Morgan David

Personality predicts social dominance in female zebra finches, Taeniopygia guttata, in a feeding context

Although personality has been defined as a suite of correlated behaviours, most studies of animal personality actually consider correlations between a few traits. We examined the repeatability and correlational structure of five potential personality traits (activity, neophobia, exploratory tendencies, risk-taking behaviour and obstinacy), in female zebra finches. In addition, we assessed to what extent personality influenced social dominance in a feeding context in this gregarious species. All personality traits were found to be highly repeatable within individuals. In addition, except for obstinacy, all of them were related to each other, thus defining a behavioural syndrome. Social dominance was predicted by personality, with proactive individuals being more likely to be dominant. Our results suggest that personality can be considered as a new static factor influencing within-group hierarchies. We finally discuss these results in terms of the consequences for the evolution of personalities and the need to take several traits into account to provide full descriptions of individual personality.

Ecologists overestimate the importance of predictor variables in model averaging: a plea for cautious interpretations

Summary 1. Information-theory procedures are powerful tools for multimodel inference and are now standard methods in ecology. When performing model averaging on a given set of models, the importance of a predictor variable is commonly estimated by summing the weights of models where the variable appears, the so-called sum of weights (SW). However, SWs have received little methodological attention and are frequently misinterpreted. 2. We assessed the reliability of SW by performing model selection and averaging on simulated data sets including variables strongly and weakly correlated to the response variable and a variable unrelated to the response. Our aim was to investigate how useful SWs are to inform about the relative importance of predictor variables. 3. SW can take a wide range of possible values, even for predictor variables unrelated to the response. As a consequence, SW with intermediate values cannot be confidently interpreted as denoting importance for the considered predictor variable. Increasing sample size using an alternative information criterion for model selection or using only a subset of candidate models for model averaging did not qualitatively change our results: a variable of a given effect size can take a wide range of SW values. 4. Contrary to what is assumed in many ecological studies, it seems hazardous to define a threshold for SW above which a variable is considered as having a statistical effect on the response and SW is not a measure of effect size. Although we did not consider every possible condition of analysis, it is likely that in most situations, SW is a poor estimate of variable’s importance.

Personality affects zebra finch feeding success in a producer–scrounger game

Recent evidence strongly suggests that natural selection can favour the evolution of consistent individual differences in behaviour (personalities). Indeed, personality shows heritable variation and has been linked to fitness in many species. However, the fitness effects of personality are highly variable within and between species. Furthermore, the nature of the causal influence of personality on an organisms fitness remains unclear so far. Competition has been proposed as a factor modulating this relationship. Thus, personality has been found to affect individual success in competition by interference in a few species, but its influence in scramble competition remains unexplored. We assessed exploratory tendencies (thought to be a key component of personality) in a model species, the zebra finch, Taeniopygia guttata. In a first session, we formed foraging flocks composed of four individuals with different exploration scores, and allowed them to play producer-scrounger games repeatedly. During a second session, individuals were reassigned to different flocks to check for consistency in the influence of exploratory tendency across different social contexts. Exploratory tendency influenced individual feeding success during the first session but not during the second one. High-exploratory birds were less successful at finding food (i.e. playing the producer tactic) and consequently had a lower feeding success, but were presumably able to adjust their behaviour between sessions. We discuss our results in relation to the interactive effects of both personality and experience, and highlight the role of competition processes on the evolution of personality.

Personality May Confound Common Measures of Mate-Choice

The measurement of female mating preferences is central to the study of the evolution of male ornaments. Although several different methods have been developed to assess sexual preference in some standardized way, the most commonly used procedure consists of recording female spatial association with different males presented simultaneously. Sexual preference is then inferred from time spent in front of each male. However, the extent to which the measurement of female mate-choice is related to exploration tendencies has not been addressed so far. In the present study we assessed the influence of variation in exploration tendencies, a trait closely associated to global personality, on the measurement of female mating preference in the zebra finch (Taeniopygia guttata) using the widely used four-chamber choice-apparatus. The number of movements performed within both exploration and mate-choice apparatus was consistent within and across the two contexts. In addition, personality explained variation in selectivity, preference strength and consistency. High-exploratory females showed lower selectivity, lower preference scores and displayed more consistent preference scores. Our results suggest that variation in personality may affect the measurement of female mating preference and may contribute to explain existing inconsistencies across studies.

Dynamics of among-individual behavioral variation over adult lifespan in a wild insect

Lay Summary Wild crickets show consistent patterns of behavior over their adult lifetimes and as they get older they become increasingly predictable. We tagged crickets and then periodically recaptured them and measured their behavior in the lab. This revealed that rather than variation in how age affects behavior, there were consistent patterns across the whole population. We do not have a situation where some crickets live fast and die young while others take it easy and slow.

Exploration behavior and parental effort in wild great tits: partners matter

The extended pace-of-life syndrome (POLS) hypothesis suggests that variation in boldness-like behaviors has co-evolved with variation in life-history strategies within populations, yet both theoretically driven experiments and evidence for phenotypic correlations between boldness-like behaviors and reproduction-related activities are scarce. Here we test the prediction that more exploratory individuals should be willing to provide more effort into current reproduction than less exploratory ones by investigating the association between exploration behavior and parental effort in wild great tits (Parus major). To this end, we assessed exploration behavior following a standardized assay. Then, we estimated individual willingness to provide parental effort into brood provisioning as (1) individual increase in nest visit rate after the brood had been artificially enlarged and (2) individual latency to return to the nest after this manipulation. Fast male explorers were quicker than slow explorers to return to the nest after the manipulation. Males paired with a partner of similar exploration score—either a fast or slow female explorer —increased their nest visit rate more than males paired with a partner of dissimilar exploration score. The relationship between exploration and parental effort then depended on one’s partner’s behavior. Our test thus provides only partial support for the extended POLS hypothesis and highlights the potential importance of the social environment in shaping the relationship between boldness-like behaviors and fitness-maximizing traits.

Handling stress does not reflect personality in female zebra finches (Taeniopygia guttata).

Although increasing attention is given to both the causes and consequences of variation in animal personality, the measurement of personality in captive or free-ranging individuals remains an issue. In particular, one important question concerns whether personality should be established from the existence of complex behavioral syndromes (a suite of correlated behavioral traits) or could be more easily deduced from a single variable. In that context, it has recently been suggested that handling stress, measured through breathing rate during handling, could be a good descriptor of personality, at least in passerine birds. The authors experimentally investigated to what extent handling stress was correlated with personality in female zebra finches (Taeniopygia guttata), as assessed from a suite of repeatable behavioral traits, including activity, exploratory behavior, neophobia, and reaction to startle. Although breathing rate was repeatable across individuals, it was not related to any behavioral trait, suggesting that it cannot be used to quickly predict personality, at least in zebra finches. Breathing rate during handling, in addition, was related to morphology, questioning the fact that breathing rate during handling reflects personality irrespective of individual state. The authors suggest that inference on global personality from a reduced number of traits should be performed with caution.

Short- and long-term repeatability of docility in the roe deer: sex and age matter

Behavioural consistency is a key assumption when evaluating how between-individual differences in behaviour influence life history tactics. Hence, understanding how and why variation in behavioural repeatability occurs is crucial. While analyses of behavioural repeatability are common, few studies of wild populations have investigated variation in repeatability in relation to individual status (e.g. sex, age, condition) and over different timescales. Here, we aimed to fill this gap by assessing within-population variation in the repeatability of docility, as assessed by the individuals response to human handling, in a free-ranging population of European roe deer, Capreolus capreolus. Docility was an equally repeatable behaviour at both short- and long-term timescales, suggesting that this behavioural trait is stable across time. Repeatability did not differ markedly between age and sex categories but tended to be higher in juvenile males than in juvenile females. Finally, contrary to expectation, individual variation in the repeatability of docility was not correlated with individual body mass. Further studies are required to assess the life history consequences of the individual variation in docility we report here.

Individual differences in behavioral consistency are related to sequential access to resources and body condition in a producer-scrounger game

Investigating the evolution of consistent between-individual behavioral differences necessitates to explain the emergence of within-individual consistency. Relying on a recent mathematical model, we here test the prediction that the emergence of differences in within-individual consistency is related to the sequential access to resources in a frequency-dependent foraging game. To this end we used flocks of zebra finches (Taeniopygia guttata) engaged in a producer-scrounger foraging game. Tactic investment (i.e. the proportion of hops with the head down) significantly predicted successful tactic use (i.e. the proportion of seeds produced). In support of predictions, we found that individuals that arrived first at a foraging area were more consistent in both their investment into and their use of the producer tactic. Also, birds in higher body condition were less consistent in their producer tactic use. These results provide the first evidence that variation in behavioral consistency can emerge through the sequential access to resources in a frequency-dependent game. They also highlight a potential physiological cost of behavioral flexibility. Our findings suggest an explanation for the link between personality traits and social information use.

Pairing context determines condition-dependence of song rate in a monogamous passerine bird

Condition-dependence of male ornaments is thought to provide honest signals on which females can base their sexual choice for genetic quality. Recent studies show that condition-dependence patterns can vary within populations. Although long-term association is thought to promote honest signalling, no study has explored the influence of pairing context on the condition-dependence of male ornaments. In this study, we assessed the influence of natural variation in body condition on song rate in zebra finches (Taeniopygia guttata) in three different situations: during short and long encounters with an unfamiliar female, and within heterosexual mated pairs. We found consistent individual differences in male directed and undirected song rate. Moreover, body condition had a positive effect on song rate in paired males. However, male song rate was not influenced by body condition during short or long encounters with unfamiliar females. Song rate appears to be an unreliable signal of condition to prospective females as even poor-condition birds can cheat and sing at a high rate. By contrast, paired females can reliably use song rate to assess their mates body condition, and possibly the genetic quality. We propose that species characteristics, such as mating system, should be systematically taken into account to generate relevant hypotheses about the evolution of condition-dependent male ornaments.