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A major challenge of biological research is to understand what generates and maintains consistent behavioral variation among animals. Time and energy trade-offs, where expressing one behavior is achieved at the expense of another, are often suggested to favor the maintenance of behavioral differences between individuals. However, few studies have investigated how individuals adjust their allocation to different functions over time and depending on resource abundance. Black widow spiders of the genus Latrodectus build persistent webs that include structural threads which protect against predators and sticky trap threads to capture prey. Web structure consistently differs among individuals in the number of trap and structural threads. To quantify the intensity of a trade-off, we assessed the relationship between the number of structural and trap threads and tested whether varying food abundance affected individual differences in web structure. We further quantified how these individual differences change over time and with food abundance. We subjected spiders to three different levels of prey abundance and monitored the structure of their webs every twelve hours. We found no evidence for a trade-off between trap and structural threads. Instead, spiders that produced more structural threads also produced more trap threads, showing that spiders invested equally in both types of threads. Interestingly, the magnitude of individual differences in web structure was greatest when spiders were fed ad libitum and at the beginning of web construction. We suggest that variation in web structure between spiders could be the result of stable developmental differences in morphology or genetic differences.

Predator–prey interactions are important drivers of community and ecosystem dynamics. With an online multiplayer videogame, we propose a novel system to explore within population variation in predator hunting mode, and how predator–prey behavioral interactions affect predator hunting success. We empirically examined how four predator foraging behaviors covary at three hierarchical levels (among environments, among individuals, and within individuals) to assess the structure of predator hunting mode. We also investigated how prey activity affects the foraging behavior and hunting success of predators. Our study supports key findings on predator foraging mode and predator-prey interactions from behavioral ecology. We found that individual predators displayed a diversity of hunting tactics that were conditioned by prey behavior. With prey movement, individual predators specialized either as cursorial or ambush hunters along a continuum of their hunting traits, but also shifted their strategy between encounters. Both types of hunters were generally better against slower moving prey, and they achieved similar prey captures over the sampling period. This suggests that virtual worlds supporting multiplayer online videogames can serve as legitimate systems to advance our knowledge on predator–prey interactions.

Familiarity between members of the same group is predicted to play a role in many biological processes. Familiarity can facilitate recognition, aggregation, communication, coordination and cooperation between group members. We tested a path of interrelated hypotheses on the effect of familiarity on survival, resource acquisition, predator avoidance and cooperation. We predicted that individuals with familiar members in their group would have a higher survival, acquire resources faster, avoid predators more easily and perform more cooperative actions. We used data from an online video game (Dead by Daylight) where small groups of four players (i.e. prey) must exploit resource patches while avoiding a predator. Prey can help fellow prey when the predator catches them (cooperation). Using a video game as a study system provided access to a large behavioural data set that would otherwise be difficult to obtain in nature. Using path analysis, we found evidence that coordinated resource acquisition and helping behaviours increased with the number of familiar individuals in the group. However, more cooperative actions increased their encounters with the predator and thus reduced their survival. When accounting for all indirect effects of familiarity on survival (through resource acquisition, cooperation and predator–prey encounters), familiarity had a small indirect net positive effect on survival.

Social interactions are ubiquitous across the animal kingdom. A variety of ecological and evolutionary processes are dependent on social interactions, such as movement, disease spread, information transmission, and density-dependent reproduction and survival. Social interactions, like any behaviour, are context dependent, varying with environmental conditions. Currently, environments are changing rapidly across multiple dimensions, becoming warmer and more variable, while habitats are increasingly fragmented and contaminated with pollutants. Social interactions are expected to change in response to these stressors and to continue to change into the future. However, a comprehensive understanding of the form and magnitude of the effects of these environmental changes on social interactions is currently lacking. Focusing on four major forms of rapid environmental change currently occurring, we review how these changing environmental gradients are expected to have immediate effects on social interactions such as communication, agonistic behaviours, and group formation, which will thereby induce changes in social organisation including mating systems, dominance hierarchies, and collective behaviour. Our review covers intraspecific variation in social interactions across environments, including studies in both the wild and in laboratory settings, and across a range of taxa. The expected responses of social behaviour to environmental change are diverse, but we identify several general themes. First, very dry, variable, fragmented, or polluted environments are likely to destabilise existing social systems. This occurs as these conditions limit the energy available for complex social interactions and affect dissimilar phenotypes differently. Second, a given environmental change can lead to opposite responses in social behaviour, and the direction of the response often hinges on the natural history of the organism in question. Third, our review highlights the fact that changes in environmental factors are not occurring in isolation: multiple factors are changing simultaneously, which may have antagonistic or synergistic effects, and more work should be done to understand these combined effects. We close by identifying methodological and analytical techniques that might help to study the response of social interactions to changing environments, highlight consistent patterns among taxa, and predict subsequent evolutionary change. We expect that the changes in social interactions that we document here will have consequences for individuals, groups, and for the ecology and evolution of populations, and therefore warrant a central place in the study of animal populations, particularly in an era of rapid environmental change.

Multiple phenotypic traits often interact with each other to determine an individual’s fitness. Behavioral and extended phenotypic traits, such as architectural constructions, can contribute to fitness in an integrated way. The goal of this study was to understand how the interaction between behavioral and extended phenotypic traits can affect foraging success. We tested this question using black widow spiders, where spiders that are aggressive in a foraging context tend to build more gumfooted silk lines that aid in prey capture, while non-aggressive spiders build webs with fewer gumfooted lines. We repeatedly assessed behavior and web structure to quantify relationships between these traits, and then allowed spiders to forage for live prey on their own web or the web of a conspecific that differed in structure. Thus, we assessed how varying combinations of behavior and web structure affect foraging success, and if correlational selection might act on them. We confirmed that aggressiveness and number of gumfooted lines are positively correlated and found that capture success increased with both aggressiveness and the number of gumfooted lines. Yet, we did not find any evidence for correlational selection: aggressiveness and number of gumfooted lines appeared to affect foraging success independently of each other. These findings highlight that a correlation between traits that contribute towards the same ecological function does not necessarily imply correlational selection. Taking advantage of the experimental convenience afforded by extended phenotypic traits can provide insight into the functional consequences of phenotypic variation within and between individuals.

In this paper we used a co-citation network analysis to quantify and illustrate the dynamic patterns of research in ecology and evolution over 40 years (1975–2014). We addressed questions about the historical patterns of development of these two fields. Have ecology and evolution always formed a coherent body of literature? What dominant ideas have motivated research activity in these two fields? How long have these ideas attracted the attention of researchers? Contrary to what was expected, we did not observe any trend towards a stronger integration of ecology and evolution into one big cluster that would suggest the existence of a single community. Three main bodies of literature have stayed relatively stable over time: population/community ecology, evolutionary ecology, and population/quantitative genetics. Other fields have disappeared, emerged or mutated over time. Besides, research organization has shifted from a taxon-oriented structure to a concept-oriented one over the years, with researchers working on the same topics but on different taxa showing more interactions.

Climate change induced phenological variation in amphibians can disrupt time-sensitive processes such as breeding, hatching, and metamorphosis, and can consequently alter size-dependent interactions such as predation. Temperature can further alter size-dependent, predator-prey relationships through changes in species' behavior. We thus hypothesized that phenological shifts due to climate warming would alter the predator-prey dynamic in a larval amphibian community through changes in body size and behavior of both the predator and prey. We utilized an amphibian predator-prey system common to the montane wetlands of the U.S. Pacific Northwest: the long-toed salamander (Ambystoma macrodactylum) and its anuran prey, the Pacific chorus frog (Pseudacris regilla). We conducted predation trials to test if changes in predator phenology and environmental temperature influence predation success. We simulated predator phenological shifts by using different size classes of the long-toed salamander representing an earlier onset of breeding, while using spring temperatures corresponding to early- and mid-season larval rearing conditions. Our results indicated that the predator-prey dynamic was highly dependent upon predator phenology and temperature, and both acted synergistically. Increased size asymmetry resulted in higher tadpole predation rates and tadpole tail damage. Both predators and prey altered activity and locomotor performance in warmer treatments. Consequently, behavioral modifications resulted in decreased survival rates of tadpoles in the presence of large salamander larvae. If predators shift to breed disproportionately earlier than prey due to climate warming, this has the potential to negatively impact tadpole populations in high-elevation amphibian assemblages through changes in predation rates mediated by behavior. Fil: Jara, Fabian Gaston. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Thurman, Lindsey. United States Geological Survey; Estados Unidos Fil: Montiglio, Piere. University of California at Davis; Estados Unidos. McGill University; Canadá Fil: Sih, Andrew. University of California at Davis; Estados Unidos Fil: Garcia, Tiffany. State University of Oregon; Estados Unidos

Widow spiders belong to the cosmopolitan genus Latrodectus (Araneae: Theridiidae), of which five species are found in North America. In part due to their medical importance and common occurrence, they are ever-more popular study organisms in a wide variety of fields. However, the literature is widely dispersed, and a broad synthesis has not been attempted since 1970. Here, we review and synthesize published information on the five North American Latrodectus species: L. hesperus, L. mactans, L. variolus, L. bishopi, and the introduced L. geometricus. We focus on distribution, ecology, anatomy, physiology, reproduction, ontogeny, behaviour, web structure, silk, venom, genetics, and phylogeny. We also include some of our own observations on L. hesperus. We conclude by highlighting areas where further research would be especially fruitful.

By shaping where individuals move, habitat configuration can fundamentally structure animal populations. Yet, we currently lack a framework for generating quantitative predictions about the role of habitat configuration in modulating population outcomes. To address this gap, we propose a modelling framework inspired by studies using networks to characterize habitat connectivity. We first define animal habitat networks, explain how they can integrate information about the different configurational features of animal habitats, and highlight the need for a bottom–up generative model that can depict realistic variations in habitat potential connectivity. Second, we describe a model for simulating animal habitat networks (available in the R package AnimalHabitatNetwork), and demonstrate its ability to generate alternative habitat configurations based on empirical data, which forms the basis for exploring the consequences of alternative habitat structures. Finally, we lay out three key research questions and demonstrate how our framework can address them. By simulating the spread of a pathogen within a population, we show how transmission properties can be impacted by both local potential connectivity and landscape-level characteristics of habitats. Our study highlights the importance of considering the underlying habitat configuration in studies linking social structure with population-level outcomes. Supplementary Information The online version contains supplementary material available at 10.1007/s00442-021-04967-y.

By shaping where individuals move, habitat configuration can fundamentally structure animal populations. Yet, we currently lack a framework for generating quantitative predictions about the role of habitat configuration in modulating population outcomes. For example, it is well known that the social structure of animal populations can shape spreading dynamics, but it remains underexplored to what extent such dynamics are determined by the underlying habitat configuration. To address this gap, we propose a framework and model inspired by studies using networks to characterize habitat connectivity. We first define animal habitat networks, explain how they can integrate information about the different configurational features of animals’ habitats, and highlight the need for a bottom-up generative model that can depict realistic variations in habitat structural connectivity. Second, we describe a model for simulating animal habitat networks (available in the R package AnimalHabitatNetwork), and demonstrate its ability to generate alternative habitat configurations based on empirical data, which forms the basis for exploring the consequences of alternative habitat structures. Finally, we use our framework to demonstrate how transmission properties, such as the spread of a pathogen, can be impacted by both local connectivity and landscape-level characteristics of the habitat. Our study highlights the importance of considering the underlying habitat configuration in studies linking social structure with population-level outcomes.

Because genes and phenotypes are embedded within individuals, and individuals within populations, interactions within one level of biological organization are inherently linked to interactors at others. Here, we expand the network paradigm to consider that nodes can be embedded within other nodes, and connections (edges) between nodes at one level of organization form “bridges” for connections between nodes embedded within them. Such hierarchically embedded networks highlight two central properties of biological systems: 1) processes occurring across multiple levels of organization shape connections among biological units at any given level of organization and 2) ecological effects occurring at a given level of organization can propagate up or down to additional levels. Explicitly considering the embedded structure of evolutionary and ecological networks can capture otherwise hidden feedbacks and generate new insights into key biological phenomena, ultimately promoting a broader understanding of interactions in evolutionary theory., Interactions are ubiquitous across biological systems. Modeling their consequences requires capturing how units are organized across biological scales: gene and protein interactions shape phenotypic traits within individuals, individuals are embedded within populations, populations within communities, and communities within ecosystems. Doing so reveals how indirect connections among units arise from the structure of connections at higher or lower levels of organization, and how effects at one level of the network propagate across neighboring levels.

Variation in extra-pair paternity (EPP) among individuals of the same population could result from stochastic demography or from individual differences in mating strategies. Although the adaptive value of EPP has been widely studied, much less is known about the characteristics of the social environment that drive the observed patterns of EPP. Here, we demonstrate how concepts and well-developed tools for the study of social behaviour (such as social network analysis) can enhance the study of extra-pair mating decisions (focussing in particular on avian mating systems). We present several hypotheses that describe how characteristics of the social environment in which individuals are embedded might influence the levels of EPP in a socially monogamous population. We use a multi-level social approach (Hinde, 1976) to achieve a detailed description of the social structure and social dynamics of individuals in a group. We propose that the pair-bond, the direct (local) social environment and the indirect (extended) social environment, can contribute in different ways to the variation observed in the patterns of EPP, at both the individual and the population level. A strength of this approach is that it integrates into the analysis (indirect) interactions with all potential mates in a population, thus extending the current framework to study extra-pair mating behaviour. We also encourage the application of social network methods such as temporal dynamic analysis to depict temporal changes in the patterns of interactions among individuals in a group, and to study how this affects mating behaviour. We argue that this new framework will contribute to a better understanding of the proximate mechanisms that drive variation in EPP within populations in socially monogamous species, and might ultimately provide insights into the evolution and maintenance of mating systems.

Lay SummaryWe still understand poorly why different groups of individuals within a given species differ in their mating behaviour. We investigated how the composition in size and behavioural tendencies of individuals in a group affected mating behaviour in water striders. In groups where striders were active, bigger, and more flexible, a single male guarded multiple females. In contrast, in groups where striders were inactive, smaller, and exhibited a more rigid behaviour, individuals mated with several partners.Twitter: @POMontiglio

For at least a century, psychologists have studied human personality differences. In contrast, they have put fewer efforts in working on animal personality differences, and biologists have only started scrutinizing these differences by the end of the twentieth century. One reason why biologists would find an interest in studying personality differences is that they represent the raw material on which natural selection can act and that may lead to evolutionary changes in behavior traits and other associated traits. Behavioral variation in animals may thus have strong ecological and evolutionary implications. Ecology and evolutionary biologists have focused on approaches that psychologists have rarely used, essentially centered around Tinbergen’s four questions. Presenting these approaches may therefore fill up some interesting gaps between the knowledge acquired in both disciplines. In this chapter, we first present a brief history of the ecological and evolutionary studies of personality. We then compare the terminology and approaches used by both fields. We finally review evidence for the role that personality differences play on ecology and evolution, at different stages of an organisms’ life. Considering individual consistent behavioral differences in a biological framework has changed the whole field of animal behavior and created more links between ecological and evolutionary biology and psychology, physiology, and developmental biology.

In this paper we used a co-citation network analysis to quantify and illustrate the dynamic patterns of research in ecology and evolution over 40 years (1975–2014). We addressed questions about the historical patterns of development of these two fields. Have ecology and evolution always formed a coherent body of literature? What ideas have motivated research activity in subfields, and how long have these ideas attracted the attention of the scientific community? Contrary to what we expected, we did not observe any trend towards a stronger integration of ecology and evolution into one big cluster that would suggest the existence of a single community. Three main bodies of literature have stayed relatively stable over time: population/community ecology, evolutionary ecology, and population/quantitative genetics. Other fields disappeared, emerged or mutated over time. Besides, research organization has shifted from a taxon-oriented structure to a concept-oriented one over the years, with researchers working on the same topics but on different taxa showing more interactions.

1. Developmental experience, for example food abundance during juvenile stages, is known to affect life history and behaviour. However, the life history and behavioural consequences of developmental experience have rarely been studied in concert. As a result, it is still unclear whether developmental experience affects behaviour through changes in life history, or independently of it. 2. The effect of developmental experience on life history and behaviour may also be masked or affected by individual condition during adulthood. Thus, it is critical to tease apart the effects of developmental experience and current individual condition on life history and behaviour. 3. In this study, we manipulated food abundance during development in the western black widow spider, Latrodectus hesperus, by rearing spiders on either a restricted or ad lib diet. We separated developmental from condition-dependent effects by assaying adult foraging behaviour (tendency to attack prey and to stay on out of the refuge following an attack) and web structure multiple times under different levels of satiation following different developmental treatments. 4. Spiders reared under food restriction matured slower and at a smaller size than spiders reared in ad lib conditions. Spiders reared on a restricted diet were more aggressive towards prey and built webs structured for prey capture, while spiders reared on an ad lib diet were less aggressive and built safer webs. Developmental treatment affected which traits were plastic as adults: restricted spiders built safer webs when their adult condition increased, while ad lib spiders reduced their aggression when their adult condition increased. The amount of individual variation in behaviour and web structure varied with developmental treatment. Spiders reared on a restricted diet exhibited consistent variation in all aspects of foraging behaviour and web structure, while spiders reared on an ad lib diet exhibited consistent individual variation in aggression and web weight only. 5. Developmental experience affected the average life history, behaviour and web structure of spiders, but also shaped the amount of phenotypic variation observed among individuals. Surprisingly, developmental experience also determined the particular way in which individuals plastically adjusted their behaviour and web structure to changes in adult condition.

The pace-of-life syndrome (i.e., POLS) hypothesis posits that behavioral and physiological traits mediate the trade-off between current and future reproduction. This hypothesis predicts that life history, behavioral, and physiological traits will covary under clearly defined conditions. Empirical tests are equivocal and suggest that the conditions necessary for the POLS to emerge are not always met. We nuance and expand the POLS hypothesis to consider alternative relationships among behavior, physiology, and life history. These relationships will vary with the nature of predation risk, the challenges posed by resource acquisition, and the energy management strategies of organisms. We also discuss how the plastic response of behavior, physiology, and life history to changes in ecological conditions and variation in resource acquisition among individuals determine our ability to detect a fast-slow pace of life in the first place or associations among these traits. Future empirical studies will provide most insights on the coevolution among behavior, physiology, and life history by investigating these traits both at the genetic and phenotypic levels in varying types of predation regimes and levels of resource abundance. We revisit the pace-of-life syndrome hypothesis, suggesting that behaviors involving a risk of death or injury should coevolve with higher metabolic rates, higher fecundity, faster growth, and heightened mortality rates. Empirical support for this hypothesis is mixed. We show how relaxing some of the assumptions underlying the pace-of-life syndrome hypothesis allows us to consider alternative relationships among behavior, physiology, and life history, and why we fail to meet the predictions posed by the pace-of-life syndrome hypothesis in some populations. Our discussion emphasizes the need to re-integrate the role of the species’ natural history, ecological conditions, and phenotypic plasticity in shaping relationships among behavior, physiology, and life history.

Individuals may vary consistently in their architectural makeup of the constructions they build, which might have tremendous implications for their ecology and fitness. In particular, the relationship between individual differences in architectural constructions and behavior (i.e., animal personalities) is largely unexplored. Individual black widow spiders, Latrodectus hesperus, build a 3D cobweb made up of distinctive components serving to support foraging (gumfooted lines) or antipredator protection (structural lines). To explore the relationship between individual differences in behavior and architectural constructions, we quantified 1) the level of consistent individual variation in several elements of web structure and 2) the level of consistent individual variation in foraging behavior and its relationship with web structure. We controlled for condition-dependent or environmental effects by satiating all spiders prior to assays and maintaining them in standardized conditions. Spiders exhibited consistent differences in the number of gumfooted lines they built for capturing preys and overall web weight, but not in the number of structural lines. Individuals also varied consistently in their tendency to attack a prey cue, despite all spiders being satiated. Finally, spiders producing more gumfooted lines exhibited a higher tendency to attack the prey cue. Our results suggest that the architectural constructions may impact the expression of individual behavioral differences (or animal personalities) and suggest that individual behavior and extended phenotype may be part of alternative foraging strategies in L. hesperus.

Natal dispersal, the movement of an organism from its birthplace to the site of first reproduction, is fundamental to many ecological and evolutionary processes. Mechanistically, individual dispersal decisions can depend on both individual phe- notype and environmental cues. In particular, many established evolutionary theories of dispersal highlight the importance of the social environment. More recent research in behavioral ecology has focused on the importance of individual behavioral pheno- types. We reviewed the literature on individual behavioral phenotypes and dispersal and suggest that how individual behavioral phenotypes interact with the immediate social environment experienced by individuals in influencing dispersal is still poorly un- derstood, despite growing interest. We found that very few studies had examined the interaction of individual behavioral pheno- types and social factors, and behavioral phenotypes related to social tendencies were less commonly measured than were beha- vioral phenotypes related to exploration or response to risk. Further, and unsurprisingly, studies on social behavioral phenotypes and dispersal behaviors during the transience stage of dispersal were underrepresented compared to the departure or settlement stages. Future studies in this area should aim to: a) make explicit links between behavioral traits and their proposed effects on dispersal decisions throughout multiple stages of dispersal, b) integrate more continuous dispersal variables, and c) consider the effects of the spatial distribution and phenotypes of conspecifics (i.e., the social landscape) encountered by individual dispersers (Current Zoology 61 (3): 543-556, 2015). Keywords Animal dispersal, Animal personality, Behavioral syndromes, Individual differences, Social landscape

Organisms express phenotypic plasticity during social interactions. Interacting phenotype theory has explored the consequences of social plasticity for evolution, but it is unclear how this theory applies to complex social structures. We adapt interacting phenotype models to general social structures to explore how the number of social connections between individuals and preference for phenotypically similar social partners affect phenotypic variation and evolution. We derive an analytical model that ignores phenotypic feedback and use simulations to test the predictions of this model. We find that adapting previous models to more general social structures does not alter their general conclusions but generates insights into the effect of social plasticity and social structure on the maintenance of phenotypic variation and evolution. Contribution of indirect genetic effects to phenotypic variance is highest when interactions occur at intermediate densities and decrease at higher densities, when individuals approach interacting with all group members, homogenizing the social environment across individuals. However, evolutionary response to selection tends to increase at greater network densities as the effects of an individual's genes are amplified through increasing effects on other group members. Preferential associations among similar individuals (homophily) increase both phenotypic variance within groups and evolutionary response to selection. Our results represent a first step in relating social network structure to the expression of social plasticity and evolutionary responses to selection. published

According to the “pace-of-life syndrome” concept, slow-fast life-history strategies favored under different ecological conditions should lead to co-adaptations between metabolic rate and personality traits such as activity, exploration, and boldness. Although the relationships between resting metabolic rate (RMR) and personality traits have been recently tested several times, we still do not know whether personality is related to the daily energy expenditure (DEE) of free-living individuals in their natural habitat. The objectives of this study were to assess the links between RMR, DEE, and two personality traits (exploration in an open-field and docility during handling) in wild eastern chipmunks (Tamias striatus). Using a multivariate mixed model, we found that exploration and docility were significantly correlated at the among-individual level, confirming the presence of a behavioral syndrome within our population. We also found that exploration, but not docility, was negatively correlated with DEE. Hence, fast explorers show lower DEE levels than slow explorers, independently of RMR and docility. This result adds to an increasingly large (and complex) literature reporting the impacts of personality traits on the biology, ecology, and physiology of animals in their natural environment.

In systems of strong sexual conflict, male harassment can constrain female feeding, which can limit fecundity. Female responses to harassment can depend on the social context or differ between individuals, and could be based on social or intrinsic behavioral cues at different spatio-temporal scales. Using experimental groupings of stream water striders (Aquarius remigis), we examined individual behavioral differences and effects of sex ratio on 4 aspects of female behavior: 1) habitat use and 2) activity, which lead to differences in 3) feeding rates and 4) mating rates. We compared effects of the immediate social environment, immediate female habitat use and activity, and consistent female behavioral tendencies (personalities) on feeding and mating probabilities, and asked if population sex ratio affected the relationships among these behaviors. We found that individual females did differ significantly in all 4 behaviors. Population sex ratio strongly influenced average female habitat use, feeding, and mating behaviors, and female feeding and mating behaviors were predicted by a combination of moment-to-moment female behavioral state, moment-to-moment social factors, and consistent individual female behavioral differences. Furthermore, habitat use tendencies correlated significantly with activity tendencies, and habitat use and activity tendencies predicted mating probabilities, but not feeding probabilities. Our study elucidates the specific individual-level behavioral mechanisms that lead to observed population-level patterns and emphasizes the benefits of studying behavior at multiple spatial and temporal scales.

Variation in extra-pair paternity (EPP) among individuals of the same population could result from stochastic demography or from individual differences in mating strategies. Although the adaptive value of EPP has been widely studied, much less is known about the characteristics of the social environment that drive the observed patterns of EPP. Here, we demonstrate how concepts and well-developed tools for the study of social behaviour (such as social network analysis) can enhance the study of extra-pair mating decisions (focussing in particular on avian mating systems). We present several hypotheses that describe how characteristics of the social environment in which individuals are embedded might influence the levels of EPP in a socially monogamous population. We use a multi-level social approach (Hinde, 1976) to achieve a detailed description of the social structure and social dynamics of individuals in a group. We propose that the pair-bond, the direct (local) social environment and the indirect (extended) social environment, can contribute in different ways to the variation observed in the patterns of EPP, at both the individual and the population level. A strength of this approach is that it integrates into the analysis (indirect) interactions with all potential mates in a population, thus extending the current framework to study extra-pair mating behaviour. We also encourage the application of social network methods such as temporal dynamic analysis to depict temporal changes in the patterns of interactions among individuals in a group, and to study how this affects mating behaviour. We argue that this new framework will contribute to a better understanding of the proximate mechanisms that drive variation in EPP within populations in socially monogamous species, and might ultimately provide insights into the evolution and maintenance of mating systems.

Understanding the mechanistic links between individual variation in life history and behavior is a major challenge in evolutionary ecology. Glucocorticoids (GC) play a major role in this link through their baseline levels into the blood and their implication in stress responses to environmental perturbations. However, very few studies have investigated the long-term joint relationships between GC stress reactivity, life history, and behavior in natural conditions. Here, we took advantage of the behavioral and life history differences among individual males and females of a wild population of eastern chipmunks (Tamias striatus): We investigated how individual exploration, age, and reproduction were linked to level and intra-individual variability (IIV) of fecal cortisol metabolites over a 5-month period. Our analyses revealed that female cortisol levels decreased during gestation and lactation compared with non-reproductive females. We also found that slower exploring females and females with a smaller litter displayed higher IIV in fecal cortisol metabolites. For males, fecal cortisol metabolites level during the mating season increased with the number of offspring produced and decreased with age. Our study highlights the necessity of considering simultaneously seasonal fluctuations in GC level and the dynamics of stress reactivity in the study of life history and behavioral co-adaptations within natural populations.

• We examine the relation between individual behavioural variation and anthropogenic contaminants (ACs).

Species use torpor, an extreme form of heterothermy, to survive periods of limited resource supply. Studies of hibernating animals have shown that torpor causes major structural and physiological changes in the brain, many of which are reversed during periodic arousals. This suggests that behaviour may change during and following the hibernation period. Here we investigate individual performance in behavioural tests prior to and during hibernation by captive eastern chipmunks (Tamias striatus). Results indicate an association between deep torpor expression and atypical habituation patterns tested directly following torpor arousals. However, no association was found between torpor expression and spatial maze performance tested more than 24h post-arousal. Therefore, any behavioural impairment induced by torpor appears to be highly transient. The detected association between torpor and behaviour may be driven by previously confirmed effects of torpor on brain structure and function, though other potential covariates, such as the activation and deactivation of the stress axis, warrant consideration. Thus, our results are consistent with transient behavioural impairments following torpor arousals, but the causes and longer-term consequences of these transient impairments remain unclear.

Summary 1.Despite a central line of research aimed at quantifying relationships between mating success and sexually dimorphic traits (e.g., ornaments), individual variation in sexually selected traits often explains only a modest portion of the variation in mating success. 2.Another line of research suggests that a significant portion of the variation in mating success observed in animal populations could be explained by correlational selection, where the fitness advantage of a given trait depends on other components of an individual's phenotype and/or its environment. We tested the hypothesis that interactions between multiple traits within an individual (phenotype-dependence) or between an individual's phenotype and its social environment (context-dependence) can select for individual differences in behaviour (i.e., personality) and social plasticity. 3.To quantify the importance of phenotype- and context-dependent selection on mating success, we repeatedly measured the behaviour, social environment, and mating success of about 300 male stream water striders, Aquarius remigis. Rather than explaining individual differences in long-term mating success, we instead quantified how the combination of a male's phenotype interacted with the immediate social context to explain variation in hour-by-hour mating decisions. We suggest that this analysis captures more of the mechanisms leading to differences in mating success. 4.Males differed consistently in activity, aggressiveness, and social plasticity. The mating advantage of these behavioural traits depended on male morphology and varied with the number of rival males in the pool, suggesting mechanisms selecting for consistent differences in behaviour and social plasticity. Accounting for phenotype- and context-dependence improved the amount of variation in male mating success we explained statistically by 30 – 274%. 5.Our analysis of the determinants of male mating success provides important insights into the evolutionary forces that shape phenotypic variation. In particular, our results suggest that sexual selection is likely to favour individual differences in behaviour, social plasticity (i.e. individuals adjusting their behaviour), niche preference (i.e. individuals dispersing to particular social conditions), or social niche construction (i.e. individuals modifying the social environment). The true effect of sexual traits can only be understood in interaction with the individual's phenotype and environment. This article is protected by copyright. All rights reserved.

The social niche specialization hypothesis predicts that animal personalities emerge as a result of individuals occupying different social niches within a group. Here we track individual personality and performance and collective performance among groups of social spiders where we manipulated the familiarity of the group members. We show that individual personalities, as measured by consistent individual differences in boldness behavior, strengthen with increasing familiarity and that these personalities can be disrupted by a change in group membership. Changing group membership negatively impacted both individual and group performance. Individuals in less familiar groups lost weight, and these groups were less successful at performing vital collective tasks. These results provide a mechanism for the evolution of stable social groups by demonstrating that social niche reestablishment carries a steep cost for both individuals and groups. Social niche specialization may therefore provide a potential first step on the path toward more organized social systems.

Consistent individual behavioural differences in exploration, docility and boldness are often correlated and are associated with differences in short-term neurophysiological responses to environmental perturbations in many animal species. These physiological mechanisms are much less studied over longer periods in wild populations. Here we report the relationships among exploration, docility measured in open-field tests and trappability, taken as an index of boldness, in a wild population of eastern chipmunks and investigate whether behavioural differences among individuals are associated with differences in autonomic nervous system reactivity. We also assess the cortisol level of individuals over several months to investigate whether chipmunks with different exploration levels display different mean cortisol levels or differences in their cortisol variability. Open-field tests showed consistent individual differences in exploration patterns (ranging from fast to slow). Faster explorers were less docile when handled and were trapped more often (males) or farther from their burrows (females) than slower explorers. Fast explorers also showed a higher sympathetic activity under restraint but more stable cortisol levels over the course of the active season, suggesting a lower hypothalamo–pituitary–adrenal reactivity. Our results show that chipmunks display individual behavioural variation and that these differences may have physiological implications over long periods in natural settings. Future studies should investigate the fitness consequences of such behavioural/physiological differences.

The Bateman gradient is increasingly used to measure sexual selection and characterize mating systems. In a landmark paper, Arnold and Duvall (Am Nat 143:317–348, 1994) formulated predictions about the relationships between sex-specific Bateman gradients and the major types of mating system. In promiscuous species, gradients are expected to be strong and similar in both sexes. Current support for this prediction however remains equivocal as reported male gradients are almost constantly steeper than female gradients. Here, we estimated Bateman gradients in a wild population of Eastern chipmunks (Tamias striatus) over two reproductive seasons characterized by extreme levels of promiscuity and unbiased operational sex ratios. We found significant and positive Bateman gradients for both sexes. The gradients were not different among sexes suggesting that the strength of sexual selection was similar for males and females. The opportunity for selection was also particularly strong for a promiscuous species and not different among sexes. Our results thus support the predicted Bateman gradients for a promiscuous mating system.

The pace-of-life syndrome (POLS) hypothesis specifies that closely related species or populations experiencing different ecological conditions should differ in a suite of metabolic, hormonal and immunity traits that have coevolved with the life-history particularities related to these conditions. Surprisingly, two important dimensions of the POLS concept have been neglected: (i) despite increasing evidence for numerous connections between behavioural, physiological and life-history traits, behaviours have rarely been considered in the POLS yet; (ii) the POLS could easily be applied to the study of covariation among traits between individuals within a population. In this paper, we propose that consistent behavioural differences among individuals, or personality, covary with life history and physiological differences at the within-population, interpopulation and interspecific levels. We discuss how the POLS provides a heuristic framework in which personality studies can be integrated to address how variation in personality traits is maintained within populations.

The open-field test, which measures animal activity or distance covered by individuals subjected to a novel arena, is used frequently in behaviour studies. Studies generally report consistent individual differences in activity level in the open-field, but no study has tested whether individuals change their activity level differently within a single open-field test. If such differences exist, then the reliability of activity levels measured over the whole test may be affected by the duration of the test. Here, we present analyses showing how a reaction norm approach can be used to account for individual differences in temporal activity patterns. Specifically, we measured individual temporal patterns of activity in wild eastern chipmunks, Tamias striatus, and house mouse, Mus musculus, strains by decomposing the total duration of open-field tests into successive shorter time intervals. Open-field tests on chipmunks and mice lasted 3 min and 5 min, respectively. We detected repeatable individual and strain differences in temporal activity patterns. Activity during the first time interval (at the beginning of the test) was positively correlated with activity measured over the whole test, meaning that short tests yield a valid measure of activity in chipmunks and mice. We recommend analysing open-field data using random regressions to obtain activity measurements that are robust against differences in temporal activity patterns.

Understanding patterns of non-random mating is central to predicting the consequences of sexual selection. Most studies quantifying assortative mating focus on testing for correlations among partners' phenotypes in mated pairs. Few studies have distinguished between assortative mating arising from preferences for similar partners (expressed by all or a subset of the population) vs. from phenotypic segregation in the environment. Also, few studies have assessed the robustness of assortative mating against temporal changes in social conditions. We tracked multiple matings by stream water striders (Aquarius remigis) across variable social conditions to investigate mating patterns by both body size and behavioural type (personality). We documented temporal changes in partner availability and used a mixed model approach to analyse individual behaviours and changes in mating status recorded on an hourly basis. We assessed whether all or only a subset of individuals in the population expressed a tendency to mate with similar phenotypes. Our analyses took into account variation in the level of competition and in the phenotypes of available partners. Males and females exhibited significant assortative mating by body size: the largest males and females, and the smallest males and females mated together more often than random. However, individuals of intermediate size were equally likely to mate with small, intermediate or large partners. Individuals also displayed two contrasting patterns of assortative mating by personality (activity level). Individuals generally mated preferentially with partners of similar activity level. However, beyond that general trend, individuals with more extreme personalities tended to exhibit disassortative mating: the most active males mated disproportionately with less active females and the least active males tended to mate with more active females. Our analyses thus revealed multiple, distinct patterns of nonrandom mating. These mating patterns did not arise from differences in partner availability among individuals and were robust to temporal changes in social conditions. Hence, mating patterns likely reflect mate preferences or arise from male-male competition coupled with sexual conflict. Our study also stresses the importance of accounting for variation in partner availability and demonstrates the influence of behavioural variation on mating patterns.

The literature on animal personality is dominated by papers lacking any data. These papers, which we will call “data-free” papers, are cited and recognized twice as much as comparable empirical studies. In this data-free paper, we highlight 4 common data-free contributions that often fail to have an impact on the topic: (a) novel conceptual frameworks suggesting novel avenues of research or hypotheses, (b) papers prescribing novel terminologies, (c) syntheses revisiting older theories, and (d) papers introducing novel statistical methods. We argue that conceptual papers presenting a novel hypothesis probably could almost always be replaced by robust empirical studies actually testing the hypotheses of interest. We hope this paper will stimulate discussion on what makes a data-free paper on animal personality impactful, beyond simply being highly cited.

An exciting area in behavioural ecology focuses on understanding why animals exhibit consistent among-individual differences in behaviour (animal personalities). Animal personality has been proposed to emerge as an adaptation to individual differences in state variables, leading to the question of why individuals differ consistently in state. Recent theory emphasizes the role that positive feedbacks between state and behaviour can play in producing consistent among-individual covariance between state and behaviour, hence state-dependent personality. We review the role of feedbacks in recent models of adaptive personalities, and provide guidelines for empirical testing of model assumptions and predictions. We discuss the importance of the mediating effects of ecology on these feedbacks, and provide a roadmap for including state–behaviour feedbacks in behavioural ecology research.

Slides from a talk presented at the annual Animal Behavior Society meeting in Anchorage, AK, June 2015. Please see the published paper in Behavioral Ecology at http://beheco.oxfordjournals.org/content/early/2015/05/22/beheco.arv065.abstract?keytype=ref&ijkey=HvKqFza048RqiBc

Virtual worlds supporting massively multiplayer games have become so complex that they exhibit temporal and spatial dynamics mostly driven by interactions between players. In this respect, virtual worlds resemble closely natural ecosystems. Studying the ecology of virtual worlds is an outstanding opportunity for ecologists as well as the game industry to collaborate in order to test several aspects of ecological theory difficult to study in nature, and build manageable, resilient virtual worlds.

Heterogeneous forces of selection associated with fluctuating environments are recognized as important factors involved in the maintenance of inter-individual phenotypic variance within populations. Consistent behavioural differences over time and across situations (e.g. personality) are increasingly cited as examples of individual variation observed within populations. However, the suggestion that heterogeneous selective pressures target different animal personalities remains largely untested in the wild. In this 5-year study, we investigated the dynamics of viability selection on a personality trait, exploration, in a population of eastern chipmunks (Tamias striatus) experiencing substantial seasonal variations in weather conditions and food availability associated with masting trees. Contrary to our expectations, we found no evidence of fluctuating selection on exploration. Instead, we found strong disruptive viability selection on adult exploration behaviour, independent of seasonal variations. Individuals with either low or high exploration scores were almost twice as likely to survive over a 6-month period compared with individuals with intermediate scores. We found no evidence of viability selection on juvenile exploration. Our results highlight that disruptive selection might play an important role in the maintenance of phenotypic variance of wild populations through its effect on different personality types across temporally varying environmental conditions.

Summary Understanding the causes of animal personality (i.e. consistent behavioural differences) is a major aim of evolutionary studies. Recent theoretical work suggests that major personality traits may contribute to evolutionary trade-offs. However, such associations have only been investigated in a few study systems, and even less so in free ranging animal populations. Eastern chipmunks exhibit consistent individual differences in exploration, ranging from slow to fast. Birth cohorts also experience dramatic differences in age at first breeding opportunity due to annual differences in beech mast. Individuals may breed for the first time at 24, 33 or 50% of their average life span, depending on year of birth. Here, we used data from a long-term survey on a wild population to investigate the relationship between reproductive life history and consistent individual differences in exploration. We determined whether predictable differences in age at first breeding opportunity among birth cohorts were associated with exploration differences and favoured individuals with different exploration. Birth cohorts with a predictably earlier age at first breeding opportunity were faster explorers on average. Slower explorers displayed their highest fecundity (females) or highest fertilization success (males) later in their life compared with faster explorers. Overall, slow explorers attained a higher lifetime reproductive success than fast explorers when given an opportunity to reproduce later in their life. Our results suggest that the timing of mating seasons, associated with fluctuating food abundance, may favour individual variation in exploration and maintain population variation through its effects on reproductive life history. Together, our result shed light on how fluctuation in ecological conditions may maintain personality differences and on the nature of the relationships between animal personality and life history.

Monitoring fecal glucocorticoid metabolites in wild animals, using enzyme immunoassays, enables the study of endocrinological patterns relevant to ecology and evolution. While some researchers use antibodies against the parent hormone (which is typically absent from fecal samples), others advocate the use of antibodies designed to detect glucocorticoid metabolites. We validated two assays to monitor fecal cortisol metabolites in the eastern chipmunk (Tamias striatus). We compared an antibody produced against cortisol and one produced against 5α-pregnane-3β, 11β, 21-triol-20-one using a radiometabolism study and an injection with adrenocorticotropic hormone (ACTH). Most cortisol metabolites were excreted in the urine (∼83%). Peak excretion in the feces occurred 8 h after injection. Both assays detected an increase in fecal cortisol metabolite levels after injection of ACTH. Males, but not females, exhibited a circadian variation in metabolite levels. The sexes did not exhibit any difference over the time course and route of excretion or the relative increase in fecal cortisol metabolite levels after ACTH injection. The cortisol assay displayed higher reactivity to ACTH injection relative to baseline than did the metabolite assay. While both antibodies gave comparable results, the cortisol antibody was more sensitive to changes in plasma cortisol levels in eastern chipmunks.

Parasites can play an important role in the dynamics of host populations, but empirical evidence remains sparse. We investigated the role of bot fly (Cuterebra spp.) parasitism in red-backed voles (Myodes gapperi) by first assessing the impacts of the parasite on the probability of vole survival under stressful conditions as well as on the reproductive activity of females. We then identified the main factors driving both the individual risk of infection and the abundance of bot flies inside red-backed voles. Finally, we evaluated the impacts of bot fly prevalence on the growth rate of vole populations between mid-July and mid-August. Thirty-six populations of red-backed voles were sampled in the boreal forest of Quebec, Canada. The presence and the abundance of parasites in voles, two host life history traits (sex and body condition), three indices of habitat complexity (tree basal area, sapling basal area, coarse woody debris volume), and vole abundance were considered in models evaluating the effects of bot flies on host populations. We found that the probability of survival of red-backed voles in live traps decreased with bot fly infection. Both the individual risk of infection and the abundance of bot flies in red-backed voles were driven mainly by vole abundance rather than by the two host life history traits or the three variables of habitat complexity. Parasitism had population consequences: bot fly prevalence was linked to a decrease in short-term growth rate of vole populations over the summer. We found that bot flies have the potential to reduce survival of red-backed voles, an effect that may apply to large portions of populations.

Several personality traits are mainly expressed in a social context, and others, which are not restricted to a social context, can be affected by the social interactions with conspecifics. In this paper, we focus on the recently proposed hypothesis that social niche specialization (i.e. individuals in a population occupy different social roles) can explain the maintenance of individual differences in personality. We first present ecological and social niche specialization hypotheses. In particular, we show how niche specialization can be quantified and highlight the link between personality differences and social niche specialization. We then review some ecological factors (e.g. competition and environmental heterogeneity) and the social mechanisms (e.g. frequency-dependent, state-dependent and social awareness) that may be associated with the evolution of social niche specialization and personality differences. Finally, we present a conceptual model and methods to quantify the contribution of ecological factors and social mechanisms to the dynamics between personality and social roles. In doing so, we suggest a series of research objectives to help empirical advances in this research area. Throughout this paper, we highlight empirical studies of social niche specialization in mammals, where available.