Environmental temperature during early life affects the personality of mosquitofish in adulthood

Personality has been observed in a variety of animal taxa with important implications in ecology and evolution. Exploring the influence of environmental temperature during early life on personality could help to understand the ontogeny of this phenotypic trait in animals. In this study, we reared newborn mosquitofish Gambusia affinis at high (30°C) and low (25°C) water temperatures and measured their shyness and exploration upon sexual maturity. We tested the repeatability of each behavioral trait; the correlation between them; and the effects of rearing temperature, sex, and body length on the behaviors. When growing up at low temperatures, female fish exhibited repeatability in shyness and exploration, and males exhibited marginal repeatability in shyness. However, neither of the 2 behaviors were repeatable when the fish were reared at high temperatures. There was a negative correlation between shyness and exploration, indicating that the 2 behaviors comprise a behavioral syndrome in this species. Mosquitofish reared at high temperatures were more explorative than those reared at low temperatures, while there was no difference in shyness between the 2 treatments. Body length and sex had no significant effects on the average values of the 2 behaviors. The results indicate that environmental temperature during early life could shape the personality of mosquitofish and modify the average of the behavioral traits. These findings might provide insights to understand the ontogeny of animal personality and how changes in environmental temperature influence animal dispersal by shaping their personality.     

Personality traits and behavioural profiles in the domestic canary are affected by sex and photoperiod

Personality traits and behavioural profiles are generally assumed to be stable in adulthood. Yet, it has been hypothesised that animals should cope with cyclical fluctuations by adjusting both single behaviours and suites of behaviour. Photoperiod is well known to induce hormonal and physiological changes, and these changes can in turn affect personality traits and behavioural profiles. This study is the first to explicitly investigate the influence of photoperiod on both behavioural profiles and personality traits. Six potential personality traits (within‐flock activity, ability to escape, response to threat, isolation calling, boldness and neophobia) and dominance were measured four times in 96 domestic canaries Serinus canaria (48 males and 48 females): twice during a long photoperiod (Long Days) and 6 months later twice during a short photoperiod (Short Days). Without regard to sex and photoperiod, most traits were highly repeatable, and bolder canaries were more dominant, less sensitive to an external threat and to isolation and less neophobic. In addition, the more active individuals within a flock were the more difficult to catch. Yet, both sex and photoperiod affected personality traits and behavioural profiles. Personality traits remained repeatable within each photoperiod though we observed behavioural plasticity and sex differences for response to threat, neophobia and within‐flock activity. Concerning behavioural profiles, the negative relationship between boldness and neophobia remained homogenous in both sexes during Short Days as well as during Long Days. Then, the more active individuals within a flock were the more difficult to catch in Short Days but not in Long Days. Finally, the other correlations not only varied with photoperiod but also with sex. Our study highlights the importance of photoperiod and sex in the expression of personality traits and behavioural profiles, and of the need to measure them across the whole photoperiodic cycle.     

Personality and urbanization: behavioural traits and <Emphasis Type="Italic">DRD4</Emphasis> SNP830 polymorphisms in great tits in Barcelona city

Most examples of adaptation to the urban environment relate to plasticity processes rather than to natural selection. Personality, however, defined as consistent individual differences in behaviour related to exploration, caution, and neophobia, is a good behavioural candidate character to study natural selection in relation to the urban habitat due to its heritable variation. The aim of this paper was to analyse variation in personality by comparing urban and forest great tits Parus major using standard tests of exploratory behaviour and boldness. We studied personality in 130 wild great tits captured in Barcelona city and nearby forests and found that urban birds were more explorative and bolder towards a novel object than forest birds. Genotype frequencies of the DRD4 SNP830 polymorphism, a gene region often associated with personality variation, varied significantly between forest and urban birds. Behavioural scores, however, were not correlated with this polymorphism in our population. Exploration scores correlated to boldness for forest birds but not for urban birds. Our findings suggest that the novel selection pressures of the urban environment favour the decoupling of behavioural traits that commonly form behavioural syndromes in the wild.     

Realized heritability and repeatability of risk-taking behaviour in relation to avian personalities

Personalities are general properties of humans and other animals. Different personality traits are phenotypically correlated, and heritabilities of personality traits have been reported in humans and various animals. In great tits, consistent heritable differences have been found in relation to exploration, which is correlated with various other personality traits. In this paper, we investigate whether or not risk-taking behaviour is part of these avian personalities. We found that (i) risk-taking behaviour is repeatable and correlated with exploratory behaviour in wild-caught hand-reared birds, (ii) in a bi-directional selection experiment on 'fast' and 'slow' early exploratory behaviour, bird lines tend to differ in risk-taking behaviour, and (iii) within-nest variation of risk-taking behaviour is smaller than between-nest variation. To show that risk-taking behaviour has a genetic component in a natural bird population, we bred great tits in the laboratory and artificially selected 'high' and 'low' risk-taking behaviour for two generations. Here, we report a realized heritability of 19.3 +/- 3.3% (s.e.m.) for risk-taking behaviour. With these results we show in several ways that risk-taking behaviour is linked to exploratory behaviour, and we therefore have evidence for the existence of avian personalities. Moreover, we prove that there is heritable variation in more than one correlated personality trait in a natural population, which demonstrates the potential for correlated evolution.     

Personality and Information Gathering in Free-Ranging Great Tits

One aspect of animal personality that has been well described in captivity, but received only little attention in studies in the wild, is that personality types may vary in their behavioural flexibility towards environmental changes. A fundamental factor underlying such differences is believed to be the degree to which individual behavior is guided by environmental stimuli. We tested this hypothesis in the wild using free-ranging great tits. Personality variation was quantified using exploratory behaviour in a novel environment, which has previously been shown to be repeatable and correlated with other behaviours in this and other populations of the same species. By temporarily removing food at feeding stations we examined whether birds with different personality differed in returning to visit empty feeders as this may provide information on how birds continue to sample their environment after a sudden change in conditions. In two summer experiments, we found that fast-exploring juveniles visited empty feeders less often compared to slow-exploring juveniles. In winter, sampling behaviour was sex dependent but not related to personality. In both seasons, we found that birds who sampled empty feeders more often were more likely to rediscover food after we again re-baited the feeding stations, but there was no effect of personality. Our results show that personality types may indeed differ in ways of collecting environmental information, which is consistent with the view of personalities as different styles of coping with environmental changes. The adaptive value of these alternative behavioural tactics, however, needs to be further explored.     

Evolutionary Perspective on the Interplay Between Family Life,and Parent and Offspring Personality

Consistent inter‐individual variation in behaviour over time and across contexts has been reported for a wide variety of animals, a phenomenon commonly referred to as personality. As behavioural patterns develop inside families, rearing conditions could have lasting effects on the expression of adult personality. In species with parental care, conflicts among family members impose selection on parental and offspring behaviour through coadaptation. Here, we argue that the interplay between the evolution of personality traits (i.e. boldness, exploration, activity, aggressiveness and sociability) expressed outside the family context and the specialized behaviours expressed inside families (i.e. offspring begging behaviour and parental response to offspring solicitations) can have important evolutionary consequences. Personality differences between parents may relate to the typically observed variation in the way they respond to offspring demand, and dependent offspring may already express personality differences, which may relate to the way they communicate with their parents and siblings. However, there has been little research on how personality relates to parental and offspring behaviours. Future research should thus focus on how and why personality may be related to the specialized parent and offspring behaviour that evolved as adaptations to family life.     

Does individual personality predict male mating preference for female body size in the Trinidadian guppy?

Within populations, individual animals vary considerably in their behaviour, including mate choice and personality. There is mounting interest in the potential covariation between these two behaviours within individuals, such that personality would influence mate choice. We experimentally tested this proposition under controlled laboratory conditions using male Trinidadian guppies (Poecilia reticulata) as a model study system. We assayed repeatedly the mating preference of individual males for females based on their body size. Additionally, we assayed repeatedly two ecologically relevant personality traits in males, namely exploration of a novel environment and boldness under a simulated predation threat. Finally, we analysed whether male mating preference and personality traits were repeatable, and tested whether the personality of individual males was correlated (covaried) with their mating preference scores. Although all but one of the measures of exploration and boldness behaviour were repeatable over time, male mating preference scores were not repeatable. Measures of male exploration and boldness were not inter-correlated among individuals, suggesting the absence of a behavioural syndrome between exploration and boldness. Unexpectedly, males did not exhibit on average a significant mating preference for larger females over smaller ones; they chose randomly between the paired stimulus females. Overall, we found no compelling evidence for a relationship between individual personality traits and mating preference in male guppies, suggesting that personality does not predict mate choice, at least in our study population and under our experimental conditions. We discuss potential factors, other than male personality and body length, that might maintain inter-individual variation in male mating preferences in the guppy in the wild.     

Long-term repeatability and stability of three personality traits in meadow voles

Consistency of animal personality traits is expected. Mounting evidence suggests that animal personalities will change with time and major life events. Research into this phenomenon is often limited to span only short periods of time in the animals’ life or have few measures across their life. We measured Exploration, Activity and Boldness of litters of meadow voles, Microtus pennsylvanicus, in a pair of novel object tests six times over a year, representing a large proportion of the lifespan of the vole. Our null hypothesis was that the personality traits would not change, and our first alternative hypothesis was that personality traits would change equally for all individuals as they aged. Neither was supported. The data support our third hypothesis that traits would change and change unequally. Activity and Boldness were consistent across time. However, Exploratory behaviour increased with the vole's age. The supported models show that personality traits change consistently for related individuals, but the litters differ in their change with age. This suggests that meadow vole life history affects how personality traits develop, but not necessarily their magnitudes. We also tested the repeatability of traits across the testing intervals. We discovered that the repeatability of these three personality traits varied across time, depending on the trait. Activity was repeatable equally across ages. Exploration became more repeatable and Boldness became less so. Thus, personality traits may be more malleable than supposed, especially over long periods of time.     

Personality over ontogeny in zebra finches: long-term repeatable traits but unstable behavioural syndromes

A crucial assumption of animal personality research is that behaviour is consistent over time, showing a high repeatability within individuals. This assumption is often made, sometimes tested using short time intervals between behavioural tests, but rarely thoroughly investigated across long time intervals crossing different stages of ontogeny. We performed such a longitudinal test across three life stages in zebra finches (Taeniopygia guttata), representing about 15-20% of their life span in captivity, and found repeatabilities ranging from 0.03 to 0.67. Fearlessness and exploration were the most repeatable traits both within and across life stages. Activity and aggression were repeatable across, but not or only partly within life stages. Boldness was not repeatable. Furthermore, we found no evidence for a consistent behavioural syndrome structure across ontogeny. Our results indicate that the consistency of behavioural traits and their correlations might be overestimated and suggest that life-long stability of animal personality should not simply be assumed.     

Animal personality as a cause and consequence of contest behaviour

We review the evidence for a link between consistent among-individual variation in behaviour (animal personality) and the ability to win contests over limited resources. Explorative and bold behaviours often covary with contest behaviour and outcome, although there is evidence that the structure of these ‘behavioural syndromes'' can change across situations. Aggression itself is typically repeatable, but also subject to high within-individual variation as a consequence of plastic responses to previous fight outcomes and opponent traits. Common proximate mechanisms (gene expression, endocrine control and metabolic rates) may underpin variation in both contest behaviour and general personality traits. Given the theoretical links between the evolution of fighting and of personality, we suggest that longitudinal studies of contest behaviour, combining behavioural and physiological data, would be a useful context for the study of animal personalities.     

The contribution of additive genetic variation to personality variation: heritability of personality

Individual animals frequently exhibit repeatable differences from other members of their population, differences now commonly referred to as ‘animal personality’. Personality differences can arise, for example, from differences in permanent environmental effects―including parental and epigenetic contributors―and the effect of additive genetic variation. Although several studies have evaluated the heritability of behaviour, less is known about general patterns of heritability and additive genetic variation in animal personality. As overall variation in behaviour includes both the among-individual differences that reflect different personalities and temporary environmental effects, it is possible for personality to be largely genetically influenced even when heritability of behaviour per se is quite low. The relative contribution of additive genetic variation to personality variation can be estimated whenever both repeatability and heritability are estimated for the same data. Using published estimates to address this issue, we found that approximately 52% of animal personality variation was attributable to additive genetic variation. Thus, while the heritability of behaviour is often moderate or low, the heritability of personality is much higher. Our results therefore (i) demonstrate that genetic differences are likely to be a major contributor to variation in animal personality and (ii) support the phenotypic gambit: that evolutionary inferences drawn from repeatability estimates may often be justified.     

Heritability and social brood effects on personality in juvenile and adult life‐history stages in a wild passerine

How has evolution led to the variation in behavioural phenotypes (personalities) in a population? Knowledge of whether personality is heritable, and to what degree it is influenced by the social environment, is crucial to understanding its evolutionary significance, yet few estimates are available from natural populations. We tracked three behavioural traits during different life‐history stages in a pedigreed population of wild house sparrows. Using a quantitative genetic approach, we demonstrated heritability in adult exploration, and in nestling activity after accounting for fixed effects, but not in adult boldness. We did not detect maternal effects on any traits, but we did detect a social brood effect on nestling activity. Boldness, exploration and nestling activity in this population did not form a behavioural syndrome, suggesting that selection could act independently on these behavioural traits in this species, although we found no consistent support for phenotypic selection on these traits. Our work shows that repeatable behaviours can vary in their heritability and that social context influences personality traits. Future efforts could separate whether personality traits differ in heritability because they have served specific functional roles in the evolution of the phenotype or because our concept of personality and the stability of behaviour needs to be revised.     

Sexual segregation occurs in bats within fragmented remnant woodlands in an agricultural landscape

Species‐specific responses to landscape configuration and landscape composition have been studied extensively. However, little work has been done to compare intraspecific differences in habitat preferences. Bats have potential as good bioindicator taxa in woodland habitats. Therefore, studying sex differences in responses to woodland and the wider landscape can allow us to gain insight into the relative importance of these habitats for both bats and other taxa. In this study, we aimed to test the predictions that (i) habitat type and connectivity will influence the probability of recording female bats in woodlands and (ii) sex differences in response to habitat type and connectivity will be species‐specific. Bat capture data was collected in 206 woodlands over 3 years in England. The probability of detecting females relative to males was modeled in response to a range of woodland characteristics and landscape metrics for six bat species. We recorded sex differences in responses to landscape features in three species. We found a higher probability of capturing female Myotis nattereri in woodlands that were surrounded by a higher proportion of improved grasslands, whereas female Myotis mystacinus were less likely to be recorded in woodlands surrounded by semi‐natural vegetation. Female Plecotus auritus were more likely to be recorded in isolated woodlands with less connectivity to other woodlands and where agriculture dominated the surrounding landscape. Our findings indicate that sexual segregation occurs across several UK bat species in response to landscape connectivity and composition. Sexual segregation in response to landscape characteristics in bats should therefore be an important consideration in the management of fragmented agricultural landscapes.     

Does personality in small rodents vary depending on population density?

Personality means an individual's unique way of behaving and reacting to the environment. It is a stable and heritable trait, which is expressed consistently in different situations. The aim of our study was to develop novel tests to depict the personality structure of the bank vole Myodes glareolus, and to determine if the phase of the population cycle, i.e. population density, affects personality. We focused on some central aspects of bank vole behaviour: mobility, risk taking, exploratory behaviour, dominance, and aggressive behaviour towards pups. These behaviours were chosen because they directly affect bank vole survival or fitness or are classified as important factors of personality in other species. In total, 192 males from different populations went through four behavioural tests, in which 20 variables were measured. The tests were repeated after 3 weeks, which verified that all traits were stable, i.e. repeatable between trials. Three personality compounds emerged, named extroversion, novelty seeking and infanticide. Extroversion included dominance and mobility, while novelty seeking consisted of risk taking and exploration. Infanticide encompassed all indices measuring harmful behaviour towards pups. Mobility and dominance were connected, possibly because both seem to depend on condition. Time spent in captivity increased extroversion, which may be explained by good food, stable conditions and acclimation to strong social cues. Novelty seeking was connected to repeatability which could mean that novelty avoiding individuals adjust their behaviour to match new environments. Population density affected the infanticide trait but not novelty seeking or extroversion.     

Habitat use, movement, and growth of young-of-the-year Fundulus spp. in southern New Jersey salt marshes: Comparisons based on tag/recapture

We examined habitat use, movement, and growth of young-of-the-year (YOY) Fundulus heteroclitus and Fundulus luciae with a tag/recapture experiment in tide-dominated salt marshes to determine if movements from Spartina marsh surface can account for the occurrence of larger, older individuals in other habitats. Evaluation of the tagging techniques in laboratory experiments with YOY F. heteroclitus (15-35 mm TL) found that coded wire tags were retained at least up to 77 days. The high rates of recapture in the field also indicate that the tagging approach generally worked well. Of a total of 5748 YOY F. heteroclitus (14-40 mm TL) and 133 YOY F. luciae (17-40 mm TL) tagged, 56.0% and 74.4% were recaptured, respectively. Most (44%) YOY F. heteroclitus recaptured occurred at or near (0-5 m) the release site, but some were captured up to 299 m away up to 166 days after tagging. By comparison, movement of F. luciae was very limited, with 99% of recaptures occurring at the exact site of release after up to 66 days at liberty. These different movement patterns by YOY Fundulus indicate that species-specific behavior plays an important role in habitat selection. In addition, it appears that dispersal of YOY F. heteroclitus can help to explain the occurrence of larger individuals of this species in Phragmites-dominated marshes even though there is little evidence of use of this habitat by small YOY.     

Alternative antipredator responses of two coexisting Daphnia species to negative size selection by YOY perch

Our study showed for the first time in nature that two coexistingDaphnia adopted alternative life history and behavioural strategiesto cope with negative size-selection predation by gape-limitedyoung-of-the-year (YOY) perch. We evaluated the phenotypic plasticityin life history and behavioural traits of two coexisting Daphniaspecies, D. pulicaria (2 mm) and D. galeata mendotae (1.4 mm),in response to seasonal changes in predation by YOY yellow perch(Perca flavescens) in a mesotrophic lake. We expected that thelarge-sized D. pulicaria, the most likely subjected to size-selectivepredation by YOY perch, will show stronger antipredator responsesthan the small-sized D. galeata mendotae. To test this hypothesis,we examined changes in life history and behavioural traits injuveniles and adults of both species during four YOY fish predationperiods that were selected based on the presence of YOY perchin the pelagic zone and the relative abundance of Daphnia preyin their gut contents. Our study supports the scenario of negativesize-selective predation by gape-limited YOY perch on both Daphniaspecies. The electivity index indicated that no daphnids witha body length > 1.75 mm were predated by YOY yellow perch.Coexisting Daphnia exhibited phenotypic plasticity in theirantipredator defenses based on their vulnerability to seasonalchanges in size-selective predation of YOY perch. Juvenile Daphniawere the targeted prey and they responded by a decreased bodylength. Behavioural defenses were the dominant strategy usedby both adult Daphnia populations to withstand high predation.A decreased size at maturity was not employed by Daphnia, exceptat the very end of the predation period. Behavioural defensesare short-term strategy adopted to avoid predation. Both antipredatordefenses became unnecessary expenses and were no longer sustainedafter the predation period.     

Correlates of dispersal extent predict the degree of population genetic structuring in bats

Dispersal is essential for maintaining demographic and genetic connectivity. For bats, correlates of dispersal extent such as morphology and movement dynamics are reported as having an influence on population genetic structure although these traits exhibit co-variance which has not been previously examined. We used a principal components framework with phylogenetically independent contrasts to compare five dispersal extent predictors (wing loading, aspect ratio, geographic range size, migratory status and median latitude) with population genetic structure among bats. We found that high wing loading values and migration negatively correlate with genetic structure after accounting for co-variance. These findings suggest that bats that can achieve higher flight speeds and migrate seasonally have higher gene flow and resultant genetic connectivity relative to bats that fly slower and do not migrate. These results represent a step towards understanding factors that shaped the genetic structure of bat populations.     

The Association Between Personality Traits,Morphological Traits and Alternative Mating Behaviour in Male Endler's Guppies,Poecilia wingei

Alternative mating behaviour, personality traits and morphological characters are predicted to be correlated. Bolder, larger and more colourful males are expected to preferentially court females, while shy, small and drab‐coloured individuals are predicted to sneak copulations. We used males of Endler's guppy, Poecilia wingei, to test this association over a long temporal period (hence including ontogenetic changes) and under two social environments (male‐biased and female‐biased). We found that personality traits (exploration, boldness, activity) of P. wingei males were highly repeatable across long time spans, but they were not correlated (formed no behavioural syndrome). Male age and social environment had no effect on any personality trait, despite their effects on alternative mating behaviour. Young males with higher activity levels were more likely to attempt sneaking. In older fish, there was an association between orange coloration, courtship and boldness, but this was not observed in young males. Our results suggest that alternative mating behaviour is more flexible than personality traits and is independent of them. Non‐colour‐based morphological traits (gonopodium length, body length, caudal straps length, dorsal fin length) were not correlated with any particular mating behaviour.     

An update on molecular genetic studies of human personality traits

Personality is a complex phenotype and people differ considerably when they are evaluated by self-report questionnaires. There is convincing evidence from twin studies that basic personality dimensions in men and women have a considerable genetic component. However, only recently have common genetic polymorphisms been associated with particular personality traits, especially the dopamine D4 receptor with novelty seeking and the serotonin transporter with anxiety-related traits or neuroticism. The current review examines progress in the past few years in molecular personality genetics and focuses on the reasons for difficulties in replicating first findings as well as the prospects for future studies in this area. The molecular genetic structure of human personality is worth studying both for its intrinsic interest in helping us to understand individual differences in human behaviour and the light it will shed on more complex behavioural disorders that are likely to partially share some common genetic variants.     

Effects of personality on territory defence in communication networks: a playback experiment with radio-tagged great tits

Individuals often differ consistently in behaviour across time and contexts, and such consistent behavioural differences are commonly described as personality. Personality can play a central role in social behaviour both in dyadic interactions and in social networks. We investigated whether explorative behaviour, as proxy of personality of territorial male great tits (Parus major), predicts their own and their neighbours'' territorial responses towards simulated intruders. Several weeks prior to playback, subjects were taken from the wild to test their exploratory behaviour in a standard context in the laboratory. Exploratory behaviour provides a proxy of personality along a slow–fast explorer continuum. Upon release, males were radio-tracked and subsequently exposed to interactive playback simulating a more or a less aggressive territorial intruder (by either overlapping or alternating broadcast songs with the subjects'' songs). At the same time, we radio-tracked a neighbour of the playback subject. Male vocal responses during playback and spatial movements after playback varied according to male explorative behaviour and playback treatment. Males with lower exploration scores approached the loudspeaker less, and sang more songs, shorter songs and songs with slower element rates than did males with higher exploration scores. Moreover, neighbour responses were related to the explorative behaviour of the subject receiving the playback but not to their own explorative behaviour. Our overall findings reveal for the first time how personality traits affect resource defence within a communication network providing new insights on the cause of variation in resource defence behaviour.