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Neophobic predator avoidance allows prey to reduce the risk of predation but is costly in terms of reduced foraging or courtship opportunities if the novel cues do not represent an actual threat. Consequently, neophobic responses to novel cues should wane with repeated exposures in the absence of an actual threat. We tested the prediction that individual personality traits shape the retention of neophobic predator avoidance in wild-caught guppies. Using extinction trials, we demonstrate that personality (measured as latency to escape or approach a novel object) did not influence the initial response of wild-caught Trinidadian guppies to a novel odour; bolder and shyer guppies both exhibited similarly strong avoidance responses. However, after several exposures, shyer guppies maintain an avoidance response, and bolder guppies no longer respond. Our results highlight the complex nature of the antipredator algorithm of prey, whereby past experience, acute risk, and individual tactics shape neophobic predator avoidance patterns.

Many aquatic prey animals release chemical cues upon being captured by a predator. These chemical cues, referred to as alarm cues, may act to warn nearby individuals of danger. For the cues to be useful, fish must be able to discern if they are indicative of a real threat; cues from conspecifics in different age groups may be irrelevant due to size- and habitat-related shifts in predation risk. We test the response of newly-hatched rainbow trout,Oncorhynchus mykiss, to three concentrations of alarm cues from conspecifics from two age groups: newly-hatched versus six-month-old juveniles. Newly-hatched trout demonstrated a significant fright response to all three concentrations of alarm cues, but showed no difference in strength of response based on either concentration or age of the cue donor. We propose that the newly-hatched trout did not respond differently because of the high risk of predation that they face during this life stage.

Individual prey often exhibit consistent behavioural differences in responses to risk. Here, we assess whether such behavioural consistency is linked to morphological changes that are known to result in differences in vulnerability to predators. Some fishes increase their depth-to-length ratio when under increased risk of predation, thereby reducing their risk to gape-limited predators. However, the development of these defences is limited by available resources. We asked whether behavioural tendencies associated with shelter seeking and activity are linked to differences in growth patterns. Common carp classified as ‘active/non-sheltering’ or ‘passive/sheltering’ based on their movement patterns and shelter use, showed consistency in behaviour over a 10-month period with active/non-sheltering fish developing a greater depth to length ratio than passive/sheltering fish. The effectiveness of anti-predator strategies in animals is an integrative function of both behaviour and morphology. Our works highlights a fascinating link between behavioural consistency and the development of adaptive morphologies.

Prey animals that experience a high background level of risk are known to exhibit considerable phenotypic plasticity in their responses to unknown predators. When background risk is high, prey exhibit neophobic responses to unknown odours, i.e. they show a fear response to any new stimulus. Here, we examine whether temporal variation in the pattern of risk to which prey are exposed influences neophobic responses. To establish prey groups with different temporal patterns of risk, embryonic woodfrogs (Lithobates sylvaticus) were exposed to conspecific alarm cues each morning and control cues in the evening, or conspecific alarm cues each evening and control cues in the morning, for their entire embryonic period. After the tadpoles hatched they were tested at both times of day for known risk cues (alarm cues), unknown predator odours or water control. Tadpoles responded to alarm cues at any time of day, but showed neophobic responses to predator odours only if their test time matched their embryonic risk exposure time. These results demonstrate a high level of sophistication of neophobic responses and points to temporal variation in risk as a key driver of antipredator decision making.

Rapidly changing climates and habitats represent challenges faced by the majority of animal species on our planet, and are leading to rapid declines in global biodiversity. However, the degree to which behaviour is influenced by changing environmental cues is not well understood. Specifically, environmental cues that have been correlated with predator abundance or performance over evolutionary history may have significant effects on prey behaviour. In the present study, we investigated the role of water clarity on foraging activity in lake sturgeon (Acipenser fulvescens) in the absence of predators. Foraging activity was significantly higher during the night than the day and was higher in turbid environments versus clear environments, indicating that decreased turbidity alone, may in part drive anti-predator behaviour and constrain foraging activity. Future work exploring the interconnectedness of environmental cues and behavioural changes will help us better understand the many ways rapidly changing environments can influence behavioural ecological processes.

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.

[Many prey animals have a remarkable ability to match the intensity of their behavioural responses to the degree of threat posed by specific predators. However, little is known about how such threat-sensitive predator avoidance develops. In a series of laboratory experiments we tested whether goldfish (Carassius auratus) could learn to recognize predator odours in a threat-sensitive manner. We exposed predator-naive goldfish to various concentrations of chemical cues of pike (Esox lucius) fed goldfish and pike fed another fish diet (swordtails,Xiphophorus helleri). During the conditioning trials goldfish showed behavioural responses to pike fed goldfish but not to pike fed swordtails. Moreover, the intensity of the responses to pike cues increased as the concentration of pike cues increased. Subsequent test trials showed that goldfish that had originally been exposed to pike fed goldfish showed responses to pike fed swordtails, indicating learned recognition of the pike as a predator. Of particular importance, the intensity of the learned responses by the goldfish matched the intensity of the responses observed in the original conditioning trials, thereby demonstrating threat-sensitive learning. Prey should have a selective advantage if they are able to adjust the intensity of their anti-predator response to match the threat posed by their predators. Our preliminary investigations revealed that this threat-sensitive learning has important survival implications during encounters with pike., Many prey animals have a remarkable ability to match the intensity of their behavioural responses to the degree of threat posed by specific predators. However, little is known about how such threat-sensitive predator avoidance develops. In a series of laboratory experiments we tested whether goldfish (Carassius auratus) could learn to recognize predator odours in a threat-sensitive manner. We exposed predator-naive goldfish to various concentrations of chemical cues of pike (Esox lucius) fed goldfish and pike fed another fish diet (swordtails,Xiphophorus helleri). During the conditioning trials goldfish showed behavioural responses to pike fed goldfish but not to pike fed swordtails. Moreover, the intensity of the responses to pike cues increased as the concentration of pike cues increased. Subsequent test trials showed that goldfish that had originally been exposed to pike fed goldfish showed responses to pike fed swordtails, indicating learned recognition of the pike as a predator. Of particular importance, the intensity of the learned responses by the goldfish matched the intensity of the responses observed in the original conditioning trials, thereby demonstrating threat-sensitive learning. Prey should have a selective advantage if they are able to adjust the intensity of their anti-predator response to match the threat posed by their predators. Our preliminary investigations revealed that this threat-sensitive learning has important survival implications during encounters with pike.]

Predation is one of the most important selective forces acting on prey animals. To respond adaptively to predation threats and increase their chances of survival, prey animals have to be able to recognize their potential predators. Even though a few studies demonstrated innate predator recognition, the vast majority of animals have to rely on learning to acquire this information. Often aquatic prey animals can learn to recognize predators when they detect conspecific alarm cues associated with cues from a novel predator. In this study, we exposed American toad (Bufo americanus) tadpoles to varying concentrations of chemical alarm cues (cues from injured conspecifics). We identified a concentration of cues which caused an overt antipredator response (supra-threshold concentration) and a lower concentration for which the prey failed to exhibit a response (sub-threshold concentration). In a second experiment, we attempted to condition the tadpoles to recognize the odour of larval dragonflies (Anax sp.) by pairing the dragonfly odour with either the sub-threshold concentration or the supra-threshold concentration of alarm cues. In both cases, the tadpoles learned to recognize the predator based on this single pairing of alarm cues and predator odour. Moreover, the intensity of the learned response was stronger for tadpoles conditioned with the supra-threshold concentration of alarm cues than the sub-threshold concentration. This is the first documented case of this mode of learning in anuran amphibians. Learned recognition of predators has important implications for survival.

We examined the influence of temporal variation in predation risk on the foraging and antipredator behaviour of juvenile convict cichlids (Archocentrus nigrofasciatus). We exposed fish to one of four treatment regimes: 100% or 20% concentrations of conspecific alarm cue, given once or three times per day, for a period of three days. On the fourth day they were exposed to either 100% conspecific alarm cue or a control of 100% swordtail (Xiphophorus helleri) skin extract. There was no significant effect of concentration of alarm cue, fish previously exposed to the same frequency of risk responded in a similar manner regardless of the concentration of alarm cue previously experienced. Fish that were exposed to predation risk three times per day exhibited moderate intensities of antipredator behaviour during periods of risk and allocated significantly more foraging to periods of safety compared to those exposed to alarm cue once per day. These results demonstrate that temporal variation can influence the trade off between antipredator behaviour and foraging and that prey can use subthreshold cues to assess temporal variability in predation risk.

A wide diversity of animals release chemical cues when attacked by a predator. Often these chemicals serve to warn other conspecifics, and in some cases heterospecifics, of danger, and hence have been termed alarm cues. Responses of animals to alarm cues produced by other species often need to be learned, yet mechanisms of learned recognition of heterospecific cues are not well understood. We tested whether fathead minnows (Pimephales promelas) could learn to recognize heterospecific alarm cues when they detected the cues in the diet of a known predator. We exposed fathead minnows to chemical stimuli collected from a known predator, northern pike (Esox lucius) fed one of two unknown prey, stickleback (Culaea inconstans) or swordtails (Xiphophorous helleri). In subsequent tests, the minnows were exposed to either swordtail skin extract or stickleback skin extract. We found that minnows that were initially exposed to the pike fed stickleback subsequently responded to stickleback skin extract with an anti-predator response but did not respond to swordtail skin extract. Likewise, minnows that were initially exposed to the pike fed swordtails subsequently responded to swordtail skin extract with an anti-predator response but they did not respond to stickleback skin extract. These results clearly demonstrate that minnows learn the identity of heterospecific alarm cues when they detect those cues in the diet of a known predator. Learned recognition of heterospecific alarm cues has important implications for predator/prey interactions.

Several species of aquatic organisms release chemical cues upon detecting predators. These chemicals may serve to 'warn' nearby conspecifics of the predator and hence have been termed disturbance cues. Disturbance cues are thought to be low-level indicators of risk to which prey animals respond with antipredator behaviour. However, little is known about the distribution of disturbance cues among different taxa or how prey animals use these cues to mediate their risk of predation. In this study we exposed brook charr (Salvelinus fontinalis) to water from a tank containing cues of disturbed or undisturbed conspecifics at the same time as we exposed them to cues of an unknown predator, northern pike (Esox lucius). In subsequent trials, we staged encounters between the charr and a pike and tested for differences in survival. We found that charr that were exposed to simultaneous cues from disturbed conspecifics and pike odour subsequently avoided the pike significantly more than charr that had been previously exposed to chemical stimuli from undisturbed charr plus pike odour. Moreover, pike took significantly longer to capture charr that had been previously exposed to disturbance cues from conspecifics plus pike stimuli compared to charr previously exposed to cues from undisturbed charr plus pike stimuli. Ours is the first study to demonstrate that detection of disturbance cues can provide a survival benefit during an encounter with a predator.

Numerous species of aquatic animals release chemical cues when attacked by a predator. These chemicals serve to warn other conspecifics, and in some cases heterospecifics, of danger, and hence have been termed alarm cues. Responses of animals to alarm cues produced by other species often need to be learned, yet mechanisms of learned recognition of heterospecific cues are not well understood. In this study, we tested whether fathead minnows (Pimephales promelas) could learn to recognize a heterospecific alarm cue when it was combined with conspecific alarm cue in the diet of a predator. We exposed fathead minnows to chemical stimuli collected from rainbow trout, Oncorhynchus mykiss, fed a mixed diet of minnows and brook stickleback, Culaea inconstans, or trout fed a mixed diet of swordtails, Xiphophorous helleri, and stickleback. To test if the minnows had acquired recognition of the heterospecific alarm cues, we exposed them to stickleback alarm cues and introduced an unknown predator, yellow perch (Perca flavescens) or northern pike (Esox lucius). Both perch and pike took longer to initiate an attack on minnows that were previously exposed to trout fed minnows and stickleback than those previously exposed to trout fed swordtails and stickleback. These results demonstrate that minnows can learn to recognize heterospecific alarm cues based on detecting the heterospecific cue in combination with minnow alarm cues in the diet of the predator. Ours is the first study to demonstrate that behavioural responses to heterospecific chemical alarm cues decreases the probability that the prey will be attacked and captured during an encounter with a predator.

The mechanisms that drive the evolution of intraspecifc predation (cannibalism) are unclear. Many authors speculate that predators can make substantial gains in nutrition and reproductive output by consuming conspecifics. However, by consuming conspecifics, predators may risk decreasing their inclusive fitness by consuming kin or increasing the chances of pathogen transmission. In fishes intraspecific predation is typically observed when resource levels are low. During these periods it is important for prey fishes to be able to accurately assess their level of predation risk from cannibalistic conspecifics. Prey animals may be able to do this by using chemical cues available in the predator's diet. The last meal consumed by the predator may give important information for prey animals to assess predation risk. We exposed juvenile yellow perch, Perca flavescens, to chemical cues of adult perch fed a diet of either juvenile perch, spot tail shiners, Notropis hudsonius, swordtails, Xiphophorus helleri, or a control of distilled water. Spot tail shiners and juvenile perch commonly form mixed species shoals and are vulnerable to the same suite of predators. Swordtails do not co-occur with yellow perch or spot tail shiners. We found that juvenile perch increased shelter use significantly more when exposed to chemical cues of adult perch fed juvenile perch or spot tails, compared to adult perch fed swordtails or those exposed to distilled water. This suggests that the level of chemosensory assessment used by juvenile perch is quite sophisticated and that the antipredator response can be mediated by specific cues in the predator's diet. This study is the first to demonstrate a response of a fish to chemical cues from intraspecific predators. Future studies should examine the importance of predator diet cues in responses to chemical cues from intraspecific predators.

Detection of an alarm pheromone may allow conspecifics to lower their risk of predation if they avoid areas where alarm pheromones are detected. Similarly, individuals that learn to recognize and avoid alarm signals produced by heterospecifics of their prcy guild (i.e. those with which they share common predators) will likely receive similar benefits. In two separate field studies we tested whether fathead minnows (Pimephales promelas) avoid areas labelled with Iowa darter (Etheostoma exile) skin extract (which contains an alarm pheromone). One population of minnows tested was sympatric with darters while thc other was allopatric from darters. Swordtails (Xiphophorus helleri) are allopatric from fathead minnows in both of the populations tested. Swordtail skin lacks ostariophysan and darter alarm pheromones, and was used to control for a general response to damaged skin of an unfamiliar fish. In the darter-sympatric population we captured significantly fewer and smaller minnows in traps marked with darter skin extract (experimental traps) than traps marked with a control of swordtail skin extract. Given the correlation between age and size, and therefore experience, these data suggest that less experienced fish do not avoid darter skin extract to the same extent as do older more experienced fish. In the darter-allopatric population there was no difference in the number of minnows or the size of minnows captured in control versus experimental traps. Taken together, these results demonstrate that fathead minnows recognize and avoid areas where darter alarm pheromone is detected and that this is a learned response. Use of heterospecific alarm pheromones to assess predation risk may be a widespread phenomenon within communities of small fishes.