Growth rate and retention of learned predator cues by juvenile rainbow trout: faster-growing fish forget sooner
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Under conditions of spatial and/or temporal variability in predation risk, prey organisms often rely on acquired predator recognition to balance the trade-offs between energy intake and risk avoidance. The question of ‘for how long’ should prey retain this learned information is poorly understood. Here, we test the hypothesis that the growth rate experienced by prey should influence the length of the ‘memory window’. In a series of laboratory experiments, we manipulated growth rate of juvenile rainbow trout and conditioned them to recognize a novel predator cue. We subsequently tested for learned recognition either 24 h or 8 days post-conditioning. Our results suggest that trout with high versus low growth rates did not differ in their response to learned predator cues when tested 24 h post-conditioning. However, trout on a high growth rate exhibited no response to the predator cues after 8 days (i.e. did not retain the recognition of the predator odour), whereas trout on a lower growth rate retained a strong recognition of the predator. Trout that differed in their growth rate only after conditioning did not differ in their patterns of retention, demonstrating growth rate after learning does not influence retention. Trout of different initial sizes fed a similar diet (percent body mass per day) showed no difference in retention of the predator cue. Together, these data suggest that growth rate at the time of conditioning determines the ‘memory window’ of trout. The implications for threat-sensitive predator avoidance models are described.
KeywordsAcquired predator recognition Memory window Antipredator behaviour Salmonids Growth rate Trade-offs
We wish to thank Drs. James Grant and Robert Weladji for comments on earlier versions of this manuscript and Matthew Murphy and Asra Toobie for assistance in the laboratory. All work reported herein was conducted in accordance with Concordia University Animal Research Ethics Protocol number AC-2008-BROW. Financial support was provided by Concordia University and the Natural Sciences and Engineering Research Council of Canada to GEB and the University of Saskatchewan and NSERC to DPC and an NSERC Postdoctoral Fellowship to MCOF.
- Adriaenssens B, Johnsson JI (2011) Shy trout grow faster: exploring links between personality and fitness-related traits in the wild. Behav Ecol. doi: 10.1093/beheco/arq185
- Brown GE (2003) Learning about danger: chemical alarm cues and local risk assessment in prey fishes. Fish Fish 4:227–234Google Scholar
- Chivers DP, Smith RJF (1998) Chemical alarm signaling in aquatic predator-prey systems: a review and prospectus. Écoscience 5:338–352Google Scholar
- Lima SL, Steury TD (2005) Perception of predation risk: the foundation of nonlethal predator-prey interactions. In: Castellanos I, Barbosa P (eds) Ecology of predator-prey interactions. Oxford University Press, Oxford, pp 166–188Google Scholar