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Within aquatic ecosystems, chemosensory cues are widely used as publicly available risk assessment information, allowing prey to optimize behavioural decisions. In sexually dimorphic species, males and females often have different responses to local predation threats. According to the ‘distracted male’ hypothesis, reproductively active males should show a reduced response to risk cues compared to conspecific females due to the potentially high costs of lost courtship and mating opportunities among males. Recent evidence supports this hypothesis, showing that adult male guppies (Poecilia reticulata) show a reduced or absent response to chemosensory risk cues. Here, we further test the ‘distracted male’ hypothesis by testing non-reproductive male and female guppies, collected from the Lopinot River (high predation) or the Upper Aripo River (low predation). We found that juvenile male and female guppies exhibited similar response patterns. Consistent with our predictions, both juvenile male and female guppies collected from a high predation site exhibited a similar antipredator response (reduced number of lines crossed) when exposed to conspecific alarm cues or a novel odour (vs. water control). Those collected from a low predation site showed similar responses to conspecific alarm cues and no response to a novel odour or the water control. Combined, our results suggest that unlike adult guppies, non-reproductive male and female guppies make similar behavioural decisions in response to acute predation cues. As predicted by the ‘distracted male’ hypothesis, the previously reported absence of a response to chemosensory risk assessment cues among adult males may be due to a devaluation of risk assessment information in favour of continued mating. [ABSTRACT FROM AUTHOR]

Many studies have shown that prey can optimize their defence mechanisms based on cues indicating predator presence and pressure. However, little is known about whether prey can assess the actual threat by considering both predator density and the motivational state of cannibalistic predators, which can be influenced by threats from higher order predators. We conducted laboratory experiments to test the hypothesis that high predator density, combined with chemical cues indicating predator stress (e.g. alarm and disturbance cues), may inhibit prey defences. Using Daphnia and Zygoptera/Anisoptera larvae, we observed that Daphnia’s strong response to low-density predator kairomones was suppressed when exposed to high-density predator kairomones and disturbance cues. Surprisingly, we found no evidence of a suppressive response to alarm cues. Our study is to our knowledge, the first to show that prey uses predator stress cues to avoid unnecessary defences, suggesting a ‘cascade of fear’ in which fear at one trophic level reduces fear at a lower level. Furthermore, it is to our knowledge the first to demonstrate that prey can reduce their anti-predator response in the presence of high densities of cannibalistic predators.

Chemical eavesdropping is a critical tool used by organisms to gain information about their environment and mediate interactions with other organisms within it, such as prey gaining information about predators and vice versa. However, most chemical eavesdropping studies focus on information used by prey species, not predators. The goal of this study was to assess whether or not a desert ambush predator, Crotalus ornatus (Eastern Black-tailed Rattlesnake), differentiates among chemical cues from nonnative familiar and novel native prey items when choosing ambush spots. Naive neonate C. ornatus were obtained from wild mothers, born and raised in captivity, and placed in an arena where they were presented with aquatic extracts from the integument from 9 known and suspected prey items, a familiar non-native prey item, and a tap water control. Their reactions to the chemical extracts were recorded under diurnal and nocturnal conditions, and they were given a tongue-flick ambush (TFAM) score based on their predatory behavior towards the chemical cue. Ten naive neonate C. ornatus were put through each of the 11 trials under diurnal and nocturnal conditions, and based on TFAM scores, snakes differentiated among the chemical cues, but there were no detectable differences based on photoperiod. Post hoc pairwise tests revealed that snakes preferred native small mammal and lizard prey. The snakes used in this study had never been exposed to wild prey stimuli in their native ecosystem and had fed exclusively on non-native mammalian prey in captivity, thus their preference for native small mammals and lizards indicates an innate basis for prey preference in C. ornatus. [ABSTRACT FROM AUTHOR]

Environmentally cued hatching is prevalent, diverse, and crucial to many animals' survival. Fish embryos use a variety of chemical cues to initiate hatching to avoid potential predators, yet the function of chemical cues released from the predatory consumption of heterospecific prey is largely unknown. Zebra cichlids (Metriaclima estherae) are ferocious predators that can feed on medaka (Oryzias latipes), though it is impossible for this to occur in their natural habitat. Zebrafish (Danio rerio) embryos have been employed as experimental subjects due to their sensitivity to a variety of chemical signals. In this study, zebrafish embryos were subjected to three types of chemical signals: predator cues (PCs, released from cichlids), heterospecific cues (HCs, released from medaka), and heterospecific dietary cues (HDCs, released from cichlids that have ingested medaka). As a result, the hatching times of zebrafish embryos were accelerated by 6.8% and 12.6% by PCs and HDCs, respectively. PCs and HDCs cause significantly reduced morphology in zebrafish embryos, including regarding total length, eye length, dorsal fin length, trunk height, caudal fin height, and body cavity, and increase yolk sac height. The PCs and HDCs diminished the larvae's motion at 120 and 144 h post fertilization (hpf), which could be attributed to non-developmental embryogenesis. Overall, the impacts of HDCs on embryonic hatching, developmental morphology, and locomotor were more pronounced in comparison with PCs. Our findings demonstrate that predators' dietary cues, even those released after predation on heterospecific prey, can modify embryogenesis, highlighting the critical functions of chemical signals in predation risk assessment using embryos. [ABSTRACT FROM AUTHOR]

Various strategies have evolved to protect animals from predators. We explored the activity and predation risk experienced by two species of aphid. Both species will drop from plants when disturbed and face a suite of predators, including wolf spiders, when they reach the ground. We focused on Aphis fabae Scopoli and Aphis nerii Boyer de Fonscolombe (Hemiptera: Aphididae, Aphidini); A. nerii sequesters cardiac glycosides when it feeds on milkweed. We explored the interactions between these aphids and the wolf spider Pardosa milvina Hentz (Araneae: Lycosidae) that is likely a predator they encounter when they are not on their host plants. We hypothesized that there would be differences in the susceptibility of the two species to predation and that the more vulnerable species would react more strongly to substrate‐borne cues deposited by the spider. We predicted that any behavioral reactions that the aphid displayed in response to predator cues would be effective in reducing risk. We documented the activity of each aphid species on chemotactile cues from P. milvina and measured predation rate in arenas with and without those same cues. Aphis fabae altered their activity in the presence of P. milvina cues but A. nerii did not. Likewise, A. fabae was more susceptible to predation by P. milvina when no cues were present, but when cues were present, predatory success was much lower. Aphis nerii, the less desirable prey for this predator, moved less and had a different locomotory pattern than A. fabae in control trials with no spider cues and so we cannot determine whether its chemical protection or activity were more important in reducing predation levels. These results provide insight into the risks faced by aphids when they are off of their host plant and in a barren environment. [ABSTRACT FROM AUTHOR]

Intraspecific sex differences in morphology, physiology, and behavior are widespread among taxa. However, despite their fundamental importance, they have been relatively understudied in the context of risk assessment. For instance, with Trinidadian guppies (Poecilia reticulata), there has been a bias toward the exclusive use of females, as males are thought to be less responsive to acute predation threats. However, there is little empirical evidence supporting this assumption. Moreover, the antipredator behavior of male guppies has been unexplored, perhaps resulting in the over-generalization of female behavior to both sexes in previous studies. Here, we conducted laboratory experiments involving wild-caught and laboratory-reared guppies. In Experiment 1, shoals of either male or female guppies from a high-predation population were tested for their response to alarm cues, novel odor, or a water control. We found that while female shoals exhibited strong antipredator responses to alarm cues and neophobic responses to novel odor, male shoals exhibited only a weak response to alarm cues and no evidence of neophobia. In Experiment 2, we exposed male and female guppies to high- or low-predation risk and then tested individuals for their responses to alarm cues, novel odor, or water control. Regardless of background risk, males did not respond to any stimulus. In contrast, low-risk females exhibited antipredator responses toward alarm cues and those from high background risk displayed neophobia. Our results suggest that females are more cautious when encountering an acute predation risk, highlighting the importance of accounting for both sexes in studies on predation. [ABSTRACT FROM AUTHOR]

Aposematic species combine a conspicuous signal with a secondary defence, the majority of which are studied in the context of a visual signal. While multimodality of the aposematic signal appears to be common in invertebrate species, we know very little about the presence or absence of multimodality in vertebrates. Here, we examine the possibility of multimodality of aposematism in the green‐and‐black poison frog, Dendrobates auratus. Using a non‐visual predator (the cat‐eyed snake, Leptodeira annulata) and extractions of chemicals in frog skins, we test whether there is sufficient non‐visual information for predators to avoid this aposematic species without using visual cues. We found that experienced predators avoid chemicals in this poison frog's skin by olfactory cues alone in trials with live frogs and extracts from captive poison frogs, whereas extracts from wild poison frogs did not lead to avoidance behaviours in predators. Further, in our limited sampling, naïve predators demonstrate no avoidance. This not only indicates that predators can make informed decisions from the frog's odour, but also indicates that avoidance based on olfactory cue is a learned response. [ABSTRACT FROM AUTHOR]

Larvae of some leaf beetles carry masses of feces covering parts or all of the body, which is called a "fecal shield". In general, the shield is thought to be a defense structure against natural enemies. However, some studies have suggested that defense effectiveness varies depending on the natural enemy. In this study, we used a fecal retention leaf beetle Ophrida xanthospilota (Coleoptera: Chrysomelidae), and 2 local generalist predators (an ant, Camponotus japonicus (Hymenoptera: Formicidae) and a stinkbug, Arma custos [Hemiptera: Pentatomidae]) as a system to test the hypothesis that the fecal shield of O. xanthospilota plays different roles in predation behavior of different predators and can provide multiple chemical communication signals in predator–prey interactions. Prey bioassays showed that the fecal shield of O. xanthospilota larvae repelled the ant C. japonicus while attracting the stinkbug A. custos. The results also strongly demonstrated that hexane extracts of the fecal shield significantly repelled C. japonicus, while dichloromethane (DCM) extracts did not inhibit ant predation. Interestingly, DCM extracts attracted A. custos, but hexane extracts did not. Therefore, we suggest that the fecal shield is a double-edged sword for the larvae of O. xanthospilota. Our results also indicated that the risk–benefit tradeoff of an insect should be estimated at a community level involving multiple enemies (predators and parasites) and herbivores, rather than in a single prey–predator pair. [ABSTRACT FROM AUTHOR]

Prey organisms need to detect predators and respond with adequate antipredator behaviours. To recognize predators, chemosensory cues play a pivotal role, particularly in aquatic ecosystems, where sight may be restricted. However, it is less known whether the ability to use these cues, enabling appropriate antipredator behaviour, varies between subpopulations occupying different habitats with different predation risks. We examined antipredator behaviour of wild‐caught larval fire salamanders (Salamandra salamandra) from two different habitats, ponds and streams. Ponds and streams are inhabited by habitat‐specific predators, such as alpine newts (Ichthyosaura alpestris), which only occur in ponds. We confronted larvae from both habitats with either tap water (control) or tap water that had contained alpine newts (newt treatment) and investigated potential behavioural differences in activity and shelter emergence. In the activity test, pond larvae, but not stream larvae, were significantly less active when faced with chemical cues (potentially kairomones) from newts than those faced with a control stimulus, but stream larvae generally exhibited significantly lower activity than pond larvae. In the shelter‐emergence test, larvae from both habitats spent significantly less time outside a shelter in the newt treatment than in control water. This suggests that larval fire salamanders, independent of their habitat, recognize chemical cues from potential predators and alter their behaviour accordingly. Larvae of both habitats were able to detect and use chemical cues released from potential predators, but they differed slightly in their response to these chemical cues. This finding reflects varying antipredator strategies in response to the habitat‐specific differences. [ABSTRACT FROM AUTHOR]

Recent range expansion of many species northward and upward in elevation suggests that the expanding species are able to cope with new biotic interactions in the leading edge. To test this hypothesis, we used a common garden experiment expanding the elevation range of an obligatorily univoltine dragonfly (Sympetrum striolatum) to investigate whether the growth, behavioral (food intake), and morphological (8th and 9th abdominal lateral spine) responses differed when confronted with dragonfly predators that dominate low-elevation (Aeshna cyanea) and high-elevation (A. juncea) lentic freshwater systems under two temperature treatments (20 °C and 24 °C). Growth rate and growth efficiency increased at higher temperature. Overall, low- and high-elevation predators induced a similar increase in growth rate and growth efficiency but a decrease in food intake at 24 °C. Lateral abdominal spines were longer only in low-elevation dragonflies at 18 °C. Our study suggests that range-expanding species may have been successful in colonizing new areas at higher elevations because they respond to dominant high-elevation predators in a similar way to the more familiar low-elevation predators. [ABSTRACT FROM AUTHOR]

The ubiquitous oceanic copepod Calanus finmarchicus is the major link between primary producers and important fish stocks in the North Atlantic Ocean and adjacent seas. Despite over a century of research on growth and development of this key species, the effect of predation risk on these processes remains elusive. We tested how food level and chemical cues from a fish predator influence growth and development of C. finmarchicus, using a predator naïve laboratory population. Copepods reached adult stage earlier both in response to high food and to predator cues in our experiment. High food also increased growth and lipid accumulation. In contrast, perceived predation risk triggered reduced size and lipid fullness, indicating a decoupling of growth and development rates. Our results demonstrate that chemical predator cues can influence life history strategies in C. finmarchicus, and suggest that present and future patterns in oceanic zooplankton size and population dynamics may also reflect differences in predation risk. [ABSTRACT FROM AUTHOR]

Biological control research often focuses on the ability of predators to reduce pest densities and protect crops through consumption. Less studied is their ability to protect crops by altering pest behaviour (non‐consumptive effects). Lab experiments were conducted to test predation rates of striped cucumber beetles (Acalymma vittatum; Coleoptera: Chrysomelidae) and spotted cucumber beetles (Diabrotica undecimpunctata howardi; Coleoptera: Chrysomelidae) by large (>10 mm) wolf spiders (Araneae: Lycosidae). Field experiments were conducted to examine how the physical presence and/or cues of spiders impact the behaviour and mortality of A. vittatum (specialist) and D. undecimpunctata (generalist) cucumber beetles as well as growth and damage of cucumber plants (Cucumis sativus; Cucurbitaceae). A. vittatum and D. undecimpunctata adults were added to caged cucumber plants without a spider, with spider cues only (spider removed before beetle inclusion), with spider only (spider introduced to plants immediately before beetle inclusion), and with spiders and their cues present (spiders introduced 24 hr in advance of beetle inclusion). A. vittatum responded to spider cues primarily by emigrating from plants. Contrarily, D. undecimpunctata did not display obvious responses, such as reduced feeding or increased emigration, to spider foraging and/or cues. Actively foraging lycosids increased A. vittatum mortality and reduced densities of D. undecimpunctata in the field when cucumber plants were flowering. This study highlights how non‐consumptive and consumptive effects can play a role in modifying pest populations, and how these effects can vary across species and plant growth stages. [ABSTRACT FROM AUTHOR]

Group-living prey rely on social information such as alarm signals and other social cues to avoid predation. By definition, "signals" imply that a message is voluntarily directed at receivers (i.e., the audience), whereas "cues" are released incidentally regardless of the audience composition. Thus, audience effects can be used to differentiate between signals and cues when communication is difficult to observe or quantify. In at least two fish species, chemical disturbance cues are released during a predator attack to signal to familiar audiences about predation risk. Here, we examined whether audience composition affects disturbance cue release in wood frog (Lithobates sylvaticus) tadpoles to better understand the function of disturbance cues across aquatic prey. Groups of tadpoles underwent simulated predator attacks to obtain disturbance cues. The groups were either familiar and related, unfamiliar and related, familiar and unrelated, or unfamiliar and unrelated. To assess the relative potency of each cue, we used a behavioral bioassay design involving activity changes in independent tadpole receivers (unfamiliar and unrelated to the donors). If tadpoles use disturbance cues to signal related and/or familiar individuals, we predicted increased fright responses in receivers to cues obtained from those groups. However, we detected no effect of audience composition, indicating that tadpoles release similar disturbance cues regardless of audience kinship or familiarity. Nevertheless, disturbance cues evoked a consistent antipredator response in receivers indicating that these chemicals still act as reliable risk cues. Further comparative studies using audience effects are necessary to understand how disturbance cues have evolved across aquatic prey. Significance statement: When aquatic prey encounter predators and are frightened, they release chemicals known as "disturbance cues" into the water. These chemicals alert other prey nearby of potential danger. For example, wood frog tadpoles release disturbance cues when they are being chased by a predator. Tadpoles that smell the disturbance cues of other tadpoles are less likely to be eaten by predators. Since wood frog tadpoles are often found in shallow ponds filled with both familiar siblings as well as other tadpoles that are unfamiliar and unrelated, we wondered if tadpoles would produce more disturbance cues when familiar or related tadpoles were nearby. Here, we show that no matter who the audience members are, familiar siblings or not, tadpoles release disturbance cues that cause similar fright. This suggests that disturbance cues are not released differently depending on the audience in this species. [ABSTRACT FROM AUTHOR]

Epidermal club cells (ECCs) are present in many species of teleost fish. In an attempt to justify their presence in the epidermis of fish, they have been associated with numerous functions. One proposed function is communication with conspecifics during a predation event, as these cells may passively release substances upon rupture, which may occur during predation. We identified the presence and distribution of ECCs in the body skin of adult cardinal tetra, Paracheirodon axelrodi (Schultz, 1956) and analyzed the animal's behavioral response to conspecific skin extract in a laboratory setting. The identification and distribution of ECCs in the epidermis of the animals were confirmed by conventional histology and immunohistochemistry. Our results demonstrated that: ECCs are present in the skin of the entire body; a high density is observed in the dorsal side from head to tail, in the insertion of the fins and in the epidermis covering them; and ventral distribution is less extensive and more dispersed than dorsal distribution. Treatment of P. axelrodi specimens with skin preparations of conspecifics resulted in behavioral changes in the animals: they showed erratic swimming movements, they showed avoidance of the area of stimulus application and they decreased the time spent moving. Overall, these results allow us to conclude that P. axelrodi possesses ECCs throughout the body, with a greater presence in areas of high exposure to predation events (dorsal area and fins). Animals exposed to conspecific skin extract showed a significant increase in behaviors described as anti-predatory in other species. This supports the hypothesis that ECCs may be the origin of chemical alarm cues that are passively released when skin damage occurs, alerting the rest of the group to the risk of predation. • Epithelial club cells of the fish Paracheirodon axelrodi are mainly localized in areas of high predation exposure. • Epithelial club cells of P. axelrodi are similar to those described in Cypriniformes. • P. axelrodi responds to conspecific skin extracts with antipredator behavior. [ABSTRACT FROM AUTHOR]

To effectively respond to predation risk, prey must assess the risk associated with different predation cues. Predation cues can stem either from the predator or from conspecifics and indicate different predation risk levels, thus eliciting different anti-predation responses. The three-spined stickleback is a well-studied fish species often found in gregarious formations. Previous studies show that sticklebacks perform a variety of anti-predation behaviours; however, little is known about how they respond to multiple simultaneous predator cues, characteristic of heterogeneous natural habitats. Here, we experimentally compare the relative importance of three types of predation cues (visual predator cue, chemical predator odour cue and chemical alarm cue from injured conspecifics) and their interactions, on anti-predation and foraging behaviour of sticklebacks. Results showed that (1) individual sticklebacks responded most strongly to visual predator cues, which resulted in reduced foraging activity, increased spine erection and increased predator inspection; (2) the presence of chemical cues (predator odour and/or conspecific alarm cues) stimulates freezing behaviour to a minor extent; and (3) anti-predation behaviour manifests as a trade-off with foraging-related activities. Overall, the results indicate that sticklebacks could assess risk and modify their behavioural responses depending on which cues are present in the environment. The experimental approach of using factorial combinations of different predatory cues can increase our understanding of the role of multimodal cues in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

The ability of prey to recognize and adequately respond to predators determines their survival. Predator‐borne, post‐digestion dietary cues represent essential information for prey about the identity and the level of risk posed by predators. The phylogenetic relatedness hypothesis posits that prey should respond strongly to dietary cues from closely related heterospecifics but respond weakly to such cues from distantly related prey, following a hierarchical pattern. While such responses have mostly been observed in prey at their first encounter with predators, whether prey maintain such hierarchical levels of investment through time remains unclear. We investigated this question by exposing Rhacophorus arboreus tadpoles to the non‐consumptive effect of gape‐limited newt predators Cynops pyrrhogaster that were fed one of five prey diets across a gradient of phylogenetic relatedness: frog tadpoles (Rhacophorus arboreus, Rhacophorus schlegelii, Pelophylax nigromaculatus, and Hyla japonica) and medaka fish (Oryzias latipes). Predators' diet, time, and their interaction significantly influenced tadpole activity level. We found support for the phylogenetic relatedness hypothesis: Investments in defense were stronger to cues from tadpole diets than to cues from fish diet. However, such a hierarchical response was recorded only in the first four days following predator exposure, then gradually disappear by day 8 on which the tadpoles exhibited similar activity level across all predator treatments. The findings suggest that, at least under the threat of gape‐limited predators, prey use phylogenetic information to evaluate risk and appropriately invest in defense during early encounters with predators; however, energy requirements may prevent prey from maintaining a high level of defense over long exposure to predation risk. [ABSTRACT FROM AUTHOR]

To understand the effects of environmental changes on ecosystems, it is important to determine the factors and mechanisms influencing the strength of species interactions in food webs. However, joint effects of predation risk and additional environmental factors on species interaction strengths in multitrophic systems remain largely unexplored, leaving a substantial gap in our understanding of the links between local environmental characteristics and food web properties.To fill this gap, we investigated the effects of habitat complexity and predation risk by top predatory dragonfly larvae (Aeshna cyanea) on feeding rates and energetic efficiency (i.e. the ratio of acquired and expended energy) of the larvae of three intermediate predatory odonate species (Libellula quadrimaculata, Sympetrum sanguineum, and Ischnura elegans) preying on cladocerans.We hypothesised that predation risk would decrease the feeding rate, especially in the structurally simple habitat, and increase the metabolic rate of all intermediate predators. We also expected higher feeding rates of intermediate predators using aquatic vegetation as a perching site (i.e. Sympetrum and Ischnura) in the structurally complex habitat. Finally, we expected to observe habitat‐ and predation risk‐dependent energetic efficiencies of the intermediate predators driven by changes in feeding and metabolic rates.The effect of predation risk on feeding rates was species specific and differed between the structurally simple and complex habitat. Habitat complexity increased feeding rates but only in the absence of predation risk. Moreover, predation risk signalled by chemical cues significantly increased Sympetrum vulgatum feeding rates but did not influence the feeding rates of the two other intermediate predators.Metabolic rates varied among the three intermediate predators but were not affected by predation risk. Estimated energetic efficiency decreased with intermediate predator body mass and depended, to a lesser extent, on the interactive effect of habitat complexity and predation risk.Our results imply that the effects of habitat complexity and predation risk on trophic interactions are likely to be determined by traits related to foraging and defence of the intermediate predators and their habitat domains, and that energetic efficiency is mainly determined by predator mass. Given that habitat complexity and predation risk can vary substantially across habitats, we conclude that it is important to consider habitat complexity and predation risk to better understand and predict the effects of environmentally driven variations on trophic interaction strength and metabolic rates that underlie the energetic efficiency of individual consumers. This has important implications for population and community dynamics as well as ecosystem functioning. [ABSTRACT FROM AUTHOR]

Predators alter prey populations via direct lethality (density‐mediated effects), but in many taxa, the indirect nonlethal threat of predation may be almost as strong an effect, altering phenotypically plastic traits such as prey morphology, behavior, and life history (trait‐mediated effects). There are costs to antipredator defenses and the strength of prey responses to cues of predation likely depends on both the perceived level of risk and food availability.The goal of this study was to test the hypothesis that the costs of nonlethal trait‐mediated interactions impacting larvae can have carryover effects that alter life‐history traits, adult characteristics, and ultimately population dynamics.The effects of Toxorhynchites rutilus kairomones and chemical alarm cues on Aedes triseriatus were assessed in a two‐level factorial design manipulating nutrient level (low or high) and chemical cues of predation (present or absent).Nonlethal chemical cues of predation significantly decreased female survivorship and significantly decreased female size. Females emerged as adults significantly earlier when exposed to predation cues when there was high nutrient availability. When raised in the low nutrient treatment and exposed to predator cues, adult females had 2.1 times the hazard of death compared to high nutrient‐no predator cues. Females raised in the high nutrient and predator cue treatment blood fed sooner than did females from other combinations.Fear of predation can substantially alter prey life‐history traits and behavior, which can cascade into dramatic population, community, and ecosystem effects. Exposure to predator cues significantly decreased the estimated cohort rate of increase, potentially altering the expected population density of the next generation. [ABSTRACT FROM AUTHOR]

Understanding the negative impact of a variety of environmental contaminants on aquatic animals is essential to curb biodiversity loss and stop degradation of ecological functions. Excessive and unrestricted use of pesticides is the most serious threat to aquatic animals including amphibians and fishes. Among the known pesticides, glyphosate based formulations have been shown to have lethal effects on many aquatic organisms. However, negative effects of pesticides on crucial ecological interactions such as prey-predator interactions are relatively unknown from tropics. In many aquatic organisms, recognition of predators is based on odor signatures; and therefore any anthropogenic alteration in water chemistry has the potential to impair recognition and learning of predators. Through a series of behavioral experiments we evaluated the effect of glyphosate based herbicide (Roundup®) on the antipredator behavior of common spiny loach, Lepidocephalichthys thermalis to understand the effects of pesticide-exposure on recognition of conspecific alarm cues, and associative learning to avoid predation. We exposed common spiny loach (for 3 h or 15 days) to sub-lethal concentration (0.5 mg a.e./L) of Roundup® and subsequently with conspecific alarm cues, signaling the proximity of a predator. Unexposed prey fish showed a significant reduction in activity level in response to conspecific alarm cues. Whereas such alarm response was not observed in prey fish that were exposed to Roundup® either for 3 h or 15 days. Such lack of response could be associated with alteration of olfactory function in prey individuals. However, this inability to detect the conspecific alarm cues was found to be transient and exposed fish recovered within 2 days. In subsequent experiments, we showed that Roundup® deactivates the conspecific alarm cues thus making them unavailable for prey to evoke the response. Furthermore, Roundup® mediated degradation of conspecific alarm cues and diminished the associative learning necessary for detection of the invasive/unknown/novel predators. Overall, due to the worldwide occurrence of glyphosate in water bodies, glyphosate mediated behavioral suppression exposes the prey animals to a considerable risk of predation, both by native and non-native predators. [ABSTRACT FROM AUTHOR]

Fiddler crabs are intertidal organisms well known to be highly adapted to low tide activity, thus a number of researches have studied their physiological, behavioral and sensory adaptations to such a tidal phase. However, recent evidences showed that some fiddler crabs are the main food item of fish, suggesting that they could also be active underwater. Based on these preliminary observations, we designed laboratory trials aimed to investigate the ability to detect underwater predators in Leptuca thayeri, across sexes and life stages. We tested a combination of chemical and visual cues, using the predator fish Sphoeroides greeleyi, and, as a control, the non-predator fish Mugil curema. Leptuca thayeri detected the presence of chemical cues coming from the predator fish, although significant differences between adults and juveniles were observed. Adults of L. thayeri remained within their burrows and avoided predator exposition, while juveniles were bold and even increased their activity on the sediment surface. We suggest that juvenile crabs' boldness could be explained by a predator inspection behavior, which allows them to gather information about the possible risk of different predatory species, while experienced adults reduce predation risk recognizing the predator itself. [ABSTRACT FROM AUTHOR]

Dory, the animated surgeonfish created by the Pixar Animation studios, famously suffered from short-term memory loss leading to many adventures. In reality, many fishes have excellent cognitive abilities and are able to learn and retain important information such as the identity of predators. However, if and how cognition can be affected by anthropogenically altered oceanic conditions is poorly understood. Here, we examine the effect of a widely used pesticide, chlorpyrifos, on the retention of acquired predator recognition in post-larval stage of the surgeonfish Acanthurus triostegus . Through associative learning, post-larvae of A. triostegus were first observed to forage significantly less in the presence of conspecific alarm cues and alarm cues associated to a predator's odor. The retention of this anti-predator behavior was estimated to last between 2 and 5 days in the absence of pesticide. However, environmentally-relevant concentrations of chlorpyrifos (1 μg.L −1 ) induced the loss of this acquired predator recognition. This reduced ability to recognize learned predators is discussed as it may lead to more vulnerable fish communities in coastal areas subjected to organophosphate pesticide pollution. [ABSTRACT FROM AUTHOR]

Anti-predator behaviors like vigilance or hiding come at the expense of other fitness increasing behaviors such as foraging. To compensate for this trade-off, prey assess predation risk and modify the frequency of anti-predator behaviors according to the likelihood of the threat. In this study, we tested the ability of house crickets (Acheta domesticus) to indirectly assess predation risk via odors from a mammalian predator, Elliot's short-tailed shrew (Blarina hylophaga). As natural differences in encounter rates and predation risk differs between sexes, we tested if male and female crickets perceive similar rates of predation risk from the presence of shrew odor measured via anti-predator behavioral response. Crickets were placed in enclosed, cardboard-lined chambers either treated with shrew odor or control, along with a food source. Time until foraging was measured for each individual and compared across treatment and sex. We found that in the presence of shrew odor, female crickets delayed foraging while males showed no response. These results suggest adult crickets can use chemical cues to detect mammalian predators. Furthermore, we demonstrate that female crickets associate greater predation risk from shrew predators than do male crickets, which are more stationary yet acoustically conspicuous. As predation risk potentially differs drastically for each sex, changes to the operational sex ratios of wild cricket populations could be influenced by the identity of the predator community. [ABSTRACT FROM AUTHOR]

The use of prey-attracting allomones is likely to be an effective foraging strategy for sit-and-wait predators. Despite this, the production and efficacy of such allomones have rarely been documented. Previous investigations into the chemical composition of spider silk have revealed the presence of a number of potential allomone chemicals such as the amide putrescine, a foul-smelling organic compound. Putrescine is attractive to several terrestrial invertebrates, many of which are also typical prey species of spiders, but whether prey attraction is an underlying mechanism promoting its inclusion in web silk is currently untested. Here, we artificially increased the amount of putrescine in the web silk of female Argiope keyserlingi and assessed the resulting variation in prey interception of normal versus putrescine augmented webs under seminatural field conditions. We demonstrated that webs misted with a putrescine solution captured significantly more prey than webs misted with a control solution and also found differences in prey capture rates between individuals from different populations. This not only suggests that web-bound putrescine acts as a prey attracting allomone, but also that there is population level variation in the web-based foraging strategies of these spiders. [ABSTRACT FROM AUTHOR]

According to the threat-sensitivity hypothesis, prey avoidance behaviour should reflect the magnitude of predation risk. Since predation can strongly affect reproduction success, ovipositing females are expected to adaptively adjust their predator avoidance response, or local breeding patch selectivity, in accordance with the perceived level of threat posed for their progeny by specific predators. However, association between avoidance and predation can be disrupted when the prey and the predator lack spatiotemporal opportunities to co-evolve, such as in cases of non-native predator introductions., We examined the interactions between mosquitoes (from the genus Culex) and three species of sympatric predaceous freshwater fish, a native cyprinid Barbus paludinosus, a cichlid Pseudocrenilabrus philander and an introduced poeciliid, the western mosquitofish Gambusia affinis., In an outdoor mesocosm experiment, we quantified patterns of Culex oviposition site selection across fish species using free-roaming, caged and fish-free treatments. In a complementary laboratory experiment, we tested the effectiveness of each fish species as predators of mosquito eggs and larvae., Synthesis and applications. We found evidence for: (i) mosquito egg raft predation by free-roaming fish; (ii) fish-specific avoidance by ovipositing Culex; and (iii) a positive association between fish-specific oviposition avoidance and fish-specific efficiency as an egg predator. These results contribute towards a better understanding of predator-prey co-evolution, predator-borne cue recognition, and suggest local native fish, the southern mouthbrooder Pseudocrenilabrus philander, as an alternative to Gambusia for the biocontrol of Culex mosquitoes. [ABSTRACT FROM AUTHOR]

Rattlesnakes use prey chemical cues for ambush site selection and for relocating envenomated (E) prey following a predatory strike. The ability to discriminate between E and non-envenomated (NE) prey cues has been widely studied in rattlesnake species that produce type I venoms, which show high levels of snake venom metalloproteinase (SVMP) activity and low lethal toxicity [lethal dose which kills 50% of test animals (LD) >1.0 µg/g]. However, E vs. NE prey discrimination studies have not been conducted on rattlesnake species that produce a type II venom that consists of low SVMP activity and high lethal toxicity (LD <1.0 µg/g). In the current study, long-term captive Crotalus oreganus concolor, which produce a type II venom, were tested for their ability to discriminate between chemical cues of natural ( Sceloporus undulatus and Peromyscus maniculatus) and non-natural ( Hemidactylus frenatus and Mus musculus) prey cues, as well as for their ability to discriminate between E and NE mouse carcasses, when prey envenomation occurred by a conspecific. Snakes showed significant levels of tongue flicking towards the chemical extracts of P. maniculatus and M. musculus, suggesting that C. oreganus concolor exhibit both innate and experience-based plasticity in response to prey chemical cues. In addition, C. oreganus concolor were able to discriminate between E and NE prey sources, when envenomation occurred by a conspecific, indicating that a type II venomous species can also discriminate between E and NE chemical cues. [ABSTRACT FROM AUTHOR]

Both predators and prey exhibit cyclic shifts in activity throughout the day, which should cause the threat posed by predators to change in a recurrent pattern. If the threat posed by a predator is dependent on their circadian foraging cycle, prey may respond more or less intensely to predators at different times of day, thereby maximizing the effectiveness and efficiency of avoidance behaviors. We examined whether predator-naïve Eurycea nana, a federally threatened neotenic salamander, exhibits a different antipredator response to chemical cues of a diurnal predator, the green sunfish (Lepomis cyanellus), and a nocturnal predator, the red swamp crayfish (Procambarus clarkii). We predicted that E. nana would show more intense antipredator responses (reduced activity) to a diurnal predator during the day and to a nocturnal predator at night. We found that, although there was significant antipredator behavior of E. nana toward sunfish, there was no detectable response to crayfish and no effect of time of day on responses to either predator, suggesting that either E. nana does not innately exhibit circadian patterns in avoidance of these species or that those patterns were undetectable in this study. Future studies should examine whether experience with predators may cause these salamanders to be more sensitive to the diel variation in threat, as has been found with some other amphibians and fish. Due to the threatened nature of this species, understanding the factors that influence antipredator behavior are crucial for management. [ABSTRACT FROM AUTHOR]

Sexual signals play a critical role in mate attraction, but fitness benefits of signal production depend on a number of external and internal influences. Sexual signaling can be energetically expensive, and has potential to attract unwanted attention from predators. Male brushlegged wolf spiders, Schizocosa ocreata (Hentz, 1844) (Araneae: Lycosidae), actively signal to females in the leaf litter habitat during their spring breeding season, but face a tradeoff between current and future reproduction as the season progresses. The terminal investment hypothesis predicts that with fewer available females, increasing risk of predation, and stronger influence of senescence as the season progresses, males should take greater risks to secure mating. We explored this idea by exposing males of increasing ages to female cues alone or female cues combined with predator cues. We found little or no direct evidence to support the terminal investment hypothesis in this species, in that males across all ages essentially ceased active courtship in the presence of predator cues, that is, there was no age related increase in courtship investment in the presence of predator cues. However, we found distinct evidence of senescence in males based on age-related changes in behavior, which has not previously been directly explored in this species. While males maintained similar levels of active courtship across all age classes (in the absence of predator cues), older males increased their relative investment in maintenance behaviors (grooming) and decreased non-courtship display behaviors such as tapping and leg raises. These findings suggest that studies of male behavior in this species should be carefully designed to control for age-related variation in behavioral response. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity is predicted to evolve when subsequent generations are likely to experience alternating selection pressures; e.g., piscine predation on mosquitoes ( Culex pipiens) varies strongly depending on habitat type. A prey-choice experiment (exp. 1) detected a predilection of common mosquito predators (sticklebacks, Gasterosteus aculeatus) for large-bodied mosquito larvae, suggesting that larvae could benefit from suppressing growth under predation risk, and experiment 2 confirmed reduced pupa size and weight when we exposed larvae to stickleback kairomones. In experiment 3, we measured adult (imago) size instead to test if altered larval growth-patterns affect adult life-history traits. We further asked how specific life-history responses are, and thus, also used kairomones from introduced Eastern mosquitofish ( Gambusia holbrooki), and from algivorous, non-native catfish ( Ancistrus sp.). Adult body mass was equally reduced in all three kairomone treatments, suggesting that a non-specific anti-predator response (e.g., reduced activity) results in reduced food uptake. However, imagines were distinctly smaller only in the stickleback treatment, pointing towards a specific, adaptive life-history shift in response to the presence of a coevolved predator: mosquito larvae appear to suppress growth when exposed to their native predator, which presumably reduces predation risk, but also affects body size after pupation. Our study suggests that (1) not all antipredator responses are necessarily predator-specific, and (2) fluctuation in the cost-benefit ratio of suppressing larval growth has selected for phenotypic plasticity in C. pipiens larval life histories. This implies costs associated with suppressed growth, for example, in the form of lower lifetime reproductive success. [ABSTRACT FROM AUTHOR]

An increasing amount of attention has been devoted to studying the impact of non-native plant and animal species on native species. In this paper, we examined the antipredator response of naïve European brown frog (Rana temporariaLinnaeus, 1758) tadpoles to water-borne chemical cues from invasive red-eared slider turtles (Trachemys scripta elegansWied, 1838) in the presence and the absence of conspecific tadpoles. The level of swimming activity was expressed as the length of the tadpoles’ trajectory. The tadpoles showed a decrease in swimming activity when predator stimuli were present, which was highly significant when the tadpoles were measured individually and did not have contact (visual and chemical) with other tadpoles. In the absence of chemical cues of slider turtles, the presence of other tadpoles had no effect on the level of swimming activity. Moreover, for the first time in tadpoles, we found that the decrease in swimming activity was also accompanied by changes in swimming trajectory, with tadpoles exposed to predator cues swimming in more zigzagged trajectories. Our experiment shows that invasive slider turtles, as a novel predator, have a measurable influence on the swimming behaviour of European brown frog tadpoles. Consequences of the reduced swimming activity of tadpoles, like its impact on growth, are discussed. [ABSTRACT FROM AUTHOR]

Recent studies suggest that direct mortality and physiological effects caused by pollutants are major contributing factors to global amphibian decline. However, even sublethal concentrations of pollutants could be harmful if they combined with other factors to cause high mortality in amphibians. Here we show that sublethal concentrations of pollutants can disrupt the ability of amphibian larvae to recognize predators, hence increasing their risk of predation. This effect is indeed much more important since very low amounts of pollutants are ubiquitous, and environmental efforts are mostly directed towards preventing lethal spills. We analyzed the effects of two common contaminants (humic acid and ammonium nitrate) on the ability of tadpoles of the western spadefoot toad ( Pelobates cultripes ) to recognize chemical cues from a common predator, nymphs of the dragonfly Anax imperator . We compared the swimming activity of tadpoles in the presence and absence of water-borne chemical cues from dragonflies at different concentrations of humic acid and ammonium nitrate. Tadpoles reduced swimming activity in response to predator cues in the absence of pollutants, whereas they remained unresponsive to these cues when either humic acid or ammonium nitrate was added to the water, even at low concentrations. Moreover, changes in tadpole activity associated with the pollutants themselves were non-significant, indicating no toxic effect. Alteration of the natural chemical environment of aquatic systems by pollutants may be an important contributing cause for declines in amphibian populations, even at sublethal concentrations. [ABSTRACT FROM AUTHOR]

In order to maximize escaping success, prey may change their predator avoidance behaviors according to their susceptibility. Morphological development during ontogeny may lead to different susceptibility to predators. Consequently, prey may exhibit different predator avoidance strategies according to the ontogenetic state. In this study, we used tadpoles of the Amazon milk frog Trachycephalus resinifictrix (Anura, Hylidae) to evaluate how variation in the ability to actively escape owed to the mobility acquired through ontogeny affects the adoption of predator avoidance strategies. We sampled tadpoles ( N = 384) in temporary ponds and divided them in four consecutive developmental stages according to body size and mobility capacity. Subsequently, we measured their movement and spatial distribution when subjected to chemical cues of predators or control solutions. We found that they spent less time moving and increased spatial aggregation after receiving solutions with predator cues, independent of their developmental stage. These results indicate that the variation in escape capacity through larval ontogeny does not determine their antipredator strategy. Since tadpoles of T. resinifictrix typically grow in environments with reduced space for active escaping, such as tree holes and bromeliads, it may be that the ability to flee from predators is absent, even when this behavior increases the survival chances. [ABSTRACT FROM AUTHOR]

Prey must manage threat from many types of predators; therefore, selection should favor sensory mechanisms that allow the refinement of defensive behavior. To assess responses to tactile and chemical stimuli related to predation, we observed drift and activity of larval black flies (Simulium vittatum) to simulated predator contact intended to imitate benthic and drift predators as well as a combination of tactile and injury-released stimuli. In the field, larvae responded to tactile stimuli applied to the head with a higher frequency of curling and posterior abdominal segments with a higher frequency of drifting. Additionally, chemical cues from injured conspecifics followed by tactile stimuli applied to the head resulted in a higher frequency of drifting than to either cue independently and this effect was more pronounced at night. The results of our study indicate that larval black flies may utilize multiple cues to determine their antipredator and predator avoidance strategies. [ABSTRACT FROM AUTHOR]

Prey use chemical cues from predation events to obtain information about predation risk to alter their phenotypes. Though we know how many prey respond to predators, we still have a poor understanding of the processes and chemical cues involved during a predation event. We examined how gray treefrog tadpoles ( Hyla versicolor) altered their behavior and morphology when raised with cues from different stages of predator attack, predators fed different amounts of prey, and predators consuming different combinations of treefrog tadpoles or snails ( Helisoma trivolvis). We found that starved predators and predators fed snails induced no defensive responses whereas tadpoles exposed to a predator consuming gray treefrogs induced greater hiding, lower activity, and relatively deeper tails. We also found that the tadpoles did not respond to crushed, chewed, or digested conspecifics, but they did respond to consumed (i.e., chewed plus digested) conspecifics. When we increased the treefrog biomass consumed by predators, tadpoles frequently increased their defenses when only tadpoles were consumed and always increased their defenses when the total diet biomass was held constant via the inclusion of snails. When predators experienced temporal variation in diet composition, including cues from snails to cause additional digestive cues or chemical noise, there was no effect on tadpole phenotypes. Our results suggest that amphibian prey rely on cues from both chewing and digestion of conspecifics and that the presence of cues from digested heterospecifics play little or no role in adding chemical noise or increased digestive enzymes and by-products that could potentially interfere with induced defenses. [ABSTRACT FROM AUTHOR]

Many anuran larvae exhibit an antipredator response to chemical cues released by potential predators. The genus Bufo is no exception, as many bufonids exhibit an antipredator response (e.g., reduction in activity) to the presence (recent and current) of predators. Using a mesocosm experiment in a field laboratory setting, we tested solo and groups of Bufo (Incilius) nebulifer tadpoles for an antipredator response to chemical cues produced by 1) the presence of anisopteran nymphs (kairomone cue) and 2) the predation of conspecifics by anisopteran nymphs (a combination of diet and alarm cues, which we termed predation cue). We quantified the magnitude of the response by calculating response strength. We analyzed data with a blocked ANOVA followed by a Tukey's honestly significant difference analysis. We found that chemical cue type (kairomone vs. predation) affected response strength, but aggregation status (solo vs. group) did not. Furthermore, solo tadpoles and groups of tadpoles reduced their activity in response to predation cues, whereas only solo tadpoles reduced their activity in response to kairomone cues, a heretofore unobserved phenomenon. Our results suggest that B. nebulifer tadpoles modulate their response to specific types of chemical cues depending on their aggregation status. As reduced activity comes at a cost to resource acquisition and growth, aggregation status may indirectly affect the life history of B. nebulifer. The elucidation of these potential life history effects may aid managers in estimating anuran population viability. [ABSTRACT FROM AUTHOR]

Many amphibians possess noxious or toxic substances for self defense. These compounds have been characterized largely as chemical defenses, but may promote ecological and evolutionary processes. The California newt, Taricha torosa, possesses a potent neurotoxin, tetrodotoxin (TTX), which serves as a chemical defense, chemical cue to conspecifics, and selection pressure that has selected for evolved resistance in a predator. However, the potential effects of TTX upon the broader community and on behavior, in general, have been overlooked. Field assays conducted during the newt breeding season indicate that the macroinvertebrate community responds to adult newt chemical cues by altering foraging behavior. In these assays, significantly fewer macroinvertebrates were found in experimental areas with enclosed newts relative to enclosures with a non-predatory amphibian. Laboratory bioassays showed that dragonfly nymphs ( Anax junius) reduced predatory behavior and moved less in the presence of adult newt chemical cues. When exposed to TTX, nymph mean angular velocities were reduced four fold and mean velocity magnitude was reduced threefold relative to controls. Overall, these results support the hypothesis that chemical stimuli from predators, and TTX specifically, can shape species interactions at lower trophic levels and potentially affect community organization. [ABSTRACT FROM AUTHOR]

• Turbid immature water (prey absence) attracts more Tx. splendens females than filtered water. • Live and dead Ae. aegypti larvae proved strongly attractive to Tx. splendens females. • Conspecific Toxorhynchites larvae caused oviposition deterrence when compared to other treatments in a dual choice test. • Turbid immature water and predator-prey turbid water can efficiently attract Tx.splendens females to deposit eggs. Oviposition preference by Toxorhynchites mosquito species is an important aspect of their biological control potential. When ovipositing, the females deposit individual eggs by hovering above the water, indicating that they may be capable of detecting chemical cues from above the water surface. These chemical cues may help the females to determine whether the water is suitable for their larvae. We investigated whether female Tx. splendens has the ability to discriminate against oviposition sites in habitats containing turbid larval/pupal rearing water and predator-prey treatments. In this study, the number of eggs in the test and control cups were compared to assess oviposition preference. According to the results, female Tx. splendens preferred ovipositing in cups with turbid immature water (prey absence) and predator-prey turbid water (prey and predator presences) over ovipositing in filtered water as a control. Results from the third experiment revealed that cups with alive and dead Ae. aegypti larvae proved strongly attractive to Tx. splendens females, while those from conspecific Toxorhynchites larvae caused oviposition deterrence when compared to other treatments in a dual choice test. Our results indicated that both turbid immature water and predator-prey turbid water can efficiently attract Tx. splendens females to deposit eggs. These findings will aid in the development of Toxorhynchites mosquito as a biocontrol agent for the control of Aede s spp. larvae. [Display omitted] [ABSTRACT FROM AUTHOR]

Exposure to predatory stimuli typically results in the elevation of circulating glucocorticoid levels and a behavioral response of freezing or escape behavior in many prey species. Corticosterone (CORT) is the main glucocorticoid in amphibians and is known to be important in modulating many behaviors and developmental functions. The federally threatened San Marcos salamander, Eurycea nana , decreases activity in response to both native and introduced predatory fish, however, experience may further influence these interactions. To better understand the indirect effects of fish predators on this salamander, we examined both the antipredator behavior and water-borne CORT release rates in response to chemical cues (kairomones) from two fish species that varied in temporal risk of predation: (1) a low encounter frequency predator (largemouth bass, Micropterus salmoides ), (2) a high encounter frequency predator (redbreast sunfish, Lepomis auritus ), and (3) a blank water control. Salamanders reduced activity (antipredator response) after exposure to both predator treatments, but not to the blank water control, and the response to M. salmoides was significantly stronger than that to L. auritus . The CORT response (post-stimulus/pre-stimulus release rates) did not differ between the blank water control and L. auritus treatments, and both were significantly less than the CORT response to M. salmoides . Overall, E. nana showed a decreased antipredator response and no CORT response towards the high encounter frequency L. auritus as compared to the low encounter frequency M. salmoides . Eurycea nana may mute antipredator and CORT responses to high temporal frequency predators. There was, however, no correlation between CORT release rates and antipredator behavior, which suggests that the presence of predators may be affecting CORT response and behavior independently. [ABSTRACT FROM AUTHOR]

1. To reduce the risk of being eaten by predators, prey alter their morphology or behaviour. This response can be tuned to the current danger if chemical or other cues associated with predators inform the prey about the risks involved. 2. It is well known that various prey species discriminate between chemical cues from predators that fed on conspecific prey and those that fed on heterospecific prey, and react stronger to the first. It is therefore expected that generalist predators are more successful in capturing a given prey species when they are contaminated with chemical cues from another prey species instead of cues from the same prey species. 3. Here, a generalist predatory mite was studied that feeds on thrips larvae as well as on whitefly eggs and crawlers. Mites were marked with cues ( i.e. body fluids) of one of these two prey species and were subsequently offered thrips larva. 4. Predators marked with thrips cues killed significantly fewer thrips than predators marked with whitefly cues, even though the predator's tendency to attack was the same. In addition, more thrips larvae sought refuge in the presence of a predatory mite marked with thrips cues instead of whitefly cues. 5. This suggests that generalist predators may experience improved attack success when switching prey species. [ABSTRACT FROM AUTHOR]

We conducted two field experiments to test the hypothesis that recruitment of the eastern oyster, Crassostrea virginica , could be enhanced through the selective deployment of artificial settlement cues. For both experiments, either dead shell or live oysters were cemented to patio blocks. In the first experiment, half of the blocks received discs that diffused the tri-peptide Glycyl-Glycyl-Arginine (GGR), a potent analog for natural settlement inducers, and only blocks with dead shell received GGR in the second experiment. Recruitment was therefore monitored on substrata with settlement cues (live oyster or shell with GGR) and no settlement cues (dead shell only). In our preliminary experiment (Experiment 1), recruitment of oysters was lower to blocks with live oyster or GGR, counter to our expectation. We repeated the experiment with the addition of anti-predation cage treatments (with partial cage controls). Again, we found no enhancement of recruitment to blocks with live oysters or with cue added. However, recruitment was significantly higher on blocks shielded from predation. These results suggest both a strong predator control in this system and that adding chemical cues are not likely to be an effective restoration strategy. [ABSTRACT FROM AUTHOR]

Wood frog Lithobates sylvaticus tadpoles develop in temporary wetlands where high population densities can force tadpoles into aggregations that intensify competition and can lead to cannibalism. However, chemical alarm cues released from injured conspecifics could also dissuade cannibalism. The purpose of this study was to test mechanisms that may influence cannibalistic behaviour. We tested whether the tendency of tadpoles to consume conspecifics would increase with the presence of competition and/or cues of profitable diets. Tadpoles placed in 1L experimental containers were tested for feeding initiation times of multiple diets, including conspecific tissues and conspecific tissues combined with chemical cues from the alternative diets (brine shrimp and cornmeal). Tadpoles were tested in the presence and absence of a competitor, and at multiple times over the course of the study. Tadpoles exhibited an altered response to diets over time; however the presence of a competitor reduced response times to all diets including conspecific tissues. Similarly, the presence of specific diets also reduced the response time of tadpoles to conspecific tissues. These results suggest competition among feeding tadpoles could result in aggressive behaviour leading to indiscriminate predation and cannibalism [Current Zoology 60 (5): 571-580, 2014 ]. [ABSTRACT FROM AUTHOR]

Successful survival and reproduction of prey organisms depend on their ability to detect their potential predators accurately and respond effectively with suitable defences. Predator detection can be innate or can be acquired through learning. We studied prey-predator interactions in the larval bronzed frogs ( Sylvirana temporalis), which have the innate ability to detect certain predators. We conducted a series of experiments to determine if the larval S. temporalis rely solely on innate predator detection mechanisms or can also learn to use more specific cues such as conspecific alarm cues for the purpose. The results of our study clearly indicate that larval S. temporalis use both innate and learned mechanisms for predator detection. Predator-naïve tadpoles could detect kairomones alone as a potential threat and responded by reducing activity, suggesting an innate predator detection mechanism. Surprisingly, predator-naïve tadpoles failed to detect conspecific alarm cues as a potential threat, but learned to do so through experience. After acquiring the ability to detect conspecific alarm cues, they could associate novel predator cues with conspecific alarm cues. Further, post feeding stages of larval S. temporalis are sensitive for learning to detect conspecific alarm cues to label novel predators. [ABSTRACT FROM AUTHOR]

The relative importance of visual and chemical cues of prey in their detection by the juveniles ofCalotes versicolorwas studied using laboratory-born, 2-month-old individuals starved for 48 hrs. Grasshoppers served as the prey in all experiments. In trials with deionized water and cologne water (pungency control), the lizards showed no tongue flicking. Presentation of prey-body chemical cues on cotton swabs also did not evoke tongue flicking in test lizards indicating a lack of response to different odors through the vomeronasal olfactory system. The same test lizards lunged at the transparent glass beaker housing an active prey, with their mouth open as if to catch it. They showed no tongue flicking. In contrast, when an immobile prey was presented similarly the test lizards ignored it. Apparently, chemical cues are of little value in prey detection inC. versicolor. The study shows thatC. versicolorjuveniles use visual cues and prey movements in detection and capture of prey. [ABSTRACT FROM PUBLISHER]

Abstract: Flexibility is an important adaptive attribute of the feeding periodicity of grazing mayfly larvae because most natural environments offer a wide variation in local predation risk in terms of space, time or predator species. In this study any changes of diel feeding periodicity and consumption rates of Baetis rhodani (Ephemeroptera) were analysed in response to different densities of benthivorous fish (Barbatula barbatula, Gobio gobio) by quantifying gut fullness using the fluorescence of algal pigments. Laboratory experiments with the grazer species B. rhodani were conducted by using different concentrations of chemical fish cues. In order to assess the transferability of the results to a larger scale, the experimental results were compared with field observations in two second order streams using different densities of freely foraging benthivorous fish. During the presence of chemical fish cues in the laboratory experiments the feeding periodicity of the B. rhodani larvae were mostly diurnal while in the absence of fish chemicals nocturnal feeding was observed. The same patterns could be detected in the field during the experiments with the different fish densities. These findings indicate that the larvae were able to assess variations in the predation risk and to alter their feeding habits by making flexible behavioural adjustments. The results from the laboratory experiments further suggested that the behavioural response is controlled by fish density. Behavioural changes were observed for medium and high concentrations of the fish cues but not for a very low concentration. In the field however, the mere presence of fish seemed to be sufficient to induce the observed behavioural shifts. Although the presence of benthivorous fish seemed to cause a lower consumption rate of the B. rhodani larvae in the field, such a reduction could not be found in the laboratory experiments. A conclusion from this study is that the identification of behavioural modifications is an essential component needed for a better understanding of complex trophic interactions in benthic communities. Accurate evaluation and detailed observation of direct and indirect effects cannot be made without the consideration of such behavioural mechanisms. [Copyright &y& Elsevier]

Prey must constantly balance foraging and predator avoidance demands. Avoidance response efficiency may be improved when prey match the intensity of their avoidance behaviours to a perceived level of predatory threat (threat sensitivity). Additionally, experience with predators may influence the intensity of avoidance responses. I examined the possibility that experience with predators in the natural habitat would influence threat sensitive avoidance behaviours of an aquatic salamander, Eurycea nana, by comparing the intensity of avoidance responses to predators that had been fed a neutral diet (low-risk) or a diet of conspecifics (high-risk) between laboratory-reared and recently-collected adult salamanders. I found that laboratory-reared salamanders exhibited graded responses to low- and high-risk predators consistent with threat-sensitive predator avoidance. Predator-experienced salamanders (recently-collected), however, responded less intensely to all predators and their responses showed little evidence of threat sensitivity. These less intense responses observed in experienced salamanders may result from mechanisms of adaptive forgetting, which allow prey to respond to environmental variation. I discuss implications of these results for E. nana and other prey as well as highlighting the need for researchers to consider the longer-term experiences of prey used in studies of predation risk. [ABSTRACT FROM AUTHOR]

Predator body size often indicates predation risk, but its significance in non-consumptive effects (NCEs) and predator risk assessment has been largely understudied. Although studies often recognize that predator body size can cause differing cascading effects, few directly examine prey foraging behavior in response to individual predator sizes or investigate how predator size is discerned. These mechanisms are important since perception of the risk imposed by predators dictates behavioral responses to predators and subsequent NCEs. Here, we evaluate the role of predator body size and biomass on risk assessment and the magnitude of NCEs by investigating mud crab foraging behavior and oyster survival in response to differing biomasses of blue crab predators using both laboratory and field methods. Cues from high predator biomass treatments including large blue crab predators and multiple small blue crab predators decreased mud crab foraging and increased oyster survival, whereas mud crab foraging in response to a single small blue crab did not differ from controls. Mud crabs also increased refuge use in the presence of large and multiple small, but not single small, blue crab predators. Thus, both predator biomass and aggregation patterns may affect the expression of NCEs. Understanding the impact of predator biomass may therefore be necessary to successfully predict the role of NCEs in shaping community dynamics. Further, the results of our laboratory experiments were consistent with observed NCEs in the field, suggesting that data from mesocosm environments can provide insight into field situations where flow and turbulence levels are moderate. [ABSTRACT FROM AUTHOR]

Rattlesnakes use chemical stimuli in ambush site selection and for relocation of envenomated prey through strike-induced chemosensory searching. Shifts in responsiveness to prey chemicals have been documented in many snakes, and often correlate with prey commonly taken as snakes increase in age and size as well as geographical locations of the species. For instance, neonate rattlesnakes that prey primarily on ectotherms responded most strongly to chemical cues of commonly taken lizard prey, whereas adult rattlesnakes that prey primarily on small mammals responded significantly to chemical cues of commonly taken rodents. In the current study, 11 Prairie Rattlesnakes Crotalus viridis viridis which were classified as large neonates based on measures of snout-vent length (SVL) and body mass, yet chronologically were at or near adulthood, were tested for their responsiveness to chemical extracts of natural and non-natural prey items. Although the snakes had eaten only neonate lab mice (Mus musculus), they responded significantly more to chemical cues of natural prey items and particularly to chemical cues of prey normally taken by subadults (Peromyscus mice and Sceloporus lizard). These results suggest that ontogenetic shifts in responsiveness to natural prey chemical cues are innately programmed and are not based on body size or feeding experience in C. v. viridis. This does not imply, however, that growth and experience are without effects, especially with novel prey or rare prey that have experienced recent population expansion [ABSTRACT FROM AUTHOR]