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Aggressive behaviour is thought to have significant consequences for fitness, sexual selection and the evolution of social interactions, but studies measuring its expression across successive encounters—both intra‐ and intersexual—are limited. We used the field cricket Teleogryllus oceanicus to evaluate factors affecting repeatability of male aggression and its association with mating success. We quantified focal male aggression expressed towards partners and received from partners in three successive, paired trials, each involving a different male partner. We then measured a proxy of focal male fitness in mating trials with females. The likelihood and extent of aggressive behaviour varied across trials, but repeatability was negligible, and we found no evidence that patterns of focal aggression resulted from interacting partner identity or prior experience. Males who consistently experienced aggression in previous trials showed decreased male mating ‘efficiency’—determined by the number of females a male encountered before successfully mating, but the effect was weak and we found no other evidence that intrasexual aggression was associated with later mating success. During mating trials, however, we observed unexpected male aggression towards females, and this was associated with markedly decreased male mating efficiency and success. Our findings suggest that nonadaptive aggressive spillover in intersexual mating contexts could be an important but underappreciated factor influencing the evolution of intrasexual aggression.

Consistent inter‐individual differences in behaviour, that is, personalities, can emerge as a result of inter‐individual differences in ontogenetic experience, and predation risk is a potent one. As personalities develop over lifetime, however, they may also be broken by ontogenetic transitions of the individual. Here we first tested the hypothesis that consistent inter‐individual differences in larval behaviour arise under predation challenge, and are entangled with differences in body size. We then tested the hypothesis that adult behavioural type is related to body size rather than to larval behavioural phenotype. To test these hypotheses, we performed a longitudinal study following the development of about 50 moor frogs, Rana arvalis. We manipulated their larval and current environment, and recorded their behaviours repeatedly, under control conditions, invertebrate predators' chemical cues or in live predator presence. Partially in line with our predictions, the ontogenetic experience of predator presence led to personality emergence in tadpoles, yet their behaviour was not explained by their body size. This pattern was lost over metamorphosis. According to predictions, pre‐adult moor frog behaviour was affected by their body size—time to exit shelter was shorter in larger frogs—but neither by their behaviour as tadpoles nor by their larval environment, that is, tadpole predator‐exposure experience. Our results show that individual behavioural tendencies can be well decoupled between prior and post metamorphosis, which adds to the growing empirical evidence supporting adaptive decoupling hypothesis. We showed that ontogenetic experience of predator presence led to personality emergence in moor frog tadpoles, whose behaviour was yet not explained by their body size. We also showed this pattern was lost over metamorphosis, as juvenile frog behaviour was affected by their body size, but neither by their behaviour as tadpoles nor by their ontogenetic environment. Our results show that individual behavioural tendencies can be well decoupled between prior and post metamorphosis in an anuran.

Background Birdsong, a key model in animal communication studies, has been the focus of intensive research. Song traits are commonly considered to reflect differences in individual or territory quality. Yet, few studies have quantified the variability of song traits between versus within individuals (i.e. repeatability), and thus whether certain song traits indeed provide reliable individual-specific information. Here, we studied the dawn chorus of male great tits ( Parus major ) to determine if key song traits are repeatable over multiple days and during different breeding stages. Additionally, we examined whether repeatability was associated with exploration behaviour, a relevant personality trait. Finally, we tested if variation in song traits could be explained by breeding stage, lowest night temperature, and exploration behaviour. Results We show that the start time of an individual’s dawn song was indeed repeatable within and across breeding stages, and was more repeatable before, than during, their mate’s egg laying stage. Males started singing later when the preceding night was colder. Daily repertoire size was repeatable, though to a lesser extent than song start time, and no differences were observed between breeding stages. We did not find evidence for an association between exploration behaviour and variation in dawn song traits. Repertoire composition, and specifically the start song type, varied across days, but tended to differ less than expected by chance. Conclusions Our findings that individuals consistently differ in key song traits provides a better understanding of the information receivers can obtain when sampling songs of different males. Surprisingly, start time, despite being influenced by a highly variable environmental factor, appeared to be a more reliable signal of individual differences than repertoire size. Against expectation, singers were more repeatable before than during their mate’s egg laying stage, possibly because before egg laying, females are less constrained to move around unguarded and thus may then already sample (and compare) different singers. Combining repeated dawn song recordings with spatial tracking could reveal if the sampling strategies of receivers are indeed important drivers of repeatability of song traits. Such a complementary approach will further advance our insights into the dynamics and evolution of animal signalling systems.

For many benthic marine invertebrates, inversion (being turned upside-down) is a common event that can increase vulnerability to predation, desiccation and unwanted spatial transport, and requires behavioural ‘self-righting’ to correct. While self-righting behaviour has been studied for more than a century, the repeatability (R) – the portion of behavioural variance due to inter-individual differences – of this trait is not well understood. Heritability and the evolution of animal behaviour rely on behavioural repeatability. Here, we examined the self-righting technique of a cold-water holothurid, Parastichopus tremulus , and assessed the repeatability of this behaviour. Under laboratory conditions, P. tremulus consistently used muscle contractions to curl its body and roll itself back to an upright position, which provided for rapid ( x̅ ± SD = 96.7 ± 49.8 s) and highly repeatable ( R = 0.75) self-righting in the short term that varied between individuals (range of individual average righting times = 34.8–217.0 s). Righting time tended to increase with animal size; however, substantial variation was evident at comparable sizes, as average righting time ranged from 34.8–155.5 s for animals ~20 cm in body length. Contrary to previous studies on other echinoderms, we found no evidence of improved righting times for P. tremulus over time. This study ultimately provides the first detailed documentation of self-righting behaviour for P. tremulus and suggests that this species displays a high degree of repeatability for this trait in the short term.

A burgeoning literature in animal behavior has demonstrated that most animals exhibit consistent individual variation in core behavioral traits or personality. However, the taxonomic spread of animal personality studies is uneven, with some ecologically important and diverse taxa still unstudied. Some of these understudied groups, such as venomous snakes, are also frequent targets of mitigation due to human–wildlife conflict, and conservation researchers have been increasingly focused on developing a general understanding of how individual personality, or temperament, mediates wildlife responses to management or mitigation actions. In this study, we used 20 captive Western Rattlesnakes (Crotalus oreganus) in standardized assays to test for repeatable behaviors (i.e., personalities) between individuals and examine possible relationships in personality traits across contexts (i.e., behavioral syndromes). Repeatability of behaviors was assessed over five repeated trials consisting of a handling assay, an open field test, and a threat assay. We found several behaviors related to exploration/avoidance, activity level, and boldness/shyness showed significant repeatability. However, we found no evidence for behavioral syndromes across contexts. Our analysis shows that, similar to many other species and taxonomic groups, viperid snakes also display individual personality traits when tested under standardized conditions, and we discuss the implications of this finding for mitigation, conservation, and comparative analyses across broadly similar species groups.Significance StatementIt has now been well established that non-human animals exhibit individual behavioral traits similar to what humans term personality, and animal personality studies are becoming more important in the field of conservation and management. However, there are no previous personality/behavioral studies on venomous snakes, which are not only important predators in many ecosystems, but also a major source of human–wildlife conflict. We used a series of standardized behavioral tests to determine whether individual Western Rattlesnakes showed distinct personalities. We found that individual snakes did indeed exhibit repeatable behavioral traits consistent with personalities, but we did not find that these temperament traits were correlated across contexts. Our findings are important to developing a more nuanced view of the behaviors of venomous snakes and could aid in the development of more humane strategies to reduce human–wildlife conflict.

Phenotypic variation in behavior exists among species and populations, as well as among and within individuals. The pace-of-life syndrome hypothesis predicts covariation between life-history strategies, ranging from slow to fast, and behavior, ranging from shy, inactive, and flexible to bold, active, and less flexible. This covariation is expected to exist at multiple hierarchical levels, from the species down to the individual. We predict that fast-lived species will differ in average levels of behavior, and additionally show lower within-individual and among-individual variation than slow-lived ones. Shrews represent a highly suitable model to test these predictions, as they comprise a range of genera which differ tremendously in life-history strategy and metabolism. We performed repeated tests of boldness and aggression on 155 wild-caught individuals of five species of shrews, two species of the slow-lived genus Crocidura, two of the fast-lived genus Sorex, and one of the intermediate-paced genus Neomys. To compare not only average levels of behavior but also its variance components between those groups, we calculated coefficients of variation at within-and among-individual levels. Our results support our first prediction that, following the framework of pace-of-life-syndromes, fast-lived species should exhibit bolder behavior than slow-lived ones. However, our prediction of lower within- and among-individual variation in fast-lived species was not supported. Instead, our data suggest that other ecological factors might influence the expression of behavioral variation in shrew species, such as the variability in habitat choice and differences in anti-predator strategies.

Describing and explaining patterns of individual animal behaviors in situ, and their repeatability over the annual cycle, is an emerging field in ecology owing largely to advances in tagging technology. We describe individual movements of adult Sakhalin taimen Parahucho perryi, an endangered salmonid fish, in the headwaters of a river in northern Japan during the spring spawning season over 2 years. Migration timing, separated into stages prior to, during, and following the spawning period, was found to be more consistent and repeatable for females than males. We hypothesized that the observed coordinated movement within seasons, and repeatability in migration timing across seasons, could result from (1) individual‐specific responsiveness resulting from endogenous, biological traits that are mediated by environmental factors, or (2) social interactions among comigrating individuals. We found that water temperature and water level experienced by fish near the river mouth approximately a week before arrival at the spawning ground explained variability in run timing between years for females but not males. We found no evidence of conspecific attraction or repulsion resulting from social interactions among the spawners and post‐spawners. We conclude that individual‐specific responsiveness to environmental cues was the likely mechanism underpinning the observed migration timing and movement patterns. Individual‐specific responsiveness to environmental cues was the likely mechanism underpinning the coordinated movement and across‐year repeatability in migration timing in the endangered salmonid, Sakhalin taimen. The species possess strong fidelity to time of reproductive activities to maintain their migratory connectivity.

The early life stage is typically a selective bottleneck during which individual performance is important for survival. We investigated size, energetic state, and activity, in relation to recapture probability in the youngest free-swimming stage of a territorial fish, the brown trout. In two experiments, we induced compensatory growth in wild-caught brown trout fry, using a restriction-refeeding protocol. Upon refeeding in the laboratory, the restricted trout showed compensatory growth in mass, but not in length. During this compensatory growth phase, we released the fish into their native stream habitat and then recaptured them after 1 month to assess survival and growth. Despite not having fully compensated body size at release, restricted fish did not show continued growth compensation in the stream, indicating that the natural environment limits growth capacity during early life. Individual baseline activity was scored in open-field tests before and after food restriction and was found repeatable but not significantly affected by growth manipulations. Under natural conditions, we found a positive association between open-field activity and survival (as indicated by recapture probability), but no significant differences between food-restricted and control fish. Initial body length positively influenced survival in the first experiment (early summer), but not in the second (late summer). These results contrast with the assumption that high baseline activity should be riskier in natural environments. For territorial animals, we hypothesize that activity is associated with high aggression and territoriality, which facilitates access to high-quality territories providing both shelter from prédation and reduced starvation risk, which reduces mortality risk.

Increasingly, individual variation in personality has become a focus of behavioral research in animal systems. Boldness and shyness, often quantified as the tendency to explore novel situations, are seen as personality traits important to the fitness landscape of individuals. Here we tested for individual differences within and across contexts in behavioral responses of captive mouse lemurs ( Microcebus murinus ) to novel objects, novel foods, and handling. We report consistent differences in behavioral responses for objects and handling. We also found that the responses to handling and novel objects were correlated and repeatable. Lastly, we show that shyer individuals may show less variability in their behavioral responses. This study provides new information on the potential for behavioral syndromes in this species and highlights differences in the degree to which behavioral types (e.g., shy/bold) vary in their behavioral responses.

Behavioural and cognitive processes play important roles in mediating an individual's interactions with its environment. Yet, while there is a vast literature on repeatable individual differences in behaviour, relatively little is known about the repeatability of cognitive performance. To further our understanding of the evolution of cognition, we gathered 44 studies on individual performance of 25 species across six animal classes and used meta-analysis to assess whether cognitive performance is repeatable. We compared repeatability (R) in performance (1) on the same task presented at different times (temporal repeatability), and (2) on different tasks that measured the same putative cognitive ability (contextual repeatability). We also addressed whether R estimates were influenced by seven extrinsic factors (moderators): type of cognitive performance measurement, type of cognitive task, delay between tests, origin of the subjects, experimental context, taxonomic class and publication status. We found support for both temporal and contextual repeatability of cognitive performance, with mean R estimates ranging between 0.15 and 0.28. Repeatability estimates were mostly influenced by the type of cognitive performance measures and publication status. Our findings highlight the widespread occurrence of consistent inter-individual variation in cognition across a range of taxa which, like behaviour, may be associated with fitness outcomes. This article is part of the theme issue ‘Causes and consequences of individual differences in cognitive abilities’.