce  when  of  group Both  were  evaluated  significantly  Blood seasons,  and  group  sizes  quality  on  differences  or  young, to  not  and  were sheep  and  the  (1963)  similar ranges  on  Geist  (1971) tests  smaller to is  of  those often  were those  found poor,  in and  of  foraging  and  most  near  Sugden to  group  of  and  that  group  found winter sheep  in  the  (Geist of  and  both  is  in  males the  sexes. I  differed  group  among  sizes  spring, while  sexes  terrain and  varied  1971).  to  Blood  escape  groups  conducted. Winter  terrain  expected  of  sizes  year.  terrain  between  maternal  the  relative  near  densities  on  females  (1961)  sizes  of  Escape  was  remain  bedding  sheep  escape  predation.  while  would  bighorn  for  to  integrity,  groups  female  the  slopes  groups,  group  bedding  ranges,  relative  reported  than  by  females  male  uniform  size. Different  separate  divergent  more  inhibit  grass  terrain, often  concentrations  group  different  sizes  statistical  were  resulting  to  open  foraging  remain  susceptible  suggested  to  another  must  their  produce  season.  no  as  and  one  influence on  of  sizes  male  from  lambs  imposed  within  females  to  females  expected  although  males  expected  are  whether  isolation young  the  that  particularly  constraint  lambs  two,  would  uniform,  broken  large  sizes  so  in  move  allow  that  distributed, so  and  size  the  their  females,  are  were males  in  with  discretely  areas  densities  season.  lived  lambs  I predicted  chapter  bed  bedded  within  females  these  limited  (1963).  range,  to  animals  groups,  in  relatively  terrain, and  expected  the  of  terrain. Sheep  foraging  compared  Junction  During  were  groups. of  consists  escape  where  those  have  range  for  slopes  smaller  were  I  use  terrain  from  groups  sheep  diverse, broken  Uniform  promoting  the  of  areas  forage. the  Junction  Winter are  for  fall food  known  to  experience  overwinter  groups  were  forage  was  require  highly  widely,  smaller  newly  changes and  expected  in  group  employed  statistic, what  experience  total sized  groups.  using  mean  be  In  little  rather  than  termed  plant  as  sheep and  of  what  nutritious  dispersed  for  dispersed,  summer,  more  form.  Seasonal  to  and  winter  females  is  foraged  groups  if  little  growth  sheep  Smaller  lactating  during  expected  1982)  the  concensus  changing  to  produce  group  sizes  and  distribution  significantly differed  in  g  reflects thus  groups I have  statistical  group  of  Hardin 1985).  et I  ai.  rather  than  the  an  to  measure  when  total  mode  x  reason  have  1976;  )  both for  observer's of  central  considering  numbers  additional  (1982)  present  animal's  evident  a  species,  (  appropriate  as  used  size  opposed  tests.  al.  group  more  provided  1982;  et  (1985)  variety  measure  size  mean  particularly as  a  Eisenberg  and  the  a  'typical'  on  Krausman  )  (  appropriate  size. Clutton-Brock  reporting  and  the  size'. Shackleton  size  becomes in  group  and  is  using  group  Robinson  size  results,  sizes  mean  Chilelli  regarding  suggested  authors,  group  group  animals  group  new  larger  was  'median  (e,g.  difference of  and  determined  (1974;1982)  'typical'  (Jarrnan  number  pregnant  spring  allow  forage,  1981;1983;  Typical  This  late  therefore,  to  size  Miura  (1982)  In  requirements  size. Other  group  comparison.  tendency.  they  group  1978;  Jarman's  I,  find  1970).  seasons.  appears  mean  Kucera  sizes.  when  McGillis  to  expected  would  nutritious  among  describe  used  forage  size. Jarrnan  descriptive  to  of  group  There  leaves.  physiological  abundance  and  also  and  dispersed  spring, when  were  plant  (Stelfox  sheep  forage,  groups  the  significantly  of  because  nutritious  distributed  different  losses  available. During  developing  uniformly  weight  of for  the  various not  METHODS  Groups were  were  considered  was  >100  sighting  m.  of  distinct  a  group.  from  standing,  standing  the  alert  If  alert.  activity  being  considered  Jarman's (  x  )  are  presented  and  was  calculated  the  sum  of  was  used  period.  to  The  groups  G-test  p:4f  pixon  1983).  The  frequency  using  all  required  a  analysis  (Fienberg  distribution  sum  group  parametric  normal  two  any  sheep  nearest  means,  was  were  percent  of  Groups  neighbors upon  that  first  group  bedding,  was  foraging,  distinguished  assumed  they  criteria.  immediately  Standing  >50  group  of  size  squares  (  according  Rohlf  1981)  of  either  an  from  'alarm'  considered  the  the  or  standing  individuals  to  than  I  were  is  of  in  a  sex  strongly  is  transform  often  time  level  of  c=0.05  using  skewed  to  precluded  categorical  BMDP  the analysis  variables  used  contingency the  impossible  by  1980)  and  analyzed  average  divided  (Fienberg  non-parametric to  size  weighted  sampled  normality  the  group  a  probability  data  attempting  distribution, which  is  analysis  a  sizes  chose  g  behaviour,  with  Also,  mean  groups  table  assumption  statistics.  ) and  all  The  group  g  Statistic  of  Contingency  technique. rather  activity  c l a s s i f i e d as  the  comparisons.  of  by  standing,  by  sizes  and  if  the  recorded  comparison.  distribution  1980), a  were  and  activity.  for  sampled.  non-parametric  into  between  running.  while  typical  the  Violation  conventional  and  group's  statistical  3.1).  distance  disturbed  performed  (Sokal  used  (Figure  were  1971)  the  as  was  right  activity  together  compare  for  and  posture;  (1974;1982)  all  distance  observing (Geist  was  priori  the  alert, w a l k i n g  by  a  analysis. Activities were  posture  group  if  sheep  'attention' The  using  Composition  excluded  standing  defined  table  skewed for  group  33  80  60 H CL  3 O o  6  40  i_ Q) .Q  E  3 20  ~ T  0  I  10  Jlhmltllrflhwifhi 1  20  1  ~ 1  30  40  1  "  50  60  70  80  Group Size  Figure 3.1. Frequency distribution of all group sizes for the Junction sheep population (n=544 groups).  sizes.  In  addition,  categorical  sizes  cells  in  were  the  four  categories:  case  so  they  were  category  was  based  foraging  efficiency  Risenhoover  and  group  in  a  sheep  per  1, 2 - 5 ,  facilitate multi-way  on  group  Single  (1978) w h o sheep  also  analysis  of  as  herd the  analysis  animals The  were  with  for  observations  in  of  low  foraging  group  s i z e , up  upper  of  the  special the  five  to  2-5  sheep or  less.  efficiency  1982).  limit  aggregated  a  on  bighorn  groups  eliminate  were  bound  that  (Simmons  to  constitute  upper  reported  reported  sheep  selected  size  category.  increased  bighorn  was  one  categories  Group  21+.  when  (1985)  efficiency  Colorado  to  low  four  table.  Berger  was  into  6-20,  assigned  Bailey  Foraging  divided  contingency  into  groups.  tables  variables.  Group empty  contingency  20  in  small  sheep  per  Consequently, third  group  20  size  category.  RESULTS  Values for  mean  smaller g  for  group  size  groups,  (  that  group.  and  but  groups  influences each  size  frequencies  group  all  typical  group  cumulative typical  of  most group Mean  group x for  (Table groups  mean  more  (22.9),  )  size  (  a  and  group  lived  sizes  proportion  in  overall  group  (Figure  occurred  to (  the x  3.2). in  the  year.  than  slopes  of  were  groups.  This  of  sheep  the  other  those the  differences  estimate  number on  higher  There  larger  the  =9.7)  of  reveals  summary  throughout  size  consistently  individuals  better  animal's  are  Comparison  size  much in  )  3.1).  individuals is  g  between  many  more  Jarman's  of  the  size  weighted  (1982) of  average  represented hand,  implies  in that  120  -I  100  A X  <_> c  CD 3 cr  80 H  <D > D  60  A A  E c  X  40 H  o  Q_  A  20 H  A  X X X  X A X X  A GROUPS X INDIVIDUALS 10  20  30  40  50  60  70  80  Group Size  Figure  Percent  3.2.  individuals  are  cumulative  contrasted.  frequency  distribution  of  all  group  sizes,  for  the  Junction  sheep  population.  The  frequencies  of  groups  and  36 T a b l e 3.1. M e a n g r o u p size ( x ) and t y p i c a l g r o u p s i z e ( g ) s u m m a r y f o r the Junction bighorn sheep population. Data were c o l l e c t e d b e t w e e n M a y , 1984 a n d J u l y , 1985.  GROUP TYPE  BEHAVIOUR  TIME PERIOD  n  9  X  S  All  All  All  544  22.9  9.7  0.49  Maternal  All  All  429  23.9  10.0  0.57  Males  All  All  115  18.9  8.7  0.88  Maternal  Foraging  All  287  24.3  9.9  0.70  Maternal  Bedding  All  142  23.2  10.1  0.97  Males  Foraging  All  65  21.4  8.3  1.30  Males  Bedding  All  50  15.9  9.1  1.13  Maternal  Foraging  Spring  123  28.6  12.3  1.28  Maternal  Foraging  Summer  101  23.3  8.5  1.12  Maternal  Foraging  Winter  63  11.5  7.3  0.70  Maternal  Bedding  Spring  75  24.2  10.6  1.40  Maternal  Bedding  Summer  27  29.3  13.3  2.86  Maternal  Bedding  Winter  40  12.4  7.1  0.98  Males  Foraging  Spring  40  25.0  10.5  1.98  Males  Foraging  Summer  16  9.5  4.8  1.23  Males  Foraging  Winter  09  7.2  4.9  1.18  Males  Bedding  Spring  26  17.8  10.3  1.75  Males  Bedding  Summer  12  15.5  8.9  2.55  Males  Bedding  Winter  12  10.6  6.8  1.53  n=number S  x  of  =standard  groups error  of  the  mean  x  sheep  live  percent >9  in  were  sheep  much  smaller  found  in  (Figure  Percent  groups  occurrence  of  groups  percentage  of  individuals  two  show  larger  middle  group  to  percent,  groups  but  (1-5  numbers  of  June);  2)  Contingency  pairs  analyses  indicated  thus were  of  no  of  no  sheep in  seen,  50  groups  of  1984,  there  summer  1984.  For  form  differences  this  group  4)  size  of  of  when  Winter  group  size  of at  sizes. but  The  the  two  contributed  frequency  in  Both  considered  animals.  1)  of  about  Sub-optimal  terms  of  Spring  1985  categories  1984  results and  sizes  three  was  seasonal  were  used  of  as  1985,  Each  a  categories  and and  and  were  was  there  1984  third  or  pair  1984-85  spring  to  these  Although  spring  between kept  June).  3.2).  four.  between  differences 1984  of  (May,  (May,  spring  (P>0.05;df =3;Table instead  1984  (December,  Spring  spring  periods group  group  size  viewed  the  3.3b).  animals  a a  the  categories. The  between  analyses,  Single  the  and  animals,  1984-85  and  summer  female  categories:  5)  1985  3.3a)  (Figure  more  as  groups.  1985;  significant  reason,  and  April  time in  class  Groups  percent  3)  season  April  two  were  13  presented  (Figure  observed  seasonal  periods  and  seen.  prevalent,  5  differences  male  were  August);  five  group-size  sheep  are  class  frequently.  numbers  March);  each  to  all  were  more  less  time  significant  In  percent  contained  much  of  summer  category.  of  sheep)  about  than  1984-85  aggregated  number  classes  between  only  (July,  February,  winter  75  group-size  sheep)  recognized  1984  compare  between  total  sheep;  each  of  (1-5  rather  tables  in  (6+  number  were  Summer  each  occurred  contained  analyses  in  classes  foraging  sheep  January(1985),  the  group-size  difference  classes  sheep)  Initial  >17  the  found  little  total  for  for  found  size  the  sub-optimal 47  very  group-size  negligibly  of  For  3.2).  percentage  figures  groups.  separate  used:  1)  38  50  IZZ overoll C Z maternal only E S 3 mole only  Group Size Categories Figure 3.3a. category, for J u l y , 1985.  R e l a t i v e p e r c e n t f r e q u e n c y o f g r o u p s in e a c h g r o u p s i z e the J u n c t i o n bighorn sheep p o p u l a t i o n b e t w e e n M a y , 1984  and  60-1  Figure 3.3b. R e l a t i v e p e r c e n t n u m b e r o f s h e e p in f o r the J u n c t i o n b i g h o r n s h e e p p o p u l a t i o n b e t w e e n  each group size category, M a y , 1984 and J u l y , 1985.  39  Table  3.2.  Results  TIME  PERIODS  of  2X4  G-tests  comparing  group  sizes  DF  among  seasons.  P =  Spring 84 /Spring 85  3.5083  0.320  Spring 84 /Summer 84  8.7354  0.033'  Spring 84-85 / S u m m e r 84  6.9634  0.073  ns  April 85 A/Vinter 85  2.4722  0.480  ns  Spring 84-85 /Winter 85  20.6118  0.000***  Summer /Winter  8.7627  0.033*  •  84 85  P<0.05  •*  P<0.01  •**  P<0.001  ns  winter  (December  (May,  June  1984-1985)  Group mid-late  1984, January,  sizes  spring  were  or  summer  much  summer  spring,  whereas  spring,  were  bedding  groups  sexes.  There  was  consistency  the  two  size  no  The  second  (P<0.05;df =6).  affecting  lambs  lambs  groups.  in  and  the  all group  There period,  of  was sex  (P>0.05;df =3).  no  separate size  (P>0.05;df =7),  There  was time  no  sex, and  significant  association among Consequently,  bedding  groups  were  found  found  relative  sizes  in  of  than  in  groups in  summer.  foraging  no  significant  and  that  group  Only  foraging  were  mid-late  groups  in  for  and  there  was  was  seasonal  effect  summer  groups, analyses  with  did  both  bedding  (P>0.05;df =3).  period  group  group  group  Gradual  potentially  size  relationships  removed so  and  size.  observed,  differ,  rejected  significant  time  lambs  between  from  lambs  these  were  reported.  3-way  association among  among  significant  group  4-way  ( P > 0 . 0 5 ; d f =5).  group  not  not  rejected  upon  I analyzed and  no  not  was  association  size, w a s  association between  nor  period  spring  spring  and  size, also  analyses  significant  early  foraging  than  was  through  maternal  and  smaller  sizes. Therefore,  behaviour,  ( P < 0 . 0 5 ; d f =6).  group  a  1 9 8 5 ) 2)  1984).  were  bedding,  hypothesis,  spring  in  the  there  and  was  group  included  Results  included  There  groups  April  seasons.  significant  from  maternal  that  and  winter  foraging  in  among  sex and a  female  consistently  foraging  between  of  and  during  3.1). M a l e  bedding  hypothesis,  was, however,  attrition  with  largest  behaviours,  association  largest  sexes  first  ( P > 0 . 0 5 ; d f =3).  There  the  between  The  The  (Table  in  March  (July, August  smaller  largest  groups  spring.  3)  February,  a  size,  size, behaviour, association of  There  size, behaviour,  I conducted  group  3-way  and  and  time  contingency  sex  group  was, however,  time  size, a  period table  analysis  of  group  only  significant  summer the  size, behaviour  groups  (39)  of  sex, for  association was  ( P < 0 . 0 5 ; d f =3).  number  and  foraging  seen  during  This  this  between  was  groups  each  due (117)  time  of  the  group  mainly  to  contrasted  period  for  three  size  and  the  wide  with  both  the  sexes.  time  periods.  behaviour  during  discrepancy number  of  The  between bedding  DISCUSSION  Cumulative bighorn  sheep  population found,  (Figure  are  found  suggesting  contribute most  group  often  3.4), in  that  more  in  used,  size  terms  data  illustrate  that  larger  groups,  the  the  mean  frequency  relationship of  size  and  bedding  most a  of  (  x  Hansen  of  the  similar  may  numbers  group  from  be  on  individuals  in  relationship  general.  animals, ),  (1980)  does  yet  not  The the  desert a  to  that  larger  groups  summary  reflect  I  statistic  this  larger  male  and  proportion.  Sizes groups  at  the  suggests two  for  foraging  Junction, did  that  the  behaviours,  although a  of  they  similar  several  may  the and  and one  sheep  of  were  Dall's  bighorn  and  Seip  whom areas  reported were  sheep  restricted  (December  later  sheep, and  using to  Factors  lack  of  difference  independently of on  of  the  sex. Those either  operating  different  maternal  sized  sex,  produce  among  groups.  factors,  seasons,  There  are  influences.  in  the  to  remained  (April)  than  windswept  Bunnell  (1971) (1985a),  windswept  ridges  1985) on in  ridges,  observation  Geist  ridges  1984-April  Snow 1985  patches. This  on  operate  differently  significantly  confined  (1944) w o r k i n g  of  independently  season.  snowmelt.  month  and  sizes  season. This  size  operate  within  produced  late  group  may  1984-85  snow-free  sheep,  and  and  within  bedding,  size  seasonal  winter  snowfall  winter,  group  differ  affecting and  differ,  reason,  approximately  snow  in  possible  The early  foraging  trend  whatever  factors  not  groups,  is  and  immediately  the  and  Petocz  above  (March). slopes  to  those  (1973),  Stone's  winter.  characterized  At the  by  ground  1984  similar  studying in  was  with of  the  shallow Murie  studying  sheep,  the two  During  all  of  Junction, these rivers,  and  120  u c  100 X  X  <D  cr CD  80-  A A  CD  > 15 3 E  3  U  A A X^X A X  60  X  A  40-  "c  CD O i_ CD Q_  *  A  X X  X X  20  A GROUPS  X X  X INDIVIDUALS 10  0  20  30  40  50  60  70  Group Size  Figure  3.4.  distributions  Percent of  groups  cumulative and  frequency  individuals  are  distribution contrasted.  of  desert  bighorn  sheep  group  sizes  (data  are  from  Hansen  1980).  The  frequency  were  small  during  and  periods  sizes  were  support  In  April,  and  scattered  in  The  foraging  (after  the  foraging  surrounding  longer low  fill  fiber  foraging  and  and  (Geist  1971).  which  their  (new  growth.  the  a  of  Most  the  forage  lamb three  marked  need  the  seen  was  in  neonates  on  be  by  in  among  limited group not  the  aspect,  with  and  fall  (fall  sheep  decreased to  be  the  Junction were  13  April in  the  the  gut,  spring  synchronous and  late  but  widely grass  as  sheep  took  facilitated  times.  by  Continuous  groups.  result  of  others  born  by  Walker  associated with lambing  found  increased selectivity  foraging,  from  S.  He  Columbia,  senescent  rumination  at  by  less  quality,  that  themselves  recorded  in  of  dissipate  could  British  winter/early  high  through  (April),  (1983).  regrowth)  continuous  passage  tend  was  Eccles  late  concluded  more  the  spring  southern  isolate  individual. Early  and  fostered  at, b e c a u s e  (1983)  lambing  1985  variable  relatively  get  would  lambs  spring  site), resulting  of  to  to  could  in  fall  during  enabled  during  patches  winter/early  sheep  the  quick  food,  sizes  of  Forage  and  scattered  reported  study  produced  rumens;  females'  I saw  was  forage  in  Eccles  why  quite  late  patterns  the  sheep  explain  would  bighorn  growth) for  dispersed  newborn  April;  periods.  patches  growth.  during  continuous  between  could  mid-late  stages  new  from  depths  small  groups  activity  gone  new  group  births,  4  had  content  Small  first  more  dispersed  to  during  California  difficult  the  seen  growth  mobility  snow the  groups  on  of  spring  and  more  small  with  winter;  nutritious  bedding  winter/early  and  plant  of  of  was  and  the  species, small  herd  snow  dispersed  with  evidence  captive  Patchy  aggregations  plant  trend  numerous,  snow.  during  search  corroborates  that  heavy  larger  elevation,  a  of  smaller  the  summer.  for  s c a t t e r e d , but  period  asynchronous to early  (pers.  four  give  birth  May.  The  comm.)  on  ewes,, one  (April),  ewes  of  with  lambs  remained  immature the  males  rivers.  females  This  much  near  other  farther  also  cliffs sheep  from  would  with  security  promote  their  ranged  non-parous  cliffs,  smaller  young  more  females,  to  widely  in  located  groups,  reduce  yearlings  search  adjacent  with  their  to  parous  exposure  of  and  to  dispersed  new  growth.  spring  the  were  the  cliffs  lambing  probably  lambing  to  to  the  cliffs  near  these  nurseries  grazed;  accumulation  of  concentrated  in  summer  the  heavily  reported  grazed,  large  The result  fall,  of  season.  During  nursery  areas  in  and  size,  with  mouth  Farwell  increased  limited  did  small  patches  groups  larger  than  To  more  widely,  during  foraging quality,  summer, ranged  found  foraging  groups  the  groups  maternal  groups  the  and  from  areas area,  and  them.  were  they  support  Shannon  and  preventing  sheep  area  River,  Foraging  far  of  rock  confluence.  numbers  stray  in  used  more  et  summer  distributed  g  the  in  later  sheep  ai. (1975)  in than  also  spring.  bedding (  and/or  Chilcotin  and  in  could  winter.  females  widely,  to  I saw  uniformly  when  more  the  gravel  the  numbers  areas in  provided  availability, by  relative  these  terrain  Canyon.  not  forage  areas  spring  escape  Canyon  very  specialized in  found  of  Farwell  larger  but  groups  silt,  past  young  maternal  for  steep  Thus,  somewhat forage  groups  lower  the  the  upstream  maternal  the  near  in  need  grass.  maternal  large  River  larger  typically  extend  senescent  and  were  small  the  continued  between  result  small  over,  River  were  could  their  Fraser  also  was  These  maternal  grazing  the  to  Chilcotin  nursery  Heavy  due  the  The  heavily  period  grounds.  adjacent  adjacent  the  terrain, whereas  distribution  while  After  by  escape  ventured  remaining  predators, plant  near  with  moved  forage lambs  groups  =23.3),  may  (  resource moved  g  although  farther  have  =29.3) not  from  out  been of of  this the  were  significantly.  escape  terrain  to  slopes  nearer  slopes  were  distribution the  year,  (1973) of  the t o p much  and  grasses  that  by  among  plots. This  corresponds  to  n=44)  forage  shrubs,  so  1979;  sheep  a  in  habitually together  larger  groups.  summer  compared  uniformly  on  would  were  cyclic  with  supply  forage.  be  1984).  ( x  10.6; n = 3 0 )  =  grassy  forage  expected  in  limited  distributed  Eccles with  synchronous  (1983)  Widespread  that  synchrony  among  summer,  forbs  and  resource  such  and  as  Jarman  probably terrain,  foraged  areas, to  form  patterns and  which  separately somewhat in  spring  bedding.  w a s a relatively  sheep, would  x  During  which  foraging  (  is a l o w  escape  activity  of  and bedding,  as  were  near  Groups  successive periods  feeding  such  groups  bedding  found  females.  1974; Jarman  areas  similar  M a y , June  l o w quality  bedding  supply.  for  types,  Hebert stage  the m i d - l a t e  April,  of  in J u l y , at  were  slopes. Grass  (Jarman  the bedding  plots  stages  during from  time  in p h e n o l o g i c a l  growth  values  this  in the s p r i n g .  phenology  grass  These  forage  and by  than  protein  Maternal  the d i s c r e t e l y addition,  plant  itself.  their  difference  similarity  other  because  In  that  uniform  to  of  terrain;  distributed, relatively  used, were  Coinciding of  largely  the plateau  distributed  10  phenological  on  summer  escape  w a s little  I found  in f e c a l  sizes  near  elevation. On  of  and Caraco  larger  there  onto  in t e r m s  evenly  and August  foraged  group  came  and  July  up  uniform,  more  and aspect, trend  and  those  summer  when  Pulliam  and  was  decline  to  with  large  slightly  a  sheep  quality  grass,  open  associated with  elevations  summer,  more  quality  various  = 12.2;  the plateau  v i s i b i l i t y , than  forage  found  of  abundant  promote  larger  groups.  Males Shackleton range  tended (1973)  groups  Shackleton  met  (1973)  to  form  reported on  a  large  spring  common  suggested  that  spring  aggregations.  aggregations range,  often  the c o m m o n  when  rams  engaging range  Both  on  in  Geist  from social  one  of  (1971)  different  and home  interactions. his  study  areas  w a s probably  winter.  Sheep  ranges;  they  females  on  occupied  were  restricted  were  documented  from  winter  the  dominance  in w i n t e r  to  a  Winter and  they  lambing  found  (June)  lambs.  summer,  winter.  feature  of  Mean  June-September, same  time  average =8.2;  females  (1971)  winter  x  =9.5)  were  (I  (1  =11.5)  January-7  very  similar  levels  of  and they  interactions  in  social  function  males  home  previously,  sheep  separation  largest  which  spring  migrated  interactions  induced  by  similarly, to  groups  maternal high  to  upon  winter re-establish  compare were  larger  to  remained  was  size  largest  data  by in  Geist  mid-late  February fall  not  1965) group group  sizes  The  reported. bighorn  (9  sizes  (male  The  sheep  May-5  June  (male x  after  of  =5.5;  x  the  small  during  dominant  groups  groups  3,  sizes).  relatively  male  Figure  throughout  maternal  than  spring  their  immediately  in the s p r i n g .  for  available.  group  large  were  There  lambing;  from  largest  relatively  larger  (1971)  sizes  rut.  the g r e g a r i o u s n e s s  w a s that  significance w a s  was  seasonal  (ewe) groups  the  before  food  group  groups  during  groups  quality  actual  considerably  to  that  in J u n e . A l l g r o u p s  group  were  social  following  seasonal  but  mentioned  observed  the  tests  size  reported  discrete  round,  Increased  among  size  than  Statistical  sizes x  the  group  1960 w e r e  as  may  inferred  maternal  group  year  protracted  abundant,  that  (1963)  period.  group  size  statistical  male  Blood's  a  no  but w a s s m a l l e r  areas  snow-free  rams.  when  maternal  have  high  observed  and attributed  Average  to  the J u n c t i o n  smallest  performed  (1963)  After  in g r o u p  were  appear  snow.  exhibited  among  period  become  (1973), w h o  aj. (1975)  spring  to  However,  deep  range  at  area  general  ranges.  ranges.  peak  groups  Blood  the  et  largest  did not  same  Petocz  relationships  the  and  by  aggregations  second  during  by  spring  Shannon was  the  separate  the spring  snows,  first  the J u n c t i o n  occupied  reaching  the  in  during  the  largest (males 1965). =5.2;  maternal  x Geist's maternal x  =9.0).  Maternal tests  groups  were  population,  in  differences  group and an  Krausman  (1981)  recorded  summer  (April,  May,  during  Leslie  size  December  in  in  used  April,  (  x  Group  groups  (1971),  in  a  of  is  at  relative  when  food  was  abundant  (1979)  found  months.  x  Group  =6.3).  decrease  in  forage  quality  with  October  size  suspect  heavy when  means  used  and  little  rainfall  rainfall  in  February,  density  to  and  specify monthly  between  April  quality;  reported  and  was  in  distinguished 1976.  The  abundant.  summary (1961),  affects the  groups  average  and  practice. Sugden  be  not  size  other  largest  size  decreased  they  study  (Chilelli  group  densities. When must  were  did  largest  was  their  maternal  availability  forage  or  population  size  The  statistical  for  group  they  sizes  forage  Poor  different  monthly  although  mean  that  group  These  lowest  in  a  winter.  (P>0.05),  no  groups  in  The  group  considered occur  (  but  groups  Maternal  compare  increased  seen  populations,  populations trends  =3.5).  were  to  1976 to  size  Comparisons  Geist  Douglas  temperature.  1975  period.  different  summer  technique  was  increase  largest  early  insignificant  July, corresponding  this  period  groups,  largest  June).  lambing  and  male  the  the  statistically  statistical  than  1971).  through  1981).  larger  (Geist  early  large  Krausman  the  and  congregated  remained  consistently  conducted  Chilelli  when  were  raw  values Blood  group data  compare  (1963)  size, and  are  group  among and sheep  unavailable,  sizes  among  populations.  The during  north  spring  were  subject  sizes  were  abundance,  temperate  when to  high  quality  different  correspondingly and  smaller  sheep  studies forage  seasonal larger  during  the  was  trends during dry  I reviewed, abundant.  in  forage  periods  season  of  when  documented Desert  large  bighorn  availability, yet increased forage  sheep group  forage  was  groups  scarce,  patchily  distributed,  followed groups  the  group  and  was  were  also  (1979)  foraging  decrease  terrain.  in  a  3.7  alone.  percent  of  considered  A  all  observed while  percent  were  comprised  both  sexes, single  seen  at  1  sheep  alone  Chilelli  lone  of  of  seen 2  the alone  percent of  of  and  1.2  Junction  represented  moved  from  fragment  Krausman  numbers  seen  were  were of  total  of  population very  of  small  total  with  is  a  Douglas  percent  of  found  that  seen;  of  other of  the  single  Combining  number  proportion  37  were  This  seen.  the  that  sheep  males  females  the as  of  I  were  females  and  22.2  time.  number  number  of  Leslie  the  males  shows  alone.  alone  escape  groups,  for  (1981)  If  to  summer.  percent  misleading.  percent  a  0.6  in  corresponded  period,  percent  total  decrease  mating  males  the  The  the  with  spring,  smaller  in  fall  when  Jarrnan  groups  be  3.4  the  comprised the  rut,  poor.  to  in  and  summer,  tends  individuals can  those  formed  distances  individuals.  all  and  of  observed  foraging  compared  statistics  percent  J u n c t i o n . For animals  were  outside  females  in  of  to  in  travelled  smaller  time  found  group  that  comprised  encountered.  the  seen  11  where  females  populations,  of  spring  and  to  was  smaller  sheep  Jarrnan  farther,  increase  outside  relative  All  and  comparisons  expected  quality  from  abundant,  (1974)  hypotheses.  forage  for  that  were  and  population  dispersed.  summer  faster  an  sheep  was  Jarman's  (1974)  distance  reported  groups  males  the  and  histogram  solitary  and  explanation  percent  in  Junction  quality  forage  groups  when  Junction  widely  with  groups  moved  the  speed,  instead,  example  (1979)  at  or  larger  season  forage  (1971)  alone  good  sizes  scarce  Jarman's  impala  plausible  Geist  found  under  The  when  consistent  style;  dry  quality.  groups  was  Smaller  that  Increased  offering  seen  feeding  the  group  larger  were  expected  during  poor  forage  abundant.  reported  groups,  time,  good  of  of  reviewed  size  forage  a  pattern  when  populations  and  those  sheep  One and  feature  their  from  should  be  It  Pulliam  9-75  it  lives,  is  important  and  attributed  This  maximizing  A  their  is  density  pool  greater  of  important  in  requirements  I  suggest  outweigh the  spring.  young is  the  can  evident  terrain  only  a  the  be  also  close  when the  a  larger  safety of  forage  swiftly  of  maternal  lambs  are  as  probably  adults  (Shackleton  increase  Population  mainly  in  terms  and  distances  of  the  will  the  can  by  be  in  to  there  young.  size. is  With  a  much  dispersion  lower  than  are  safety  period.  quality  density on  important Haywood  group when  1985).  travelled  from  affect  group  potential  and  predation.  and  group  forage  sheep  lambing  population  less  density  on  spring  forage  become  discussed  Junction  females  ranked  sheep  and  McLeery  that  the  that  and  critical  and  dispersion  groups  older.  s e a s o n , but  the  and  flexibility  in  effect  be  size  environment  vulnerable  for  obvious  must  group  considerable  during  most  quality  requirements  run when  but  is  that  of  living.  terrain  one  range  reasons  with  sizes  are  observed,  the  dimension  sheep  group  it  Forage  for  for  group  important  area,  density  requirements  as  an  size,  of  urgent  a  (Krebs  opportunities  young  in  suggests  group,  escape  most  were  two  individual  to  groups.  group  of  large  the  given  population  effects  to  the  a  sizes  requirements,  precise  advantages  contributes in  in no  permit  contributing to  is  range  would  via  to  group  optimality  biological  there  Safety  when  regardless  but  probably  that  of  be  determining and  animal's  sheep  interval  for  concept  of  observed  a  animals  potential  sheep  for  need  is  of  range  between  (1984),  the  wide  interactions  factor  requirement  larger  an  group;  the  the  the  fitness  period;  Population  The  variability  major  population  This  that  is  majority  by  and  Caraco  to  variability.  nursery  data,  animals.  constrained  which  1984).  the  variability. The  groups  in  of  for  size the  This  trend  escape size  larger  in  groups.  In  absence  spring,  of  the  maternal  increased  groups  at  requirement  the  Junction  they  choose,  within  reasonable  their  relative  effect  on  importance to and on  predation. quality, group  The on  once  the  Year which  to  are  size.  In  physical  year  variation  in  foraging  snow  behaviour,  the free  dynamics  winter,  declining  of  relatively  limits. Foraging  as  affect  safety  safety  young to  during  forage  would  then  requirements  condition  increases  depths,  and  thus  impose  other  wherever increase  increase  in  vulnerability  forage  sources  quantity  of  variation  size.  relative  Junction  determine  again,  group  for  the  anti-predator  importance  sheep  sizes  range  of  strategy  groups is  of vary  general  factors  considerably  observed,  determined  while  affecting  among formimg  evolutionarily  sheep  season. groups  through  group  These as  natural  size  factors  an selection.  LITERATURE  A l e x a n d e r , R.D. 1 9 7 4 . 5:325-383.  The  A s h c r o f t , G.E.W. 1986. sheep. J . M a m m . Bell,  R.H.V.  1971.  A  evolution  of  A n attempted 67:427-428.  grazing  CITED  social  defense  ecosystem  in  the  behavior.  of  a  Ann.  lamb  Rev.  by  Serengeti.  a  of  behaviour  of  a  bighorn  Syst.  female  Sci. Amer.  B e r g e r , J . 1978. 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