Abstract: Two recent meta-analyses have suggested that boldness, as assessed by the Psychopathic Personality Inventory (PPI) Fearless Dominance dimension, is largely unrelated to total or factor scores on the Psychopathy Checklist-Revised (PCL-R), raising questions concerning the relevance of largely adaptive features to psychopathy. Nevertheless, given that the PCL was developed and validated among prisoners, it may place less emphasis than do other psychopathy measures on adaptive traits, such as fearlessness, social poise, and emotional resilience. We conducted a meta-analysis (N = 10,693) of the relations between (a) boldness, as assessed by the PPI and its derivatives or measures of the triarchic model of psychopathy, and (b) non-PCL-based psychopathy measures across 32 samples. The average weighted correlation between boldness and psychopathy was medium to large (r = .39) and considerably higher than reported in prior meta-analyses; when analyses were restricted to well-validated psychopathy measures, the correlation rose to r = .44. We did not find support for the position that boldness is significantly less related to psychopathy than are the other 2 dimensions of the triarchic model. Our findings strongly suggest that boldness is relevant to at least some well-validated measures of psychopathy, and raise further questions regarding the boundaries of this condition. (PsycINFO Database Record

Abstract: Whether individual behavior in social settings correlates with behavior when individuals are alone is a fundamental question in collective behavior. However, evidence for whether behavior correlates across asocial and social settings is mixed, and no study has linked observed trends with underlying mechanisms. Consistent differences between individuals in boldness, which describes willingness to accept reward over risk, are likely to be under strong selection pressure. By testing three-spined sticklebacks (Gasterosteus aculeatus) in a risky foraging task alone and repeatedly in shoals, we demonstrate that the expression of boldness in groups is context-specific. Whereas personality is repeatable in a low-risk behavior (leaving a refuge), the collectively made consensus decision to then cross the arena outweighs leadership by bolder individuals, explaining the suppression of personality in this context. However, despite this social coordination, bolder individuals were still more likely to feed. Habituation and satiation over repeated trials degrade the effect of personality on leaving the refuge and also whether crossing the arena is a collective decision. The suppression of personality in groups suggests that individual risk-taking tendency may rarely represent actual risk in social settings, with implications for the evolution and ecology of personality variation.

Abstract: Translocation is an important conservation management tool. However, not all individuals are equally suited to translocation, and temperament traits (e.g., boldness, reactivity, exploration, sociability, and aggression) are likely to influence survival in a new environment. A few empirical studies have examined the consequences of personality differences on captive-bred translocated animals, but this has not been done for wild-caught animals. We compared behavioral responses to trapping, processing, holding, and release for 56 wild common brushtail possums (Trichosurus vulpecula). Twenty individuals were captured twice, once to attach radio-tracking collars, the second time (2 weeks later) for the translocation. Consistency of behavioral responses was compared between capture events and radio-tracking allowed estimates of pretranslocation home range, rest site selection, and foraging behavior. Survivors (n = 10 survivors, 5 months later) were individuals showing the most fear or emotional reactivity during holding (less likely to have slept, eaten, defecated, or nested) and those that had the smallest home ranges and selected the safest den sites in their original habitat. Conversely, the greatest increase in body mass was recorded for individuals that had demonstrated "unsafe" behavior in their original habitat. To our knowledge, this is the first time this type of behavioral screening during handling and holding prior to release as part of a translocation has been undertaken. These methods have broad applicability for screening potential translocation candidates and are easily translated to a range of threatened and vulnerable animal species.

Abstract: Despite the importance of host attributes for the likelihood of associated microbial transmission, individual variation is seldom considered in studies of wildlife disease. Here, we test the influence of host phenotypes on social network structure and the likelihood of cuticular bacterial transmission from exposed individuals to susceptible group-mates using female social spiders ( Stegodyphus dumicola ). Based on the interactions of resting individuals of known behavioural types, we assessed whether individuals assorted according to their behavioural traits. We found that individuals preferentially interacted with individuals of unlike behavioural phenotypes. We next applied a green fluorescent protein-transformed cuticular bacterium, Pantoea sp., to individuals and allowed them to interact with an unexposed colony-mate for 24 h. We found evidence for transmission of bacteria in 55% of cases. The likelihood of transmission was influenced jointly by the behavioural phenotypes of both the exposed and susceptible individuals: transmission was more likely when exposed spiders exhibited higher ‘boldness’ relative to their colony-mate, and when unexposed individuals were in better body condition. Indirect transmission via shared silk took place in only 15% of cases. Thus, bodily contact appears key to transmission in this system. These data represent a fundamental step towards understanding how individual traits influence larger-scale social and epidemiological dynamics.

Abstract: Animal personalities, i.e. consistent individual differences in behaviour, are currently of high interest among behavioural and evolutionary biologists. The topic has received increasing attention also in fisheries science because selective harvesting of certain behavioural types might impose fishing-induced selection on personality. Here, we ice-fished wild Eurasian perch (Perca fluviatilis) from three native populations and investigated whether differences in relative catchability would explain behavioural differences observed in experimental conditions. We inferred relative catchability differences indirectly by fishing each location first with generally inefficient artificial bait and then by more efficient natural bait. The captured, individually tagged fish were tested in groups for their exploration tendency, activity and boldness under authentic predation risk in semi-natural stream channels. Fish that were easily captured first with artificial bait expressed fast exploration and acute activity, whereas the fish captured with natural bait showed less active and explorative behaviour. Differences in relative catchability did not explain variation in boldness or body size. In conclusion, we found that (1) Eurasian perch differing in relative catchability differ in certain behavioural traits, (2) fast explorers are more common among fish that get easily caught compared to fish that are more difficult to catch, (3) relative catchability explains more behavioural variation in a novel environment than in a familiar one and (4) selectivity of recreational angling on fish behaviour may depend on applied angling method and the effort spent on each location.

Abstract: The present study examined the effects of the selective serotonin reuptake inhibitor, fluoxetine, on the behavior of female Siamese fighting fish, Betta splendens, in three different boldness assays (Empty Tank, Novel Environment, Social Tendency). When females were unexposed to fluoxetine, boldness was consistent within a context and correlated across assays. Fluoxetine exposure affected behavior within and among individuals on multiple levels. Exposure reduced overall boldness levels, made females behave in a less consistent manner, and significantly reduced correlations over time and across contexts. Fluoxetine exerted its effects on female Betta splendens behavior in a dose-dependent fashion and these effects persisted even after females were housed in clean water. If fluoxetine exposure impacts behaviors such as exploration that are necessary to an individual’s success, this may yield evolutionary consequences. In conclusion, the results show that fluoxetine exposure alters behavior beyond the level of overall response and highlights the importance of studying the behavioral effects of inadvertent pharmaceutical exposure in multiple contexts and with different dosing regimes.

Abstract: This study examined interindividual personality differences between Port Jackson sharks Heterodontus portusjacksoni utilizing a standard boldness assay. Additionally, the correlation between differences in individual boldness and stress reactivity was examined, exploring indications of individual coping styles. Heterodontus portusjacksoni demonstrated highly repeatable individual differences in boldness and stress reactivity. Individual boldness scores were highly repeatable across four trials such that individuals that were the fastest to emerge in the first trial were also the fastest to emerge in subsequent trials. Additionally, individuals that were the most reactive to a handling stressor in the first trial were also the most reactive in a second trial. The strong link between boldness and stress response commonly found in teleosts was also evident in this study, providing evidence of proactive-reactive coping styles in H. portusjacksoni. These results demonstrate the presence of individual personality differences in sharks for the first time. Understanding how personality influences variation in elasmobranch behaviour such as prey choice, habitat use and activity levels is critical to better managing these top predators which play important ecological roles in marine ecosystems.

Abstract: Geffroy et al. [1] proposed that nature-based tourism reduces the fearfulness and antipredator behavior of animals, leading towards a boldness syndrome that elevates natural predation rates and could trigger cascading effects on populations and communities. We agree with the framework, hypotheses, and future research needs proposed in [1], but they apply strictly to nonthreatening human–wildlife interactions. However, nature-based tourism is often consumptive, where wild-living animals are chased, stressed, and eventually harvested in activities such as recreational fishing and hunting.

Abstract: Researchers are vigorously debating whether psychopathic personality includes seemingly adaptive traits, especially social and physical boldness. In a large sample (N = 1,565) of adult offenders, we examined the incremental validity of 2 operationalizations of boldness (Fearless Dominance traits in the Psychopathy Personality Inventory [Lilienfeld & Andrews, 1996]; Boldness traits in the triarchic model of psychopathy [Patrick, Fowles, & Krueger, 2009]), above and beyond other characteristics of psychopathy, in statistically predicting scores on 4 psychopathy-related measures, including the Psychopathy Checklist-Revised (PCL-R). The incremental validity added by boldness traits in predicting the PCL-R's representation of psychopathy was especially pronounced for interpersonal traits (e.g., superficial charm, deceitfulness). Our analyses, however, revealed unexpected sex differences in the relevance of these traits to psychopathy, with boldness traits exhibiting reduced importance for psychopathy in women. We discuss the implications of these findings for measurement models of psychopathy. (PsycINFO Database Record

Abstract: Population density is an important social environmental factor influencing various life history traits of individuals in many species. In how far density also affects behavioral traits, and particularly at which life stage during ontogeny the adult behavioral phenotype is shaped, has been rarely examined, especially in holometabolous insects. We tested the effects of larval versus adult density on development, reproductive success, and the adult behavioral phenotype of a non-social beetle, Phaedon cochleariae. Therefore, we reared individuals either constantly isolated, in groups, or switched them to the other rearing density condition after metamorphosis. We expected beneficial consequences on the growth and reproduction of isolated individuals because these individuals did not have to compete for food and resting sites. The development time was significantly influenced by the larval density with isolated larvae developing faster than group-reared individuals. Furthermore, the reproductive success was higher for individuals kept isolated as larvae, regardless of the adult density, pointing to a silver spoon effect (i.e., persisting fitness advantage based on favorable, less competitive early conditions). Three behavioral dimensions were found in adult beetles, boldness, activity, and exploration. Adult boldness behavior and activity were influenced by either larval or adult density conditions in dependence of the context and/or sex. Thus, the present study highlights the major influence of the experienced larval density on adult reproductive success and demonstrates the high complexity in which the behavioral phenotype of a holometabolous insect is shaped by a social environmental factor. We investigated the effects of keeping larvae and/or adults either isolated or in a group on the adult reproduction and behavior of a leaf beetle. This study was performed to understand which life stage has a stronger impact on the adult phenotype in an organism that undergoes a metamorphosis. We found that the larval stage was most decisive for the adult reproductive success, with isolated larvae laying more eggs as adults than individuals kept in groups. Furthermore, adult boldness and activity behavior were shaped by larval and adult density conditions differently between females and males. These results demonstrate that both larval and adult experience can be involved in shaping the adult behavioral phenotype of a holometabolous insect.

Abstract: Consistent individual differences (CIDs) in behavior are of interest to both basic and applied research, because any selection acting on them could induce evolution of animal behavior. It has been suggested that CIDs in the behavior of fish might explain individual differences in vulnerability to fishing. If so, fishing could impose selection on fish behavior. In this study, we assessed boldness-indicating behaviors of Eurasian perch Perca fluviatilis using individually conducted experiments measuring the time taken to explore a novel arena containing predator (burbot, Lota lota) cues. We studied if individual differences in boldness would explain vulnerability of individually tagged perch to experimental angling in outdoor ponds, or if fishing would impose selection on boldness-indicating behavior. Perch expressed repeatable individual differences in boldness-indicating behavior but the individual boldness-score (the first principal component) obtained using principal component analysis combining all the measured behavioral responses did not explain vulnerability to experimental angling. Instead, large body size appeared as the only statistically significant predictor of capture probability. Our results suggest that angling is selective for large size, but not always selective for high boldness.

Abstract: One commonly studied behavioral syndrome is the correlation between aggression and boldness. Studies in song sparrows (M. melodia) have found greater aggression and boldness in urban populations and a correlation between aggression and boldness in rural populations, but not within urban populations. In previous studies, boldness was measured as flight initiation distance (FID), which may reflect habituation by urban birds to human presence. In this study, we measured boldness using playbacks of heterospecific alarm calls and investigated whether higher boldness is a general trait of urban birds and whether the same pattern of correlations between aggression and boldness would be seen. We conducted trials involving FID, alarm call playbacks and conspecific song playbacks on 25 birds from both an urban and a rural site. The results showed that urban birds were bolder, as measured by FID and response to alarm calls. Boldness and aggression were correlated in rural birds with each method of measuring boldness but were correlated in urban birds only when using alarm call playbacks. Our results suggest that a behavioral syndrome exists in both urban and rural populations but that urban birds are able to decrease their response to human disturbance.

Abstract: Research on psychopathic personality has been dominated by a focus on criminality and social deviance, but some theoretical models argue that certain putatively adaptive features are important components of this construct. In 3 samples (forensic mental health practitioners, probation officers and a layperson community sample), we investigated adaptive traits as conceptualized in the Triarchic model of psychopathy (Patrick et al., 2009), specifically the relevance of boldness to construals of psychopathic personality. Participants completed prototypicality ratings of psychopathic traits, including 3 items created to tap components of boldness (Socially bold, Adventurous, Emotionally stable), and they also rated a series of attitudinal statements (e.g., perceived correlates of being psychopathic, moral judgments about psychopaths). The composite Boldness scale was rated as moderately to highly prototypical among forensic mental health practitioners and probation officers and positively associated with other theoretically relevant domains of psychopathy. Across samples, higher composite Boldness ratings predicted greater endorsement of adaptive traits (e.g., social skills) as characteristic of psychopathy. For the individual items, Socially bold was rated as highly prototypical and was associated with theoretically relevant correlates. Adventurous also was seen as prototypical, though to a lesser degree. Only forensic mental health practitioners endorsed Emotionally stable as characteristic of psychopathy. Our results provide partial support for the contention that the boldness concept is viewed as an important component of psychopathy, particularly among professionals who work directly with offender populations. (PsycINFO Database Record

Abstract: To investigate the link between personality and maximum food intake of inactive individuals, food-deprived three-spined sticklebacks Gasterosteus aculeatus at rest in their home compartments were provided with ad libitum prey items. Bolder individuals ate considerably more than shyer individuals, even after accounting for body size, while sociability did not have an effect. These findings support pace-of-life theory predicting that life-history strategies are linked to boldness.

Abstract: Variation in state, which is any factor that alters the value of decision options, is likely one of the most common drivers of personality differences. However, the general relationship between individuals’ body state and various personality metrics/average behavioral type, repeatability of behavior, and behavioral syndrome structure is still poorly resolved. Here, we manipulate body condition in three spider species (Agelenopsis aperta, Latrodectus hesperus, and Anelosimus studiosus) using contrasting feeding schedules. We then assessed the effects of historic feeding regime on individuals’ body condition, boldness, and foraging aggressiveness. We further assessed the effects of feeding regimes on the repeatability of boldness and aggressiveness and the presence/absence of correlations between these two traits. We found that feeding treatment impacted individuals’ average boldness and aggressiveness in two species (A. aperta and A. studiosus). We also noted that among-individual variance in both boldness and aggressiveness was severely reduced when A. aperta and A. studiosus were subjected to prolonged food restriction, steeply reducing repeatability in these traits. Finally, we noted that correlations between boldness and foraging aggressiveness were detectable only in one case, revealing no compelling relationship between food restriction and the presence/absence of behavioral correlations. Taken together, our results suggest that food restriction has only weak, circumstantial effects on individuals’ average personality type and the correlations between behavioral traits. However, there appears to be a robust positive relationship between food availability and the signature of consistent individual differences in behavior. Under laboratory conditions, we found that lower feeding rates sharply decreased the repeatability of aggressiveness and boldness in two spider species. In doing so, we provide the second body of evidence suggesting that a highly prevalent and ecologically relevant state variable, higher body condition, can increase the repeatability of foraging-related behavioral traits. Additionally, under some feeding regimes, we found that hunger levels could alter the average individual aggressiveness and boldness but not correlations between these traits. This work highlights the importance of state variables such as hunger in eroding behavioral repeatability, the defining trait of personality.

Abstract: One aspect of premating isolation between diverging, locally-adapted population pairs is female mate choice for resident over alien male phenotypes. Mating preferences often show considerable individual variation, and whether or not certain individuals are more likely to contribute to population interbreeding remains to be studied. In the Poecilia mexicana-species complex different ecotypes have adapted to hydrogen sulfide (H2S)-toxic springs, and females from adjacent non-sulfidic habitats prefer resident over sulfide-adapted males. We asked if consistent individual differences in behavioral tendencies (animal personality) predict the strength and direction of the mate choice component of premating isolation in this system. We characterized focal females for their personality and found behavioral measures of ‘novel object exploration’, ‘boldness’ and ‘activity in an unknown area’ to be highly repeatable. Furthermore, the interaction term between our measures of exploration and boldness affected focal females’ strength of preference (SOP) for the resident male phenotype in dichotomous association preference tests. High exploration tendencies were coupled with stronger SOPs for resident over alien mating partners in bold, but not shy, females. Shy and/or little explorative females had an increased likelihood of preferring the non-resident phenotype and thus, are more likely to contribute to rare population hybridization. When we offered large vs. small conspecific stimulus males instead, less explorative females showed stronger preferences for large male body size. However, this effect disappeared when the size difference between the stimulus males was small. Our results suggest that personality affects female mate choice in a very nuanced fashion. Hence, population differences in the distribution of personality types could be facilitating or impeding reproductive isolation between diverging populations depending on the study system and the male trait(s) upon which females base their mating decisions, respectively.

Abstract: In animal societies, individuals’ behavioral idiosyncrasies often guide which tasks they perform. Such personality-specific task participation can increase individual task efficiency, thereby improving group performance. While several recent studies have documented group-level benefits of within-group behavioural (i.e., personality) diversity, how these benefits are realized at the individual level is unclear. Here we probe the individual-level benefits of personality-driven task participation in the social spider Stegodyphus dumicola . In S. dumicola the presence of at least one highly bold individual catalyzes foraging behaviour in shy colony members, and all group constituents heavily compete for prey. We assessed boldness by examining how quickly spiders resumed normal movement after a simulated predator attack. We test here whether 1) participants in collective foraging gain more mass from prey items and 2) whether bold individuals are less resistant to starvation than shy spiders, which would motivate the bold individuals to forage more. Next, we assembled colonies of shy spiders with and without a bold individual, added one prey item, and then tracked the mass gain of each individual spider after this single feeding event. We found that spiders that participated in prey capture (whether bold or shy) gained more mass than non-participators, and colonies containing a single bold spider gained more total mass than purely shy colonies. We also found that bold spiders participated in more collective foraging events and were more susceptible to starvation than shy spiders, suggesting that the aggressive foraging of bold individuals may represent a strategy to offset starvation risk. These findings add to the body of evidence that animal personality can shape social organization, individual performance, and group success.

Abstract: The expression of animal personality is indicated by patterns of consistency in individual behaviour. Often, the differences exhibited between individuals are consistent across situations. However, between some situations, this can be biased by variable levels of individual plasticity. The interaction between individual plasticity and animal personality can be illustrated by examining situation-sensitive personality traits such as boldness (i.e. risk-taking and exploration tendency). For the weakly electric fish Gnathonemus petersii, light condition is a major factor influencing behaviour. Adapted to navigate in low-light conditions, this species chooses to be more active in dark environments where risk from visual predators is lower. However, G. petersii also exhibit individual differences in their degree of behavioural change from light to dark. The present study, therefore, aims to examine if an increase of motivation to explore in the safety of the dark, not only affects mean levels of boldness, but also the variation between individuals, as a result of differences in individual plasticity. Boldness was consistent between a novel-object and a novel-environment situation in bright light. However, no consistency in boldness was noted between a bright (risky) and a dark (safe) novel environment. Furthermore, there was a negative association between boldness and the degree of change across novel environments, with shier individuals exhibiting greater behavioural plasticity. This study highlights that individual plasticity can vary with personality. In addition, the effect of light suggests that variation in boldness is situation specific. Finally, there appears to be a trade-off between personality and individual plasticity with shy but plastic individuals minimizing costs when perceiving risk and bold but stable individuals consistently maximizing rewards, which can be maladaptive.

Abstract: Consistent individual differences in personality traits should be favoured when those traits contribute to consistent individual fitness differences. However, how variations in behaviours are related to productivity remains scarcely explored in social species, particularly in insects. Here, we investigated whether exploratory, boldness, and brood rescue behaviours expressed at the colony-level are associated with group productivity that is, colony growth, queen and worker production, and larvae survival in the gypsy ant Aphaenogaster senilis. We found that group-level exploratory activity, boldness, and brood rescue efficiency were highly correlated. Furthermore, both exploratory activity and brood rescue efficiency were significantly consistent across 11 weeks. Finally, differences in brood rescue efficiency correlated positively with colony growth, queen and worker production, and larvae survival. These results show that colony-level personality may be linked with differences in colony life-history strategy, which may promote the emergence and maintenance of personality traits in group-living species. When groups of individuals show variation in a series of behaviours that are related to exploratory activity and parental care, is it related to differences in groups’ productivity? This is a key question to understand the process underlying the evolution and maintenance of consistent behavioural differences in a population. Here, we investigated whether exploratory, boldness, and brood rescue behaviours expressed at the colony-level are associated with group productivity that is, colony growth, queen and worker production, and larvae survival in the gypsy ant Aphaenogaster senilis. Overall, this experiment reveals that behaviours in group-living species are linked with group productivity.

Abstract: Social dynamics in territorial species often reflect underlying variation in aggression and other aspects of social dominance among individuals. In ornate tree lizards (Urosaurus ornatus), males differing in dewlap color differ in social dominance: while blue males are the dominant, aggressive morph and always territorial, yellow males tend to exhibit a less-aggressive satellite behavioral tactic. However, in habitats with fewer available territorial resources, yellow males defend territories and increase in relative abundance. These observations suggest that consideration of social dominance alone may be insufficient to explain U. ornatus' territorial dynamics in the wild. Here, we tested how both dominance and another important behavioral trait, boldness, contribute to the outcome of territorial disputes in tree lizards. We recorded the territorial behavior of blue and yellow male tree lizards (entered in pairs) in an experimental arena. At the end of each trial, we then approached each male and recorded whether it fled (shy) or not (bold) in response to our approach. As expected, dominant blue males exploited the higher quality perch more often than yellow males. However, when approached by a simulated predator, blue males were more likely to flee than yellow males. Thus, while blue males are more dominant, yellow is likely the bolder morph. As a result, this morph may be better equipped to defend territories in riskier environments. We conclude that although dominance asymmetries may predictably drive initial territorial interactions among competing males, variation in other behaviors (like boldness) may perturb the long-term outcome of these interactions across variable environments.

Abstract: Among-individual differences in behavior are now a widely studied research-focus within the field of behavioral ecology. Furthermore, elements of an animal's internal state, such as energy or fat reserves, and infection status can have large impacts on behaviors. Despite this, we still know little regarding how state may affect behavioral variation. Recent exposure to pathogens may have a particularly large impact on behavioral expression given that it likely activates costly immune pathways, potentially forcing organism to make behavioral tradeoffs. In this study we investigate how recent exposure to a common bacterial pathogen, Serratia marcescens, affects both the mean behavioral expression and the among-individual differences (i.e. variation) in boldness behavior in the field cricket, Gryllus integer. We find that recent pathogen exposure does not affect mean behavioral expression of the treatment groups, but instead affects behavioral variation and repeatability. Specifically, bacterial exposure drove large among-individual variation, resulting in high levels of repeatability in some aspects of boldness (willingness to emerge into a novel environment), but not others (latency to become active in novel environment), compared to non-infected crickets. Interestingly, sham injection resulted in a universal lack of among-individual differences. Our results highlight the sensitivity of among-individual variance and repeatability estimates to ecological and environmental factors that individuals face throughout their lives.