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Behavioral variation in natural contests: integrating plasticity and personality
Couchoux, Charline; Garant, Dany; Aubert, Maxime; Clermont, Jeanne; Réale, Denis — 2020-11-04 <p>Animals often interact aggressively when competing over limited resources. Aggressive decisions can be complex, and may result from multiple sources of behavioral variation. The outcome of contests may be explained through contest theory and personality, by considering conjointly plasticity and individual consistency. This integrative approach also allows investigating individual differences in responsiveness to environmental changes. Here we observed multiple agonistic interactions occurring among eastern chipmunks (Tamias striatus) competing for food resources supplied at different distances from their burrows. Using an individual reaction norm approach, we found that the probability of winning a contest depended on an individual’s own intrinsic characteristics (mass, age, but not sex) but was also adjusted to characteristics of its opponents. Winning a contest also depended on extrinsic environmental characteristics such as distance to the contestants’ burrows, but not the order of arrival at the feeding patch. We found consistent individual differences in the probability of winning, potentially related to differences in aggressiveness and territoriality. We also found that individuals differed in their plasticity level in response to changes in different characteristics of their social and physical environments. Plasticity, personality and individual differences in responsiveness may thus all play a role in predicting contest outcome and in the evolution of animal contests.</p> https://creativecommons.org/publicdomain/zero/1.0/
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A mechanistic model of functional response provides new insights into indirect interactions among arctic tundra prey
Beardsell, Andréanne; Gravel, Dominique; Clermont, Jeanne; Berteaux, Dominique; Gauthier, Gilles; Bêty, Joël — 2022-03-16 Prey handling processes are considered a dominant mechanism leading to short-term positive indirect effects between prey that share a predator. However, a growing body of research indicates that predators are not necessarily limited by such processes in the wild. Density-dependent changes in predator foraging behavior can also generate positive indirect effects but they are rarely included as explicit functions of prey densities in functional response models. With the aim of untangling proximate mechanisms of species interactions in natural communities and improving our ability to quantify interaction strength, we extended the multi-prey version of the Holling disk equation by including density-dependent changes in predator foraging behavior. Our model, based on species traits and behavior, was inspired by the vertebrate community of the arctic tundra, where the main predator (the arctic fox) is an active forager feeding primarily on cyclic small rodent (lemming) and eggs of various tundra-nesting bird species. Short-term positive indirect effects of lemmings on birds have been documented over the circumpolar Arctic but the underlying mechanisms remain poorly understood. We used a unique data set, containing high-frequency GPS tracking, accelerometer, behavioral, and experimental data to parameterize the multi-prey model, and a 15-year time series of prey densities and bird nesting success to evaluate interaction strength between species. We found that: (i) prey handling processes play a minor role in our system and (ii) changes in arctic fox daily activity budget and distance traveled can partly explain the predation release on birds observed during lemming peaks. These adjustments in predator foraging behavior with respect to the main prey density thus appear as the dominant mechanism leading to positive indirect effects commonly reported among arctic tundra prey. Density-dependent changes in functional response components have been little studied in natural vertebrate communities and deserve more attention to improve our ability to quantify the strength of species interactions.
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Prey availability influences the effect of boldness on reproductive success in a mammalian predator
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Clermont, Jeanne; Couchoux, Charline; Lai, Sandra; Berteaux, Dominique — 2023-05-18 <p>Boldness is an important trait in wild populations and among-individual differences can link to individual fitness<span lang="EN-GB">. </span>The strength and direction of relationships between behavioral and life-history traits may however vary according to environmental conditions, where fluctuating selection acting on behavioral traits contributes to the maintenance of personality differences. <span lang="EN-GB">We </span>explored sources of variation in <span lang="EN-GB">Arctic fox (<em>Vulpes</em> <em>lagopus</em>) boldness </span>and <span lang="EN-GB">investigated how temporal variation in the abundance of a main prey (lemmings) influences the relationship between fox boldness and reproductive success. We measured the behavioral reaction of individuals when escaping after handling, as an indicator of their boldness. We obtained 70 measurements from 42 individuals </span>during two years of low lemming abundance and two years of high lemming abundance<span lang="EN-GB"> and assessed fox litter size as an indicator of reproductive success. First, individual characteristics (age, sex, mass) did not affect Arctic fox boldness, while individual identity generated variation in boldness. Next, </span>we found that during years of low lemming density, individuals behaving boldly had more pups than those behaving less boldly, suggesting boldness may provide an advantage when lemmings are scarce by increasing hunting success or allowing access to alternative resources. However, all <span lang="EN-GB">individuals tended to show high levels of boldness when lemming density was high, and all produced large litters. </span>Temporal variation in the abundance of a main prey might therefore influence the relation between boldness and reproductive success of a predator, and if individuals consistently differ in their level of boldness, fluctuating selection could contribute to the maintenance of personality.</p>
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Data from: Signaler and receiver boldness influence response to alarm calls in eastern chipmunks
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Couchoux, Charline; Clermont, Jeanne; Garant, Dany; Reale, Denis — 2017-10-03 Using social information can benefit individuals in many ways. Responding to alarm signals can, for instance, maximize survival under predation risk. However, foraging individuals should consider the reliability of such risk-based information to balance anti-predator behavior and resource acquisition. Receiver decisions could depend on personality effects, as individual variation in risk-taking tendencies (i.e. boldness) could not only affect receiver perception of the signaled threat but also signaler reliability. Recent theoretical models support the possibility of coevolution between personality and communication strategies. Using a playback experiment, we show that wild eastern chipmunks (Tamias striatus) respond to alarm calls according to their own boldness level (measured as consistent individual differences in basal vigilance) and that they increase their vigilance response to bolder callers potentially considered as more reliable. Further, receivers respond to the callers' boldness regardless of their own boldness and independently of their familiarity level with callers, therefore decoding this information from vocalizations. Such effects of individual behavioral variation on the perception and interpretation of social information could apply to signals used in a variety of ecological contexts.

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(Author: Clermont, Jeanne)

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