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Invasive species threaten biodiversity globally. Amphibians are one of the most threatened vertebrate taxa and are particularly sensitive to invasive species, including other amphibians. African clawed frogs (Xenopus laevis) are native to Southern Africa but have subsequently become invasive on multiple continents-including multiple parts of North America-due to releases from the pet and biomedical trades. Despite their prevalence as a global invader, the impact of X. laevis remains understudied. This includes the Pacific Northwest of the USA, which now hosts multiple expanding X. laevis populations. For many amphibians, chemical cues communicate important information, including the presence of predators. Here, we tested the role chemical cues may play in mediating interactions between feral X. laevis and native amphibians in the Pacific Northwest. We tested whether native red-legged frog (Rana aurora) tadpoles display an antipredator response to non-native frog (X. laevis) or native newt (rough-skinned newts, Taricha granulosa) predator chemical stimuli. We found that R. aurora tadpoles exhibited pronounced anti-predator responses when exposed to chemical cues from T. granulosa but did not display anti-predator response to invasive X. laevis chemical cues. We also began experimentally testing whether T. granulosa-which produce a powerful neurotoxin tetrodotoxin (TTX)-may elicit an anti-predator response in X. laevis, that could serve to deter co-occupation. However, our short-duration experiments found that X. laevis were attracted to newt chemical stimuli rather than deterred. Our findings show that X. laevis likely poses a threat to native amphibians, and that these native species may also be particularly vulnerable to this invasive predator, compared to native predators, because toxic native newts may not limit X. laevis invasions. Our research provides some of the first indications that native Pacific Northwest species may be threatened by feral X. laevis and provides a foundation for future experiments testing potential management techniques for X. laevis.

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Mounting evidence has shown that personality and behavioral syndromes have a substantial influence on interspecific interactions and individual fitness. However, the stability of covariation among multiple behavioral traits involved in antipredator responses has seldom been tested. Here, we investigate whether sex, gravidity, and parasite infestations influence the covariation between risk aversion (hiding time within a refuge) and escape response (immobility, escape distance) using a viviparous lizard, Zootoca vivipara, as a model system. Our results demonstrated a correlation between risk-averse and escape behavior at the among-individual level, but only in gravid females. We found no significant correlations in either males or neonates. A striking result was the loss of association in postparturition females. This suggests that the "risk-averse - escape" syndrome is ephemeral and only emerges in response to constraints on locomotion driven by reproductive burden. Moreover, parasites have the potential to dissociate the correlations between risk aversion and escape response in gravid females, yet the causal chain requires further examination. Overall, our findings provide evidence of differences in the association between behaviors within the lifetime of an individual and indicate that individual states, sex, and life stages can together influence the stability of behavioral syndromes.

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In Mediterranean rocky shores, the black sea urchin Arbacia lixula is often associated with communities dominated by encrusting corallines, devoid of fleshy algae. While it is commonly known as a diurnal herbivore, this species also migrates at night from hidden to more exposed habitats. Here, we provide the first experimental evidence of an adjustment to a predominant nocturnal behaviour in a population of A. lixula. Sea urchin densities changed from nearly zero during daytime to more than 16 urchins m-2 at night in treatment plots where the sea urchins were removed. We suggest that the observed behaviour was triggered by our experimental manipulations and was a response to the presence of dead conspecifics and small predatory fishes attracted by the urchin culling. Further research is needed to assess whether our findings can be generalised to the behaviour of A. lixula in areas where sea urchins are under strong pressure from diurnal predators. In these cases, it is important to perform sea urchin density counts at night to avoid misleading assessments about the herbivore pressure in a littoral area.

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Predator-prey relationships are fundamental components of ecosystem functioning, within which the spatial consequences of prey social organization can alter predation rates. Group-living (GL) species are known to exploit inadvertent social information (ISI) that facilitates population persistence under predation risk. Still, the extent to which non-grouping (NG) prey can benefit from similar processes is unknown. Here we built an individual-based model to explore and compare the population-level consequences of ISI use in GL and NG prey. We differentiated between GL and NG prey only by the presence or absence of social attraction toward conspecifics that drives individual movement patterns. We found that the extent of the benefits of socially acquired predator information in NG highly depends on the prey's ability to detect nearby predators, prey density and the occurrence of false alarms. Conversely, even moderate probabilities of ISI use and predator detection can lead to maximal population-level benefits in GL prey. This theoretical work provides additional insights into the conditions under which ISI use can facilitate population persistence irrespective of prey social organisation.

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The decline of terrestrial predator populations across the globe is altering top-down pressures that drive predator-prey interactions. However, a knowledge gap remains in understanding how removing terrestrial predators affects prey behavior. Using a bifactorial playback experiment, we exposed fox squirrels to predator (red-tailed hawks, coyotes, dogs) and non-predator control (Carolina wren) calls inside terrestrial predator exclosures, accessible to avian predators, and in control areas subject to ambient predation risk. Fox squirrels increased their use of terrestrial predator exclosures, a pattern that corresponded with 3 years of camera trapping. Our findings suggest fox squirrels recognized that exclosures had predictably lower predation risk. However, exclosures had no effect on their immediate behavioral response towards any call, and fox squirrels responded most severely to hawk predator calls. This study shows that anthropogenically driven predator loss creates predictably safer areas (refugia) that prey respond to proactively with increased use. However, the persistence of a lethal avian predator is sufficient to retain a reactive antipredator response towards an immediate predation threat. Some prey may benefit from shifting predator-prey interactions by gaining refugia without sacrificing a sufficient response towards potential predators.

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Chemical information has an important role in the sensory ecology of aquatic species. For aquatic prey, chemical cues are a vital source of information related to predator avoidance and risk assessment. For instance, alarm cues are released by prey that have been injured by predators. In addition to providing accurate information about current risk, repeated exposure to alarm cues can elicit a fear response to novel stimuli (neophobia) in prey. Another source of chemical information is disturbance cues, released by prey that have been disturbed or harassed (but not injured) by a predator. While disturbance cues have received much less attention than alarm cues, they appear to be useful as an early warning signal of predation risk and have the potential to be used as a priming cue for learning. In this study, we used wood frog (Lithobates sylvaticus) tadpoles to test whether repeated exposure to disturbance cues during the embryonic stage can induce neophobic behaviour. Three weeks following repeated exposure to disturbance cues, tadpoles showed reduced activity when exposed to a novel odour, but they no longer displayed an antipredator response to disturbance cues. In a second experiment, we found that tadpoles failed to learn that a novel odour was dangerous following a pairing with disturbance cues, whereas alarm cues facilitated such learning. Our results add to the growing body of information about disturbance cues and provide evidence of their function as an embryonic risk cue but not as an associative learning cue.

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Certain traits of recipient environments, such as the availability of limiting resources, strongly determine the establishment success and spread of non-native species. These limitations may be overcome through behavioral plasticity, allowing them to exploit alternative resources. Here, we show how a secondary cavity nester bird, the rose-ringed parakeet Psittacula krameri, innovates its nesting behavior as a response to the shortage of tree cavities for nesting in its invasive range in Tenerife (Canary Islands). We observed that some breeding pairs excavated their own nest cavities in palms, thus becoming primary cavity nester, whereas others occupied nests built with wood sticks by another invasive species, the monk parakeet Myiopsitta monachus. The use of these novel nesting strategies increased the number of breeding pairs by up to 52% over 6 years, contributing to a 128.8% increase of the whole population. Innovative nests were located at greater heights above ground and were more aggregated around conspecifics but did not result in greater breeding success than natural cavities. Occupation of monk parakeet colonies by rose-ringed parakeets also benefited the former species through a protective-nesting association against nest predators. Our results show how an invasive species innovate nesting behaviors and increase nest-site availability in the recipient environment, thus facilitating its population growth and invasion process. Potential behavioral innovations in other invasive rose-ringed parakeet populations may be overlooked, and should be considered for effective management plans.

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In high-risk environments with frequent predator encounters, efficient antipredator behavior is key to survival. Parental effects are a powerful mechanism to prepare offspring for coping with such environments, yet clear evidence for adaptive parental effects on offspring antipredator behaviors is missing. Rapid escape reflexes, or "C-start reflexes," are a key adaptation in fish and amphibians to escape predator strikes. We hypothesized that mothers living in high-risk environments might induce faster C-start reflexes in offspring by modifying egg composition. Here, we show that offspring of the cichlid fish Neolamprologus pulcher developed faster C-start reflexes and were more risk averse if their parents had been exposed to cues of their most dangerous natural predator during egg production. This effect was mediated by differences in egg composition. Eggs of predator-exposed mothers were heavier with higher net protein content, and the resulting offspring were heavier and had lower igf-1 gene expression than control offspring shortly after hatching. Thus, changes in egg composition can relay multiple putative pathways by which mothers can influence adaptive antipredator behaviors such as faster escape reflexes.

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Food availability and temporal variation in predation risk are both important determinants of the magnitude of antipredator responses, but their effects have rarely been examined simultaneously, particularly in wild prey. Here, we determine how food availability and long-term predation risk affect antipredator responses to acute predation risk by monitoring the foraging response of free-ranging snowshoe hares (Lepus americanus) to an encounter with a Canada lynx (Lynx canadensis) in Yukon, Canada, over four winters (2015-2016 to 2018-2019). We examined how this response was influenced by natural variation in long-term predation risk (2-month mortality rate of hares) while providing some individuals with supplemental food. On average, snowshoe hares reduced foraging time up to 10 h after coming into close proximity (≤75 m) with lynx, and reduced foraging time an average of 15.28 ± 7.08 min per lynx encounter. Hares tended to respond more strongly when the distance to lynx was shorter. More importantly, the magnitude of hares' antipredator response to a lynx encounter was affected by the interaction between food-supplementation and long-term predation risk. Food-supplemented hares reduced foraging time more than control hares after a lynx encounter under low long-term risk, but decreased the magnitude of the response as long-term risk increased. In contrast, control hares increased the magnitude of their response as long-term risk increased. Our findings show that food availability and long-term predation risk interactively drive the magnitude of reactive antipredator response to acute predation risk. Determining the factors driving the magnitude of antipredator responses would contribute to a better understanding of the indirect effects of predators on prey populations.

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Tonic immobility (TI) is an important antipredator response employed by prey in the last stages of a predation sequence. Evolution by natural selection assumes consistent individual variation (repeatability) in this trait. In ectotherms, which experience variable body temperatures, TI should be repeatable over a thermal gradient to be targeted by natural selection; however, information on thermal repeatability of this trait is missing. We examined thermal repeatability of TI in juveniles of two sympatric amphibians, smooth (Lissotriton vulgaris) and alpine (Ichthyosaura alpestris) newts. Both species showed disparate TI responses to body temperature variation (13-28 °C). While the proportion of TI response was repeatable in both taxa, it increased with body temperature in alpine newts but was temperature independent in smooth newts. Duration of TI decreased with body temperature in both taxa but was only repeatable in smooth newts. Our results suggest that a warming climate may affect population dynamics of sympatric ectotherms through asymmetry in thermal reaction norms for antipredator responses.

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Individuals differ in personality and immediate behavioural plasticity. While developmental environment may explain this group diversity, the effect of parental environment is still unexplored-a surprising observation since parental environment influences mean behaviour. We tested whether developmental and parental environments impacted personality and immediate plasticity. We raised two generations of Physa acuta snails in the laboratory with or without developmental exposure to predator cues. Escape behaviour was repeatedly assessed on adult snails with or without predator cues in the immediate environment. On average, snails were slower to escape if they or their parents had been exposed to predator cues during development. Snails were also less plastic in response to immediate predation risk on average if they or their parents had been exposed to predator cues. Group diversity in personality was greater in predator-exposed snails than unexposed snails, while parental environment did not influence it. Group diversity in immediate plasticity was not significant. Our results suggest that only developmental environment plays a key role in the emergence of group diversity in personality, but that parental environment influences mean behavioural responses to the environmental change. Consequently, although different, both developmental and parental cues may have evolutionary implications on behavioural responses.

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As glyphosate-based herbicides, sold under the commercial name Roundup®, represent the most used herbicides in the world, contamination of the freshwater environment by glyphosate has become a widespread issue. In Italy, glyphosate was detected in half of the surface waters monitoring sites and its concentrations were higher than environmental quality standards in 24.5% of them. It can last from days to months in water, leading to exposure for aquatic organisms and specifically to amphibians' larvae that develop in shallow water bodies with proven effects to development and behaviour. In this study, we tested the effects of a 96 h exposure during embryonic development of marsh frog's tadpoles to three ecologically relevant Roundup® Power 2.0 concentrations. As expected, given the low concentrations tested, no mortality was observed. Morphological measurements highlighted a reduction in the total length in tadpoles exposed to 7.6 mg a.e./L, while an increase was observed at lower concentrations of 0.7 and 3.1 mg a.e./L compared to control group. Tadpoles raised in 7.6 mg a.e./L also showed a smaller tail membrane than those raised in the control solution. Regarding behaviour, we tested tadpoles in two different sessions (Gosner stages 25 and 28/29) for lateralization, antipredator response and basal activity. Lower intensity of lateralization was detected in tadpoles raised at the highest Roundup® concentration in the first session of observation, while no significant difference among treatments was observed in the second one. In both sessions, effects of Roundup® Power 2.0 embryonic exposure on antipredator response, measured as the proportional change in activity after the injection of tadpole-fed predator (Anax imperator) cue, were not detected. Tadpoles exposed during embryonic development to Roundup® exhibited lower basal activity than the control group, with the strongest reduction for the 7.6 mg a.e./L treatment. Our results reinforce the concern of Roundup® contamination impact on amphibians.

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Recognising the nature of the predation risk, and responding to it accurately, is crucial to fitness. Yet, even the most accurate adaptive responses to predation risk usually entail costs, both immediate and lifelong. Rooting in life-history theory, we hypothesize that an animal can perceive the nuances of prey size and age selectivity by the predator and modulate its life history accordingly. We test the prediction that-contrary to the faster or earlier senescence under predation risk that increases with prey size and age-under predation risk that decreases with prey size and age either no senescence acceleration or even its deceleration is to be observed. We use two species of indeterminate growers, small crustaceans of the genus Daphnia, Daphnia Pulex and Daphnia magna, as the model prey, and their respective gape-limited invertebrate predators, a dipteran, midge larva Chaoborus flavicans, and a notostracan, tadpole shrimp Triops cancriformis. We analyse age-specific survival, mortality and fertility rates, and find no senescence acceleration, as predicted. With this study, we complete the picture of the expected non-consumptive phenotypic effects of perceived predation pressure of different age-dependence patterns.

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The ability to predict how predators structure ecosystems has been shown to depend on identifying both consumptive effects (CEs) and nonconsumptive effects (NCEs) of predators on prey fitness. Prey populations may also be affected by interactions between multiple predators across life stages of the prey and by environmental factors such as disturbance. However, the intersection of these multiple drivers of prey dynamics has yet to be empirically evaluated. We addressed this knowledge gap using eastern oysters (Crassostrea virginica), a species known to suffer NCEs, as the focal prey. Over 4 months, we manipulated orthogonally the life stage (none, juvenile, adult, or both) at which oysters experienced simulated predation (CE) and exposure to olfactory cues of a juvenile oyster predator (crab), adult predator (conch), sequentially the crab and then the conch, or none. We replicated this experiment at three sites along an environmental gradient in a Florida (USA) estuary. For both juvenile and adult oysters, survival was reduced solely by CEs, and variation in growth was best explained by among-site variation in water flow, with a much smaller and negative effect of predator cue. Adults exposed to conch cue exhibited reduced growth (an NCE), but this effect was outweighed by a positive CE on growth: Surviving oysters grew faster at lower densities. Finally, conch cue reduced larval settlement (another NCE), but this was swamped by among-site variation in larval supply. This research highlights how strong environmental gradients and predator CEs may outweigh the influence of NCEs, even in prey known to respond to predator cues. These findings serve as a cautionary tale for the importance of evaluating NCE processes over temporal scales and across environmental gradients relevant to prey demography.

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Fish are warned about the presence of predators via an alarm cue released from the skin of injured conspecifics. The detection of this odor inherently initiates an antipredator response, which increases the chance of survival for the individual. In the present study, we assessed the effect of three commonly used pesticides on the antipredator response of zebrafish (Danio rerio). For this, we analyzed the behavioral response of zebrafish to a conspecific skin extract following 24 h of exposure to the respective contaminants. Results demonstrate that fish exposed to 20 µg/L of the organophosphate insecticide chlorpyrifos significantly reduced bottom-dwelling and freezing behavior, suggesting an impairment of the antipredator response. For the urea-herbicide linuron and the pyrethroid insecticide permethrin, no statistically significant effects could be detected. However, linuron-exposed fish appeared to respond in an altered manner to the skin extract; some individuals failed to perform the inherent behaviors such as erratic movements and instead merely increased their velocity. Furthermore, we determined whether zebrafish would avoid the pesticides in a choice maze. While fish avoided permethrin, they behaved indifferently to chlorpyrifos and linuron. The study demonstrates that pesticides may alter the olfactory-mediated antipredator response of zebrafish in distinct ways, revealing that particularly fish exposed to chlorpyrifos may be more prone to predation.

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Selection of favourable micro-habitat conditions at nest-sites and nest defence can be important anti- predatory strategies in open-cup nesting birds. In response to nest predation risks, some species of birds appear to form protective nesting associations in which both may gain benefits due to mutual warning and nest defence. Despite the many studies assessing the impact of various factors on nest defence and nest placement, how interactions between species while breeding can modify these strategies is still poorly understood. Here I evaluate whether nesting associations in two species influence nest defence intensity and nest-site selection. An observational approach was used to analyse the defensive behaviours of the Barred Warbler Sylvia nisoria and Red-backed Shrike Lanius collurio in an agricultural landscape in eastern Poland. Association was determined by the position of the nest with respect to that of the associated species (by the nest of one species being within the breeding territory of the other). Nest defence behaviour of these two passerines was assessed as their response to a human intruder near an active brood. This study showed that the nest size and visibility were similar in nest-sites of pairs nesting in association and in spatial isolation. Barred Warblers nesting within shrike breeding territories strongly defended their nests. Warblers breeding alone displayed a lower level of defence than birds nested in association. Shrikes not nesting with warblers were significantly more aggressive than those breeding in the protective nesting association. I suggest that shrikes tried to compensate for the lack of assistance by warblers in joint nest defence and were forced to invest more into defending their own nests. This research suggests that positive interactions within the heterospecific network of relations in ecosystems may be one of the factors responsible for diversifying the intensity of avian nest defence.

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Neonicotinoids are water-soluble neurotoxic insecticides widely used in agriculture that are being detected in nontarget aquatic environments. Nontarget aquatic wildlife, such as amphibians, may be at risk of exposure. Studies using larval stages suggest neonicotinoids are a minor concern to amphibians; however, behavioral effects manifesting later in life are not often considered. Behavioral endpoints could further our understanding of potential sublethal neurotoxic effects after exposure has ended. Using juvenile wood frogs (Lithobates sylvaticus), we investigated the effects of chronic larval exposure to 3 concentrations (1, 10, and 100 µg/L) of formulations containing imidacloprid or thiamethoxam on the putative escape response to a simulated heron attack. We found that control frogs actively responded (i.e., moved or jumped) to the simulated predator attack but frogs exposed to imidacloprid at 10 and 100 µg/L were less likely to respond. The exposed frogs, specifically from the imidacloprid treatment at 10 µg/L (tendency at 100 µg/L) were less likely to leave the attack area compared with controls. However, frogs used refuge similarly among all treatments. Finally, there were no differences in locomotor performance, as measured by total number of jumps and distance traveled during a trial among treatments. In conclusion, our study suggests that exposure to neonicotinoids during amphibian larval development may affect a juvenile frog's ability to perceive or respond to a predator, potentially increasing their vulnerability to predation. Future studies should validate and explore this potential effect further. Environ Toxicol Chem 2018;37:3115-3123. © 2018 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.

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Predation is a very powerful force that shapes many ungulate traits. It is widely known that increasing vigilance intensity is costly and leads to a decline of forage intake. Consequently, ungulates gather into larger groups to reduce an individual vigilance burden by using the "many eyes" effect and to enhance their survival through the "safety in numbers" effect. Vigilance rate and related aggregation changes are two of the most discussed antipredator responses of ungulates to predation risk, but less considered factors also have a significant impact. To enhance our knowledge on these impact factors, I investigated the antipredator responses (vigilance, staring, and escape running) of goitered gazelles. I found that: a) adult females demonstrated vigilance, staring and escape running significantly more often than adult males, sub-adults and fawns; b) adult gazelles (females and males), having more experience in responding to threats, were more vigilant than young individuals (sub-adults and fawns), having likely more involvement in finding food; c) during the birthing and hiding periods, mothers displayed higher rates of vigilance than in other seasons, while staring and escape running were observed most often at the end of the hiding period, when fawns altering their hiding strategy to following one, started to walk a lot in the absence of mothers, as well; and d) goitered gazelles changed their vigilance rate in response to predation risks before changing group size. The events of the yearly biological cycle (birthing/rearing young for females; rutting for males) also had significant impacts on the antipredator responses (vigilance rate and aggregation) in adult gazelles.

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Predator-induced plasticity has been in the focus of evolutionary ecological research in the last decades, but the consequences of temporal variation in the presence of cues predicting offspring environment have remained controversial. This is partly due to the fact that the role of early environmental effects has scarcely been scrutinized in this context while also controlling for potential maternal effects. In this study, we investigated how past environmental conditions, that is different combinations of risky or safe adult (prenatal) and oviposition (early post-natal) environments, affected offspring's plastic responses in hatching time and locomotor activity to predation risk during development in the smooth newt (Lissotriton vulgaris). We found that females did not adjust their reproductive investment to the perceived level of risk in the adult environment, and this prenatal environment had generally negligible effect on offspring phenotype. However, when predator cues were absent during oviposition, larvae raised in the presence of predator cues delayed their hatching and exhibited a decreased activity compared to control larvae developing without predator cues, which responses are advantageous when predators pose a threat to hatched larvae. In the presence of predator cues during oviposition, the difference in hatching time persisted, but the difference in general locomotor activity disappeared between risk-exposed and control larvae. Our findings provide clear experimental evidence that fine-scale temporal variation in a predictive cue during and after egg-laying interactively affects offspring phenotype, and highlight the importance of the early post-natal environment, which may exert a substantial influence on progeny's phenotype also under natural conditions.

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In aquatic environments, uninjured prey escaping a predator release chemical disturbance cues into the water. However, it is unknown whether these cues are a simple physiological by-product of increased activity or whether they represent a social signal that is under some control by the sender. Here, we exposed wood frog tadpoles (Lithobates sylvaticus) to either a high or low background risk environment and tested their responses to disturbance cues (or control cues) produced by tadpoles from high-risk or low-risk backgrounds. We found an interaction between risk levels associated with the cue donor and cue recipient. While disturbance cues from low-risk donors did not elicit an antipredator response in low-risk receivers, they did in high-risk receivers. In addition, disturbance cues from high-risk donors elicited a marked antipredator response in both low- and high-risk receivers. The response of high-risk receivers to disturbance cues from high-risk donors was commensurate with other treatments, indicating an all-or-nothing response. Our study provides evidence of differential production and perception of social cues and provides insights into their function and evolution in aquatic vertebrates. Given the widespread nature of disturbance cues in aquatic prey, there may exist a social signalling system that remains virtually unexplored by ecologists.

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