Variation In Antipredator Behavior Research Articles

Barn swallow antipredator behavior covaries with melanic coloration and predicts survival

Conspecific individuals often consistently differ in their behavioral responses to specific exogenous stimuli. Such individual differences in have been shown to be heritable, suggesting that selection maintains variation in personality. However, survival selection on a major personality trait, antipredator behavior, and its sex-dependency, has been seldom measured in the wild. Here, we found that yearling barn swallows (Hirundo rustica) showed consistency in agitation upon repeated exposure to a restraint-handling protocol, probably reflecting antipredator behavior, and that males were more agitated than females. Females that exhibited larger antipredator behavior were more likely to survive until the next breeding season with no variation among 3 study years nor across 7 breeding colonies, suggesting that variation in antipredator behavior is not maintained by spatiotemporal variation in viability selection on antipredator behavior. In both sexes, the intensity of melanin-based ventral plumage coloration positively covaried with antipredator behavior, consistent with previous observations from diverse vertebrate species. In some barn swallow populations, male coloration is targeted by directional intersexual selection, suggesting that melanization signals antipredator behavior to prospecting females and that sexual selection for antipredator behavior, or other correlated personality traits, can drive the evolution of sexual color dimorphism in barn swallows. Thus, we showed that viability selection occurs on antipredator behavior and that spatiotemporal variation in selection has no major role in promoting variation in antipredator behavior. More melanized individuals were more agitated, implying that melanization may signal personality in a sexual communication context in a species where male coloration is an epigamic trait.

Anti-predator behavioral variation among Physa acuta in response to temporally fluctuating predation risk by Procambarus

Research in behavioral ecology routinely quantifies individual variation in behavior using transitions between discrete environments, for example prey moving from a no predator to predator treatment. This research often ignores behavioral variation in response to temporal fluctuations in environmental conditions around an unchanging mean environment. In this study we evaluate the effects of temporal fluctuations in predation risk (predator cue concentration of Procambarus spp.), without the confounding effects of a changing mean, on among-individual variation in anti-predator behavior in freshwater snails (Physa acuta). We also evaluate how the interaction between environmental and individual variation affects snail survival and reproduction by exposing snails to lethal predators following the behavioral assays. Our analyses revealed a trend towards higher among-individual variation in mean behavior when snails were exposed to intermediate levels of environmental variation compared to highly variable or constant environments. However, because of large uncertainty in estimates of among-individual variation, differences among treatments were indistinguishable from noise for most, but not all behaviors. In the lethal predator trials, snail survival and time to mortality was the lowest in the high variation environment. Also, as environmental variation increased snail egg production decreased and snails laid more of their eggs underneath a provided shelter.

Antipredator behavior QTL: differences in rainbow trout clonal lines derived from wild and hatchery populations.

Variation in antipredator behavior may partially explain the survival differences seen between wild and hatchery trout and salmon. Antipredator behavior is thought to change during the domestication process, along with other traits. Investigations of antipredator behavior could benefit conservation efforts and supplementation programs. Our goal was to characterize the antipredator behavior in clonal rainbow trout lines derived from either wild or hatchery populations and identify genetic loci associated with variation between lines. We identified several behaviors that varied between clonal lines and QTL for several behavioral and size traits. Characterizing genetic variation underlying these behaviors may prove valuable in future conservation efforts by enabling monitoring of allele frequencies of loci affecting predation in wild populations.

Age and sex influence marmot antipredator behavior during periods of heightened risk

Animals adjust their antipredator behavior according to environmental variation in risk, and to account for their ability to respond to threats. Intrinsic factors that influence an animal’s ability to respond to predators (e.g., age, body condition) should explain variation in antipredator behavior. For example, a juvenile might allocate more time to vigilance than an adult because mortality as a result of predation is often high for this age class; however, the relationship between age/vulnerability and antipredator behavior is not always clear or as predicted. We explored the influence of intrinsic factors on yellow-bellied marmot (Marmota flaviventris) antipredator behavior using data pooled from 4 years of experiments. We hypothesized that inherently vulnerable animals (e.g., young, males, and individuals in poor condition) would exhibit more antipredator behavior prior to and immediately following conspecific alarm calls. As expected, males and yearlings suppressed foraging more than females and adults following alarm call playbacks. In contrast to predictions, animals in better condition respond more than animals in below average condition. Interestingly, these intrinsic properties did not influence baseline time budgets; animals of all ages, sexes, and condition levels devoted comparable amounts of time to foraging prior to alarm calls. Our results support the hypothesis that inherent differences in vulnerability influence antipredator behavior; furthermore, it appears that a crucial, but poorly acknowledged, interaction exists between risk and state-dependence. Elevated risk may be required to reveal the workings of state-dependent behavior, and studies of antipredator behavior in a single context may draw incomplete conclusions about age- or sex-specific strategies.

Correlated geographic variation in predation risk and antipredator behaviour within a wide‐ranging snake species (Notechis scutatus, Elapidae)

AbstractGeographic variation in antipredator behaviour within wide‐ranging species may be driven by both genetic and environmental influences. We quantified antipredator responses in neonatal (laboratory born, n = 555) and adult (field caught, n = 346) tiger snakes (Notechis scutatus) from 11 mainland and island sites in southern Australia. We used these data to test predictions from Bonnet et al.'s hypothesis that the vigour of antipredator responses in this species reflects behavioural plasticity (in turn, driven by an individual snake's exposure to predators during its lifetime) rather than by genetic variation in this trait. We used the number of predator taxa in each area as an index of predator risk. As predicted, adult snakes from predator‐rich areas had more vigorous defensive responses when handled, whereas neonatal behaviour (although also variable among populations) was unrelated to predator species richness. Adult males bit more readily than adult females (as expected from the greater predation exposure of males during mate searching) but no such sex difference was evident in neonates. Although alternative models remain possible, our data are most consistent with the hypothesis that geographic divergence in antipredator tactics within this species primarily reflects developmentally plastic responses to local predation risk.

Antipredator behavior in blackbirds: habituation complements risk allocation

Several studies showed that animals allow closer approaches (measured through flight initiation distances, FIDs) by potential predators (e.g., humans) in high--predator density areas, which has been explained by habituation effects. We assessed whether this pattern could be produced by not only habituation but also risk allocation by simulating attacks on blackbirds Turdus merula by both usual (pedestrians) and novel (radio-controlled vehicle) potential predators in parks with different levels of human visitation. Individual blackbirds from parks with higher pedestrian rates showed lower FID than individuals from parks with lower pedestrian rates, in response to both usual and novel approaches. Blackbirds adjusted their antipredator behavior to the specific level of pedestrian rate encountered every morning and evening in each park, with higher FID in the period with lower pedestrian rate. Similar responses to usual and novel potential predators among parks and daily variation in antipredator behavior support the risk allocation hypothesis and could not be explained by habituation. However, the rate at which FID was reduced in individuals from low-visited parks to high-visited parks was greater for pedestrian attacks than for novel potential predator attacks, suggesting that habituation is also present in our system and complements the effects of risk allocation. Our results have applied implications: the reduction in FID with increasing human visitation in natural areas is usually attributed to habituation; however, we propose that risk allocation can also reduce antipredator behavior effort to survive in habitats with high levels of recreational activities at the expense of potential physiological costs. Copyright 2009, Oxford University Press.

Variation in Anti-Predator Behavior Among Five Strains of Inbred Guppies, Poecilia reticulata

Quantitative genetic studies frequently utilize inbred strains of animals as tools for partitioning the direct and indirect effects of genes from environmental effects in generating an observed phenotype, however, this approach is rarely applied to behavioral studies. Guppies, Poecilia reticulata, perform a set of anti-predator behaviors that may provide an ideal system to study how complex behavioral traits are generated. To assess the utility of ornamental guppies in quantitative genetics studies of behavior, we assayed five morphologically distinct strains of ornamental guppies for response to predator cues and for variation in response among strains. Despite individual variation, all five strains responded to predator cues and differences among strains were found for all assayed behaviors, including measures of boldness and predator avoidance.

The Multipredator Hypothesis and the Evolutionary Persistence of Antipredator Behavior

Invited ReviewAbstractIsolation from predators affects prey behavior, morphology, and life history, but there is tremendous variation in the time course of these responses. Previous hypotheses to explain this variation have limited predictive ability. I develop a ‘multipredator’ hypothesis to explain the evolutionary persistence of antipredator behavior after the loss of some, but not all, of a species’ predators. The hypothesis assumes pleiotropy, whereby elements of antipredator behavior may function in non‐predatory situations, and linkage, such that genes influencing the expression of antipredator behavior do not assort independently. The hypothesis is restricted to species with multiple predators (most species) and aims to predict the conditions under which antipredator behavior will persist following the loss of one or more of a species’ predators. I acknowledge that the relative costs of non‐functional antipredator behavior will influence the likelihood of linkage and therefore persistence. The hypothesis makes two main predictions. First, genes responsible for antipredator behavior will not be scattered throughout the genome but rather may be found close together on the same chromosome(s). Secondly, the presence of any predators may be sufficient to maintain antipredator behavior for missing predators. Advances in behavioral genetics will allow tests of the first prediction, while studies of geographic variation in antipredator behavior provide some support for the second.

Interspecific variation in antipredator behaviour leads to differential vulnerability of mule deer and white‐tailed deer fawns early in life

SummaryUngulates are viewed as being highly susceptible to predation during the initial weeks or months of life. Yet aggressive defence by adult females is common in many ungulates and has the potential to reduce the vulnerability of the young significantly.We observed naturally occurring predatory encounters between coyotesCanis latransSay and deer fawns to test the hypothesis that a difference in aggressive defence leads to the differential vulnerability of mule deerOdocoileus hemionusRafinesque and white‐tailed deerO. virginianusZimmermann fawns in summer, when fawns are 0–14 weeks in age. Whitetail fawns suffer higher levels of coyote predation than do mule deer fawns at that time. The two species of deer are similar in size, but are known to differ in their antipredator behaviour in winter when fawns are older.Coyotes were less likely to attack mule deer than whitetail fawns they encountered, and were less likely to kill mule deer than whitetail fawns they attacked.The presence of a mule deer, but not a whitetail, female with a fawn deterred coyotes from attacking the fawn. Once attacked, fawns of both species were less likely to be killed when females defended them, but mule deer females were far more likely to defend fawns.Mule deer females defended fawns that were not their own offspring, including heterospecific fawns. Mule deer fawns were more likely to be defended if they had a larger number of females nearby when encountered. These observations raise the possibility that mule deer, and even whitetail, fawns may have improved survival in areas with higher densities of mule deer females.These results show that higher levels of defence by mule deer females reduced the vulnerability of mule deer fawns, contributing to the lower predation rates reported for mule deer than for whitetail fawns of this age group.

Why do salmonid antipredator responses weaken in hatchery rearing?

The Arctic charr of Lake Saimaa are the most endangered fish population in Finland, and reintroduction programs have been unsuccessful. Low success of reintroduction programs has drawn attention to behavioural properties of hatcheryreared fish. Mortality due to predation often is a principal cause of failure. Antipredator behaviour may degenerate rapidly under hatchery conditions due to (i) reduced genetic variation in antipredator behaviour and/or (ii) selection that would favour bold and fast growing individuals and disfavour predator awareness supposedly associated with slow growth. To test the relative importance of these two factors we first analysed the amount of variation in innate antipredator responses between and within families of hatchery‐bred Arctic charr of the Lake Saimaa stock. We then tested whether fast growing individuals would show reduced responses to chemical cues from their natural predators compared to their slow growing counterparts. Based on the results we propose procedures for maintaining and improving antipredator skills of hatchery‐reared salmonids.

Sources of individual shy–bold variations in antipredator behaviour of male Iberian rock lizards

Individual animals from the same population, sex, age and reproductive status often respond differently and consistently to predators. One important dimension of this behavioural variation is the shy–bold continuum. Innate differences in boldness might explain why individuals differ in their antipredator behaviour. In a laboratory experiment, we examined the sources of individual variation in antipredator behaviour of adult male lizards Lacerta monticola. We simulated in the laboratory repeated predatory attacks of low or high risk and analysed activity levels and refuge use in both situations. Multivariate analyses suggested the existence of two consistent and independent shy–bold continua. The first described a gradient from bold lizards that spent shorter times in the refuge after predatory approaches to shy lizards with longer emergence times, whereas the other described a gradient from bold lizards with a low propensity to hide when the predator was close but risk was low to shy lizards that hid more often. We analysed whether morphological characteristics, body condition and health (estimated from their T cell immunocompetence) of individuals might account for the differences observed. Bold individuals had smaller absolute body size, but relatively larger heads, better body condition and better health. Bold individuals with a low propensity to hide when risk was low had larger absolute body sizes, whereas relative head size, and body condition and health were not important. We suggest that the position of an individual in the shy–bold continua might reflect its optimal antipredator behaviour, which would be a function of its health, general quality and ability to evade predators.

Size-based variation in antipredator behavior within a snake (Agkistrodon piscivorus) population

Variation in an animal's response to a predator likely reflects the complex interaction of factors that influence predation risk. Due to their high degree of behavioral variation and simplified bauplan, snakes offer a unique model for investigating the influence of sex and body size on antipredator behavior. We examined variation in antipredator behavior within a cottonmouth (Agkistrodon piscivorus leucostoma) population. Behavioral responses to human-induced predation risk were compared across a continuous scale of body size. Defensive responses significantly declined with increasing body size. After controlling for body size, no differences between the sexes were detected. Although this study suggests that variation in antipredator behavior is, in part, related to body size, some studies on snakes have not found this relationship. Likewise, some studies have demonstrated differences between sexes. Such disparate patterns of variation indicate a need for future comparative studies examining the complex interaction of factors that may influence predator–prey relationships.

Learned predator recognition and antipredator responses in fishes

AbstractEarly research into the causes of geographical variation in antipredator behaviour in fishes revealed that population differences have an underlying genetic basis. However, evidence from a variety of fish species suggests that learning plays an important role in the development of antipredator responses. Here, we consider the opportunities for learning during the three main stages of a predator–prey interaction: detection, recognition and assessment, and attack avoidance. Much of the evidence for learning is based on the recognition and assessment stage of the predator–prey interaction, but this may reflect methodological biases. We also examine the relative roles of different sensory cues, in particular, vision and olfaction, and the importance of individual vs. social learning. We provide evidence that visual predator recognition skills are largely built on unlearned predispositions, whereas olfactory recognition typically involves experience with conspecific alarm cues. Populations display variation in their propensity to learn, and we predict that ecological factors are likely to mediate the balance between individual and social learning.

Ontogenetic variation in antipredator behavior of Iberian rock lizards (Lacerta monticola): effects of body-size-dependent thermal-exchange rates and costs of refuge use

In lizards, ontogenetic changes in body size affect thermal-exchange rates. This simple physical property may have consequences for thermoregulation, and also for antipredator behavior. We examined how ontogenetic changes in body mass affect rates of heating and cooling of the lizard Lacerta monticola, confirming the general result obtained for other lizards. We further analyzed the differences between juveniles and adults in approach distances to a simulated predator and in time to emerge from refuges. Juvenile lizards have a lower absolute running speed, making them more vulnerable to predation. However, in contrast to results expected from optimal-escape theory, approach distances were shorter for juveniles than for adults. Juveniles may be confident in their small size and only flee when the probability of being detected is high. On the other hand, differences in thermal properties might affect costs of refuge use. Thus, juveniles might delay fleeing because their costs of hiding are higher, as they cool faster than adults. Differences in thermal costs may also explain the juveniles' shorter times of emergence from refuges. Because of the behavioral adjustments involved in antipredator behavior, the physiological costs of reaching a low body temperature in refuges probably do not differ between age classes.

Environmental and Physiological Factors Influence Antipredator Behavior in Scinax hiemalis (Anura: Hylidae)

Individual variation in antipredator behavior may be influenced by ecological factors, such as ambient temperature and predation pressure, and by intrinsic factors, such as physiological condition. We tested the hypothesis that both types of factors interact to induce a specific antipredator response in the treefrog, Scinax hiemalis. When disturbed by the threat of predation, individuals of this species exhibit either a passive response by feigning death or immobility, or an active escape response by jumping away. We examined the responses of 24 adult male S. hiemalis to simulated predation in the laboratory at 10, 15, and 20 C. In addition, responses from a single stimulus were compared with those from a series of stimuli. We determined physiological condition from measures of body length and mass, jumping performance, aerobic metabolism, and estimated energy reserves. Temperature had the most influence on antipredator behavior, with more frogs exhibiting passive responses at 10 C than at higher temperatures. If stimulated more than once, the proportion of active responses increased at all three temperatures. Larger individuals were more likely to exhibit an active response, but no mass-independent physiological variables were related to response type. These results suggest that frogs respond to both extrinsic and intrinsic factors that may affect their behavioral performance.

Comparison of responses to alarm calls by patas (Erythrocebus patas) and vervet (Cercopithecus aethiops) monkeys in relation to habitat structure.

We studied responses to alarm calls of sympatric patas (Erythrocebus patas) and vervet (Cercopithecus aethiops) monkeys in relation to habitat structure, with the intention of understanding the relationship between the environment and predator avoidance. Patas and vervet monkeys are phylogenetically closely related and overlap in body size. However, while patas monkeys are restricted to nonriverine habitats at our study site, vervets use both nonriverine and riverine habitats, allowing us to "vary" habitat structure while controlling for effects of group size, composition, and phylogeny. Patas monkeys in the nonriverine habitat responded to mammalian predator alarm calls with a greater variety of responses than did vervets in the riverine habitat, but not when compared with vervets in the nonriverine habitat. Ecological measurements confirm subjective assessments that trees in the riverine habitat are significantly taller and occur at lower densities than trees in the nonriverine habitat. Despite the lower density of trees in the riverine habitat, locomotor behavior of focal animals indicates that canopy cover is significantly greater in the riverine than the nonriverine habitat. Differences in responses to alarm calls by the same groups of vervets in different habitat types, and convergence of vervets with patas in the same habitat type, suggest that habitat type can be a significant source of variation in antipredator behavior of primates.

Escape Behavior and Predation Risk of Mainland and Island Spiny‐tailed Iguanas (Ctenosaura hemilopha)

AbstractWe investigated the relationships between predator avoidance behavior and predation risk by comparing the wariness of iguanas (Ctenosaura hemilopha) belonging to an island population with few predators with that of iguanas belonging to a mainland population under high predation pressure. We predicted that island iguanas would be less wary than mainland ones. Island iguanas allowed the closer approach of potential predators before their first reaction and fleeing. The responses of both sexes did not differ statistically, except for the frequent displays shown by males as the first reaction. These results suggest that island iguanas, which were probably introduced onto the island by man, have modified their behavior in response to a decline in predation risk, supporting the hypothesis that predation pressure can contribute to intraspecific variation in antipredator behavior. The results also quantify the tameness of prey on islands without terrestrial predators, and their consequent vulnerability if foraneous predators are introduced. No significant difference was found between the populations in the time needed by frightened iguanas to resume their normal activity, suggesting that the island iguanas could learn to recognize predators and develop a suitable antipredator behavior.

The Evolutionary Biology of the Threespine Stickleback

Introduction to the evolutionary biology of the threespine stickleback. 1: Systematics and morphology of the Gasterosteiformes. 2: Allozyme variation of the Gasterosteus aculeatus complex. 3: Physiological ecology and evolution. 4: Energy allocation. 5: Life history variation in females. 6: Ecology on the breeding grounds. 7: Evolution of foraging behaviour. 8: Predators and morphological evolution. 9: Adaptive variation in antipredator behaviour. 10: Proximate determinants of stickleback behaviour. 11: Evolution of aggresive behaviour. 12: Evolution of reproductive behaviour. 13: Speciation and the evolution of reproductive isolation in the sticklebacks of south-western British Columbia. 14: Palaeobiology and evolution. 15: Evolutionary inference: the value of viewing evolution through stickleback-tinted glasses. References. Author index. Subject index

Inter-specific variation in anti-predator behavior in sympatric species of kangaroo rat

Inter-specific variation in anti-predator behavior in sympatric species of kangaroo rat

Inter-specific variation in anti-predator behavior in sympatric species of kangaroo rat

Kangaroo rats, Dipodomys, occupy desert habitats with little cover and thus are under high predation risk from diverse predators. The behavior used to assess predation risk or to escape capture is unknown. We therefore compared anti-predator behavior of two sympatric species of kangaroo rat of different sizes, D. merriami and D. spectabilis. We first examined whether kangaroo rats use olfaction as a first line of defense against snake predation and tested the rats for their responses to scent extracted from two species of snake that live sympatrically with the kangaroo rats, the Mojave rattlesnake (Crotalus scutulatus) and the gopher snake (Pitophis melanoleucus). We also tested for species differences in anti-predator behavior through 15-min interactions between the kangaroo rats and free-moving gopher snakes. We found that D. spectabilis actively approached the scent of both rattlesnakes and gopher snakes more than controls of vegetable oil and evaporated solvent (Fig. 1). In contrast, D. merriami did not differentiate snake odors from controls in the experimental arena, but they sniffed the sand where a free-moving snake had passed more than D. spectabilis. Both species successfully avoided predation in encounters with live snakes. Although total numbers of approaches and withdrawals were similar (Fig. 2), D. spectabilis spent significantly more time within striking distance of the snake than D. merriami. D. spectabilis approached the head of the snake in 93% of its approaches and often engaged in nose to snout contact with the snake. If the snake struck, D. spectabilis jumped directly backward to avoid a strike and footdrummed at a safe distance. In contrast, D. merriami oriented to the snake more than D. spectabilis, but approached the head in only 41% of the approaches and rarely engaged in nose-to-snout contact. The snakes struck, hissed and decreased predatory approaches with D. spectabilis but not with D. merriami (Fig. 3). These results show that kangaroo rats can behaviorally influence the risk of being preyed on by snakes. The two species differ, however, in how they react to snakes. The larger D. spectabilis confronts snakes while the smaller D. merriami monitors snakes from a safe distance and avoids them.