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Aggressive behaviour, territoriality, and parental success in three-spined sticklebacks Black, William Robert 1969

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AGGRESSIVE BEHAVIOUR, TERRITORIALITY, AND PARENTAL SUCCESS IN THREE-SPINED STICKLEBACKS BY WILLIAM ROBERT BLACK B.A. (Honours), University of Saskatchewan, 1965 (1966) A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Zoology We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH. COLUMBIA May, 1969 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 of the r e q u i r e m e n t s 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 C olumbia, I a g r e e 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 a g r e e 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 c o p y i n g of t h i s t h e s i s f o r s c h o l a r l y p u rposes may be g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d 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 thes,is f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department of. The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date 5 Q ^ > ^ / ^ f i i ABSTRACT Male three-spined sticklebacks without t e r r i t o r i e s cannot reproduce; and i n order to e s t a b l i s h and maintain a t e r r i t o r y , a male must behave aggressively toward other f i s h . Such s o c i a l organization r a i s e s questions about determination of the si z e of the breeding population and the s e l e c t i v e advantage of p a r t i c u l a r l e v e l s of aggressive behaviour. Experiments varying the amount and kind of s o c i a l contact with other f i s h showed some of the e f f e c t s of s o c i a l organization. Grouped males b u i l d nests sooner, and hatch a smaller proportion of clutches of eggs than i s o l a t e d males. Fry survive less well with grouped males. There are consistent differences between i n d i v i d u a l males i n aggressiveness during the reproductive cycle. changes i n aggressive behaviour and t e r r i t o r y size have sim i l a r U-shaped temporal patterns which are common to a l l males. Aggression i s lowest and t e r r i t o r y s i z e smallest just before the clutch hatches when the male spends most time fanning. Males without clutches sometimes attack the nests of other males. Interference by these males i s often responsible for hatching f a i l u r e . Individuals that hatch clutches seem no more aggressive than those that do not. However, males hatching clutches have larger t e r r i t o r i e s during the f i r s t part of the reproductive cycle. They spend more time at the nest, and tend to remain closer to i t . i i i TABLE OF CONTENTS PAGE ABSTRACT ' i i TABLE OF CONTENTS " i i i LIST OF TABLES V LIST OF FIGURES v i i ACKNOWLEDGMENTS v i i i INTRODUCTION 1 MATERIALS AND METHODS 3 The f i s h 3 The aquaria 3 Treatment of males 4 Behaviour patterns 4 Recording procedures 6 i) A c t i v i t y 6 i i ) Tester male aggressive behaviour test 6 i i i ) p a r t i t i o n i n t e r a c t i o n s 7 iv) Interactions among grouped males 7 v) U t i l i z e d area and aggressive behaviour of s o l i t a r y males 8 Reproductive cycle events 8 FIELD OBSERVATIONS 10 The f i e l d s i t e 10 Nest s i t e s 11 Disperson 12 Removal of t e r r i t o r i a l males 12 Discussion 15 LABORATORY RESULTS 17 The e f f e c t of other sticklebakcs 17 i) Behaviour during the reproductive cycle 17 • i i ) Days to nest-building 20 i i i ) Hatching of clutches. 20 iv) Fanning 24 v) Number of f r y per cl u t c h 24 vi) Survival of f r y 24 v i i ) Manipulation of t e r r i t o r i a l males 28 v i i i ) Reproductive e f f i c i e n c y i n laboratory experiments v;ith grouped males 31 i v Page Analysis of measures of behaviour 33 i ) Temporal patterning — - 33 i i ) Consistency of i n d i v i d u a l s ' scores within a reproductive cycle 38 i i i ) S i m i l a r i t y between repeated reproductive .cycles 38 iv) Relation among measures of behaviour 41 Measures of behaviour and parental success 45 i ) Behaviour of males hatching and not hatching clutches 46 i i ) A c t i v i t y of males hatching and not hatching clutches 46 i i i ) T e r r i t o r y s i z e and i n i t i a t i o n s of inte r a c t i o n s . 49 DISCUSSION ...... 55 The e f f e c t of other sticklebacks 55 Analysis of measures of behaviour 56 Measures of behaviour and parental success 59 CONCLUSIONS 63 REFERENCES 64 APPENDIX I Description of aggressive behaviour patterns 67 V LIST OF TABLES TABLES . PAGE I Behaviour patterns recognized i n the q u a n t i f i c a t i o n of a c t i v i t y and aggressive behaviour. 5 II Frequency d i s t r i b u t i o n of inter-nest distances. 13 III Dispersion of f i s h i n the f i e l d and laboratory. 14 IV Days to nest-building. 21 V Hatching success of clutches with males of d i f f e r e n t treatments. 22 VI Clutch hatching success of males under d i f f e r e n t treatments. 23 VII Analysis of variance of fanning. 26 VIII Numbers of f r y hatching per clutch by males of d i f f e r e n t treatments. 27 IX Expectation of further l i f e at hatching for f r y with s o l i t a r y parents. 29 X Expectation of further l i f e at hatching for f r y with grouped parents. 30 XI Reproductive e f f i c i e n c y i n laboratory experiments with grouped males. 32 XII. Analysis of variance of tester male aggressive behaviour scores at s i x distances from the nest during the reproductive cycle. 36 XIII C o e f f i c i e n t s of concordance. 37 XIV S i m i l a r i t y between repeated reproductive cycles by the same males for tester male scores. 40 XV Correlation c o e f f i c i e n t s between measures of aggressive behaviour. 42 XVI Analysis of variance of aggressive behaviour scores and t e r r i t o r y size according to parental success. 47 v i TABLE PAGE XVII Differences i n t e r r i t o r y s i z e of males -hatching clutches and not hatching clutches. 48 XVIII Analysis of variance of a c t i v i t y data for selected measures. 50 VX1 LIST OF FIGURES FIGURE PAGE 1 Frequency of i n t e r a c t i o n s among grouped males from the s t a r t of the experiments. 19 2 Days to n e s t - b u i l d i n g . 19 3 Fanning during the reproduct ive c y c l e . 25 4 Temporal pat tern of measures of aggressive behaviour and t e r r i t o r y s i z e . 34 5 Frequency d i s t r i b u t i o n of tes ter male scores (2 0 cm from the nest) at nest—building. 39 6 Mean number of i n i t i a t i o n s of in t erac t ions per neighbour and t e r r i t o r y s i z e . 43 7 Mean number of r e c e i p t s of in t erac t ions per neighbour and t e r r i t o r y s i ze 43 8 Temporal patterns of measures of behaviour expressed on a b i o l o g i c a l time sca le . 44 9 Behavioural measures from the a c t i v i t y data comparing males which d i d hatch c lutches with those which d i d not,. 51 10 Behavioural measures from the a c t i v i t y data comparing cycles of a male which d i d hatch clutches with a cyc le i n which he d i d not hatch the c l u t c h . 52 11 I n i t i a t i o n s of i n t e r a c t i o n s and t e r r i t o r y s i ze for males hatching c lutches . 54 v i i i ACKNOWLEDGMENTS I wish to thank Dr. Dennis Chitty for his help and encouragement during t h i s study. I benefitted from Dr. N. R. L i l e y ' s knowledge of behaviour and from Dr. J.D. McPhail's f a m i l i a r i t y with sticklebacks, and from their c r i t i c i s m of the the s i s . S. Borden gave advice on the s t a t i s t i c a l analysis and wrote computer programs for me. R. and Maureen Wootton a s s i s t e d me i n obtaining f i e l d observations. My work benef i t t e d from discussions with J . Bryan, G. Calef, E. Carl, W. Hamilton, B. Hargrave, D. Kramer, Jennifer Maynard, J . Stimson, and R. Wootton. N. G i l b e r t helped me greatly i n organizing my ideas during the writing of the thesi s . I was supported by a bursary and scholarships from the National Research Council of Canada. 1 INTRODUCTION This study i s a laboratory inves t i g a t i o n of the freshwater three-spined stickleback, Gasterosteus aculeatus. The purpose was 1) to describe s o c i a l organization of a t e r r i t o r i a l animal with s p e c i a l reference to ways i n which s o c i a l s t a b i l i t y i s achieved and disrupted, 2) to develop methods of quantifying aggressive behaviour i n order to determine whether there are behavioural morphs with d i s t i n c t and consistent i n d i v i d u a l differences, and 3) to determine whether parental success i s associated v/ith s p e c i f i c l e v e l s of the measured behavioural a t t r i b u t e s . The approach to these problems was f i r s t to compare parameters of reproduction and behaviour of animals i n s i t u a t i o n s allowing d i f f e r e n t degrees of s o c i a l contacts. Some differences would give clues about mechanisms which might be acting i n natural s i t u a t i o n s . Besides monitoring reproductive events, I chose several quantitative measures of male behaviour during the reproductive cycle to measure the v a r i a b i l i t y within and between i n d i v i d u a l s . These r e s u l t s would indicate v/hether animals are s i m i l a r , or i n what ways they are d i f f e r e n t . I used analysis of variance techniques to examine the association between the measures of behaviour and parental success to determine whether ce r t a i n kinds and frequencies of behaviour are linked with reproductive success. The r a t i o n a l e behind t h i s approach i s that a d e t a i l e d analysis of interactions among animals and behaviour of 2 i n d i v i d u a l s might give i n s i g h t into processes operating at the population l e v e l . Behaviour i s one expression of the way i n which animals cope with their environment. Since environment includes conspecifics, the interactions between animals as well as the presence of others are l i k e l y to be involved i n processes a f f e c t i n g numbers. The three-spined stickleback i s a popular experimental animal. Tinbergen (1953) and van den Assem (1967) give accounts of i t s behaviour. The breeding male i s t e r r i t o r i a l , b u i l d s a nest, courts a female and then cares for the eggs and f r y . The f i s h i s suitable for t h i s study because i t i s aggressive, t e r r i t o r i a l , and easy to keep i n the laboratory. Most e t h o l o g i c a l studies of sticklebacks, however, have used s o l i t a r y males, and have been concerned with behaviour per se rather than with i t s e c o l o g i c a l s i g n i f i c a n c e . Van den Assem's (1967) work i s a notable exception; he performed extensive experiments with groups of males i n large tanks. Some of his r e s u l t s have e c o l o g i c a l implications: 1) simultaneous, rather than sequential, introduction of f i s h into a tank r e s u l t s i n a larger number of established t e r r i t o r i e s , 2) males with larger t e r r i t o r i e s are more successful i n courtship of females, and 3) males without clutches i n t e r f e r e with the courtship of other males, and s t e a l eggs from other males' nests. These features could not only determine the si z e of the breeding population, but also i t s composition. 3 MATERIALS AND METHODS The f i s h The f i s h used, i n the laboratory study came from the upper L i t t l e Campbell River i n south-west B r i t i s h Columbia, and according to Hagen (1967), were a l l G. aculeatus form l e i u r u s . Periodic c o l l e c t i o n of f i s h and manipulation of the photoperiod and temperature (Baggerman 1957) provided reproductively mature f i s h at most times of the year. As nearly as possible, the f i s h used i n experiments experienced the same environmental conditions: day length of sixteen hours, and water temperatures of 16 to 22 C. Food for the f i s h was mainly frozen adult brine shrimp; occasionally Daphnia and tubifex worms supplemented the d i e t of females. Fry received newly hatched brine shrimp n a u p l i i u n t i l they could eat the adult shrimp. I fed the f i s h once or twice at s i m i l a r times each day. The aquaria . The aquaria used for experiments were: 1) 17.5-, 37.5-, and 49.4-litre glass aquaria, 2) 269-litre wooden tanks 240 x 56 x 20 cm, with one pl e x i g l a s s side, used as a single container or, with p a r t i t i o n s , as eight separate ones, and 3) 190 x 127 x 20 cm paddling pools. Aquaria and tanks had a layer of sand on the bottom, and a r t i f i c i a l p l a s t i c plants or Ceratopteris sp. and Chara sp 0 planted or f l o a t i n g . The paddling pools had both sand and 4 l i v e plants located i n f i f t e e n uniformly d i s t r i b u t e d dishes.: A l l containers had an a i r supply, most had a f i l t e r i n g system. Treatment of males Experimental males were- kept under one of the following conditions: 1) S o l i t a r y i n glass aquaria. These f i s h could not see other f i s h i n adjacent tanks, but perhaps could see f i s h i n tanks across the room. 2) Isolated-with-visual-contact (hereafter r e f e r r e d to as IVC). These were i n 3 3 . 6 - l i t r e compartments i n the wooden tanks. The p a r t i t i o n s were p a r t i a l l y p l e x i g l a s s so neighbouring males could see and i n t e r a c t with each other at the transparent section. 3) Grouped i n wooden tanks or paddling pools. These f i s h could see and f i g h t each other a l l the time. Behaviour patterns The behaviour of sticklebacks i s well described by Tinbergen (1953) and van I e r s e l (1953). I used the same categories i n describing behaviour associated with the nest and mating. In describing aggressive behaviour, however, I defined patterns somewhat d i f f e r e n t l y than other workers. D e f i n i t i o n s of these appear i n Appendix I. Table I shows which patterns I recorded i n each procedure. 5 Table I Behaviour patterns recognized i n the q u a n t i f i c a t i o n of a c t i v i t y and aggressive behaviour. An "x" indicates that the p a r t i c u l a r pattern was recorded i n the t e s t . Behaviour pattern A c t i v i t y Tester Male Aggressive Behaviour p a r t i t i o n Interaction I n i t i a t i o n s of Interactions Aggressive Hesitate x Approach x Charge x Chase x Bite x Bump Spine Fight x Threaten x Back Off x Flee x Swim x Rest x SwiirirfF l u t ter ing x x x x x X x x x X X X X X X X X X X X X X X X X X X X Nest Building and Sexual Spit Sand Push Bore Glue Zig Zag Quiver Fan x x x x x x x x x x x 6 Recording procedures i.) Activity-While viewing the f i s h i n the wooden tanks, I recorded the a c t i v i t y of i n d i v i d u a l s i n the groups of males. Each 30 x 30 cm area of the bottom had a name to describe i t s l o c a t i o n . For t h i r t y minutes each day, I wrote down the behaviour pattern and l o c a t i o n of each f i s h every twenty seconds. i i ) Tester male aggressive behaviour test For t h i s test I placed a n u p t i a l l y colored male stickleback i n a p l e x i g l a s s cylinder, 7 cm i n diameter and 10.5 cm high; the cylinder was usually 20 cm from the experimental male's nest. During each test I l i s t e d the behaviour patterns of the experimental male for f i v e minutes a f t e r he f i r s t approached the tester male. The scores of the te s t were t o t a l frequencies of some of the types of behaviour; Bites per f i v e minutes, Bites and Bumps per f i v e minutes, and Approaches, charges, Bites, Bumps, and Swim-Fluttering per f i v e minutes. . A modification of t h i s technique involved a cylinder 5.5 cm i n diameter f i l l e d with water to the l e v e l i n the aquarium. Instead of making handwritten notes, I used a Rustrak c four-channel event-recorder to show 1) how long the experimental male oriented to the tester male, 2) how long the experimental males oriented to the nest and how long the 7 male fanned, 3) the number of Bumps, and 4) the number of B i t e s . This method gave higher numbers of Bites than the handwritten record. i i i ) P a r t i t i o n i n t e r a c t i o n s JVC (isolated-with-visual-contact) males attacked each other at the transparent p a r t i t i o n s . Although I recorded a l l the behaviour patterns i n each bout, the score for t h i s measure was the number of bouts of aggressive i n t e r a c t i o n s at the p a r t i t i o n during f i f t e e n minutes. iv) Interactions among grouped males Grouped males interacted aggressively, with varying frequencies and i n t e n s i t i e s . High i n t e n s i t y i nteractions involved Charging, Charging and B i t i n g , Charging and Chasing and Spine-Fighting; low i n t e n s i t y i n t e r a c t i o n s consisted of Approaching and Hesitating. For each i n t e r a c t i o n , I recorded the i n i t i a t i n g and r e c e i v i n g p a r t i c i p a n t s and the i n t e n s i t y of the i n t e r a c t i o n . These raw data were entered into a table to show which males i n i t i a t e d i n t e r a c t i o n s , and which received them, during the fifteen-minute recording. After each recording session, I mapped the t e r r i t o r y of each male. By " t e r r i t o r y " I mean a topographical area i n which a male spends most of his time, and from which he excludes conspecifics. Since t e r r i t o r i e s i n this s i t u a t i o n are almost always contiguous, there i s no difference between "defended area" and " u t i l i z e d area". 8 v) U t i l i z e d area and aggressive behaviour of s o l i t a r y males To measure the u t i l i z e d area, I recorded the l o c a t i o n o f s o l i t a r y males i n the wooden tanks every f i v e seconds f o r f i f t e e n minutes on each day of the r e p r o d u c t i v e c y c l e . I converted these data to d i s t a n c e s from the nest by measuring the d i s t a n c e from the nest to the center of.each 30 x 30 cm u n i t . Mean d i s t a n c e from the nest on each day of the c y c l e was the index of u t i l i z e d area. Data from the a c t i v i t y records of grouped males were analysed s i m i l a r l y . On each day of the r e p r o d u c t i v e c y c l e I i n t r o d u c e d a t e s t e r male a t 20, 40, 60, 80, 100, and 120 cm from the nest, and recorded aggressive behaviour on the Rustrak r e c o r d e r . These records gave measures of changes i n i n t e n s i t y of aggressive behaviour w i t h d i s t a n c e from the nest during the r e p r o d u c t i v e c y c l e . Reproductive c y c l e events I use the term r e p r o d u c t i v e c y c l e to designate the p e r i o d during which the male s t i c k l e b a c k b u i l d s a nest, f e r t i l i z e s a c l u t c h of eggs, and cares f o r the eggs and f r y . I made rec o r d i n g s on the day of n e s t - b u i l d i n g (NB), on the day of f e r t i l i z a t i o n (day 0), and on each subsequent day up to about day 10. For each male I recorded the f o l l o w i n g events i n i t s career as an experimental animal; 1) date of c o l l e c t i o n from the f i e l d , 2) date the f i s h s t a r t e d i n an experiment, 9 3) date of n e s t - b u i l d i n g , 4) date o f f e r t i l i z a t i o n of a c l u t c h of eggs, 5) date of egg hatching or 6) date of disappearance o f eggs from the nest, 7) the number o f f r y hatching from the c l u t c h , and 8) the number of f r y on each subsequent day up to tw e n t y - f i v e days a f t e r hatching. Because males were extremely aggressive to females, I in t r o d u c e d the females o n l y when they were r i p e , and removed them as soon as they had spawned. 10 FIELD OBSERVATIONS Detailed descriptions and analyses of stickleback behaviour are c l a s s i c a l studies i n ethology (Tinbergen 1953, van I e r s e l 1953, and Sevenster 1961). These were done under laboratory conditions, and, as far as I know, l i t t l e has been published about reproductive behaviour of the stickleback i n the f i e l d , van Mullem (1967), van Mullem and van der vlugt (1964), and Greenbank and Nelson (1959) reported d e t a i l s of f i e l d biology of sticklebacks, but these deal with population s i z e and growth r e l a t i o n s h i p s rather than behaviour and dispersion. This section describes some features of behaviour and dispersion of Gasterosteus  aculeatus form trachurus i n a natural splash pool. The f i e l d s i t e I found the sticklebacks i n splash pools formed i n depressions among outcroppings of volcanic rock just offshore from Chesterman Beach on the west coast of Vancouver Island. The tv/o main pools each receive sea water during storms at high tid e and fresh water v/hich drains o f f the extensive rock surfaces surrounding the system. There are two areas of deep water, but the remaining pool area i s shallow* Sea water inundations and r a i n run-off can f l u s h the system e a s i l y . 11 In most places a layer of s i l t , and mats and t u f t s of algae cover the rock bottom, while crushed mussel s h e l l s and rocks cover a smaller proportion. The f i s h l i v e d i n two major pools. The large one consisted of two regions: l a was roughly rectangular but two rock peninsulas divided i t into two sections. The edges sloped rather steeply to the maximum depth (150 cm). The f i s h b u i l t nests on the ; shallow edges. Females and young of the year remained i n deeper water. l b was a lin e a r channel 50 cm deep with steep sides., T e r r i t o r i a l males occupied the ent i r e channel. Pool 2 had a maximum depth of 100 cm. Boulders and rocks and extensive a l g a l growths increased the s t r u c t u r a l d i v e r s i t y of thi s habitat, but also made observation d i f f i c u l t . Two aggregations of t e r r i t o r i a l males occurred i n the pool. The sticklebacks were by far the most abundant f i s h but crabs, c o t t i d s , and some u n i d e n t i f i e d f i s h shared the pool. Nest s i t e s I determined the exact locations of nests by observing nest-building and sexual behaviour associated with the nest and by a c t u a l l y seeing the nest entrance. In pool l a , nine nests were i n rock crevices, twenty were among low t u f t s of algae, and f i v e were exposed on the bottom. In pool l b , of thirteen nests, seven were concealed to some extend i n or under clumps of algae, three were close to v e r t i c a l rock surfaces, and three were on patches of s i l t not covered by algae. 12 Dispers ion I measured distances between nests for f i s h i n pools 2 (1967) and 1 (1968). The distance between nests i s presented i n the frequency d i s t r i b u t i o n i n Table I I . The mean inter-nest distance i s 73.00 cm with a standard error of 2.45 cm. Table III i s an ana lys i s of distance to nearest neighbour for pool la., l b , and laboratory experiments. In pool l a the f i s h claimed t e r r i t o r i e s i n the p e r i p h e r a l shallow water; i n pool lb the f i s h claimed the e n t i r e channel; i n the laboratory pools , the f i s h chose nest s i t e s from locat ions spaced uniformly on centers of a g r i d 38 x 43 cm. The index of d i s p e r s i o n , R, has a maximum value of 2.1419 for a p e r f e c t l y uniform d i s t r i b u t i o n , 1.00 for a random d i s t r i b u t i o n , and 0.0 for completely aggregated d i s t r i b u t i o n . The R's for l a , l b , and the laboratory pools r e s p e c t i v e l y are 1.325, 2.050, and 1.967. These are a l l s i g n i f i c a n t l y d i f f e r e n t from random d i spers ion and ind ica te uniform dispers ions of various degrees. Removal of t e r r i t o r i a l males • I removed t e r r i t o r i a l males from the pools to determine the fate of undefended areas . Two f i s h , removed for two hours, e a s i l y defended the ir o r i g i n a l t e r r i t o r i e s when they were returned, even though neighbouring males had encroached on t h e i r t e r r i t o r i e s during the i r absence. 13 Table II Frequency d i s t r i b u t i o n of inter-nest distances i n a f i e l d population of trachurus sticklebacks at Frank Island i n 1967 and 1968. Class Interval 0-9 10-19 20-29 30-39 40-49 50-59 60-69 (cm) Number Observed 0 0 0 3 12 8 27 Number Expected for a Normal .57. 1.12 2.60 5.17 8.89 12.56 15.64 D i s t r i b u t i o n Class Interval ,70-79 80-89 90-99 100-109 110-119 120-129 >130 (cm) Number Observed 18 10 14 6 1 1 3 Number Expected for a Normal 16.41 14.66 11.20 7.84 3.36 1.48 1.52 D i s t r i b u t i o n Mean inter-nest distance 73.00 cm Standard error of the mean 2.45 cm Goodness of f i t to a normal d i s t r i b u t i o n X 2 = 24.18 13 df 0.01* p * 0.05 Table III Dispersion of f i s h i n pool l a , l b and laboratory-tanks. Distance to nearest neighbour (Clark and . Evans 1954). Pool l a Pool l b Laboratory Number of f i s h 33 24., 19 Density of males (males/cm2) .0001233 .0002727 .0001963 Mean distance (cm) to nearest neighbour 59.69 62.08 70.21 Expected mean distance to nearest neighbour i f population i s 45.03 d i s t r i b u t e d at random 30.27 3.5.68 R = *A / ? E 1.325 2.050 1.967 4.097 5.135 4.279 3.578 6.193 8.069 15 I also removed and marked s i x males with adjacent t e r r i t o r i e s and returned them to the pool 50 m away from the i r t e r r i t o r i e s . Two r e s u l t s are i n t e r e s t i n g . F i r s t , one of the removed males had a nest containing eggs. An adjacent t e r r i t o r i a l male raided the nest to s t e a l the eggs. His a c t i v i t i e s attracted other f i s h (up to twenty-six : at one time), which soon ate the remaining eggs and destroyed the nest, but remained aggregated at the nest for twenty minutes. Second, a f t e r eighteen hours two of the males which I had displaced had returned to t h e i r t e r r i t o r i e s . Less b r i g h t l y colored males claimed the remaining area. These new-comers were s t i l l i n possession two weeks l a t e r . Discussion This b r i e f report of some of my f i e l d observations i s s u f f i c i e n t , I hope, to indicate the following. The male sticklebacks appear to prefer to b u i l d their nests close to other objects such as algae or rock faces. This tends to conceal the nest and prevent other f i s h from approaching i t from any d i r e c t i o n . Nevertheless, some f i s h b u i l d nests i n exposed locations. The s p a t i a l pattern of nest s i t e s i s remarkably uniform, e s p e c i a l l y i f one just considers the area where the nests occur. No nests were closer than 3 0 cm. Aggressive behaviour probably produced t h i s spacing as neighbours f i g h t each other continually. 16 The number of t e r r i t o r i a l males was high and the i r even d i s t r i b u t i o n suggested that space might be l i m i t i n g . The removal experiments were designed to resemble the experiment of Stewart and A l d r i c h (1951), who showed that there was a considerable number of bachelor males that s e t t l e d immediately onto vacated t e r r i t o r i e s . My experiments indicated that adjacent males, at lea s t for a short time, continued to respect undefended boundaries. New males, however, claimed permanently vacated t e r r i t o r i e s within eighteen hours. The return of two of the removed males suggests that the f i s h can recognize large areas within the pool system. The f i e l d observations of t e r r i t o r i a l and aggressive behaviour, and egg-robbing were remarkably si m i l a r to those made i n the laboratory. This gives some assurance that the laboratory observations were not merely a r t i f a c t s produced by the unnatural conditions. 17 LABORATORY RESULTS The e f f e c t of other sticklebacks The following section describes a series of experiments which compare sticklebacks i n d i f f e r e n t conditions: s o l i t a r y , IVC, and grouped. The object i s to indicate how grouping males can a f f e c t the performance of i n d i v i d u a l males. i ) Behaviour during the reproductive cycle S o l i t a r y males perform a l l the behaviours described by Tinbergen (1953) except those associated v/ith other males. They p a t r o l their t e r r i t o r y , but never have to f i g h t to defend i t . IVC males behave s i m i l a r l y , but they receive a d d i t i o n a l s t i m u l i from the sight of other f i s h , and they react to and i n t e r a c t with these others a g o n i s t i c a l l y . Some f i s h react r e g u l a r l y and intensely with one or both of their neighbours; others react sp o r a d i c a l l y and weakly. F i s h which react strongly seem se n s i t i v e to movements of the neighbouring males, so that p a r t i t i o n interactions are mutual attacks by neighbours at the p a r t i t i o n . Those f i s h which i n t e r a c t weakly do not swim a c t i v e l y around their compartment, but remain near their nests and behind the opaque part of the p a r t i t i o n s . Grouped males at s i m i l a r reproductive stages, when introduced into large tanks, b u i l d nests i n the tank corners and near the sides. Later s e t t l e r s have to b u i l d between 18 established males, i n more exposed locations. High i n t e n s i t y i nteractions occur more often at the beginning of the experiment than l a t e r (Fig. 1). Each male i n the grouped treatment engages i n aggressive encounters i n order to maintain his t e r r i t o r y . Males repulse not only attacks on themselves, but also on their nest. Each male recognizes his neighbours, and knows the exact l o c a t i o n of their nests. — Males r a i d each other's nests, not only when the owner i s absent, but also when he i s present. These attacks are of two kinds. One r e s u l t s i n the t h e f t of nesting material, the other i n loss of well-developed eggs, which are r a r e l y adopted but usually eaten. The attacking male : takes l i t t l e notice of the resident male; he does not f l e e , but p e r s i s t s i n boring into the nest, keeping his body v e r t i c a l and t a i l waving'above the nest. At the same time, the resident male attacks the r a i d e r e n e r g e t i c a l l y . This a c t i v i t y seems to a t t r a c t other males i f i t l a s t s long enough. If other males come to the nest, the owner cannot keep them a l l away, and they destroy the nest, and s t e a l or eat the eggs. To compare the u t i l i z e d area of s o l i t a r y and grouped males, I analysed distances from the nest. I compared three s o l i t a r y with four grouped males during days 1 to 8 of the reproductive cycle, using d a i l y means of distances from the nest squared (excluding occurrences at the nest). This index gives a better i n d i c a t i o n of area than just the mean 19 80r co z . o 60 u. 40 O rr ui 03 = 20 z < UJ 5 I 5 10 15 DAYS FROM INTRODUCTION FIGURE I 40 o |30 ca to 20 UJ z o r -52 10 a-F E s f E IV c F E G FIGURE 2 Figure 1 Mean number of i n i t i a t i o n s of interactions per 15 minutes among grouped males from the day that the f i s h were introduced to the paddling pools. Open bars are low l e v e l i n t e r a c t i o n s ; bars with the broken l i n e are high l e v e l i n t e r a c t i o n s , n = 3 Figure 2 Days to nest-building from the s t a r t of the experiment for males taken d i r e c t l y from the f i e l d (F) and for males with experience of laboratory conditions (E). S - s o l i t a r y , IVC - isolated-with visual-contact, G - grouped. Bars give the Means, l i n e s give the standard errors. Sample sizes appear i n Table IV. 20 distance from the nest. The i n d i v i d u a l males show considerable v a r i a b i l i t y , but grouped males have s i g n i f i c a n t l y larger u t i l i z e d areas. i i ) Days to nest-building C h a r a c t e r i s t i c behaviour patterns indicate the onset of nest-building i n sticklebacks. Both the i n t e r n a l state of the f i s h and the s t i m u l i from the environment act i n s t a r t i n g t h i s behaviour. Males taken d i r e c t l y from the f i e l d and kept alone take a long time to b u i l d nests; but comparable males put together i n a group take much less time and are no slower than experienced males kept i n a group (Table IV, F i g . 2). part of these differences i s probably due to the traumatic change from the f i e l d to the laboratory. S o l i t a r y f i s h , i n p a r t i c u l a r , take considerable time to become tame, and to learn to eat laboratory food. i i i ) Hatching of clutches A smaller proportion of clutches hatched among grouped males than among s o l i t a r y and IVC males (Table V). However, equal proportions of males hatched clutches i n a l l three treatments (Table VI). (The t o t a l s i n these tables are d i f f e r e n t because some males received more than one clutch.) This r e s u l t could occur i f some of the grouped males were p r o f i c i e n t at obtaining clutches, but, at the same time, unable to hatch them. I could not account for the disappearance of a l l the clutches. With s o l i t a r y and IVC males, eggs which Table IV Analysis of days to nest-building for three treatments of males. There are two c l a s s i f i c a t i o n s of males: Di r e c t from the f i e l d and experienced with laboratory conditions. Males D i r e c t from the F i e l d Mean days to Treatment Sample Size ne s t-bui1ding S.E. S o l i t a r y 7 34.14 6.79 IVC 10 13.90 3.29 Grouped 27 7.81 1.59 Source df ~~ Mean Square F Treatments 2 1928 16.88 Error 41 114.1 F 0 > 0 1 , 2 , 4 0 d f = 5 . 1 8 Experienced Males Mean days to Treatment Sample Size nest-building S.E. S o l i t a r y 13 9.46 2.85 IVC 11 1.36 0.20 Grouped 45 8.33 1.51 Source df Mean Square F Treatments 2 247.5 2.82 Error 66 87.8 F o . 0 5 ' 2 ' 6 0 d f = " 3 ' 1 5 Comparisons between Di r e c t from F i e l d and Experienced Males. Experienced ' 9.46 3 105.93 178.11 3.70 2.101 8.33 45 102.68 89.82 .225 2.00 F i e l d S o l i t a r y Mean days to Males nest-building 34.14 n 7 variance 322.47 weighted variance t to .05' 18 df Grouped Mean days to Males nest-building 7.81 n 27 variance 68.08 weighted variance t to.05' 6 0 d f 22 Table V Hatching success of clutches of eggs with d i f f e r e n t treatments of males. The entries represent clutches of eggs. The expected values, assuming independence of hatching and treatment of male, are i n parentheses. Treatment of 1 Number of Number of parent males clutches hatching clutches not Total hatching S o l i t a r y 15 3 18 (10.9) (7.1) isolated-with- 16 8 24 visual-contact (14.6) (9.4) Grouped 19 21 40 (24.4) (15.6) Tot a l 50 32 82 X 2 = 7.28, 2 df, P < 0.05 23 Table VI Hatching success of clutches belonging to males under d i f f e r e n t treatments. The entries represent the numbers of males. The expected values, assuming independence of hatching success and treatment, are i n parentheses. Treatment of Number of Number of parent males males hatching males not Tot a l clutches hatching clutches S o l i t a r y 12 2 14 (10) (4) Isolated-with 12 9 21 visual-contact (15) (6) Grouped 10 3 13 (9) (4) Total . 34 14 48 X 2 = 3.86, 2 df, .20>p>.10 24 f a i l to hatch must be i n f e r t i l e or neglected by the parent. Among grouped males, I assume these causes were augmented by r a i d i n g . I d i d observe r a i d i n g several times just before the c l u t c h was to hatch; many clutches disappeared a t . t h i s time. i v ) Fanning . Fanning i s an important a c t i v i t y because i t i s necessary for the proper development of the eggs (van den Assem 196.7), and because i t occupies a large amount of time, e s p e c i a l l y just before the eggs hatch. My records show that the amount of fanning i s the same for s o l i t a r y and grouped males (Table V I I ) . F i g . 3 shows how the amount of fanning changes during the reproductive cycle. On day 6, approximately one day before hatching, the males spend 41% of their time fanning. v) Numbers of f r y hatching per clutch When f r y hatch, they are not only small, but also inconspicuous i n c o l o r a t i o n and movements. The most complete counts of f r y ( i . e . the maximum number counted per clutch) are made before the f r y disperse from the nest. Table VIII shows that the numbers of f r y hatched per clutch i s the same whether the parent male i s s o l i t a r y , IVC, or grouped. vi) S u r v i v a l of f r y I calculated the expectation of further l i f e at the day of hatching ( L e s l i e , Tenor, Vizoso, and Chitty 1955). Fry of s o l i t a r y males have an expectation of further l i f e of 25 8 0 O f NB 0 2 4 6 8 10 DAY O F R E P R O D U C T I V E C Y C L E Figure 3 Seconds of fanning per 30 minutes on days of the reproductive cycle. Fanning was recorded foi-l s min before and 15 min after a tester male had been present. Fanning was similar at both times. Mean day of hatching i s 7.1. NB i s day of nest b u i l d i n g and 0 i s day of f e r t i l i z a t i o n , n = 6. 26 Table VII Analysis of variance of fanning comparing S o l i t a r y and Grouped males during the reproductive cycle. Fanning data are seconds of fanning per 3 0 minutes, from 15 minutes before and 15 minutes a f t e r a t e s t with a tester male. Mean day of hatching of the clutches i s 7.1. Source df Mean Sauare Treatment of male Error a Day Treatment x Day Error b Total 1 4 7 7 28 47 26932.7 43736.7 275458.6 1819.5 41030.3 .62 6.71 .04 F = 3 36 0.01, 7,28df * ° Duncan's New Multiple Range Test Means included above the same l i n e are not s i g n i f i c a n t l y d i f f e r e n t from one another Day 6 5 4 7 3 8 2 1 Mean 742 712 569 557 432 328 235 164 27 Table V I I I Numbers of f r y hatched per clutch by males i n d i f f e r e n t treatments. Treatment of Males S o l i t a r y IVC Grouped 1 1 8 1 2 10 •5 ' 4 15 6 7 17 10 7 36 12 8 56 32 10 64 34 13 68 39 17 39 18 56 31 66 40 53 Kruskal-Wallis One-Way Analysis of Variance by Ranks (Siegel 1956) H = 3.405 p 0.20 (X 2 = 5.99 for 0.05, 2 df) 28 20.04 days, while f r y of grouped males have an expectation of 14.41 days. These are s i g n i f i c a n t l y d i f f e r e n t . The major mortality among f r y with grouped males occurs between days 3 and 10, the period of di s p e r s a l from the nest and from the parents' t e r r i t o r y (Tables i x : and X). M o r t a l i t y of f r y with s o l i t a r y males i s d i s t r i b u t e d throughout the twenty-five days. The i n t e r p r e t a t i o n of these r e s u l t s depends on circumstantial evidence which i s as follows: The newly-dispersed f r y are not strong swimmers; they r e s t at the surface, usually hidden among plants or near the sides of the tank. Because they disperse, they often end up i n t e r r i t o r i e s of males other than th e i r parent. Although Tinbergen (1953) claims that parent males do not eat th e i r own f r y , I often observed s o l i t a r y and grouped males attempting to catch f r y . Most attempts were unsuccessful, but some were successful, because males sometimes choked on f r y which were too large to swallow. Since the disappearance of f r y with grouped males coincidedwith the f r y ' s d i s p e r s a l , one possible explanation i s that males ate them. v i i ) Manipulations of t e r r i t o r i a l males a) Additions of males to e x i s t i n g assemblages of t e r r i t o r i a l males Groups of males i n large tanks hold contiguous t e r r i t o r i e s which cover the entir e area of the tanks. New males face considerable opposition to their attempts to s e t t l e . When 29 Table IX Survival of f r y with s o l i t a r y males as parents. Fry from 10 clutches were summed and analysed together. I - day . N(I) - number of f r y on day I A(I) - number of accidental deaths on day I D(I) - number of deaths on day I P(D - p r o b a b i l i t y day I + 1 of s u r v i v a l from day I to L(I) - proportion a l i v e on day I. I N(I) A(I) D(I) P(D L(I) 0 385. 0. , 3. 0.9922 1.0000 1 382. 0. 0. 1.0000 . 0.9922 2 382. 0. 6. 0.9842 0.9922 3 376. 0. 0. 1.0000 0.9766 4 376. 0. 0. 1.0000 0.9766 5 . 1 376. 0. 12. 0.9680 0.9766 6 364. 0. 0. 1.0000 0.9454 7 364. 0. 12. 0.9670 0.9454 8 352. 0. 0. 1.0000 0.9142 9 352. 0. 3. 0.9914 0.9142 10 349. 0. 2. 0.9942 0.9064 11 347. 0. 0. 1.0000 0.9012 12 347. 0. 19. 0.9452 0o9012 13 3 28. 0. 14. 0.9573 0.8519 14 314. 0. 4. 0.9872 0.8155 15 310. 0. 9. 0.9709 0.8051 16 3 01. 0. 18. 0.9401 0.7818 17 283. 0. 11. 0.9611 0.7350 18 272. 0. 22. 0.9191 0.7064 19 250. 0. 44. 0.8240 0.6493 20 206. 0. 2. 0.9902 0.5350 21 204. 0. 4. 0.9803 0.5298 22 200. 0. 3. 0.9850 0.5194 23 197. 0. 1. 0.9949 0.5116 24 196. 0. 0. 1.0000 0.5090 25 196. 0.5090 The Expectation i s 20.04801 Its Variance i s 0.10214 It s Standard Error i s 0.31959 The 95 Percent Confidence Interval i s ( 19.38995, 20.70606) 30 Table X Survival of f r y with Grouped males as parents. Fry from 6 clutches were summed and analysed together. Table headings are i d e n t i c a l to those i n Table IX. .1 N(I) A (I) D(I) P(D L(I) 0 294. 0. 0. l . ooob 1.0000 1 294. 0. 5. 0.9829 1.0000 2 289. 0. 4. 0.9861 0.9829 3 285. 0. 37. 0.8701 0.9693 4 248. 0. 3. 0.9879 . 0."8435 5. 245. •o. 26. 0.8938 0.8333 6 219. .0. 2. 0.9908 0.7448 7 217. 0. 38. 0.8248 0.7380 8 179. 0. 17. 0.9050 0.6088 9 162. 0. 6. 0.9629 0.5510 10 156. 0. 13. 0.9166 0.53 06 11 . . 143. 0. 1. 0.9930 0.4863 12 142. 0. 0. 1.0000 0.4829 13 142. 0. 6. 0.9577 0.4829 14 . 136. 0. 3. 0.9779 0.4625 15 133. 0. 8. 0.9398 0.4523 16 125. 0. 0. 1.0000 . 0.4251 17 125. 0. 0. 1.0000 0.4251 18 125. 0. 9. 0.9280 0.4251 19 116. 0. 0. 1.0000 0.3945 20 116. 0. 1. • 0.9913 0.3945 21 115. 0. 3. 0.9739. 0.3911 22 112. 0. 5. 0.9553 0.3809 23 107. 0. 0. 1.0000 0.3639 24 107. 0. 1. 0.99 06 0.3639 25 106. 0.3605 The expectation i s 14.41493 Its variance i s 0.27440 Its standard error i s 0.52383 The 9 5 percent confidence i n t e r v a l i s ( 13.33637, 15,49350) 31 adding one, two, or three males to e x i s t i n g groups of t e r r i t o r i a l males, I found that no more than two add i t i o n a l males could s e t t l e i n the size of tanks I used. The o r i g i n a l density of males was si m i l a r i n a l l cases (four males i n the wooden tanks, and s i x males i n the paddling pools). b) Removal of t e r r i t o r i a l males In some cases, males with nests co-existed with males without nests and with males Without t e r r i t o r i e s . In an experiment with four males with nests and three without t e r r i t o r i e s , two of the n o n - t e r r i t o r i a l males b u i l t nests a f t e r I removed two of the males with nests. In another experiment, a male that was t e r r i t o r i a l but without a nest, b u i l t a nest immediately a f t e r another t e r r i t o r i a l male died. v i i i ) Reproductive e f f i c i e n c y i n laboratory experiments with grouped males Under laboratory conditions few clutches hatch and few f r y survive. Some reasons for th i s are purely technical, such as u n a v a i l a b i l i t y of gravid females and inadequate control of disease, but others are lack of extensive cover or natural food for the f r y i n the simple laboratory habitats. Table XI summarises reproductive data on the grouped males. Some males never obtained t e r r i t o r i e s . . Not a l l those with t e r r i t o r i e s b u i l t nests. Some did not obtain clutches, and some males which obtained eggs d i d not hatch them. Some f r y which hatched did not survive to disperse from the nest. Table XI Reproductive e f f i c i e n c y i n laboratory experiments with Grouped males. Males Females Number of males used i n experiments .53 Number of males obta in ing t e r r i t o r i e s 46 -Number of males b u i l d i n g nests 38 Number of males obta in ing c lutches (some males b u i l t nests but had no chance to get eggs) 27 Number of c lutches spawned 54 Number of males hatching clutches 16 Number of c lutches appearing i n nests 4.3 Number of males whose clutches hatched and the f r y survived severa l days 9 Number of c lutches hatched 24 S u r v i v a l of f r y to day 25 af ter hatching 106 of 294 In my experiments, only 20% of those males which obtained t e r r i t o r i e s had f r y which survived more than a few days. From a sample of these only 36% of the f r y hatched l i v e d for at l e a s t twenty-five days. Analysis of measures of behaviour The r e s u l t s presented i n t h i s section analyse the behavioural measurements. I f i r s t describe the average pattern of the responses shown by the f i s h through the reproductive cycle, and then examine the i n d i v i d u a l s ' response more c l o s e l y to determine whether in d i v i d u a l s react s i m i l a r l y i n i n t e n s i t y and pattern. Only one measure i s r e p l i c a t e d s u f f i c i e n t l y to check for bimodality i n the frequency d i s t r i b u t i o n which would be one i n d i c a t i o n of the existence of d i s t i n c t behavioural morphs. F i n a l l y I look at the r e l a t i o n s h i p s between some of the behavioural measures to determine how general the pattern of the responses i s . i ) Temporal patterning I measured aggressive behaviour and t e r r i t o r y size by each method every day, or every second day, during the reproductive cycle. The day of nest-building and day of f e r t i l i z a t i o n are standard reference times. F i g . 4 shows the average temporal pattern of the scores for each measure of behaviour. A l l measures, except the tester male test at 20 cm from the nest, show a general u-shape with highest values on the days before and after the clutch hatches 34 .70 Figure 4 Measures of aggressive behaviour and t e r r i t o r y s i z e during the reproductive cycle. NB i s day of nest-building and 0 i s day of f e r t i l i z a t i o n . a) Tester male aggressive behaviour scores (Bites plus Bumps per 5 min) with tester male 20 cm from the nest, for s o l i t a r y (S), isolated-with-visual-contact (IVC), and grouped (G) males. n = 1 0 for each treatment of males. b) Mean tester male aggressive behaviour scores (Bites per 5 min) for" 6 distances from the nest for s o l i t a r y males i n the wooden tanks. Mean day of hatching i s 7.0. n = 3. c) p a r t i t i o n interactions of IVC males. Mean day of hatching i s 6.0. n = 12. d) I n i t i a t i o n s of interactions of grouped males. Mean day of hatching i s 8.5. n = 9 . e) T e r r i t o r y size i n m~ for grouped males which do hatch (0) and which do not hatch (8) clutches. Mean day of hatching i s 8.0. n = 4 for both kinds of males. f) Index of u t i l i z e d area (mean distance from nest) for s o l i t a r y males i n the wooden tanks, n = 3. 35 The tester male scores at 20 cm from the nest are also unique i n being d i f f e r e n t i n each of the three treatments.. Scores are lowest i n IVC males, intermediate i n grouped males, and highest i n s o l i t a r y males. IVC males often attacked t h e i r neighbours as well as the tester male. These attacks were not included i n the tester male score. Grouped males r a r e l y fought with neighbours during a tester male test, but they were d i s t r a c t e d by other males during the t e s t . S o l i t a r y males devoted a l l t h e i r time and attention to the tester male. I also investigated the responses to tester males, for each of three s o l i t a r y males i n wooden tanks. I recorded tests at 20, 40, 60, 80, 100, and 120 cm from the nest on each day during the reproductive cycle. The means of the t o t a l number of Bites delivered to the tester male i n the s i x tests on each day show the U-shape sim i l a r to the other measures (Fig. 4b, Table XII). The mean number of Bites at each distance decreases with distance from the nest, and appears to l e v e l o f f at 100 cm (Table XII). F i g s . 4a,c,d,e, show the mean temporal pattern of some measures of behaviour. The changes i n l e v e l s of these measures are common to a l l males for p a r t i t i o n i n t e r a c t i o n s , i n i t i a t i o n s of i n t e r a c t i o n s , and t e r r i t o r y size of males which hatch clutches (Table XIII). The tester male scores at 20 cm from the nest for d i f f e r e n t males fluctuate i r r e g u l a r l y (Table XIII), but the mean for a l l males i s constant during the reproductive cycle (Fig. 4a). 36 Table XII Analysis of variance of aggressive behaviour of s o l i t a r y males during t h e i r reproductive cycle. (Bites per 5 min at tester male at s i x d i f f e r e n t distances from nest.) Source df ' Mean Square F Days 13 5077 4.44 .000 Error 65 1142 Distance 5 63370 34.40 .000 Days X Distance ,65 1142 .42 1.000 Error 168 2708 Mean Bites per 5 Minutes Day ( a l l distance's) NB 0 1 2 3 4 5 6 7 8 9 10 44.9 98.1 88.9 82.8 75.5 80.7 86.1 57.4 62.4 88.1 91.6 93.9 11 12 96.3 98.0 Standard error t 13.8 Distance ( a l l days) 20 cm 40 60 80 100 120 146.9 102.7 88.2 60.6 48.4 46.6 Standard error * 13.9 37 Table XIII C o e f f i c i e n t s of concordance for the aggressive behaviour and t e r r i t o r y s i z e measurements. A s i g n i f i c a n t c o e f f i c i e n t indicates that temporal changes i n the si z e of the measurements are common to a l l males or that the males are consistant i n t h e i r scores r e l a t i v e to the other f i s h i n the treatment. (See Siegel (1956) for the c o e f f i c i e n t of concordance.) Measurement Treatment of males Number Consistency of of males i n d i v i d u a l s ' l e v e l of response Common Temporal pattern W P W P Tester male aggressive behaviour test S o l i t a r y IVC Grouped 10 10 10 0.334 .3101 .3716 • • • 02 02 01 .0890 .111 .Q67 .50 .40 .60 p a r t i t i o n Inter-actions IVC 12 .7161 • 001 .2661 .05 I n i t i a t i o n s of i n t e r -actions Grouped 8 .8409 • 001 .3817 .001 T e r r i t o r y Size Grouped Hatching 4 .5504 001 .493 .05 cl u t c h Grouped Not .hatching clu t c h .861 001 ,3545 <T.20 >.10 38 i i ) Consistency of i n d i v i d u a l s ' scores wi th in a reproduct ive cyc le I n d i v i d u a l males, whether s o l i t a r y or grouped, are cons is tent i n t h e i r responses to the tester male. The responses to the measure of p a r t i t i o n i n t e r a c t i o n s , i n i t i a t i o n s of i n t e r a c t i o n s , and t e r r i t o r y s i ze are consis tent a lso (Table X I I I ) . . The frequency d i s t r i b u t i o n of the tester male scores at 20 cm from the nest on the day of n e s t - b u i l d i n g " i s not bimodal' ( F i g . 5 ) . Thus there i s no i n d i c a t i o n of d i s cre t e behavioural morphs i n the response to the tester male at n e s t - b u i l d i n g . i i i ) S i m i l a r i t y between repeated reproduct ive cycles The preceding sec t ion considered the temporal pattern and consistency of the l e v e l of aggressive behaviour for many d i f f e r e n t males. Some males went through more than one reproduct ive c y c l e . Table XIV shows the s t a t i s t i c s on temporal pat tern and consistency of l e v e l response to the . tes ter male at 20 cm from the nest of d i f f e r e n t reproduct ive cycles of the same male. The pat tern of changes i n tes ter male scores i s s i m i l a r i n only two of ten repeated c y c l e s . In a d d i t i o n , the l e v e l of response for three of nine males i s d i f f e r e n t . There are i n s u f f i c i e n t data for the other measures to made comparable analyses for them. 39 15 10 U\0 LU ZD O 5 LU or Li_ G R O U P E D I S O L A T E D - W I T H -V I S U A L - G O N T A C T S O L I T A R Y 0 20 40 60 80 100 120 140 9 29 49 69 89 109 129 149 B I T E S + B U M P S P E R 5 M\H A T N B gure 5 Frequency d i s t r i b u t i o n of tester male aggressive behaviour scores at 2 0 cm from the nest for males i n the three treatments on the day of nest-building. 40 Table XIV S i m i l a r i t y between repeated reproduct ive cycles by the same males i n t h e i r tester male scores . The s t a t i s t i c -^compares the temporal pat tern of the scores i n the two cyc le s , and the matched p a i r s , signed ranks compares the l e v e l of the scores i n the two c y c l e s . A p r o b a b i l i t y of less than 0.05 for ind ica tes that the temporal . patterns are s i m i l a r , and for the matched p a i r s , sighed ranks ind ica te that the l eve l s are d i f f e r e n t . Each l i n e i n the table i s for one i n d i v i d u a l . Matched p a i r s , signed ranks p r o b a b i l i t y S o l i t a r y .715 .015 .05 both cycles .190 .320 NS Grouped .333 .191 NS both cycles .525 .035 NS -.143 .386 NS .048 .500 NS IVC . •. - - .095 .420 .05 both cycles .238 .281 NS Grouped one cyc le .500 .062 _ IVC, one cyc le .048 .500 .05 Treatment of males 1 41 iv) Relation among measures of behaviour I exposed a l l males to tester males every day or every second day. I measured the number of p a r t i t i o n i n t e r a c t i o n s of IVC males and the number of i n i t i a t i o n s of interactions of grouped males every day. Table XV shows the c o r r e l a t i o n c o e f f i c i e n t s between two measures of aggressive behaviour exhibited by the same f i s h . There i s no s t r i k i n g c o r r e l a t i o n between scores for any of the grouped males; the c o e f f i c i e n t s are both p o s i t i v e and negative. Therefore, there is' no close r e l a t i o n between these scores. IVC males have scores which are p o s i t i v e l y correlated i n s i x of a possible twenty-eight cases. Here also the remaining c o e f f i c i e n t s are p o s i t i v e and negative. Those f i s h with large t e r r i t o r i e s usually started more inte r a c t i o n s between neighbours (Fig. 6 ) , while those with smaller t e r r i t o r i e s tended to be on the re c e i v i n g end (Fig. 7 ) . (These observations, of course, are not independent.) The comparison of measures of aggressive behaviour and t e r r i t o r y s i z e i s complicated because the days of hatching are d i f f e r e n t . This i s due to differences i n water temperature among tanks and seasons of the year. Troughs i n the curves occur from day 4 to day 6 . However, i f the time scale i s adjusted so that the b i o l o g i c a l l y s i g n i f i c a n t events, day of f e r t i l i z a t i o n and day of hatching, occur i n phase, and the intervening time i s scaled accordingly, the correspondence improves greatly (Fig. 8 ) . Therefore, i f we think i n terms of 42 Table XV Correlation c o e f f i c i e n t s between measures of aggressive behaviour for i n d i v i d u a l males. Grouped males: Tester male scores and i n i t i a t i o n s of int e r a c t i o n s . r n r n -.4924 14 ' .23 08 10 -.3840 14 .3487 10 -.3371 14 . 3 599 10 -.2149 14 .4552 14 .0479 10 .4604 10 .0721 14 Isolated-with-visual-contact males: Tester male scores and p a r t i t i o n i n t e r a c t i o n s with each of the neighbouring males. r n r. n -.3362 12 • -.5717* 12 -.0399 12 -.3241 12 -.'5177 12 -.2904 12 .0252 12 -.2061 12 -.0390 • 12 .1248 12 .5338 12 ..3195 12 - .2913. 12 .4706 12 .5837* 12 .2366 12 .3741 12 .6558* 12 -.4318 12 .4886 12 .9930** 12 .3770 12 .9237** 12 .0832 12 .9624** 12 .5365 12 -.2942 12 -.0712 12 * p ^ 0.05, * * p<0 .01 43 o .13 .26 .39 .52 .65 .77 .13 .26 .39 .52 .65 .77 MEAN TERRITORY SIZE ( M 2 ) MEAN TERRITORY SIZE (M 2) FIGURE 6 FIGURE 7 Figure 6 Changes i n mean number of i n i t i a t i o n s of i n t e r a c t i o n s per neighbour v/ith changes i n mean t e r r i t o r y s i z e . Each po int represents the means for one f i s h . p = 0.0546 Figure 7 Changes i n mean number of rece ip t s of in t erac t ions per neighbour with changes i n mean t e r r i t o r y s i z e . Each point represents the means for one f i s h , p = 0.2453. 4 4 NB 0 H BI O L O G I C A L T I M E S C A L E Figure 8 Temporal patterns of measures of aggressive behaviour and t e r r i t o r y s i ze during the reproduct ive cyc le with day of f e r t i l i z a t i o n and day of hatching corresponding for each measure. o + + + T e r r i t o r y s i ze (m2) © U t i l i z e d area (mean distance from the nest) A_ _ _ _ i n i t i a t i o n s of in t erac t ions .-c - „ p a r t i t i o n in terac t ions ° Mean tester male score for 6 distances from the nest (Bites per 5 min) . 45 a b i o l o g i c a l time sca le , rather than a d i e l one, the measures of aggressive behaviour, t e r r i t o r y s i z e , and u t i l i z e d area i n d i c a t e s i m i l a r change's i n i n t e n s i t y at corresponding b i o l o g i c a l t imes. Measures of behaviour and parenta l success Reproductive success i s assessed by contr ibut ion to the next generat ion. In th i s laboratory study, such an approach was imposs ib le . Therefore, i n the f o l i o wing sec t ion , the operat iona l d e f i n i t i o n of parenta l success i s the a b i l i t y to hatch a c l u t c h of eggs. I chose th i s because 1) some males hatched c lutches while others f a i l e d , 2) the number of f r y hatched per c l u t c h was s i m i l a r , although v a r i a b l e , f o r s o l i t a r y , IVC, and grouped males, and 3) among grouped males, f a i l u r e of c lutches to hatch was associated with inter ference with nest and eggs by other males. This sec t ion examines the measured behavioural c h a r a c t e r i s t i c s of grouped males which d i d hatch clutches and of those which d i d not . I attempt here to f i n d di f ferences between success ful and unsuccessful animals i n characters which are e a s i l y measurable and seem to have e c o l o g i c a l s i g n i f i c a n c e . The approach i s s t r i c t l y c o r r e l a t i v e , but , i f a r e l a t i o n s h i p i s e s tab l i shed , i t provides pred ic t ions which can be tested independently. 46 i ) Behaviour of males hatching and not hatching c lutches An ana lys i s of variance (Table XVI) shows the trend of the means of tests over successive days, the data being repeated observations on each subject each day. The behavioural measurements were 1) tes ter male aggressive behaviour scores for-grouped males, 2) p a r t i t i o n i n t e r a c t i o n s of IVC males, 3) i n i t i a t i o n s of i n t e r a c t i o n s and 4) r e c e i p t s of i n t e r a c t i o n s by grouped males, and 5) t e r r i t o r y s ize of grouped males. The. only scores which vary from day to day are p a r t i t i o n i n t e r a c t i o n s , i n i t i a t i o n s of i n t e r a c t i o n s , and t e r r i t o r y size.-F i g . 4e and Table XVII show that a d i f ference i n t e r r i t o r y s i ze occurs only during the f i r s t part of the reproduct ive cyc le ; at th i s time, those males which l a t e r f a i l to hatch t h e i r c lutches have smaller t e r r i t o r i e s . i i ) A c t i v i t y of males hatching and not hatching clutches The a c t i v i t y data on grouped males ind ica te what behaviour patterns the f i s h perform and where. The data treated here are for four f i s h only; two that hatched c lutches , and two.that d id not . The conclusions drawn from th i s -sect ion must be t en ta t ive . On any day only one f i s h appeared i n some of the 30 x 30 cm areas . In that case, that f i s h was an "exclusive occupant" of that square. The number of squares which a male occupied e x c l u s i v e l y i s one measure of t e r r i t o r y s i z e . Another measure i s the number of squares i n which a f i s h appeared at l eas t 47 Table XVI Ana lys i s of variance of aggressive behaviour scores and t e r r i t o r y s i ze c l a s s i f i e d according to parenta l success. Treatment Behavioural Measurement Source df Mean Square F P Grouped Tester male Hatch 1 1739.88 1.159 (Bites and E r r o r a 15 1500.004 Bumps) Day 6 506.34 1.054 H :x D 6 629.65 1.3117 E r r o r b 90 480.02 Grouped Tester male Hatch 1 3004.8 1.84 (Approaches, E r r o r a 15 1625.02 B i t e s , Bumps, Day 6 680.44 1.33 Charges and H X D 6 982.25 1.91 Swim-Flutter- E r r o r b 90 512.39 ing) IVC p a r t i t i o n Hatch 1 91.12 .1035 Inter - E r r o r a 10 879.80 act ions Day 7 189.017 3.397 .01 H X D 7 52.59 .945 E r r o r b 70 55.64 -Grouped I n i t i t a t i o n s Hatch -1 .04 .000063 of In ter - E r r o r a 7 633.95 act ions Day 11 131.57 2.097 : o5 H X D 11 15.49 .2468 E r r o r b 77 62.74 Grouped Receipts Hatch 1 26.748 .205 of In ter - E r r o r a 7 130.424 act ions Day 11 18.272 1.59 H X D 11 19.264 1.68 E r r o r b 77 11.459 Grouped T e r r i t o r y Hatch 1 .394 2.689 Size (m2) Error a 6 .1465 Day 10 .0337 3.844 .01 H X D 10 .0281 3.205 .01 E r r o r b 60 .00876 .01 48 Table XVII Dif ferences i n mean t e r r i t o r y s ize oif males hatching and males not hatching the i r c lu tches . Sample s i ze for each c lass of f i s h i s four . Day Mean T e r r i t o r y Size 2" SE fc Hatch Not Hatch NB .42 + .0946 .33 ± .0715 0.758 0 .62 - .0945 .32 - .0629 2.643 1 .67 - .0929 .32 - .0687 3.026 2 .68 ^ .0924 .40 - .0641 2.489 3 .49 - .1013 .46 - .0539 0.261 t 0.05, 7 df = 2.365 49 75% of the time that any f i s h was i n that square. A t h i r d i s the mean distance from the nest of a l l a c t i v i t i e s not at the nest . For the se lec ted measures of t e r r i t o r y s ize and a c t i v i t y , males hatching clutches are s i m i l a r to males not hatching c lutches i n the area of exc lus ive occupancy, the mean distance from the nest at which aggressive encounters occur, and the proport ion of a c t i v i t i e s which are aggress ive . However, males not hatching clutches spend less time at the nest , have almost s i g n i f i c a n t l y greater mean distances from the nest , and larger (bu.t not s i g n i f i c a n t l y so) areas of 75% occupancy during most of the reproduct ive cyc le (Table XVIII , F i g . 9 ) . F i g . 10 shows the same measures as F i g . 9 for three reproduct ive cycles of the same f i s h . The means of the measures for the two cyc les i n which the f i s h hatched his c l u t c h , are s i m i l a r to the measurements for the cyc le i n which the f i s h f a i l e d to hatch his c l u t c h ; except that aggressive encounters were c loser to the nest during the cyc le i n which the c l u t c h d i d not hatch. i i i ) T e r r i t o r y s i ze and i n i t i a t i o n s of i n t e r a c t i o n s for males hatching c lutches , not hatching c lutches , and without eggs F i g . 6 shows the r e l a t i o n s h i p between i n i t i a t i o n s of i n t e r a c t i o n s per neighbour and t e r r i t o r y s i z e , for a l l f i s h . There were, however, three c lasses of f i s h : those that had no eggs, those that had eggs but d i d not hatch them, and those Table XVIII A n a l y s i s of variance of A c t i v i t y data Measure Source df MS F 100% Occupancy Hatch 1 9. 19 .158 T e r r i t o r y Size E r r o r a 2 58. 02 Day 11 3. 96 11.31 Day X Hatch 11 6. 16 17.61 E r r o r b 22 o 35 75% Occupancy Hatch 1 63. 33 1.489 T e r r i t o r y Size E r r o r a 2 43\ 87 Day 11 1. 87 .66 Day X Hatch. 11 1. 69 .61 E r r o r b 22 p Mean Distance from Nest A l l A c t i v i t i e s Hatch E r r o r a Day Day X Hatch E r r o r b Proport ion of A c t i v i t i e s at Nest Hatch E r r o r a Day Day X Hatch E r r o r b Proport ion of A c t i v i t i e s i n Aggressive Behaviour Hatch E r r o r a Day Day X Hatch E r r o r b 1 2 11 11 22 15236.81 1081.20 130.16 280.93 136.61 14.09 <-!,>. .95 2.056 .1 . 1 2 11 11 22 1.411 . 148 .0522 .0390 .029 9.533 1.80 1.34 .1 1 2 11 11 22 0005 0182 00196 00202 0134 027 146 150 Figure 9 Behavioural measures during the reproduct ive cyc le from data on a c t i v i t y comparing grouped males hatching (o) and not hatching (©) c lu tches , n = 2 for both kinds of males. a) T e r r i t o r y s i ze as numbers of 30 x 30 cm uni ts occupied exc lus ive ly by the male. b) T e r r i t o r y s i ze as numbers of 30 x 30 cm uni t s i n which the male occurs at l eas t 75% of the observations i n those u n i t s . c) T e r r i t o r y s i ze - u t i l i z e d area (mean distance from the nest of a l l a c t i v i t i e s not at the n e s t ) . d) Mean distance from the nest of aggressive a c t i v i t i e s . e) proport ion of observations of the f i s h at the nest . f) proport ion of observations of the f i s h i n which they were engaged i n aggressive a c t i v i t i e s . 52 r ALL ACTIVITIES NOT AT NEST NB 0 N8 0 2 4 6 8 10 DAY OF REPRODUCTIVE CYCLE Figure 1 0 Behavioural measures during the reproduct ive cyc le from data on a c t i v i t y of one grouped male for two cycles i n which he hatched a c l u t c h (o), and one i n which he d i d not ( © ) . a) to f) as i n F igure 9. 53 that had eggs and d id hatch them. There i s no c o r r e l a t i o n between t e r r i t o r y s ize and i n i t i a t i o n s of i n t e r a c t i o n s for males without eggs and males not hatching c lutches , but there i s for males hatching c lu tches . A decrease i n t e r r i t o r y s i ze i s accompanied by a decrease i n i n i t i a t i o n s of i n t e r a c t i o n s (F ig . 11). 54 5 0 ? 2 .13 .26 .39 .52 .65 7J .90 1.03 T E R R I T O R Y S I Z E (M*) ' F i g u r e 11 Change i n i n i t i a t i o n s of i n t e r a c t i o n s and t e r r i t o r y s i ze for 4 grouped males which hatched c lutches . Each point i s the t e r r i t o r y s ize and number of i n i t i a t i o n s of i n t e r a c t i o n s i n one day for one male. r = 0.66, b = 0.022, p< 0.01, n = 103. 55 DISCUSSION The e f f ec t of other s t i ck lebacks Comparison of s o l i t a r y , IVC, and grouped males, which d i f f e r i n the k i n d and i n t e n s i t y of contacts with other males ind ica te s that the presence of other males inf luences the outcome and suggests some mechanisms of the in f luence . The data on days to n e s t - b u i l d i n g , although they do not . a c t u a l l y tes t , do support van Mullem's (1967) contention that i n the f i e l d s t i ck lebacks are synchronized i n producing f r y . Environmental condit ions st imulate reproduct ive maturi ty (Baggerman 1957), promoting the males to group together i n areas su i tab le for t e r r i t o r i e s . I f th i s grouping st imulates immediate n e s t - b u i l d i n g , so that a l l males are ready to rece ive eggs at about the same time, f r y w i l l be r e c r u i t e d i n waves. Among males taken d i r e c t l y from the f i e l d , grouped males took l eas t time to b u i l d i n my experiment. Grouping, however, increases opportuni t i es for males to interfere with each other , van den Assem (1967) says that males without c lutches s t e a l eggs from those males which have. This c e r t a i n l y d i d happen i n my experiments, and was a lso observed i n the f i e l d . Thus asynchrony of males v / i t h c lutches may reduce the production of f r y . Recruitment i s decreased not only by th i s loss of c lutches of eggs, but a l so by cannibalism of free-swimming f r y . Fry belonging to grouped, asynchronous males survive less we l l than do f r y belonging to s o l i t a r y males (Tables IX and : X ) 0 56 The observat ion that grouped males have larger means of distances from the nest squared, and thus perhaps larger u t i l i z e d areas, can be in terpre ted i n r e l a t i o n to the behaviour of the s o l i t a r y and grouped f i s h . The f o c a l po in t of a s t i ck leback t e r r i t o r y i s the nest . This provides the component of t e r r i t o r i a l i t y c a l l e d s i t e attachment by Tinbergen (1957). The second component, i n t r a s p e c i f i c h o s t i l i t y , i s absent for s o l i t a r y males, but c l e a r l y present for grouped males. Because grouped males are involved i n boundary c o n f l i c t s while s o l i t a r y males are not, i t seems l i k e l y that the d i f ferences i n means of distances from the nest squared are due to the involvement of grouped males i n boundary defence. Consequently, the presence or absence of other males modifies the way males u t i l i z e area. A n a l y s i s of measure of behaviour On a b i o l o g i c a l time sca le , mean tester male scores , p a r t i t i o n i n t e r a c t i o n s , i n i t i a t i o n s of i n t e r a c t i o n s , t e r r i t o r y s i z e , and u t i l i z e d area have s i m i l a r temporal patterns (F ig . 8) . These behaviour- patterns are a l l expressed at the t e r r i t o r i a l boundary, so perhaps one would expect s i m i l a r temporal pa t terns . The one measure which d i d not fo l low th i s common temporal pa t t ern , namely the tes ter male aggressive behaviour tes t at 20 cm from the nest , was l eas t inf luenced by the t e r r i t o r i a l boundary because of the nearness of the tester male to the nest . 57 Although others (Segaar 1961 and Wootton 1968) have obtained U-shaped patterns for th i s t e s t , my tes ts at 20 cm apparently , produced a maximal response from the s o l i t a r y males at a l l times. The decreased l e v e l of response i n grouped and IVC males was probably due to the s t i m u l i rece ived from the other males, but the proximity to the nest l e f t the day-to-day levels .unchanged during the c y c l e . Males d i f f e r both i n the l e v e l and i n the pattern of changes i n response to a tester male 20 cm from the nest; and i f the same male repeats a reproduct ive cyc le , both the l e v e l and pat tern of these scores are a lso l i k e l y to be d i f f e r e n t . My data on repeated cycles are l i m i t e d but van den Assem (1967) compared the t e r r i t o r y s i zes of males i n repeated s e t t l i n g s i n i d e n t i c a l and d i f f e r e n t h a b i t a t s . There was good c o r r e l a t i o n between t e r r i t o r y s izes of males i n repeated s e t t l i n g s i n i d e n t i c a l habi ta t s , but not i n d i f f e r e n t hab i ta t s . Van den Assem concluded that males can recognize a s i t u a t i o n i n which they have nested before . The tester male t e s t s . a t s i x distances from the nest show the U-shap.e when the scores for each day are averaged for a l l distances (F ig . 4b), but , i f the scores for each distance are p l o t t e d separate ly , the scores at 20'cm are r e l a t i v e l y constant, and the others are U-shaped. Fanning and time spent at the nest show changes inverse to the aggressive behaviour measures. This impl ies that there i s a switch from aggressive a c t i v i t i e s to fanning. When near 58 t h e i r nest , s t i ck lebacks are aggressive throughout the reproduct ive cyc le ; but when they have to care for t h e i r eggs, they do not defend o u t l y i n g parts of the i r o r i g i n a l t e r r i t o r i e s . The choice of a measure of aggressive behaviour which i s f u n c t i o n a l l y s i g n i f i c a n t depends upon the kinds of questions one asks. The tester male scores at 20 cm from the nest seem to produce a consis tent maximal response during one reproduct ive c y c l e . P a r t i t i o n in terac t ions and i n i t i a t i o n s of i n t e r a c t i o n s of males are consis tent i n both l e v e l and temporal p a t t e r n . A r t i f i c i a l manipulations of the f i s h produce the t e s t ing condit ions for both the tes ter male tests and the p a r t i t i o n i n t e r a c t i o n s , while a simulated na tura l s i t u a t i o n provides the condit ions for the i n i t i a t i o n s of i n t e r a c t i o n s . This l a t t e r s i t u a t i o n has more uncontro l led v a r i a b l e s , such as number of neighbours and s tructure of hab i ta t . One cannot, from my data, separate cause and e f fec t i n the r e l a t i o n s h i p between i n i t i a t i o n s of i n t e r a c t i o n s and t e r r i t o r y s i ze (Fig . 11). E c o l o g i c a l l y , s t a r t i n g a f i g h t seems to be the most meaningful. On the other hand, the tester male test at 20 cm from the nest may give a bet ter measure of "innate aggressiveness", and t e r r i t o r y s ize may be an even bet ter index of a l l the behavioural c h a r a c t e r i s t i c s necessary for success fu l r e a r i n g of young. 59 Measures of behaviour and parenta l success There are di f ferences between males which hatch and which do riot hatch c lu tches . Males with small t e r r i t o r i e s a t the beginning of the reproduct ive cyc le f a i l to hatch t h e i r c lutches , but the loss of the eggs does not occur u n t i l jus t , before hatching. Why th i s r e l a t i o n s h i p holds i s d i f f i c u l t to e x p l a i n . Just before the eggs.are to hatch, males whose eggs l a t e r hatch have s i m i l a r s i zed t err i tor i e s ." The data on a c t i v i t y ind i ca te that males which do hatch clutches remain c loser to the nest and spend more time at the nest than males which do not hatch c lu tches . Both types of males engage i n aggressive concounters at s i m i l a r distances from the nest . The proport ion of these encounters of the t o t a l a c t i v i t y i s a lso s i m i l a r . - Perhaps something of the male's behaviour wi th in his t e r r i t o r y r e s u l t s i n others attempting to r a i d the nest . Judged by my tes t s , males that hatch clutches are not more aggressive than those that do not . This seems incons i s tent , since, the temporal pat tern of changes i n t e r r i t o r y s ize of males hatching clutches i s the same ajs the aggressive behaviour measure (Fig . 8) , but the t e r r i t o r y s ize measure does d i s t i n g u i s h between males hatching clutches and those that f a i l . E i t h e r the behaviour tests are not s ens i t ive to the d i f ference between the c l a s s i f i c a t i o n of males, or there r e a l l y may be no di f ferences i n these behaviours. A l s o , t e r r i t o r y s ize must be a r e s u l t of many a t t r i b u t e s of the male, not only i t s aggressive behaviour. 60 The fo l lowing scheme seemsplausible as an explanation df the observations on parenta l success. A combination of increas ing day length and temperature (Baggerman 1957) and s o c i a l s t i m u l i (van den Assem 1967 and th i s study) induce reproduct ive maturity among s t i c k l e b a c k s . The males c la im t e r r i t o r i e s i n su i tab le areas . Distances between nests are rather uniform, but there are d i f ferences i n t e r r i t o r y s i ze dependent on s tructure of the habi ta t , order of s e t t l i n g , and many i n d i v i d u a l c h a r a c t e r i s t i c s . Males i n t e r a c t c o n t i n u a l l y . Each male learns the l o c a t i o n of h i s neighbours' nests , and assesses his neighbours' pugnacity. The competition for grav id females i s won by the males with the larges t t e r r i t o r i e s (van den Assem 1967). Some males f a i l to obtain eggs. These males are a t t r a c t e d to nests of males which have clutches about to hatch. Males without clutches make success fu l r a i d s on other nests , but only on nests of males which, during the f i r s t part of the reproduct ive cyc le have small t e r r i t o r i e s . At the time of r a i d i n g these t e r r i t o r i e s have contracted to the same s i ze as those of the other f i s h . Males suscept ib le to r a i d s spend more time away from the nest , and do not change the frequency of i n i t i a t i o n s of in t erac t ions with the s ize of the i r t e r r i t o r i e s . Once the eggs hatch and the f r y become free-swimming, the male guards them for a few days, but when the f r y disperse they r i s k ge t t ing eaten by other males. S u r v i v a l of the f r y depends on the ir behaviour and on the a v a i l a b i l i t y of refuges . 61 One must chose between the rea l i sm of the f i e l d and the prec i se contro l s poss ib le i n the laboratory . i t i s exceedingly d i f f i c u l t to know how c l o s e l y most laboratory studies apply to the f i e l d . This study i s no exception e s p e c i a l l y because i t lacks extensive f i e l d observat ions . However, the processes going on i n the laboratory such as nest des t ruc t ion , egg s t e a l i n g and f r y predat ion , do occur i n the f i e l d . The present data can not answer whether the frequencies of such behaviour are the same. The dens i t i e s o f males and the mean distance to the nearest neighbour are s i m i l a r i n laboratory and f i e l d . Q u a l i t a t i v e l y the aggressive i n t e r a c t i o n s are i d e n t i c a l . At th i s po int , one could speculate about the s u r v i v a l value of these kinds of behaviour and the s e l e c t i v e pressures exerted on them. I have already suggested how my observations f i t together, and I think further speculat ion i s inadv i sab le . Instead, I w i l l suggest the kinds of observations and experiments I would perform i n the f i e l d . F i r s t , to check the s i m i l a r i t y between the f i e l d and the laboratory , I would quantify aggressive behaviour and . t e r r i t o r y s ize i n the f i e l d as I d i d i n the laboratory . In a d d i t i o n , a count of the number of clutches i n each nest would check van den Assem 1s observation that males with larger t e r r i t o r i e s are most success fu l i n obta in ing c lutches . I would remove t e r r i t o r i a l males ana watch for subsequent s e t t l i n g of other males. This experiment, s i m i l a r ' t o that of 62 Stewart and A l d r i c h (1951), would ind ica te whether there were a segment of the populat ion unable to breed. I f "bachelor" males d i d s e t t l e , a f ter the removal of terr i tory-holders , I would compare t h e i r behaviour with that of the males they rep laced . I would place the males I removed i n an i s o l a t e d area and compare the i r behaviour i n the new area with that i n the o r i g i n a l t e r r i t o r y . This would check on the consistency of the i r behaviour i n d i f f e r e n t reproduct ive cyc le s . With assembled populat ions composed or d i f f e r e n t proportions of r e l a t i v e l y aggressive the r e l a t i v e l y doc i l e males, I could compare frequency of nest and egg interference and production of f r y . 63 CONCLUSIONS The aims of th i s study were p a r t l y met. The feature of s o c i a l organ iza t ion of aggregations of t e r r i t o r i a l males which r e s u l t s i n s t a b i l i t y i s a decrease i n aggressive encountors as males recognize the t e r r i t o r i a l claims of the i r neighbours. The cause of most d i s r u p t i o n i s the presence of males without c lutches which destroy nests and s t e a l eggs about to hatch. Males suscept ib le to such r a i d s have small t e r r i t o r i e s at the beginning of the reproduct ive cyc l e , spend less time at the nest , and stay farther from i t * The measures of aggressive behaviour seem to ind ica te that males do" have d i s t i n c t and cons is tent aggressive behaviour, but the l e v e l may d i f f e r i n o'ther reproduct ive c y c l e s . Success of hatching clutches i s not assoc iated with the measured aggressive behaviour, but rather with s i ze and u t i l i z a t i o n of the t e r r i t o r y . 64 REFERENCES Assem, J . van den 1967. T e r r i t o r y i n the three-spined s t i ck leback Gasterosteus aculeatus L . Behaviour Suppl . 16, 1-164. Baggerman, B. 1957. An experimental study on the timing of breeding and migrat ion i n the three-spined s t i ck leback (Gasterosteus aculeatus L . ) A r c h s n e e r l . z o o l . 12, 105-312. C l a r k , p . J . and Evans, F . C . 1954. Distance to nearest neighbor as a measure of s p a t i a l r e l a t i o n s h i p s i n populat ions . Ecology 35, 445-453. Edwards, A . L . 1960. Experimental design i n psycho log ica l research . H o l t , Rinehart and Winston. New York. 398 pp. Greenbank, J . and Nelson, P .R. 1959. L i f e h i s t o r y of the threespine s t i ck leback Gasterosteus aculeatus Linnaeus i n Karluk Lake and Bare Lake, Kodiak Is land, A l a s k a . F i s h e r y B u l l . F i s h W i l d l . Serv. U . S . 59, 537-559. Hagen, D.W. 1967. I s o l a t i n g mechanisms i n threespine s t i ck lebacks (Gasterosteus) . J . F i s h . Res. Bd- Can. 24, 1637-1692. ' I e r s e l , J .J.A. van 1953. An ana lys i s of the parenta l behaviour of the male three-spined s t i ck leback , Gasterosteus aculeatus L . Behaviour Suppl . 3_, 1-159. 65 L e s l i e , P . H . , Tener, J . S . , V izoso , M. and C h i t t y , H . 1955. The longevi ty and f e r t i l i t y o f the Orkney vo le , Microtus orcadensis , as observed i n the laboratory . Proc . z o o l . Soc. Lond. 125, 115-125. Mullem, P . J . van 1967. On synchronizat ion i n the reproduct ion of the s t i ck leback (Gasterosteus aculeatus L . forma l e i u r a C u v . ) . Archs n e e r l . Z o o l . 17, 258-274. Mullem, P . J . van and V l u g t , J . C . van der 1964. On the age, growth and migration' of the anadromous s t i ck leback , Gasterosteus aculeatus L . inves t iga ted i n mixed populat ions . Archs n e e r l . Z o o l . 16_, 111-139. Segaar, J . 1961. Telencephalon and behaviour i n Gasterosteus aculeatus . Behaviour 18, 256-287. Sevenster, P. 1961. A causal ana lys i s of a displacement a c t i v i t y (fanning i n Gasterosteus aculeatus L . ) . Behaviour Suppl . 9_, 1-170. S i e g e l , S. 1956. Nonparametric s t a t i s t i c s for the behaviora l sc iences . McGaw-Hill Book Company, Inc. Toronto. 312 pp. Stewart, R . E . and A l d r i c h , J.W. 1951. Removal and repopulat ion of breeding b i r d s i n a s p r u c e - f i r fores t community. Auk 68_, 471-482. Tinbergen, N. 1953. S o c i a l behaviour i n animals. Methuen & Co. L t d . London. 150 pp. Tinbergen, N. 1957. The funct ions of t e r r i t o r y . B i r d Study 4, 14-27. 66 Wootton, R . J . 1968. A comparative study of tes t procedures and measures of behaviour i n the male three-spined s t i ck l eback , (Gasterosteus aculeatus L . ) Ph.D. t h e s i s . U n i v e r s i t y of B r i t i s h Columbia. 153 pp. 67 APPENDIX I The fo l lowing l i s t gives the d e f i n i t i o n s of each pat tern of aggressive behaviour that I recognized. I have fol lowed the convention, here and i n the text , of c a p i t a l i z i n g the words which r e f e r to the s p e c i f i c behaviour' patterns; th i s sets them o f f and also impl ies a d i s t i n c t meaning as provided i n the d e s c r i p t i o n . Hes i ta te . - The f i s h makes short movements toward and then away from the other male, but remains or iented toward the other f i s h a l l the whi le . Approach. - The male d e f i n i t e l y or ientes towards and moves to the tes ter male or neighbour-male. Charge. - This i s an extremely r a p i d movement d i r e c t l y to another f i s h . Charges usua l ly end.with B i t e s . Chase. - One f i s h swims r a p i d l y a f ter another one which t r i e s ' to evade the aggressor. B i t e . - A B i t e consis ts of contact between a f i s h with an open mouth and another f i s h or the p l e x i g l a s s separating the two f i s h . Bump. - A Bump i s a contact between a f i s h with i t s mouth c losed and the p l e x i g l a s s separating i t from another f i s h . Bumps often occur i n r a p i d succession or a l ternate with Swimming. 68 S p i n e - F i g h t . - This occurs when two f i s h attack each other s imultaneously. They c i r c l e each other r a p i d l y with r a i s e d v e n t r a l spines and t r y to , and often succeed i n , B i t i n g each other . Threaten. - The f i s h assumes a v e r t i c a l p o s i t i o n with i t s head touching or digging in to the sand. There i s a gradat ion of i n t e n s i t y of th i s d i s p l a y from head down, v e n t r a l spines r a i s e d , to Boring head f i r s t in to the sand, a l l spines r a i s e d and vigorous undulations of the body. Back-Off . - When a f i s h performs t h i s a c t i v i t y i t swims backwards from another f i s h , but remains or iented toward i t . F l e e . - A f i s h Flees when i t swims r a p i d l y away from an a t tack ing f i s h . Swim. - This i s any locomotory movement without d i r e c t o r i e n t a t i o n toward other males. Rest . - The f i s h remains motionless . Swim-Flut ter ing . - The at tacking f i s h swims p e r s i s t e n t l y around or up and down the cy l inder wa l l with i t s snout pressed against the p l e x i g l a s s wa l l of the tester male c y l i n d e r . Table I shows which behaviour patterns occurred i n each of the behaviour tests performed i n th i s study. The nest-b u i l d i n g and sexual behaviours fo l low descr ip t ions given by Tinbergen (1953) and van I e r s e l (1953). 

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