"Science, Faculty of"@en . "Zoology, Department of"@en . "DSpace"@en . "UBCV"@en . "Goodey, Wayne"@en . "2010-05-12T16:11:15Z"@en . "1984"@en . "Master of Science - MSc"@en . "University of British Columbia"@en . "Adult guppies (Poecilia reticulata) frequently chase, but only infrequently capture and eat, young conspecifics. On average, young in planted tanks containing 6-14 adults and 1-4 young experienced over 270 chases per individual per day. Does the experience of being chased affect escape behavior? I tested this in two experiments on individual guppies. In the first, the escape behavior of three groups of guppies - control fish (those chased by adults in the first 48 hr of life), partially experienced fish (exposed to chemical cues from chasing adults, visual cues from chasing adults, or chemical cues from predatory fish), and inexperienced fish - was compared for their response to an aerial predator stimulus. Response intensity varied among the treatments, but deprivation had no effect on the appearance of stereotyped escape behaviors. Deprivation had no influence on the drop response elicited by the aerial stimulus, but it caused a general increase in the length of time spent freezing in response to the stimulus. Fish exposed to chemical cues from adult guppies, on the other hand, developed a near-control response.\r\nIn the second experiment, I exposed guppies from the same experience groups to predation to see if long freezing times were selected against. Controls were not attacked with greater latency nor did they survive longer than any deprived group, but it took more attacks to kill control fish than to kill any deprived fish. I propose that chasing by adults is an ontogenetic mechanism for conditioning the young to avoid predation. This is selected for because guppies which are chased as juveniles survive better than those not chased as juveniles."@en . "https://circle.library.ubc.ca/rest/handle/2429/24619?expand=metadata"@en . "FACTORS AFFECTING THE DEVELOPMENT AND EXPRESSION OF ESCAPE BEHAVIOR IN THE GUPPY (POECILIA RETICULATA) by WAYNE GOODEY B . S c , U n i v e r s i t y of B r i t i s h Columbia, 1980 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l 1984 \u00C2\u00A9 Wayne Goodey, 1984 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department o r by h i s o r her r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department o f Zoology The U n i v e r s i t y o f B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date 27 A p r i l 1984 DE-6 (3/81) i i ABSTRACT Adult guppies ( P o e c i l i a r e t i c u l a t a ) f r e q u e n t l y chase, but only i n f r e q u e n t l y capture and eat, young c o n s p e c i f i c s . On average, young i n p l a n t e d tanks c o n t a i n i n g 6-14 a d u l t s and 1-4 young experienced over 270 chases per i n d i v i d u a l per day. Does the experience of being chased a f f e c t escape behavior? I t e s t e d t h i s i n two experiments on i n d i v i d u a l guppies. In the f i r s t , the escape behavior of three groups of guppies - c o n t r o l f i s h (those chased by a d u l t s i n the f i r s t 48 hr of l i f e ) , p a r t i a l l y experienced f i s h (exposed to chemical cues from c h a s i n g a d u l t s , v i s u a l cues from chasing a d u l t s , or chemical cues from predatory f i s h ) , and inexperienced f i s h - was compared f o r t h e i r response to an a e r i a l predator s t i m u l u s . Response i n t e n s i t y v a r i e d among the treatments, but d e p r i v a t i o n had no e f f e c t on the appearance of s t e r e o t y p e d escape b e h a v i o r s . D e p r i v a t i o n had no i n f l u e n c e on the drop response e l i c i t e d by the a e r i a l s t i m u l u s , but i t caused a general i n c r e a s e i n the l e n g t h of time spent f r e e z i n g in response to the s t i m u l u s . F i s h exposed to chemical cues from a d u l t guppies, on the other hand, developed a n e a r - c o n t r o l response. In the second experiment, I exposed guppies from the same experience groups to p r e d a t i o n to see i f long f r e e z i n g times were s e l e c t e d a g a i n s t . C o n t r o l s were not a t t a c k e d with g r e a t e r l a t e n c y nor d i d they s u r v i v e longer than any d e p r i v e d group, but i t took more a t t a c k s to k i l l c o n t r o l f i s h than to k i l l any d e p r i v e d f i s h . I propose that chasing by a d u l t s i s an ontogenetic mechanism f o r c o n d i t i o n i n g the young to a v o i d p r e d a t i o n . T h i s i s s e l e c t e d f o r because guppies which are chased as j u v e n i l e s s u r v i v e b e t t e r than those not chased as j u v e n i l e s . TABLE OF CONTENTS ABSTRACT i i LIST OF TABLES v i i LIST OF FIGURES v i i i ACKNOWLEDGEMENTS ix General I n t r o d u c t i o n 1 General Methods 3 The chasing of young guppies by a d u l t s 4 I n t r o d u c t i o n 4 Methods 4 Re s u l t s 5 D e s c r i p t i o n of behavior 5 A n a l y s i s 5 D i s c u s s i o n 6 The e f f e c t of chasing d e p r i v a t i o n on the development and express i o n of guppy escape behavior 9 I n t r o d u c t i o n 9 Methods 10 Res u l t s 15 D e s c r i p t i o n of behavior 15 A n a l y s i s 15 D i s c u s s i o n 22 Sex and age d i f f e r e n c e s 22 Treatment d i f f e r e n c e s 23 Experience and pr e d a t i o n 24 V The e f f e c t of chasing d e p r i v a t i o n on the s u r v i v a l of guppies under f i s h p r e d a t i o n 27 I n t r o d u c t i o n 27 Methods 28 R e s u l t s 29 D i s c u s s i o n 31 An a l t e r n a t i v e e x p l a n a t i o n of sex d i f f e r e n c e s i n s u r v i v a l a b i l i t y 35 The e f f e c t of immediate s o c i a l d e p r i v a t i o n on the e x p r e s s i o n of escape behavior 37 I n t r o d u c t i o n 37 Methods 38 R e s u l t s 38 D i s c u s s i o n 40 General D i s c u s s i o n 42 P r e d a t i o n p r e s s u r e s o p e r a t i n g on guppies 42 The e f f e c t of e a r l y chasing experience on escape responses and s u r v i v a l under p r e d a t i o n 43 P o s s i b l e mechanisms through which chasing experience might a f f e c t escape behavior 44 The p o s s i b l e f u n c t i o n a l s i g n i f i c a n c e of chasing i n guppies 45 Suggestions f o r f u r t h e r r e s e a r c h 46 C o n c l u s i o n s 49 References 51 Appendix - Summary of d i s t a n c e - t i m e c o r r e l a t i o n t e s t s 56 D e p r i v a t i o n experiment 56 v i Immatures 56 Matures 57 Immediate s o c i a l d e p r i v a t i o n experiment 58 LIST OF TABLES Table I. Summary of c o n t r o l chasing experience 6 Table I I . Summary of experience given i n the d e p r i v a t i o n treatments 12 Table I I I . Summary of sample s i z e s of groups in the a e r i a l model response experiment 15 Table IV. Mean body lengths of f i s h i n the treatment groups. (standard lengths i n cm) 19 Table V. Summary of sample s i z e s f o r a l l treatment groups i n the p r e d a t i o n experiment 29 v i i i LIST OF FIGURES F i g u r e 1. D e r i v a t i o n of treatment groups : d e p r i v a t i o n s exper iment 11 Fi g u r e 2. Experimental apparatus 13 F i g u r e 3. A, stimulus model. B, model c a r r i e r d e t a i l 14 F i g u r e 4. Sex d i f f e r e n c e s i n escape response 16 F i g u r e 5. Age d i f f e r e n c e s i n escape response 18 F i g u r e 6. Treatment d i f f e r e n c e s i n males 20 F i g u r e 7. Treatment d i f f e r e n c e s i n females 21 Fi g u r e 8. I n i t i a l a t t a c k l a t e n c i e s f o r t r e a t e d groups under f i s h p r e d a t i o n 30 F i g u r e 9. T o t a l s u r v i v a l times f o r t r e a t e d groups under f i s h predat ion 32 Fi g u r e 10. Numbers of a t t a c k s per k i l l f o r t r e a t e d groups under f i s h p r e d a t i o n 33 F i g u r e 11. Group e f f e c t s on escape response 39 i x ACKNOWLEDGEMENTS A l l e n B i l l y , Pam McDonald, Jim Cardwell, and Doug Reid acted as in f o r m a l examiners f o r v a r i o u s p a r t s of my work. I am indebted to Ben Seghers and Don Kramer f o r background i n f o r m a t i o n , to Don Ingram f o r the Cren i c i c h l a used i n the p r e d a t i o n experiment, and to Dave Z i t t i n and Susan E r t i s f o r t h e i r computing s k i l l s and p a t i e n c e . Drs. J.N.M. Smith and R.W. Blake p o i n t e d out many problem areas d u r i n g the re s e a r c h , and helped me sol v e them. F i n a l l y , I thank Dr. N.R. L i l e y f o r many h e l p f u l suggestions and e s p e c i a l l y f o r h i s c r i t i c a l comments on the f i r s t two d r a f t s of the t h e s i s . 1 GENERAL INTRODUCTION \"... i s o l a t e d f i s h o f t e n show exaggerated f r i g h t responses. I t would be i n t e r e s t i n g to i n v e s t i g a t e i f experience with c o n s p e c i f i c s i s important f o r the development of a normal e q u i l i b r i u m between the d i f f e r e n t b e h a v i o r a l systems ...\" (Baerends 1971, p.326) When I began to i n v e s t i g a t e the e x p r e s s i o n of escape behavior i n the guppy, I turned to the work of Seghers (1973,1974a,b), who found d i f f e r e n c e s between i s o l a t e d n a t u r a l p o p u l a t i o n s of the guppy. He proposed that these d i f f e r e n c e s were due to the s e l e c t i v e e f f e c t s of d i f f e r e n t p r e d a t i o n regimes. I planned to b u i l d on Seghers' work, but i n order to do so I had to ensure that my f i s h and techniques resembled h i s . In the course of determining an e f f i c i e n t shape for a predator model to use i n a e r i a l s timulus t e s t s , I d i s c o v e r e d that I knew nothing about the i n f l u e n c e that e a r l y experience might have on the behavior of a d u l t guppies. I decided that unless I c o u l d determine the importance of e a r l y experience, I would be u n s a t i s f i e d with the data that c o u l d be gathered from experimental manipulation of a d u l t s of unknown background. I hypothesized that e x p e r i e n t i a l f a c t o r s i n f l u e n c e the development of guppy escape behavior, and that s u r v i v a l of a d u l t 2 guppies under p r e d a t i o n i s i n f l u e n c e d by these f a c t o r s . These hypotheses were suggested in p a r t by the work of Thompson (1966), who i n c r e a s e d the s u r v i v a l of j u v e n i l e P a c i f i c salmon r e l e a s e d from a hatchery by exposing them to an a v e r s i v e stimulus (an e l e c t r i f i e d t r o u t model). F i s h r a i s e d i n the absence of the stimulus ( i . e . i n the normal hatchery technique) s u f f e r e d g r e a t e r m o r t a l i t y when r e l e a s e d . I supposed that in guppies, e a r l y experience of being chased by a d u l t s c o u l d p r o v i d e analogous experience f o r the young. If t h i s i s so, then I c o u l d p o s t u l a t e a p o t e n t i a l l y s e l e c t i v e l y advantageous c o n d i t i o n i n g f u n c t i o n f o r e a r l y chasing experience. L i v e - b e a r i n g f i s h are good s u b j e c t s f o r e a r l y - e x p e r i e n c e experiments, because they are s m a l l , easy to maintain, and independent of the mother immediately a f t e r b i r t h (Stearns 1 9 8 3 ) . In mammals, e a r l y experience i s u s u a l l y d e f i n e d as post-weaning (e.g. Fox and S t e l z n e r 1966, Wilhelmsson amd Larsson 1973), but i n p o e c i l i i d f i s h l i k e the guppy the i d e a l t a b u l a rasa i s more c l o s e l y approached. 3 GENERAL METHODS The guppies I used were bred from f i s h c o l l e c t e d at the Guayamare R i v e r , T r i n i d a d , W.I., i n the s p r i n g of 1980. The f i s h were shipped by a i r to Vancouver, where I e s t a b l i s h e d them in 37.5 1 aquaria at a d e n s i t y of 30 f i s h per tank. F i s h were maintained in aged water over sand (with submerged p l a n t s ) at a temperature of 23 i 1 degrees C. Each tank had a f i l t e r and a g l a s s l i d . The photoperiod was 10.5L:13.5D (short days to c o n t r o l algae) under cool-white f l u o r e s c e n t lamps. Young born i n a l l tanks of breeding a d u l t s were removed, between 24 and 48 hr a f t e r b i r t h , to unoccupied a q u a r i a . I added young to such new tanks u n t i l there were 35-40 pres e n t . By the end of my re s e a r c h , I had r a i s e d i n excess of 1600 f i s h , some as many as f i v e g e n e r a t i o n s removed from the founder group. With a few ex c e p t i o n s , a l l f i s h used in the experiments were t e s t e d only once each, then r e p l a c e d in tanks set a s i d e f o r used f i s h . Thus a l l f i s h were in e x p e r i e n c e d i n t e s t c o n d i t i o n s . The exce p t i o n s are c o n s i d e r e d l a t e r i n the t e x t . 4 THE CHASING OF YOUNG GUPPIES BY ADULTS I n t r o d u c t i o n In t h i s experiment I q u a n t i f i e d the c h a s i n g of young guppies by a d u l t s . I hypothesized that i f escape behavior i s developed through experience, then being chased by a d u l t s i s an important p a r t of that experience. I expected that i f chasing was important, i t should occur f r e q u e n t l y and be a p p l i e d to a l l young. I a l s o expected that c h a s i n g i n t e n s i t y would be a d i r e c t f u n c t i o n of a d u l t guppy d e n s i t y , and that chasing i n t e n s i t y would be an i n v e r s e f u n c t i o n of the amount of cover a v a i l a b l e . Methods I observed tanks of breeding a d u l t s with newborn young. I counted the numbers of a d u l t s and young present and estimated the p r o p o r t i o n of the tank volume occupied by p l a n t m a t e r i a l ( p o t e n t i a l c o v e r ) . I counted the number of chases o c c u r r i n g per 10 min f o r each tank ( i . e . one a d u l t chasing two young or two a d u l t s c hasing one young would each count as two c h a s e s ) . I d i d not score chases of i n d i v i d u a l young, because I observed no apparent p r e f e r e n c e by the a d u l t s f o r s p e c i f i c young. A given tank was observed no more o f t e n than once per day, and a l l young were removed immediately a f t e r the o b s e r v a t i o n was f i n i s h e d . 5 R e s u l t s D e s c r i p t i o n of behavior I found that s e v e r a l d i f f e r e n t a d u l t behaviors e l i c i t e d withdrawal or escape in the young guppy. A chase was d e f i n e d as an o b s e r v a t i o n of any one of these behaviors or any combination of these behaviors as long as i t e l i c i t e d a response. The behaviors were: s e v e r a l vigorous t a i l beats by the a d u l t moving i t i n the d i r e c t i o n of the young; course c o r r e c t i o n s by the a d u l t d u r i n g an approach to the young; and jaw snapping by the a d u l t at c l o s e approach to the young. I observed a l l three behaviors together in most cases, but o f t e n one or two of them were s u f f i c i e n t to e l i c i t a response. A n a l y s i s To show how I used some tanks more than once, I presented a l l the data i n Table I. I found no s i g n i f i c a n t c o r r e l a t i o n between the number of a d u l t s present and the i n t e n s i t y of chasing (Spearman r a n k - c o r r e l a t i o n c o e f f i c i e n t , df=l8, Rs=0.16, p>0.05) and no s i g n i f i c a n t c o r r e l a t i o n between the amount of cover present and the i n t e n s i t y of chasing (df=l8, Rs=-0.10, p>0.05) . 6 Table I. Summary of c o n t r o l c h asing experience. day(1) tank #adults #young #chases(2) chases/young %cover(3) 1 G4 6 2 6 3 5 1 G8R 1 4 2 10 5 1 5 1 G2R 8 2 1 1 5.5 25 2 G7R 10 1 5 5 20 3 G7R 10 2 1 2 6 20 3 G2R 8 2 6 3 25 4 G2R 8 4 5 1 .25 25 5 G1 5A 9 1 5 5 1 0 5 G2R 8 1 4 4 25 5 G4 6 1 4 4 5 8 G1 5A 9 1 1 1 1 1 10 8 G17 9 2 1 0 5 5 9 G1 0 1 2 2 3 1 .5 5 9 G2R 8 2 4 2 25 9 G1 3 1 1 1 7 7 1 0 1 0 G7R 10 2 3 1 .5 20 10 G8R 1 3 2 10 5 15 1 0 G1 4 1 0 3 6 2 1 5 1 0 G2R 8 2 6 3 25 1 1 G2R 8 1 8 8 25 N=20 mean= 9.3 1.8 6.8 4.4 16.5 Notes:(1) A f t e r t e s t , young removed. No young used more than once. (2) T o t a l chases= chases of a l l young by a l l a d u l t s . (3) Volumetric e s t i m a t e . P i s c u s s i o n The r e s u l t s i n d i c a t e d no i n f l u e n c e of cover on chasing i n t e n s i t y . I assumed f o r subsequent experiments that data taken from t e s t tanks without cover were e q u i v a l e n t to those from p l a n t e d tanks. I a l s o assumed that f i s h taken from tanks with d i f f e r e n t amounts of cover should not d i f f e r as a r e s u l t of any e f f e c t s of the amount of cover p r e s e n t . I expected chased young 7 to u t i l i z e cover , and that t h e r e f o r e chasing i n t e n s i t y would be reduced i n h e a v i l y p l a n t e d tanks. I cannot e x p l a i n why t h i s t r end d i d not appear. V a r i a t i o n in a d u l t d e n s i t y a l s o f a i l e d to produce s i g n i f i c a n t d i f f e r e n c e s i n chasing i n t e n s i t y . T h i s i s i n d i r e c t c o n t r a d i c t i o n to the r e s u l t s of Rose (1959) with the guppy and T h i b a u l t (1974) with the r e l a t e d s p e c i e s P o e c i l i o p s i s monacha . In Rose's study, chasing and c a n n i b a l i s m appeared only when ad u l t d e n s i t y exceeded 10 per 12 1. T h i s i s much higher than any of my d e n s i t i e s . T h i b a u l t , however, used d e n s i t i e s of from 0-20 f i s h per 75 1 ( e q u i v a l e n t to 0-10 f i s h i n my 37.5 1 tank s ) , and found a s i g n i f i c a n t p o s i t i v e r e l a t i o n between c a n n i b a l i s m and d e n s i t y (128 t r i a l s , p<0.00l, two-way a n a l y s i s of v a r i a n c e ) . P. monacha i s re p o r t e d by T h i b a u l t to be an extremely predaceous s p e c i e s ; the much l e s s frequent c a n n i b a l i s m that I observed i n guppies may be due simply to s p e c i e s d i f f e r e n c e s in predatory behavior. I found the mean number of chases per i n d i v i d u a l young per 10 min to be 4.4. E x t r a p o l a t e d to a 10.5 hr day, t h i s i s 277 chases per day. A l l young I used had at l e a s t t h i s much ch a s i n g experience. Those remaining in the n a t a l tank f o r 48 hr probably had more experience of c h a s i n g , but I d i d not separate the f i s h r e c e i v i n g t h i s a d d i t i o n a l experience from the o t h e r s . The c a l c u l a t e d f i g u r e may even be an underestimate of 24 hr experience, s i n c e I recorded chasing data i n the morning, and 8 c a s u a l o b s e r v a t i o n suggests that the hunger l e v e l (and presumably the a t t a c k readiness) of the a d u l t s i n c r e a s e s as l a t e - a f t e r n o o n feeding time approaches. F i e l d data on the yellow bass a l s o suggests that c o n s p e c i f i c young are a t t a c k e d only when the a d u l t s are short of t h e i r r e g u l a r d i e t ( B u l k l e y 1970) . Chasing was frequent and d i r e c t e d toward a l l young. It was i n s e n s i t i v e to a d u l t d e n s i t y and cover d e n s i t y . I conclude that i f e a r l y experience i s important in the development of the escape response, chasing by a d u l t s may be an important part of that experience. 9 THE EFFECT OF CHASING DEPRIVATION ON THE DEVELOPMENT AND EXPRESSION OF GUPPY ESCAPE BEHAVIOR Int r o d u c t ion Is the development and e x p r e s s i o n of escape behavior i n f l u e n c e d by the experience of being chased by a d u l t s ? If so, in what way i s the experience important? I assumed that c h a s i n g by a d u l t s was the only form of e a r l y predatory experience i n the l a b o r a t o r y . The extent of c h a s i n g i n the w i l d i s unknown, but there must be chasing t h e r e . I a l s o assumed that while a d u l t guppies may be subject to a e r i a l a t t a c k s , j u v e n i l e s are not. Based on these assumptions, I hypothesized that e a r l y chasing experience determines general escape responsiveness to a v e r s i v e s t i m u l i , e i t h e r a q u a t i c or a e r i a l . By a v e r s i v e I mean producing withdrawal; r a p i d l y approaching o b j e c t s i n the v i s u a l f i e l d have been shown to produce escape r e a c t i o n s i n f i s h ( D i l l 1974a,b). A l l the guppies i n my experiments had no p r e v i o u s exposure to the a e r i a l predator s t i m u l u s . The experimental groups I used d i f f e r e d only in t h e i r exposure to chasing by a d u l t s when young. I c o u l d not p r e d i c t how d i f f e r e n t types of experience might a f f e c t development. I c o u l d only p r e d i c t that those f i s h with no chasing experience (group n) would be the most d i f f e r e n t from c o n t r o l s (group c ) . I expected that i f d i f f e r e n t types of experience were a d d i t i v e i n t h e i r e f f e c t , then groups with p a r t i a l experience of being chased (through chemical cues from 10 a d u l t s [ g ] , v i s u a l cues from a d u l t s [ v ] , or chemical cues from predatory s p e c i e s [p]) would be intermediate i n response between n and c f i s h . . Methods I produced the experimental groups as f o l l o w s . I p l a c e d g r a v i d females i n net bags suspended i n unoccupied a q u a r i a . These females r e l e a s e d young which escaped through the meshes of the net. I removed spent females and r e p l a c e d them with more g r a v i d ones as r e q u i r e d . Young f i s h were not n e t t e d or otherwise d i s t u r b e d u n t i l t h e i r escape responses were measured. The v i s u a l cues group c o u l d see a group of a d u l t guppies i n the n e i g h b o r i n g tank. These a d u l t s c o u l d be observed chasing the young i n t h e i r tank. F i s h r e c e i v i n g guppy chemical cues had water from a tank of chasing a d u l t s pumped through t h e i r tank. Those r e c e i v i n g chemical cues from predatory f i s h had water from tanks of predatory f i s h added p e r i o d i c a l l y to t h e i r tank. F i n a l l y , guppies r e c e i v i n g no c h a s i n g cues were i s o l a t e d both v i s u a l l y and c h e m i c a l l y from t h e i r surroundings. The treatments are summarized in Table I I , and the apparatus used i s shown in F i g u r e 1. I t e s t e d f i s h at two ages: immature (10-15 wk, the time of e a r l i e s t appearance of m o r p h o l o g i c a l sex d i f f e r e n c e s ) and mature 11 w n te =0= t \u00E2\u0080\u00A2 od Figure 1. Derivation of treatment g r o u p s : deprivations experiment. groups: p - predator chemical cues n - no cues g - guppy chemical cues c - control (one of many) v - visual cues c od - opaque divider pw - water taken from predator tanks s - s iphons w - wall / - water flow v te \u00E2\u0080\u00A2w 1 2 Table I I . Summary of experience given i n the d e p r i v a t i o n treatments treatment symbol c o n t r o l c no cues n v i s u a l cues v guppy chemical cues g predator chemical cues p experience with a d u l t s f u l l sensory c o n t a c t : 24-48 hr c h a s i n g none v i s u a l c o n t a c t with a d u l t s chemical (water) c o n t a c t with a d u l t s chemical c o n t a c t with predatory f i s h (20-25 wk, a f t e r breeding had been noted i n the t a n k ) . I used the apparatus i n F i g u r e 2 and the a e r i a l stimulus model in F i g u r e 3. I gave each i n d i v i d u a l f i s h 10 min a c c l i m a t i o n i n the t e s t tank. I then observed i t u n t i l i t was swimming w i t h i n 2.5 cm of the water s u r f a c e and at l e a s t 2 cm from the nearest w a l l , when I r e l e a s e d the model. I recorded the drop response by eye to the nearest 0.5 cm and the f r e e z i n g response by e l e c t r o n i c stopwatch to the nearest 0.1 sec. (These behaviors are d e s c r i b e d below.) Upon t e r m i n a t i o n of the escape response, I measured the standard l e n g t h to the nearest 0.1 cm. Sample s i z e s f o r a l l groups are presented i n Table I I I . A b b r e v i a t i o n s f o r treatment groups in a l l f i g u r e s and t a b l e s are r e i t e r a t e d i n in the c a p t i o n of F i g u r e 4. Figure 2 .Experimental apparatus. Views: A ,s ide ; B . top . (as - air supply ; fw - flight \"window\" for model ; gw - guide wire ; I - light source ; me - model ca r r ie r ; os - observat ion s l i t ; ps - plastic sheeting ; r - release mechan ism ; w - weight ) o 14 1 5 Table I I I . Summary of sample s i z e s of groups i n the a e r i a l model response experiment. sex aqe c a \u00C2\u00A3 V n males immature 20 1 9 19 26 28 mature 20 9 1 9 24 24 females immature 20 1 7 20 19 22 mature 20 1 4 18 1 3 22 R e s u l t s D e s c r i p t i o n of behavior Exposure to the a e r i a l model e l i c i t e d two c h a r a c t e r i s t i c behaviors i n every guppy I t e s t e d . The f i r s t was the drop response, i n which the guppy a b r u p t l y descended through the water column a v a r i a b l e depth. The second behavior was the f r e e z i n g response. T h i s began immediately upon the t e r m i n a t i o n of the drop, and was c h a r a c t e r i z e d by immobility of the f i s h and by r a p i d , low-amplitude o s c i l l a t i o n s of the f i n s and o p e r c u l a . At the end of the fre e z e there was always a sudden r e t u r n to swimming behavior. A n a l y s i s I found s e v e r a l d i f f e r e n c e s when comparing the r e s u l t s f o r males with those f o r females ( F i g u r e 4). Males r e c e i v i n g only v i s u a l cues had a l a r g e r d i s t a n c e response than females (t t e s t , c m c g p v n Immatures-..distance. cm c g p v n Matures: d is tance. sec c g p v n Immatures: t ime. sec c g p v n Matures: t ime. F igure A . Sex differences in escape response . (Means and standard errors . ) ( c , c o n t r o l ; g, g u p p y c h e m i c a l c u e s ; p, p r e d a t o r c h e m i c a l c u e s ; v, v i s u a l c u e s ; n, no c u e s ) 1 7 p< 0 . 0 0 8 ) , but t h i s disappeared at m a t u r i t y . In the matures, females had a l a r g e r d i s t a n c e response among the c o n t r o l s (p=0.003) and longer f r e e z i n g times among the c o n t r o l s (p< 0 . 0 0 l ) , the group exposed to v i s u a l cues only (p< 0 . 0 4 ) , and the f i s h exposed to predator chemical cues only (p<0 .006) . I found a s l i g h t t r e n d toward l a r g e r responses i n the o l d e r f i s h of a given treatment (Figure 5 ) . Older males exposed to the guppy chemical cues had a l a r g e r d i s t a n c e response than younger ones (t t e s t , p< 0 . 0 0 l ) . Older females had l a r g e r d i s t a n c e responses i n the c o n t r o l (p< 0 . 0 0 l ) , v i s u a l cues (p< 0 . 0 2 ) , and predator chemical cues (p=0.04) groups. There were a l s o s i g n i f i c a n t i n c r e a s e s i n f r e e z i n g time with age i n some females ( v i s u a l and predator chemical cues groups, each p<0.002) . I conclude that these r e s u l t s i n d i c a t e l a r g e r responses from the l a r g e r f i s h i n a given comparison ( i . e . females i n sex comparisons, matures i n age comparisons; standard l e n g t h data are summarized i n Table I V ) . I found immature males to d i f f e r s i g n i f i c a n t l y by treatment i n t h e i r drop responses (one-way a n a l y s i s of v a r i a n c e , F= 7 . 2 5 , d f = 4 , l 0 7 , p< 0 . 0 0 l ) . T h i s was due mainly to the l a r g e d e p r e s s i o n in the response of the g group ( S c h e f f e ' s t e s t , g 0 . 1 ; see F i g u r e 6B ) . I i n t e r p r e t t h i s change as evidence f o r an experience-independent maturation of the drop response i n males. 18 Males : distance. Females : distance. 50' 40-sec 30-20-C 175-1 [^Immature \u00C2\u00A3 Mature c g p v Males : t ime n sec c g p v n Females : t ime. Figure 5 .Age d i f f e r e n c e s in escape response (Means and s tandard errors . ) A b b r e v i a t i o n s as in F i g u r e 4 . 19 Table IV. Mean body lengths of f i s h i n the treatment groups, (standard l engths i n cm) treatment males females immature mature immature mature c o n t r o l 1 .37 1 . 58 1 .61 2.35 no cues 1 .40 1 .56 1 .65 2.27 v i s u a l cues 1.41 1.61 1 .66 2. 35 guppy chemical cues 1 .37 1 .54 1 .64 2.32 predator 1 .43 1 .57 1 .70 2.25 chemical cues Immature males showed no d i f f e r e n c e s i n f r e e z i n g time among treatments (F=1.66, df=4,l07, p>0.1; see F i g u r e 6C), and mature males showed only one s i g n i f i c a n t d i f f e r e n c e i n t h i s parameter (n>c, p=0.05; see F i g u r e 6D). There appears to be l i t t l e e f f e c t of d e p r i v a t i o n on the f r e e z i n g response i n males. Immature females d i f f e r e d s i g n i f i c a n t l y by treatment i n t h e i r drop d i s t a n c e s (F=7.41, df=4,93, p<0.00l), due to a de p r e s s i o n i n the g group's response (gv, p=0.04; n>g, p=0.03; see 20 c m 6 51 4-i 3-1 2-1-0 ] A c g p v n Immatures: d istance. cm 6-5-4\" 3-2-1: 0 B rh c g p v n Matures : d is tance. sec 50 40-30-20 10-0 c rfl rh rh c g p v n Immatures: t ime. sec 60-50 40 301 20-10-0 D rh r+T c g p v n Matures : t ime. Figure 6. Treatment di f ferences in males. ( M e a n s a n d s tandard errors. ) A b b r e v i a t i o n s a s in F i g u r e 4 . 6-1 A 8- B 4-cm 3-2-1-0 c g p v n Irnmatures: d istance. cm 4' 0 Ml rh c g p v n Matures: distance 100i 80-sec 60 40-I 20 0 C rh c g p v n Immatures: t ime . 175i 140-sec 105-70-35-j 0 D rh rh c g p v n Matures: t ime. F igure 7.Treatment dif ferences in females (Means and s tandard errors . ) A b b r e v i a t i o n s a s in F i g u r e 4 . 22 F i g u r e 7C). These s i g n i f i c a n t d i f f e r e n c e s disappeared i n the matures, a p p a r e n t l y due to v a r i a b i l i t y i n the r e s u l t s f o r the p, v, and n groups (F=2.45, df=4,82, p=0.052). The f r e e z i n g response i n females i s somewhat i n f l u e n c e d by d e p r i v a t i o n , but the trends are not very s t r o n g . In summary, both males and females showed a t r a n s i e n t d e p r e s s i o n i n d i s t a n c e response i f they were exposed only to guppy chemical cues. No groups responded more s t r o n g l y than c o n t r o l s . The constancy of drop depths was not simply an a r t i f a c t of constant tank depth. I a l s o t e s t e d f i s h i n tanks of 1.5 and 2 times the depth of t h i s t e s t tank and found no d i f f e r e n c e i n response (U t e s t , N=10 f i s h of each sex at each depth, a l l p>0.05). F r e e z i n g time d i f f e r e d l i t t l e i n e i t h e r sex in s p i t e of d e p r i v a t i o n , except f o r the t r e n d to i n f l a t e d responses among the n, p, and v groups. F i s h from the g group most c l o s e l y resembled c o n t r o l s i n the f r e e z i n g response. D i s c u s s i o n Sex and age d i f f e r e n c e s I found that three of four sex d i f f e r e n c e s were in the d i r e c t i o n of l a r g e r responses i n females. I found that a l l s i x of the s i g n i f i c a n t d i f f e r e n c e s by age were i n the d i r e c t i o n of l a r g e r responses i n the o l d e r f i s h . Females of a given age and matures of a given sex were l a r g e r than males and immatures 23 r e s p e c t i v e l y . Thus I cannot separate the e f f e c t s of sex, age, and body s i z e . Whichever of the three f a c t o r s may have caused d i f f e r e n c e s , I conclude that a l l f u r t h e r analyses should be separate by age and sex, i n order to a v o i d confounding the treatment d i f f e r e n c e s . F i e l d study of the i n f l u e n c e of sex and body s i z e on p r e d a t i o n i n Gambusia ( B r i t t o n and Moser 1982) suggested that the l a r g e r females were s e l e c t e d p r e f e r e n t i a l l y by herons. The females were a r i c h e r food source, but they were a l s o p r e f e r r e d because they were slower swimmers than the males and p r e f e r r e d shallower (warmer) water than the males. They r e q u i r e d only s l i g h t l y more h a n d l i n g than males. Confounded sex and s i z e e f f e c t s may a l s o e x p l a i n behavior d i f f e r e n c e s in the guppy (Seghers 1973), but cannot be d i s t i n g u i s h e d i n my experiments. Treatment d i f f e r e n c e s The f i s h exposed only to guppy chemical cues had reduced drop response when they were immature, but by m a t u r i t y they were not d i f f e r e n t from c o n t r o l s . I i n t e r p r e t t h i s as delayed maturation of the response. Guppy chemical cues were not s u f f i c i e n t to b r i n g about the normal t i m i n g of response maturation. These cues, and any other degree of experience, c o u l d not a f f e c t the eventual appearance of a p p a r e n t l y normal drop responses. The constancy i n drop response might be evidence f o r a f i x e d hunting depth i n a e r i a l p r e d a t o r s (found i n 24 k i n g f i s h e r s , Eastman 1969), but there i s i n s u f f i c i e n t data on the a e r i a l p r e d a t i o n of guppies to t e s t t h i s s p e c u l a t i o n . I found c h a s i n g d e p r i v a t i o n to have a d i f f e r e n t e f f e c t on the development of f r e e z i n g responses. Although the d i f f e r e n c e s were not always s i g n i f i c a n t , they showed a t r e n d f o r longer f r e e z i n g times i n the f i s h exposed to v i s u a l cues, predator chemical cues, or no cues. The f i s h exposed to guppy chemical cues developed a n e a r - c o n t r o l response. I conclude from these r e s u l t s that exposure to s p e c i f i c e a r l y experience (guppy chemical cues) i s necessary in order to a v o i d the development of e x c e s s i v e responses. (I w i l l d i s c u s s the disadvantage of long f r e e z i n g times a f t e r c o n s i d e r i n g the r e s u l t s of the p r e d a t i o n exper iment.) Experience and p r e d a t i o n The Guayamare stream i s i n h a b i t e d by s e v e r a l l a r g e c h a r a c i d and c i c h l i d p r e d a t o r s ( L i l e y and Seghers 1975). These s p e c i e s put guppies at c o n s i d e r a b l e r i s k of p r e d a t i o n , e s p e c i a l l y l a r g e guppies. Endler (1978,1980; Reznick and Endler 1982) has shown that there i s a s t r o n g i n f l u e n c e of p r e d a t i o n i n t e n s i t y on s e l e c t i o n f o r a d u l t s i z e . Guppies are smaller at maturity i n areas with heavy p r e d a t i o n . I assume t h e r e f o r e that small guppies are r e l a t i v e l y l e s s s u b j e c t to p r e d a t i o n from these l a r g e s p e c i e s . I made a c a s u a l o b s e r v a t i o n which supports t h i s . While a d u l t guppies s u r v i v e d f o r only a few minutes in the 25 presence of l a r g e c i c h l i d s ( d e t a i l e d r e s u l t s below), j u v e n i l e s were a l i v e even s e v e r a l days or weeks a f t e r i n t r o d u c t i o n . As I found i n the present experiment, f i s h exposed to predator chemical cues f a i l e d to respond i n the same way as c o n t r o l s . T h i s suggests that the young lack the a b i l i t y to a l t e r t h e i r escape responses when exposed to predator chemicals i n the environment. T h e r e f o r e I assume that d e s p i t e the presence of l a r g e p r e d a t o r s i n the stream, young guppies do not r e c e i v e s i g n i f i c a n t experience from them. The only cues s u f f i c i e n t to form a c o n t r o l response when presented alone were the guppy chemical cues. Since chemical cues from a v a r i e t y of predator s p e c i e s were i n e f f e c t i v e , I conclude that there i s a s p e c i e s - s p e c i f i c chemical cue i n the guppy which b r i n g s about a normal f r e e z i n g response. T h i s might be c a l l e d a \"chasing pheromone\". No pheromones have been i s o l a t e d i n f i s h ( L i l e y 1982). If there i s a pheromone i n v o l v e d in the development of escape behavior, i t might be p o s s i b l e to i s o l a t e i t by t a k i n g a v a r i e t y of e x t r a c t s from water i n which a d u l t s have been chasing young and then exposing young to these e x t r a c t s and t e s t i n g t h e i r escape responses l a t e r . The f i n a l step would be the a n a l y s i s of the a p p r o p r i a t e e x t r a c t and the c h a r a c t e r i z a t i o n of the c h e m i c a l ( s ) i n v o l v e d . I have not c o n s i d e r e d a more d e t a i l e d scheme. I found the guppy chemical cues to have a priming e f f e c t , s i n c e e a r l y a d m i n i s t r a t i o n r e s u l t e d i n the l a t e r response 26 i n t e n s i t y . There might a l s o be a r e l e a s i n g e f f e c t , but I cannot say because I d i d not give l a t e treatments. Seghers (1973) observed no overt r e a c t i o n i n guppies to water taken from tanks of predatory f i s h . Rose (1959) showed that water from tanks with a high d e n s i t y of a d u l t guppies e l i c i t e d slower r e a c t i o n s from the young than d i d water from tanks with fewer a d u l t s p r e s e n t . I d i d not observe such an e f f e c t , p o s s i b l y because the a d u l t d e n s i t i e s I used were lower than those Rose used. A l l the f i s h i n the treatments I used responded i n q u a l i t a t i v e l y the same way. I conclude that as i n Gasterosteus and other s p e c i e s d i s c u s s e d by G i l e s (1984), guppy escape responses appear independently of experience with r e a l or p o t e n t i a l p r e d a t o r s , but the i n t e n s i t y of the response i s a f f e c t e d by experience. 27 THE EFFECT OF DEPRIVATION FROM CHASING ON THE SURVIVAL OF GUPPIES UNDER FISH PREDATION I n t r o d u c t i o n I found i n the preceding experiment that f i s h d e p r i v e d of chasing by a d u l t s develop l a r g e r escape responses than those developed by chased guppies. If chasing i s v i t a l to the normal development of the response, I hypothesized that the l a r g e escape responses would be disadvantageous. In t h i s experiment, I t e s t e d f i s h with v a r i o u s e a r l y chasing experiences by s u b j e c t i n g them to p r e d a t i o n ; I expected that i f l a r g e escape responses were d e l e t e r i o u s , then the f i s h showing these responses should not s u r v i v e as w e l l as c o n t r o l s . I expected that c o n t r o l f i s h would be more e f f i c i e n t at a v o i d i n g p r e d a t i o n . As I c o u l d not p r e d i c t i n what way they might be more e f f i c i e n t , I recorded s e v e r a l measures of avoidance. I s p e c u l a t e d that i f the c o n t r o l s l i v e d longer, i t would suggest that being chased when young i s advantageous f o r guppies. Circumstances d i c t a t e d the use of d i f f e r e n t p redators on the male and female guppies. T h i s may have had the f o r t u i t o u s e f f e c t of i n c r e a s i n g the g e n e r a l i t y of the experiment. I f two types of a q u a t i c predator produce the same e f f e c t in guppies, the e f f e c t i s u n l i k e l y to be an a r t i f a c t . I hope that f u t u r e p r e d a t i o n experiments w i l l adhere more c l o s e l y to the g u i d e l i n e s of Hu n t i n g f o r d (1984), who has suggested 28 design improvements to maximize the i n f o r m a t i o n gained from such s t u d i e s . Methods I used the t r e a t e d f i s h from the preceding ( d e p r i v a t i o n ) experiment as s u b j e c t s . I a c q u i r e d one C r e n i c i c h l a sp. ( C i c h l i d a e ; standard l e n g t h 22 cm) and one Pseudotropheus sp. ( C i c h l i d a e ; s . l . 9 cm) to use as p r e d a t o r s on the female guppies. I a c q u i r e d three Cichlasoma n i q r o f a s c iatum ( C i c h l i d a e ; s . l . 9 cm each) to use as p r e d a t o r s on the male guppies. The t e s t tank f o r females measured 45x110x30 cm, and the one f o r males measured 45x90x15 cm. I i n t r o d u c e d the guppies s i n g l y to the t e s t tanks by g e n t l y decanting them from small b o t t l e s of water. I presented no more than two guppies of a given treatment c o n s e c u t i v e l y . I d e f i n e d time zero as the time of i n t r o d u c t i o n , and measured a t t a c k times as seconds el a p s e d s i n c e time zer o . I analyzed time to f i r s t a t t a c k ( i n i t i a l a t t a c k l a t e n c y ) , time to l a s t a t t a c k ( i . e . the k i l l ; t o t a l s u r v i v a l time), and the number of a t t a c k s per k i l l . Sample s i z e s f o r a l l treatments are summarized in Table V. 29 Table V. Summary of sample s i z e s f o r a l l treatment groups i n the p r e d a t i o n experiment. sex c a E V n males 1 5 7 18 7 1 1 females 1 5 7 1 7 7 1 1 R e s u l t s I found that a l l the escape behaviors known to be e l i c i t e d i n guppies by aq u a t i c p r e d a t o r s (Seghers 1973) appeared i n a l l my t r e a t e d groups. In males, the i n i t i a l a t t a c k l a t e n c y scores d i f f e r e d s i g n i f i c a n t l y among treatments (one-way a n a l y s i s of v a r i a n c e , F=3.65, df=4,53, p=0.0l; see F i g u r e 8A). I d i d not expect such a d i f f e r e n c e because i n a s m a l l , bare tank a l l guppies should have been about e q u a l l y v i s i b l e to p r e d a t o r s . The females d i d not d i f f e r i n i n i t i a l a t t a c k l a t e n c y (F=1.05, df=4,52, p>0.1; see F i g u r e 8B). Since the r e s u l t s are d i f f e r e n t f o r the two sexes, I i n t e r p r e t i n i t i a l a t t a c k l a t e n c y to be r e l a t i v e l y independent of guppy experience. I found that t o t a l s u r v i v a l time d i f f e r e d s i g n i f i c a n t l y among the t r e a t e d males (F=2.55, df=4,53, p=0.05; see F i g u r e 9A), but no two groups d i f f e r e d by S c h e f f e ' s t e s t . The trend was f o r c o n t r o l males to l i v e longer, but there was too much va r i a n c e to allow a f i r m c o n c l u s i o n . The females d i d not d i f f e r 30 2001 sec . 100-0 m rh c g p v n M a l e s 2001 sec . 100 0 c g p v n F e m a l e s F i g u r e 8 . In i t ial a t t a c k l a t e n c i e s for t r e a t e d g r o u p s u n d e r f i s h p r e d a t i o n . ( M e a n s a n d s t a n d a r d e r ro rs . ) A b b r e v i a t i o n s a s in F i g u r e 4 31 in s u r v i v a l time (F=0.94, df=4,52, p>0.1; see F i g u r e 9B), and there were no t r e n d s . I conclude that there i s evidence of a weak trend f o r longer s u r v i v a l by c o n t r o l f i s h . I found a s i g n i f i c a n t e f f e c t of treatment on the number of a t t a c k s r e q u i r e d f o r a k i l l i n both sexes (males, F=4.61, df=4,53, p=0.003; see F i g u r e 10A; females, F=3.57, df=4,52, P=0.012; see F i g u r e 10B). The d i f f e r e n c e s were due to the l a r g e r number of a t t a c k s r e q u i r e d to k i l l c o n t r o l f i s h ( S c h e f f e ' s t e s t : males, o n , p=0.08; c>g, p=0.04; o p , p=0.02; females, o n , g , p<0.05). These r e s u l t s are the s t r o n g e s t evidence of a d e f i c i t i n s u r v i v a l a b i l i t y among the f i s h d e p r i v e d of f u l l c hasing experience when young. D i s c u s s i o n Although the i n i t i a l a t t a c k l a t e n c y was s i g n i f i c a n t l y d i f f e r e n t among the males, I conclude that s i n c e the females showed no e f f e c t at a l l (not even a t r e n d ) , evading the p r e d a t o r ' s i n i t i a l a t t e n t i o n was not a key f a c t o r i n p r e d a t i o n avoidance. A l s o , s i n c e no two groups of males d i f f e r e d i n s u r v i v a l time, and s i n c e there was no t r e n d among the females, I conclude that t o t a l s u r v i v a l time was not a f f e c t e d by the e a r l y experience of being chased by a d u l t s . I found that the d e p r i v e d groups took s i g n i f i c a n t l y fewer a t t a c k s to k i l l than d i d the c o n t r o l s . The only d i f f e r e n c e 800- 800-sec sec 400i 400-0 c g p v M a l e s n 0 c g p v n F e m a l e s F i g u r e 9 . Total s u r v i v a l t i m e s for t r e a t e d g r o u p s under f i s h p r e d a t i o n . ( M e a n s a n d s t a n d a r d e r r o r s . ) A b b r e v i a t i o n s as in F i g u r e 4 . 33 81 a t t a c k s / k i l l 4-0 rh rh c g p v n M a l e s 8 a t t a c k s / . k i l l 0 c g p v n F e m a l e s F i g u r e 10 . N u m b e r s of a t t a c k s per k i l l for t r e a t e d g r o u p s under f i s h p r e d a t i o n . ( M e a n s and s t a n d a r d e r r o r s . ) A b b r e v i a t i o n s a s in F i g u r e 4 . 34 between c o n t r o l s and the d e p r i v e d f i s h was the experience of being chased by a d u l t s . I t h e r e f o r e conclude that the experience of being chased by a d u l t s enhanced the l i k e l i h o o d that a c o n t r o l guppy would s u r v i v e a predatory a t t a c k . I p r e d i c t e d that l a r g e escape responses would prove to be disadvantageous. Indeed, d e p r i v e d guppies responded s t r o n g l y and took few a t t a c k s to k i l l . E xperience improves the l i k e l i h o o d of s u r v i v a l of the young i n two ways. F i r s t , by moderating the response i n t e n s i t y , chasing experience l e s s e n s the p r o b a b i l i t y of a guppy d i v i n g too f a r i n t o deeper water (where pre d a t o r s l i v e ) or s t a y i n g there f o r long. Second, by enhancing the a b i l i t y to evade each a t t a c k , chasing experience i n c r e a s e s the p r o b a b i l i t y that the guppy w i l l s u r v i v e a predatory encounter. Both of these mechanisms would operate to keep the guppy i n \" s a f e \" areas and away from \"unsafe\" ones. Safe areas f o r guppies are probably l i m i t e d to stream edges, s i n c e there i s l i t t l e submerged v e g e t a t i o n i n the Guayamare R i v e r (B.H. Seghers, p e r s . comm.). Shallow edges are known to be refuges f o r Gambusia ( P o e c i l i i d a e ; Goodyear 1973). Under t h i s model, the guppy would appear to use a couple of simple r u l e s to a v o i d p r e d a t o r s , and there would be no need to know what the p r e d a t i o n r i s k was i n order to apply these r u l e s . 35 An a l t e r n a t ive explanat ion of sex d i f ferences in s u r v i v a l a b i l i t y I have thought of at l e a s t one other i n t e r p r e t a t i o n of the r e s u l t s . The p r e d a t o r s I used on the male guppies were u n f a m i l i a r with l i v e food. The predator ( C r e n i c i c h l a ) I used on the female guppies was r a i s e d with l i v e food only. I t i s p o s s i b l e that the male guppies d e r i v e d c o n s i d e r a b l e advantages from small d i f f e r e n c e s i n s u r v i v a l a b i l i t y because t h e i r p r e d a t o r s were e a s i e r to a v o i d . I f t h i s were so, then the d i f f e r e n c e s among the males for i n i t i a l a t t a c k l a t e n c y and t o t a l s u r v i v a l time, which I minimized above, c o u l d be r e a l d i f f e r e n c e s . C r e n i c i c h l a i s an extremely e f f i c i e n t p r e d a t o r . In an experiment r e p o r t e d by L i l e y and Seghers (1975), t h i s predator took female guppies of 1.9 cm standard l e n g t h ( s m a l l e r than the f i s h I used) on the f i r s t a t t a c k , but r e q u i r e d more a t t a c k s to k i l l s m aller f i s h . I t i s p o s s i b l e , then, that small d i f f e r e n c e s in s u r v i v a l a b i l i t y among the females were obscured by the r e l a t i v e l y high e f f i c i e n c y of the p r e d a t o r . If t h i s were the case, I would expect that the l a c k of d i f f e r e n c e i n my r e s u l t s f o r i n i t i a l a t t a c k l a t e n c y and t o t a l s u r v i v a l time in females was due to type II e r r o r . In e i t h e r i n t e r p r e t a t i o n made above, there was a s u b s t a n t i a l e f f e c t of e a r l y chasing experience on s u r v i v a l . The 36 i n t e r p r e t a t i o n s I gave are probably not mutually e x c l u s i v e , and are c e r t a i n l y not the only i n t e r p r e t a t i o n s p o s s i b l e . The f i r s t i n t e r p r e t a t i o n i s the more c o n s e r v a t i v e , but even i t i s s t i l l c l e a r l y i n t h i s d i r e c t i o n : c o n t r o l guppies avoided p r e d a t i o n b e t t e r than d e p r i v e d ones. 37 THE EFFECT OF IMMEDIATE SOCIAL DEPRIVATION ON THE EXPRESSION OF ESCAPE BEHAVIOR I n t r o d u c t i o n Guppies l i v e i n groups. I t e s t e d i n d i v i d u a l guppies i n the a e r i a l response and p r e d a t i o n experiments. Could t e s t i n g s o c i a l f i s h i n d i v i d u a l l y have a f f e c t e d the r e s u l t s ? In t h i s experiment, I looked f o r response d i f f e r e n c e s in f i s h t e s t e d both alone and i n groups. I c o u l d not p r e d i c t what the d i f f e r e n c e might be, but any d i f f e r e n c e would cause me to q u e s t i o n my i n t e r p r e t a t i o n s of the r e s u l t s from these experiments on s o l i t a r y f i s h . L i v i n g i n groups has been i n t e r p r e t e d as advantageous, e s p e c i a l l y f o r the p r e v e n t i o n of p r e d a t i o n i n f i s h (review i n Burgess and Shaw 1979). In the guppy congener P o e c i l i a v i v i p a r a , grouping lowers predator hunting success i n the l a b o r a t o r y ( N e i l l and C u l l e n 1974). The e x p l o r a t o r y behavior of guppies i s enhanced i n groups (Amouriq 1969); presumably t h i s r e f l e c t s reduced r i s k that guppies in groups may p e r c e i v e . Seghers (1974b) found that t i g h t l y s c h o o l i n g guppies ( i n c l u d i n g the Guayamare R i v e r p o p u l a t i o n ) s u r v i v e b e t t e r under p r e d a t i o n than those which school l o o s e l y . For these reasons, I expected that guppies t e s t e d i n groups might respond d i f f e r e n t l y from those t e s t e d alone. 38 Although a lack of d i f f e r e n c e would not prove that t e s t i n g f i s h alone was the same as t e s t i n g them i n groups, i t would i n d i c a t e that f o r the purposes of my experiments, the number of f i s h t e s t e d was unimportant. Methods I used a tank i d e n t i c a l in s i z e , shape, and water depth to the tank used i n the a e r i a l response experiment ( F i g u r e 2). I i n s t a l l e d a two-part d i v i d e r a c r o s s the c e n t r e of the tank. One l a y e r was t r a n s p a r e n t , p e r f o r a t e d , and f i x e d i n p o s i t i o n . The second l a y e r was opaque and removable. On one s i d e of the d i v i d e r , I e s t a b l i s h e d a stimulus group of guppies. I p l a c e d t e s t i n d i v i d u a l s s i n g l y i n the c e l l on the other s i d e of the d i v i d e r . Test c r i t e r i a were i d e n t i c a l to those i n the a e r i a l response experiment. Each t e s t e d f i s h was s t i m u l a t e d twice with the a e r i a l model: once alone (opaque d i v i d e r i n place) and once in the presence of the group (opaque d i v i d e r removed). R e s u l t s I found no d i f f e r e n c e between group and alone treatments for males or females i n drop d i s t a n c e or f r e e z i n g time (Wilcoxon matched-pairs signed-rank t e s t , N=20, a l l p>0.05; see F i g u r e 11). I found a h i g h l y s i g n i f i c a n t d i f f e r e n c e between the males and females i n the group c o n d i t i o n f o r f r e e z i n g time (t t e s t , df=39, p<<0.00l). T h i s d i f f e r e n c e was much g r e a t e r than that i n Dis tance . Time. F igure 11 . G r o u p effects on escape response (Means and s tandard errors. ) 40 the sex comparison of alone f i s h or i n the e q u i v a l e n t comparison in the a e r i a l response experiment (p<0.02 , p<0.00l r e s p e c t i v e l y ) . T h i s d i f f e r e n c e may i n d i c a t e t hat females i n a group responded more, but s i n c e the p a i r e d comparison showed no d i f f e r e n c e I w i l l ignore i t . D i s c u s s i o n I found that there was no d i f f e r e n c e i n response between f i s h t e s t e d alone and those t e s t e d i n groups. T h i s does not prove the absence of a group i n f l u e n c e on escape behavior. I t does show t h a t , f o r the purposes of my experimental design and techniques, I do not have to worry about the t e s t i n g of lone f i s h being u n n a t u r a l . I found that f i s h separated by a t r a n s p a r e n t , p e r f o r a t e d d i v i d e r responded s o c i a l l y to each other. I saw o r i e n t a t i o n s and c o u r t s h i p behaviors e l i c i t e d by and e l i c i t e d i n the t e s t i n d i v i d u a l s . Pinckney and Anderson (1967) showed that guppies co u l d r e c o g n i z e and d i r e c t s o c i a l behavior toward c o n s p e c i f i c s in g l a s s e n c l o s u r e s ; indeed, there may not have been any need to p e r f o r a t e the transparent d i v i d e r i n the t e s t tank. My r e s u l t s a p p a r e n t l y c o n t r a d i c t many experiments that show a reduced i n d i v i d u a l response i n groups. Examples range from mammals ( c e r v i d s , Altmann 1958; bighorn sheep, Berger 1978; p r a i r i e dogs, Hoogland 1 979) and b i r d s (penguins, M i i l l e r -41 Schwarze and Mliller-Schwarze 1970; s t a r l i n g s , Powell 1 974 ; weaverbirds, Lazarus 1979; o s t r i c h e s , Bertram 1980) to f i s h (zebra danios, Gleason et a l . 1977) and i n s e c t s (ocean s k a t e r s , Treherne and F o s t e r 1980,1981). I cannot account f o r the c o n t r a d i c t i o n ; I have i n s u f f i c i e n t data to e s t a b l i s h the cause, but from my r e s u l t s there seems to be no i n f l u e n c e of grouping on responses to the a e r i a l s t i m u l u s . 42 GENERAL DISCUSSION Pre d a t i o n p r e s s u r e s o p e r a t i n q on guppies Guppies l i v i n g i n lowland streams l i k e the Guayamare are exposed to a v a r i e t y of l a r g e predatory f i s h ( L i l e y and Seghers 1975). Predation by these f i s h has been i m p l i c a t e d i n the e v o l u t i o n of d i f f e r e n c e s between guppy p o p u l a t i o n s i n morphology, behavior, and l i f e h i s t o r y s t r a t e g y ( L i l e y and Seghers 1975; Endler 1978, 1980; Reznick and Endler 1982), although f a c t o r s such as temperature and t u r b i d i t y are l i k e l y to be i n v o l v e d as w e l l ( L i l e y and Seghers 1975). I found l i m i t e d c a n n i b a l i s m i n the l a b o r a t o r y , and there seems to be l i t t l e i n the w i l d (D.L. Kramer, p e r s . comm.). Adult guppies chase t h e i r young, but seldom c a t c h and eat them. P o p u l a t i o n d i f f e r e n c e s i n response to an a e r i a l stimulus have been a s c r i b e d to d i f f e r e n c e s i n a q u a t i c p r e d a t i o n i n t e n s i t y between streams (Seghers 1974a). Thus guppies appear to set response i n t e n s i t y to one type of stimulus by using input from another type of stimulus i n the course of n a t u r a l s e l e c t i o n . I propose that the e a r l y chasing of the young by a d u l t guppies enables the young to set t h e i r f u t u r e escape responses to other stimulus types i n the course of i n d i v i d u a l ontogeny. 43 The e f f e c t of e a r l y chasing experience on escape responses and s u r v i v a l under p r e d a t i o n E a r l y experience of being chased by a d u l t s had l i t t l e e f f e c t on the s p a t i a l extent of the escape response e l i c i t e d by an a e r i a l model. I i n t e r p r e t the u n i f o r m i t y of the response as a predetermined escape r e a c t i o n , which matures r e g a r d l e s s of environmental i n p u t . The amount of time a guppy spent f r e e z i n g in response to the model seemed to be determined by e a r l y exposure to guppy chemical s e c r e t i o n s . A l a r g e f r e e z i n g response was d e l e t e r i o u s i n the presence of predatory f i s h , so the r e d u c t i o n i n response caused by the guppy chemical cues was c l e a r l y a p o s i t i v e a d a p t a t i o n to predatory c o n d i t i o n s . Chased guppies were s u p e r i o r to d e p r i v e d ones in the number of a t t a c k s r e q u i r e d f o r a k i l l . E a r l y c h asing experience a p p a r e n t l y enables the guppy to a v o i d predatory a t t a c k s more e f f e c t i v e l y . I conclude that under n a t u r a l c o n d i t i o n s , f i s h e i t h e r do not venture f a r i n t o p r e d a t o r - i n f e s t e d areas or do not get taken e a s i l y by p r e d a t o r s i f they do. I t i s c l e a r that the procedures i n v o l v e d i n r a i s i n g and m a i n t a i n i n g guppies may have a c o n s i d e r a b l e e f f e c t on the e x p r e s s i o n of behavior. I f a r e s e a r c h e r cannot d e f i n e the e a r l y experience of h i s f i s h , any c o n c l u s i o n s he may draw about behavior should be viewed s k e p t i c a l l y . 44 P o s s i b l e mechanisms through which chasing experience might a f f e c t escape behavior The f i s h t e l e n c e p h a l o n i s the most l i k e l y l o c a t i o n f o r n e u r a l pathways c o n t r o l l i n g escape and avoidance r e a c t i o n s . T h i s region of the b r a i n i s a l s o concerned with o l f a c t i o n . (For a recent review of the i n t e r a c t i o n among t e l e n c e p h a l i c f u n c t i o n s , see Flood et a l . 1976.) In mammals, the hippocampus i s an a r c h i p a l l i a l s t r u c t u r e which i n t e g r a t e s o l f a c t o r y input and c o n t r o l s emotional behavior (Ewert 1980); i t i s a l s o the only s u b c o r t i c a l s t r u c t u r e which shows f u n c t i o n a l d e f i c i t s under d e p r i v a t i o n . The f i s h b r a i n i s mostly a r c h i p a l l i u m (Romer and Parsons 1977). T h e r e f o r e , on analogy, I propose that guppy chemical cues act through the t e l e n c e p h a l o n to c o n t r o l the e x p r e s s i o n of escape behavior. The behavior cannot be expressed p r o p e r l y i n the absence of these cues. Guppy chemical cues were not s u f f i c i e n t to produce c o n t r o l -l e v e l a b i l i t y to escape from p r e d a t o r s . There must be some a d d i t i o n a l f a c t o r i n v o l v e d here ( p o s s i b l y t a c t i l e ) which i s a l s o gained through c o n t a c t with a d u l t guppies. I found that there was no c o r r e l a t i o n between the i n t e n s i t i e s of the two p a r t s of the escape response (see Appendix). These two p o i n t s suggest that d i f f e r e n t p a r t s of the b r a i n , i n t e g r a t i n g input from d i f f e r e n t sensory sources, may be i n v o l v e d i n the development of escape behavior. Walsh (1981) has shown that d i f f e r e n t p a r t s of the mammal b r a i n are d i f f e r e n t i a l l y s u b j e c t to the e f f e c t s of 45 d e p r i v a t i o n . The p o s s i b l e f u n c t i o n a l s i g n i f icance of chasing i n guppies Adult guppies chase the young but very seldom c a t c h and eat them. I found a s u b s t a n t i a l advantage for chased f i s h under p r e d a t i o n . I propose that chasing by a d u l t s i s a p a r e n t a l behavior evolved through s e l e c t i o n f a v o r i n g the improved s u r v i v a l (and presumably subsequent rep r o d u c t i o n ) of chased f i s h . T h i s hypothesis does not c o n t r a d i c t the n o t i o n that c a n n i b a l i s m i s a disadvantageous t r a i t (reviews in Fox 1975, P o l i s 1981). Attempted c a n n i b a l i s m , or what looks to us l i k e attempted c a n n i b a l i s m , i s the process i n v o l v e d . If the s e l e c t i v e pressure i s severe enough, a g g r e s s i v e p a r e n t a l behaviors c o u l d be s e l e c t e d f o r . Keenleyside (1978) d e f i n e s p a r e n t a l care behavior as \"..any behavior, performed a f t e r breeding, by one or both p a r e n t s , that c o n t r i b u t e s to the s u r v i v a l of t h e i r o f f s p r i n g . \" Given the advantages I have demonstrated f o r p a r e n t a l c h a s i n g , i t seems reasonable to d e f i n e i t as a form of p a r e n t a l c a r e . Even c a n n i b a l i s m i t s e l f can be a s t a b l e s t r a t e g y i n some circumstances (e.g. p r o v i d e d l i f e t i m e net r e p r o d u c t i v e r a t e of the p o p u l a t i o n i s g r e a t e r than one; G u r t i n and Levine 1982). I propose that chasing a d u l t s would have increased i n c l u s i v e f i t n e s s r e l a t i v e to non-chasing a d u l t s . A problem with t h i s hypothesis i s that a d u l t s are not n e c e s s a r i l y chasing 46 only t h e i r own young. I observed that a l l a d u l t s chased a l l young. Guppies l i v e in groups which are r e l a t i v e l y i s o l a t e d in s t r e t c h e s of streams. During the wet season, f l o o d i n g can cause mixing between groups (Seghers, p e r s . comm.). Under these c o n d i t i o n s , n a t u r a l s e l e c t i o n can favor the e v o l u t i o n of t r a i t s which maximize i n d i v i d u a l f i t n e s s through maximizing group f i t n e s s (Wilson 1980). Any r e l a t e d n e s s of the i n d i v i d u a l s i n a group would enhance t h i s s e l e c t i o n , but kin s e l e c t i o n i s not necessary; the frequency of genes coding f o r the t r a i t of chasing c o u l d i n c r e a s e through the feedback e f f e c t s of s e l e c t i o n in s t r u c t u r e d demes. In c o n c l u s i o n , I propose that chasing by a d u l t s has an analogous e f f e c t i n the ontogeny of escape behavior to that of p r e d a t i o n i n the phylogeny of escape behavior. A d u l t s c o n d i t i o n t h e i r young to d i s p l a y a p p r o p r i a t e behavior. Suggest ions f o r f u r t h e r r e s e a r c h The d e t a i l s of escape behavior are d i f f i c u l t to d i s c e r n with unaided o b s e r v a t i o n . Therefore I do not know i f the behavior employed by a d u l t guppies i n escaping from p r e d a t o r s i s the same as that employed by j u v e n i l e guppies i n escaping from a d u l t chases. I a l s o do not know i f guppies d e p r i v e d of chasing use the same method to escape from p r e d a t o r s that chased guppies use. If chased guppies use the same behavior as a d u l t s that they l e a r n e d as young, t h i s would argue f o r d i r e c t p a r e n t a l 47 c o n d i t i o n i n g of the young. If chased and unchased guppies use d i f f e r e n t escape t a c t i c s , t h i s would a l s o be strong evidence f o r p a r e n t a l c o n d i t i o n i n g . I t would a l s o be i n t e r e s t i n g to compare the attack method used by a d u l t s in chasing to the normal a d u l t guppy feeding behavior and to the a t t a c k method of guppy p r e d a t o r s . If a d u l t a t t a c k s were s u b s t a n t i a l l y d i f f e r e n t from normal guppy feeding behavior, i t would suggest that chasing evolved not simply as a s i d e e f f e c t of normal fee d i n g or c a n n i b a l i s m , but r a t h e r s p e c i f i c a l l y f o r the c o n d i t i o n i n g of the young. If guppy chasing behavior a l s o resembled the a t t a c k t a c t i c s of p r e d a t o r s , t h i s would be s t i l l s t r o n ger evidence f o r a c o n d i t i o n i n g f u n c t i o n of a d u l t c h a s i n g . A l l these hypotheses and s p e c u l a t i o n s c o u l d be t e s t e d by high-speed cinematography of the behaviors i n v o l v e d . P r e d a t i o n pressure (and presumably the s e l e c t i o n f a v o r i n g a d u l t chasing as I have d e s c r i b e d i t ) v a r i e s i n d i f f e r e n t h a b i t a t s . For example, guppies in h i g h l a n d streams are subject to p r e d a t i o n only from the small c y p r i n o d o n t i d R i v u l u s h a r t i i , and as a r e s u l t the morphology, behavior, and l i f e h i s t o r y s t r a t e g i e s of guppies in these streams are c o n s i d e r a b l y d i f f e r e n t from those i n lowland streams ( L i l e y and Seghers 1975). I would expect that the a c q u i s i t i o n of escape behavior in these h a b i t a t s would d i f f e r i f c o n d i t i o n i n g f o r p r e d a t i o n avoidance i s an important f a c t o r i n the e v o l u t i o n of guppy 48 behavior. 49 CONCLUSIONS 1. Young f i s h are chased by a d u l t s ; the average number of chases i s 277 per i n d i v i d u a l per day. 2. The amount of cover or number of a d u l t s present has no e f f e c t on chasing i n t e n s i t y . 3. Escape responses are q u a l i t a t i v e l y i d e n t i c a l i n s p i t e of e a r l y c h asing d e p r i v a t i o n , immediate s o c i a l i s o l a t i o n , and changes i n the a b i o t i c environment. 4. Response d i f f e r e n c e s based on body s i z e can not be separated from those based on sex and age d i f f e r e n c e s . 5. A \"chasing pheromone\" i s proposed to account f o r the p a t t e r n of development of escape responses i n p a r t i a l l y d e p r i v e d f i s h . 6. S u b s t a n t i a l independence of the two p a r t s of the response suggests independent c o n t r o l of dropping and f r e e z i n g b e h aviors. 7. B r a i n c e n t r e s f o r o l f a c t o r y i n t e g r a t i o n are l i k e l y s i t e s f o r the c o n t r o l of escape response development. 8. A l l a q u a t i c escape response types known to e x i s t i n guppies develop independently of e a r l y c h a s i n g experience. 50 9. The a b i l i t y to a v o i d predatory a t t a c k s , at which the chased f i s h are s u p e r i o r , may be l e a r n e d from a d u l t s i n the course of j u v e n i l e c h a s i n g . 10. The enhanced s u r v i v a l and moderated r e a c t i v i t y of chased f i s h may be the r e s u l t of s e l e c t i o n f o r chasing by a d u l t s as an a g g r e s s i v e p a r e n t a l s t r a t e g y . 11. Grouping has no e f f e c t on the i n t e n s i t y of guppy escape responses. 12. The o r i g i n and experience of guppies used as experimental s u b j e c t s must be d e f i n e d i f c o n c l u s i o n s are drawn about e f f e c t s on behavior. 51 REFERENCES Altmann, M. 1958. 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APPENDIX - SUMMARY OF DISTANCE-TIME CORRELATION TESTS D e p r i v a t i o n experiment Immatures sex treatment coef \u00C2\u00A3 i c i e n t d i r e c t ion males c o n t r o l -0.15 NS no cues 0.52 + v i s u a l cues 0.03 NS guppy chemical cues 0.23 NS predator chemical cues 0.10 NS females c o n t r o l 0.02 NS no cues 0.33 NS v i s u a l cues 0.14 NS guppy chemical cues 0.27 NS predator chemical cues 0.12 NS t o t a l s - \"+\"=9, \"-\"=1 NS=9, S=1 Matures sex treatment coef f i c i e n t d i r e c t i o n males c o n t r o l 0.15 NS no cues 0.16 NS v i s u a l cues 0.30 NS guppy chemical cues -0.20 NS predator chemical cues 0.20 NS females c o n t r o l -0.10 NS no cues 0.33 NS v i s u a l cues 0.43 NS guppy chemical cues 0.55 + predator chemical cues 0.06 NS t o t a l s = +\"=8, \"-\"=2 NS=9, S=1 sex Immediate soc i a l depr i v a t ion experiment treatment c o e f f i c i e n t d i r e c t i o n males alone 0.17 NS group 0.35 NS females alone 0.24 NS group 0.35 NS t o t a l s = \" + \" = 4 \" - \" = 0 NS=4, S=0 "@en . "Thesis/Dissertation"@en . "10.14288/1.0096066"@en . "eng"@en . "Zoology"@en . "Vancouver : University of British Columbia Library"@en . "University of British Columbia"@en . "For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use."@en . "Graduate"@en . "Some factors affecting the development and expression of escape behavior in the guppy (Poecilia reticulata)"@en . "Text"@en . "http://hdl.handle.net/2429/24619"@en .