Understanding when and how nonhuman primates respond to inequity is essential for uncovering the evolutionary roots of human fairness. Previous studies have shown that some species will refuse to participate or refuse rewards in some contexts when outcomes are unequal, but in these studies, subjects experienced inequity on every trial. This is likely not a realistic reflection of daily life, and we do not know whether these responses persist when inequity is experienced inconsistently. We tested four primates'-chimpanzees, capuchins, squirrel monkeys, and owl monkeys-responses in conditions in which inequity occurred in either 25% or 50% of trials. None exhibited increased refusal rates in response to inequity or contrast relative to controls, despite the fact that in prior studies with inequity on every trial, these capuchin monkeys and chimpanzees responded to inequity and these squirrel monkeys showed contrast effects. Their lack of response suggests that while primates will refuse to participate due to inequity in some cases, such inequity must be experienced relatively frequently or consistently to trigger refusals to participate. Future work should explore the thresholds at which inequity prompts these refusals and develop other paradigms to test if they notice and/or respond in other ways to inequity, particularly at lower thresholds.

OBJECTIVE:The anti-GnRH immunotherapeutic product Improvest was administered to intact male large flying foxes (Pteropus vampyrus) under managed care for androgen mitigation, leading to a decrease in agonistic behaviors, falls, and injuries from conspecific attention.ANIMALS:12 males were included in this study.PROCEDURES:Eleven bats received subcutaneous (SC) Improvest interscapular, and 1 animal received Improvest SC in its leg. Assessments included clinical presentation, treatment, behavior, and urine and fecal glucocorticoid metabolites and testosterone (T5) concentrations.RESULTS:Eleven of the 12 bats developed reactions, which included facial edema, localized irritation, swelling of the head and neck, and pruritus with varying degrees of skin ulceration and subsequent necrosis. Three of the animals required extensive treatments, and the 1 animal who received the injection in its leg was unaffected. Posttreatment, fecal glucocorticoid metabolite and/or T5 values were at or below the nonbreeding season baseline for 3 successive breeding seasons, and there was a reduction in agonistic interactions, falls, and injuries.CLINICAL RELEVANCE:A behavioral characteristic of this species is to focus on areas of irritation that exacerbated the extent of the skin wounds. Some cases required medical, surgical, and behavioral intervention. Large flying foxes may be particularly sensitive to this immunotherapeutic when given subcutaneously in the interscapular region. Despite this reaction, the positive long-term effects on behavior and multiyear reduction of hormones suggest that the use of this immunotherapeutic warrants further investigation, although the results should be taken into consideration with other factors such as handling, treatments, chronicity of lesions.

Visitor presence has been shown to affect the behavior of animals in zoos. However, studies to date have not included a wide range of taxonomic groupings, and thus, the effect is poorly understood for many species. Here, we compared the behavior of Nile crocodiles (Crocodylus niloticus) in the presence and absence of visitors for the first time. Data were collected at Disney’s Animal Kingdom® over two months during normal operating conditions and during the same two months the following year when the park was closed due to the COVID-19 pandemic, totaling 158 observation hours. Significant differences in crocodile behavior were observed between park operating conditions; however, the direction of change varied by behavior and average differences were generally small. In addition, we found that time of day, temperature and month significantly affected behavior, often with greater magnitude than visitor presence. This highlights the importance of accounting for environmental variables when evaluating and interpreting the behavior, and ultimately welfare, of reptiles in zoos. Collectively, the data suggest the overall effect of visitors on crocodile behavior was small and neutral from a welfare perspective. This study highlights the importance of taxonomic diversity in studying the visitor effect.

Links between the human facial width-to-height ratio (fWHR) and aggressive behaviours have been debated in recent years. The question of whether fWHR is a cue to dominance could benefit from the study of primate species that are closely related to humans. We therefore built on the broad literature in humans, and recent research in capuchins, macaques and bonobos, and examined associations between fWHR in 131 captive chimpanzees from the United States, United Kingdom and Japan, and measures of age, sex, subspecies (Pan troglodytes verus, P. t. schweinfurthii, P. t. troglodytes), and six personality components (Dominance, Extraversion, Conscientiousness, Agreeableness, Neuroticism, and Openness). We found no evidence for sexual dimorphism in fWHR, as has been found in humans. We did find a positive relationship between fWHR and Dominance in P. t. verus, but only in adult females. This finding contrasts with that in humans, where dominant males have wider faces. We discuss these results in light of male-female differences in temporal rank stability, and in contrast to findings for bonobos, providing a useful perspective for fWHR research in humans.

Personality factors analogous to the Big Five observed in humans are present in the great apes. However, few studies have examined the long-term stability of great ape personality, particularly using factor-based personality instruments. Here, we assessed overall group, and individual-level, stability of chimpanzee personality by collecting ratings for chimpanzees (N = 50) and comparing them with ratings collected approximately 10 years previously, using the same personality scale. The overall mean scores of three of the six factors differed across the two time points. Sex differences in personality were also observed, with overall sex differences found for three traits, and males and females showing different trajectories for two further traits over the 10 year period. Regardless of sex, rank-order stability analysis revealed strong stability for dominance; individuals who were dominant at the first time point were also dominant 10 years later. The other personality factors exhibited poor to moderate rank-order stability, indicating that individuals were variable in their rank-position consistency over time. As many studies assessing chimpanzee cognition rely on personality data collected several years prior to testing, these data highlight the importance of collecting current personality data when correlating them with cognitive performance.

Serotonin is a neurotransmitter that plays an important role in regulating behavior and personality in humans and other mammals. Polymorphisms in genes coding for the serotonin receptor subtype 1A (HTR1A), the serotonin transporter (SLC6A4), and the serotonin degrading enzyme monoamine oxidase A (MAOA) are associated with anxiety, impulsivity, and neurotic personality in humans. In primates, previous research has largely focused on SLC6A4 and MAOA, with few studies investigating the role of HTR1A polymorphic variation on behavior. Here, we examined variation in the coding region of HTR1A across apes, and genotyped polymorphic coding variation in a sample of 214 chimpanzees with matched measures of personality and behavior. We found evidence for positive selection at three amino acid substitution sites, one in chimpanzees-bonobos (Thr26Ser), one in humans (Phe33Val), and one in orangutans (Ala274Gly). Investigation of the HTR1A coding region in chimpanzees revealed a polymorphic site, where a C/A single nucleotide polymorphism changes a proline to a glutamine in the amino acid sequence (Pro248Gln). The substitution is located in the third intracellular loop of the receptor, a region important for serotonin signal transduction. The derived variant is the major allele in this population (frequency 0.67), and is associated with a reduction in anxiety, decreased rates of male agonistic behavior, and an increase in socio-positive behavior. These results are the first evidence that the HTR1A gene may be involved in regulating social behavior in chimpanzees and encourage further systematic investigation of polymorphic variation in other primate populations with corresponding data on behavior.

Large flying foxes (Pteropus vampyrus) are a socially complex species. In situ colonies typically comprise thousands of individuals in small harems of one male to many females. In ex situ environments, all-male colonies are becoming more common due to a surplus of males in the population. There is limited information describing the hormonal and behavioral patterns of all-male colonies during the breeding season. We assessed seasonal changes in hormones and behavior in an all-male colony of 12 large flying foxes at Disney's Animal Kingdom((R)). We validated hormone assays using morning urine and fecal samples to assess seasonal changes in excreted immunoreactive testosterone and glucocorticoid metabolites. We collected behavior data using an all-occurrence method, recording agonistic behaviors related to territorial defense (hooking, biting, wing flexing, vocalizing, and wrestling), and sexual behavior (mounting and frontal grabbing). Results indicated that (i) we could reliably measure testosterone and glucocorticoid metabolites concentrations from fecal and urine samples collected from individual bats; (ii) there were distinct relationships between changes in levels of agonism and hormone concentrations throughout the year; and (iii) three agonistic behaviors (chasing, wrestling, and open-mouth threat) peaked prior to the increase in testosterone and glucocorticoid hormones measured during the breeding season. These three behaviors could potentially be used as early indicators to signal the onset of the breeding season and allow time to implement ex situ management changes to reduce the incidence of agonism between individuals.

Experiences during early development are influential on the lives of human and non-human primates into adulthood. The population of captive chimpanzees in the USA can provide insight into this relationship, as collectively they have experienced a wide range of exposure to both conspecifics (those raised in natal groups) and humans (those raised as personal pets or performers). Our study investigated chimpanzee exposure to humans using a continuous measure of categorization, the chimpanzee–human interaction index, and the relationship between this experience and cortisol concentrations in adulthood. Historical records and hair samples were collected from 60 chimpanzees which were socially housed in 13 zoos and sanctuaries. We found that more human exposure throughout the life of a chimpanzee was associated with higher hair cortisol concentrations in adulthood. Sex was also a significant factor affecting cortisol concentration, with male chimpanzees having higher cortisol concentrations than female chimpanzees. These results build upon the extensive literature about aversive effects of atypical social histories for chimpanzees and emphasize to managers the importance of monitoring potential negative health consequences and social deficits these individuals may exhibit.

The current study undertook analyses of genealogical data from a sample of 178 socially-housed chimpanzees (Pan troglodytes) with well-documented pedigrees, to clarify the etiologic bases of triarchic psychopathy dimensions and the influence of early social rearing experiences. Whereas biometric analyses for the full sample indicated significant heritability for the boldness dimension of psychopathy only, heritability estimates varied by early rearing, with all three triarchic dimensions showing significant heritabilities among mother-reared but not nursery-reared apes. For mother-reared apes, both genes and environment contributed to covariance between meanness and disinhibition, whereas environment contributed mainly to covariation between these dimensions and boldness. Results indicate contributions of both genes and environment to psychopathic tendencies, with an important role for early-rearing in their relative contributions to distinct phenotypic subdimensions. In conjunction with findings from human studies, results provide valuable insights into core biobehavioral processes relevant to psychological illness and health.

There is evidence that plumage coloration is related to mate choice in several different bird species. However, the relationship between plumage coloration to mate or other social partner choice has rarely been investigated in flamingos. This is important to study because we know plumage coloration can be an indicator of welfare. We assessed plumage color score in relation to sex, age, and social partner choice over a 9-month period in a flock of 34 adult greater flamingos (Phoenicopterus roseus) living at Disney's Animal Kingdom® . When looking at primary social partners, redder males were more likely to have primary social partners compared to less red males. In addition, primary social partners tended to have similar color scores to each other. These findings provide insight into one factor that might influence social partner choice in greater flamingos living in ex situ situations. Future studies should investigate how these results relate to reproductive success as part of ex situ management. Zoo Biol. 35:409-414, 2016. © 2016 Wiley Periodicals, Inc.

ABSTRACTAlthough much research has been conducted to understand personality development in humans, there remain substantial gaps in our understanding of these processes, particularly in relation to social influences. As such, investigations into personality development in our closest living relative, the chimpanzee, may provide useful insight. We evaluated the impact of early social exposure (to both humans and conspecifics) on personality development by studying 88 chimpanzees, including former pets and entertainers, living in accredited zoos and sanctuaries. During infancy, subjects varied in the amount of time spent with conspecifics compared with humans. Caregivers familiar with the chimpanzees rated them using a modified version of the Hominoid Personality Questionnaire (HPQ) and the ratings were found to have strong inter‐rater reliability. We used the published structure of the HPQ to evaluate our results in relation to differences in early life experience. Chimpanzees who as infants spent less time with conspecifics were rated as lower in Extraversion later in life in comparison with chimpanzees who as infants spent more time with conspecifics. These results suggest that a broad range of social influences should be considered when evaluating the impact of early social environment on later personality expression. © 2016 Wiley Periodicals, Inc. Dev Psychobiol 58: 519–527, 2016.

There are still gaps in our understanding of personality development in humans, particularly in relation to social influences. Chimpanzee personality development may provide useful insight. We evaluated the impact of early life experiences on personality development by studying 88 chimpanzees living in accredited zoos and sanctuaries. During infancy, subjects varied in the amount of time spent with conspecifics compared with humans. Caregivers familiar with the chimpanzees rated them using a modified version of the Hominoid Personality Questionnaire (HPQ). The ratings were found to have strong inter-rater reliability. We used the six-factor structure of the HPQ to evaluate our results in relation to differences in early life experience. Chimpanzees who as infants were less exposed to conspecifics were rated as lower in Extraversion later in life. These results suggest that a broader range of social influences should be considered when evaluating the impact of early social environment on later personality expression.

For captive chimpanzees, 'abnormal' behaviours include behaviours observed only in captivity (i.e. species-atypical behaviours) and those that are performed at higher rates in captivity compared to in the wild. Both types are used as metrics for evaluating captive primates' welfare. However, categorizing all abnormal behaviours together ignores variation in their etiologies, which limits our ability to understand them and provide useful interventions. Coprophagy (deliberately eating faeces) is an intriguing abnormal behaviour because, unlike many abnormal behaviours, it is performed at higher rates among captive chimpanzees that were mother reared, compared to those that were human reared, and it has been proposed that it represents a socially learnt 'cultural' behaviour. Furthermore, coprophagy is observed among both wild and captive animals, although at higher rates in captivity. Typically, coprophagy is classed with other abnormal behaviours by those evaluating captive chimpanzee welfare, but such categorization has arisen from a top-down approach based on a priori assumptions. To apply a bottom-up approach, which would allow us to identify relations between behaviours in chimpanzees' repertoire, in this study we ran a principal components analysis on the behaviours performed by 60 captive chimpanzees, to determine whether coprophagy should be classified with other abnormal behaviours. The principal components analysis revealed seven factors that we termed social, aggressive, playful, active, feed, abnormal and self-directed. Furthermore, the analysis revealed that coprophagy loaded onto the 'social' factor, which included positive social behaviours, and not onto the 'abnormal' factor, which included other abnormal behaviours. Supporting previous research, we also found that those chimpanzees that were mother reared showed higher rates of coprophagy than those that were human reared; there was a significant positive correlation between time spent with conspecifics during the first four years of life and the rate of coprophagy performed by the subjects as adults (r=0.575, N=60, P<0.001). We discuss these results giving consideration to the practical applications for monitoring and evaluating captive chimpanzee welfare and also from a theoretical perspective about the social learning mechanisms that may underpin the transmission of coprophagy among captive chimpanzees. (C) 2016 Elsevier B.V. All rights reserved.

The current work sought to operationalize constructs of the triarchic model of psychopathy in chimpanzees (Pan troglodytes), a species well-suited for investigations of basic biobehavioral dispositions relevant to psychopathology. Across three studies, we generated validity evidence for scale measures of the triarchic model constructs in a large sample (N=238) of socially-housed chimpanzees. Using a consensus-based rating approach, we first identified candidate items for the chimpanzee triarchic (CHMP-Tri) scales from an existing primate personality instrument and refined these into scales. In Study 2, we collected data for these scales from human informants (N=301), and examined their convergent and divergent relations with scales from another triarchic inventory developed for human use. In Study 3, we undertook validation work examining associations between CHMP-Tri scales and task measures of approach-avoidance behavior (N=73) and ability to delay gratification (N=55). Current findings provide support for a chimpanzee model of core dispositions relevant to psychopathy and other forms of psychopathology.

Converging empirical data suggests that a set of largely consistent personality traits exist in both human and nonhuman primates; despite these similarities, almost nothing is known concerning the neurobiological basis of these traits in nonhuman primates. The current study examined associations between chimpanzee personality traits and the grey matter volume and asymmetry of various frontal cortex regions in 107 captive chimpanzees. Chimpanzees rated as higher on Openness and Extraversion had greater bilateral grey matter volumes in the anterior cingulate cortex. Further, chimpanzee rated as higher on Dominance had larger grey volumes in the left anterior cingulate cortex and right Prefrontal Cortex (PFC). Finally, apes rated higher on Reactivity/Unpredictability had higher grey matter volumes in the right mesial PFC. All associations survived after applying False Discovery Rate (FDR) thresholds. Results are discussed in terms of current neuroscientific models of personality which suggest that the frontal cortex, and asymmetries in this region, play an important role in the neurobiological foundation of broad dispositional traits.

A reliable literature finds that traits are related to each other in an organized hierarchy encompassing various conceptualizations of personality (e.g., Big Three, five-factor model). Recent work suggests the potential of a similar organization among our closest nonhuman relative, chimpanzees (Pan troglodytes), with significant links to neurobiology suggesting an evolutionarily and neurobiologically based hierarchical structure of personality. The current study investigated this hierarchical structure, the heritability of the various personality dimensions across levels of the hierarchy, and associations with early social rearing experience in a large sample (N = 238) of socially housed, captive chimpanzees residing in 2 independent colonies of apes. Results provide support for a hierarchical structure of personality in chimpanzees with significant associations with early rearing experiences. Further, heritabilities of the various dimensions varied by early rearing, with affective dimensions found to be significantly heritable among mother-reared apes, whereas personality dimensions were largely independent of relatedness among the nursery-reared apes. Taken together, these findings provide evidence for the influence of both genetic and environmental factors on personality profiles across levels of the hierarchy, supporting the importance of considering environmental variation in models of quantitative trait evolution.

Several species besides humans respond negatively to inequity (i.e. receiving a less preferred outcome as compared to a social partner). Among primates, the taxon for which inequity responses have been most comprehensively studied, there are large individual differences in responses that have, thus far, not been well explained by demographic features such as sex, rank and age. Recent evidence shows that individuals' personalities are important in explaining differences in behavioural outcomes in other contexts. Thus, in the current study, we explored whether personality was associated with chimpanzees' responses to both inequity and contrast (i.e. receiving less than anticipated). Chimpanzees were paired with multiple members of their social groups. These pairs alternated trading a token to receive food rewards that either differed from what their partner received (inequity condition) or from what was initially offered (contrast condition) and we compared their responses to a control in which both subjects were offered and received the same reward for trading the token. We predicted that both personality and the quality and length of the pairs' relationship would influence subjects' reactions to unequal outcomes, as measured by their refusal to exchange tokens. The quality of subjects' relationships, based on a weighted average of grooming, contact and proximity, did not correlate with refusals to exchange, whereas pairs that had lived together longer were less likely to refuse in the contrast condition than were pairs that had lived together for less time. Considering personality, some of the dimensions influenced responses to both inequity and contrast similarly, but the more 'social' personality dimensions ('extraversion' and 'agreeableness') were more strongly correlated with sensitivity to inequity. These results highlight the importance of considering individual differences, including personality, when evaluating responses in cognitive and behavioural tests.

It is widely accepted that an animal's early history, including but not limited to its rearing history, can have a profound impact on later behavior. In the case of captive animals, many studies have used categorical measures such as mother reared or human reared that do not account for both the influence of human and conspecific interaction. In order to account for the influence of both human and conspecific early exposure to later behavior, we collected 1385 h of data on 60 chimpanzees, of which 36 were former pets or performers, currently housed at accredited zoos or sanctuaries. We developed a unique metric, the Chimpanzee-Human Interaction (CHI) Index that represented a continuous measure of the proportion of human and chimpanzee exposure subjects experienced and here focused on their exposure during the first four years of life. We found that chimpanzees who experienced less exposure to other chimpanzees as infants showed a lower frequency of grooming and sexual behaviors later in life which can influence social dynamics within groups. We also found chimpanzees who experienced more exposure to other chimpanzees as infants showed a higher frequency of coprophagy, suggesting coprophagy could be a socially-learned behavior. These results help characterize some of the long-term effects borne by chimpanzees maintained as pets and performers and may help inform managers seeking to integrate these types of chimpanzees into larger social groups, as in zoos and sanctuaries. In addition, these results highlight the necessity of taking into account the time-weighted influence of human and conspecific interactions when assessing the impact that humans can have on animals living in captivity.