Learned recognition of novel predators allows prey to respond to ecologically relevant 27 threats. Prey could minimize the costs associated with learning the identity of both 28 predators and nonpredators by making educated guesses on the identity of a novel species 29 based on their similarities with known predators and nonpredators, a process known as 30 generalization. Here, we tested whether juvenile rainbow trout, Oncorhynchus mykiss, 31have the ability to generalize information from a known predator (experiment 1) or a 32 known harmless species (experiment 2) to closely related but novel species. In 33 experiment 1, we taught juvenile trout to recognize a predatory pumpkinseed sunfish, 34Lepomis gibbosus, by pairing pumpkinseed odour with conspecific alarm cues or a 35 distilled water control. We then tested the trout for a response to pumpkinseeds and to 36 novel longear sunfish, Lepomis megalotis (same genus as pumpkinseed), rock bass, 37 Ambloplites rupestris (same family as pumpkinseed) or yellow perch, Perca flavenscens 38 (different family). Trout showed strong learned recognition of pumpkinseed and longear 39 sunfish odour and a weak learned response to rock bass odour but no recognition of 40 yellow perch. In experiment 2, we used latent inhibition to teach juvenile trout that 41 pumpkinseeds were harmless. During subsequent predator learning trials, trout did not 42 learn to recognize pumpkinseed or longear sunfish odour as potential threats, but they did 43 learn that rock bass and yellow perch were threatening. Taken together, these results 44 demonstrate that juvenile rainbow trout can generalize learned recognition of both 45 predator and nonpredator odours based on the phylogenetic relatedness of predators.
Under conditions of spatial and/or temporal variability in predation risk, prey 19 organisms often rely on acquired predator recognition to balance the trade-offs between 20 energy intake and risk avoidance. The question of 'for how long' should prey retain this 21 learned information is poorly understood. Here, we test the hypothesis that the growth 22 rate experienced by prey should influence the length of the 'memory window'. In a 23 series of laboratory experiments, we manipulated growth rate of juvenile rainbow trout 24 and conditioned them to recognize a novel predator cue. We subsequently tested for 25 learned recognition either 24 hours or 8 days post-conditioning. Our results suggest that 26 trout with high versus low growth rates did not differ in their response to learned predator 27 cues when tested 24 hours post-conditioning. However, trout on a high growth rate 28 exhibited no response to the predator cues after 8 days (i.e., did not retain the recognition 29 of the predator odour), whereas trout on a lower growth rate retained a strong recognition 30 of the predator. Trout that differed in their growth rate only after conditioning did not 31 differ in their patterns of retention, demonstrating growth rate after learning does not 32 influence retention. Trout of different initial sizes fed a similar diet (% body mass.day -1 ) 33 showed no difference in retention of the predator cue. Together, these data suggest that 34 growth rate at the time of conditioning determines the 'memory window' of trout. The 35 implications for threat-sensitive predator avoidance models are described. 36 37 38 However, simply responding to any local threat may not represent an optimal strategy 42 (Lima and Dill 1990), as predation pressure is known to be spatially and temporally 43 variable (Griffin 2004; Lima and Steury 2005; Ferrari et al. 2009). A wide variety of 44 taxonomically diverse prey species rely, therefore, on associative learning (acquired 45 predator recognition) to assess the risk associated with potential predators (Brown 2003; 46 Griffin 2004). Learned, versus 'innate', predator recognition allows prey to make 47 dynamic adjustments to predation threats, and to balance the conflicting pressures of 48 predator avoidance and energy intake (i.e., threat-sensitive learning; Ferrari et al. 2005; 49 Ferrari and Chivers 2006; Gonzalo et al. 2010). Within aquatic ecosystems, such predator 50 recognition learning is often facilitated through the pairing of damage released chemical 51 alarm cues (Chivers and Smith 1998) with the sight or smell of a novel predator (Brown 52 2003). Acquired predator recognition has been shown to increase probability of survival 53 during staged encounters with live predators (Mirza and Chivers 2000; Darwish et al. 54 2005; Eiben and Persons 2007; Shier and Owings 2007). 55Given that predation is indeed variable, a relevant, yet poorly understood question 56 is how long should prey exhibit (i.e., retain) an overt response to acquired information? 57 Following a single pairing of a...
Freshwater vertebrate and invertebrate prey species commonly rely on chemosensory information, including non-injury released disturbance cues, to assess local predation threats. We conducted laboratory studies to (1) determine if urea can function as a disturbance cue in juvenile convict cichlids and rainbow trout and (2) determine if the background level of urea influences the behavioral response to a subsequent pulse of urea (‘background noise’ hypothesis). In the first series of trials, juvenile cichlids and trout were exposed to urea at varying concentrations (0 to 0.5 mg L-1 for cichlids and 0 to 1.0 mg L-1 for trout). Our results suggest that both cichilds and trout exhibited functionally similar responses to urea and conspecific disturbance cues and that increasing the concentration of urea results in an increase intensity of antipredator behaviour. In the second series of trials, we pre-exposed cichlids or trout to intermediate or high concentrations of urea (or a distilled water control) and then tested for the response to a second pulse of urea at at intermediate or high concentrations (versus a distilled water control). Our results demonstrate that pre-exposure to urea reduces or eliminates the response to a second pulse of urea, supporting the background noise hypothesis. Together, our results suggest that pulses of urea, released by disturbed or stressed individuals, may function as an early warning signal in freshwater prey species [Current Zoology 58 (2): 250–259 , 2012].
There is a wealth of studies that have examined the way in which prey animals acquire information about their predators, yet the literature on how long prey retain this information is almost non-existent. Here, we investigated if the memory window associated with learned recognition of predators by juvenile rainbow trout was fixed or variable. Specifically, we tested whether the retention of predator recognition was influenced by the risk level associated with the predator. We conditioned juvenile trout to recognize predatory pumpkinseed sunfish posing a high, low or no threat and tested their response to the predator after either 1 or 8 days, and found that trout responded to the odour of the pumpkinseed longer if the risk associated with the predator was higher. We discuss the way in which memory associated with predator risk information provides fundamentally different costs/benefits trade-offs than those associated with foraging.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.