Coping strategies in captive capuchin monkeys ( Sapajus spp.)

Repeatability of measures of behavioral organization over two years in captive infant rhesus macaques, Macaca mulatta

Individual differences of infant temperament have been associated with future health outcomes that provide explanatory power beyond adult personality. Despite the importance of such a metric, our developmental understanding of personality-like traits is poor. Therefore, we examined whether young primates show consistency in personality traits throughout development. We replicated a Biobehavioral Assessment (BBA) at three time periods: 3-4 months, 1 year, and 2 years of age in 47 rhesus macaque (Macaca mulatta) subjects from large mixed-sex outdoor social housing units at the California National Primate Research Center. We report results for tests focused on responses and adaptation to the temporary separation and relocation, responses to a threatening stimulus, and ratings of overall temperament. We found consistently repeatable associations in measures of Emotionality; these associations were stronger in males, but also present in females, and broadly consistent between Years 1 and 2. We also explored whether behavioral responses to this experimental relocation might be influenced by their experience being relocated for other reasons (i.e., hospitalizations) as individuals' responses might be influenced by similar experiences to the BBA procedure. Only locomotion, during one of the assessments, was associated with past hospitalization events. Overall, repeatability in Emotionality-associated behaviors was evident across the 2 years, in both sexes. We did, however, find evidence of the emergence of sex differences via differentiated expression of behavioral responses during the BBA. We emphasize that there is likely contextual nuance in the use of these BBA factor-associated behaviors. Further research is required to determine whether and how shifts occur in underlying factor structure and the expression of associated behaviors.

Towards an Integrated Concept of Personality in Human and Nonhuman Animals

Every individual has an idiosyncratic way of feeling, thinking and behaving, which is relatively stable across time and situations. Usually known as Personality, today this phenomenon is recognized in many species, including arthropods, fish, avian or mammals. From an evolutionary perspective, research has shown that personality differences are manifest in distinctive forms of dealing with selective pressures, with consequences for fitness. Despite these facts, the study of personality in animals other than humans is relatively new. Only two decades ago, consistent behavioral individual differences were considered 'noise' around an optimal strategy for behavioral ecologists. Also, psychologists were not interested in animal personality as a consequence of the fear of anthropomorphization and the erroneous belief that humans are unique in nature. Fortunately, this misconception seems already overcome but there are still conceptual issues preventing a unified concept of personality. Throughout this review, we first explore the etymological origins of personality and other terminological issues. We further revise the historical course of the study of personality in humans and other animals, from the perspectives of Psychology and Behavioral Ecology, on the basis of the most used approach, the trait theory. We present the study of nonhuman primates as a paradigmatic example in between both frameworks. Finally, we discuss about the necessity of a unified science of personality.

Ontogenesis of sociability of wild immature capuchin monkeys (Sapajus libidinosus): Sex more than personality explains interindividual variation

Sociability is a fundamental trait that social animals need to survive and reproduce in societies. Sociability predicts how an individual can consistently interact with its conspecifics across time and situations. By studying capuchin monkeys (Sapajus libidinosus), a neotropical primate with complex social behavior and high cognitive capacity, our research aims to analyze the development of the social axis of personality of immature individuals, from birth to the third year of life. We studied wild monkeys belonging to a group with infants, juveniles, and adults of both sexes that inhabits northeastern Brazil. We analyzed the behavior of 12 immature capuchins (6 males and 6 females) in 94 h of videos recorded weekly from birth until 36 months, through daily focal sampling. We verified whether there was intraindividual consistency throughout development by fitting regression models for the effect of age on initiating affiliative social behaviors, controlling for monkey identity and sex. Our results indicate that the individuals of this study exhibit high variation in the initiation of behaviors at the beginning of infancy; there was low repeatability and high intra-individual variation during the first 3 years of life of these individuals, indicating that the social personality is not consolidated in this period. Immature females were more sociable than immature males. Therefore, differences in sociability in early life of bearded capuchin monkeys are best explained by sex rather than personality. We suggest that the high initial behavioral variation in the social axis of personality allows for plasticity influenced by the environment throughout development. The high sociability of females in infancy may be related to female philopatry and their high sociability in adulthood.

Behavioural effects of noise on Linnaeus's two-toed sloth (Choloepus didactylus) in a walk-through enclosure

Anthropogenic noise has been related to stress in captive animals; despite this there have been few studies on animal welfare assessment in walk-through zoo enclosures. We aimed to investigate the behavioural effects of noise on a male-female pair of two-toed sloths (Choloepus didactylus), housed in a walk-through enclosure in a zoo in the UK. The animals were filmed for 24 h per day, during three days per week, including days with potential low and high flow of visitors, for three weeks. Sound pressure measurement was performed four times each collection day (twice in the morning, once at noon and once in the afternoon), for 15 min per session, using a sound level meter. The number of visitors passing the enclosure during each session was also recorded. The videos were analysed using focal sampling, with continuous recording of behaviour. Correlations between noise and the behaviours expressed during, and in the 24 h after the acoustic recording, were investigated. The number of visitors correlated with the acoustic parameters. At the moment of exposure, higher levels of noise correlated with decreased inactivity, and longer expression of locomotion and maintenance behaviours for the male; the female spent more time inside a box in these moments. During the 24 h hours after exposure to loud noise, the female showed no behavioural changes while the male tended to reduce foraging. The behavioural changes observed in both individuals have already been reported in other species, in response to stressful events. Our study indicates the need for a good acoustic management in walk-through zoo enclosures where sloths are housed.

Observation of Masturbation After Visual Sexual Stimuli From Conspecifics in a Captive Male Bearded Capuchin (Sapajus libidinosus)

Masturbation is part of the natural behavioral repertoire of primates, with visual sexual stimuli known to trigger this behavior. Here, we report masturbation events triggered by visual sexual stimulus (VSS) in the South American primate Sapajus libidinosus. We observed a multi-male multi-female captive colony of 17 bearded capuchins between January and October 2014. Over this period, we registered 11 copulation events, 68 attempt copulations, and five masturbation events. The same low-ranking male (named Fu) performed all masturbation events. Fu directly looked at other individuals engaged in sexual displays while he masturbated in three events. The masturbation events associated with VSS lasted up to 2 min and 40 s. Our observations show that VSS can trigger masturbation in capuchin monkeys. The low hierarchy rank of the male, and the consequent lack of mating opportunities in the multi-male multi-female recently formed group in captivity, may have prompted the masturbation events.

"The influence of olfactory enrichment on the behavior of two captive New World primates: Black-capped capuchin (Sapajus apella) and common marmoset (Callithrix jacchus)"

Environmental enrichment is an animal husbandry principle that seeks to provide the stimuli necessary for the optimal physiological and psychological well-being of animals. Due to primates having highly developed visual systems, there have been limited attempts to quantify the benefit of olfactory enrichment on captive primate populations. We aim to investigate how a range of odors may influence the behaviors of two captive New World primate species that have varying reliance on olfactory pathways, black-capped capuchin (Sapajus apella) and common marmoset (Callithrix jacchus), at the National Zoo and Aquarium, Canberra, Australia. We presented three odors (rosemary oil, Salvia rosmarinus, banana essence and white-tailed deer urine, Odocoileus virginianus) four different times to the two species following a 12-week randomized schedule. Using instantaneous scan sampling we collected behavioral and direct cloth interaction (DCI) data on 40 days. We then calculated activity budgets. Results show both species significantly respond to different olfactory conditions. S. apella responded to banana by decreasing inactivity (df = 4, F = 6.600, p = .007), and increasing DCI frequencies (df = 3, F = 116.196, p < .0001) whereas C. jacchus was influenced by rosemary and deer urine-also reducing inactivity levels (df= 4, F = 15.938, p < .0001), but not changing DCI frequencies. We also tested habituation however it is not significant for either species over the course of the study. This comparative investigation is one of the first of its kind and uncovers the possibility for olfactory stimulus to be successfully used as a type of beneficial environmental enrichment for captive primates, supporting the constructive and ongoing development of enrichment programs at captive facilities.

Survey-rated personality traits and experimentally measured coping style and stress reactivity, in wild baboons

The coping style and stress reactivity framework for individual differences in the stress response has been of increasing utility within primatological research. Such differences are often quantified using an experimental approach, but many primatological studies have historically been reliant on a personality-like framework. The personality-like research is derived from human personality literature using survey ratings, while approaches focused on coping styles are often used to interpret differences in small rodents and birds. Experimental approaches benefit from a constrained situation that facilitates control, but sacrifice utility via the generalizability afforded via ratings. Resolving how these two theoretical and methodological approaches intersect is paramount to establishing a biological synthesis between two robust fields of research on individual differences. We applied these frameworks to adult wild olive baboons (Papio anubis) at a field site in Laikipia, Kenya. We quantified coping style and stress reactivity using individually targeted field experiments. We quantified personality trait differences using observer ratings of the monkeys. We isolated three personality trait factors: Neuroticism, Assertiveness, and Friendliness. Personality trait differences showed little association with coping style, but Neuroticism was predicted by stress reactivity.

Measuring behavioral coping style and stress reactivity experimentally in wild olive baboons

Many nonhuman animals have been used as subjects to elucidate intra-individual variation in the stress response - understood via coping styles and stress reactivity. Given the evidence and theory supporting evolutionary trade-offs associated with such differences, it is surprising, then, how few studies have used wild nonhuman primates to develop this theoretical framework. In the current study, we evaluated this framework using a combination of behaviours from focal follows and an experimental method, novel to the field - collected during a 17 month project on olive baboons (Papio anubis) in Laikipia, Kenya. Our experimental design simultaneously introduces a risk with an incentive: a model snake with a real chicken egg, respectively. Such an approach facilitates multiple solutions to a stressor, a key element of coping style theory. General behavioral tendencies did not associate with the experimental measures of coping style and stress reactivity. These results, however, demonstrated the utility and validity of this experimental approach for measuring coping style and stress reactivity in wild nonhumans. Fear grimaces represented stress reactivity. A factor solution represented coping style - summarizing decision making under stress. The treatment experiment, with a snake and egg, elicited a behavioral stress response, relative to control trials with just an egg.

Recommendations for Abnormal Behaviour Ethograms in Monkey Research

Laboratory monkey ethograms currently include subcategories of abnormal behaviours that are based on superficial morphological similarity. Yet, such ethograms may be misclassifying behaviour, with potential welfare implications as different abnormal behaviours are likely to have distinct risk factors and treatments. We therefore investigated the convergent validity of four hypothesized subcategories of abnormal behaviours ('motor', e.g., pacing; 'self-stimulation', e.g., self-sucking; 'postural', e.g., hanging; and 'self-abuse', e.g., self-biting). This hypothesis predicts positive relationships between the behaviours within each subcategory. Rhesus macaque (Macaca mulatta) data on 19 abnormal behaviours were obtained from indoor-housed animals (n = 1183). Logistic regression models, controlling for sex, age, and the number of observations, revealed that only 1/6 'motor' behaviours positively predicted pacing, while 2/3 'self-abuse' behaviours positively predicted self-biting (one-tailed p-value < 0.05). Furthermore, 'self-stimulation' behaviours did not predict self-sucking, and none of the 'postural' behaviours predicted hanging. Thus, none of the subcategories fully met convergent validity. Subsequently, we created four new valid subcategories formed of comorbid behaviours. The first consisted of self-biting, self-hitting, self-injurious behaviour, floating limb, leg-lifting, and self-clasping. The second comprised twirling, bouncing, rocking, swinging, and hanging. The third comprised pacing and head-twisting, while the final subcategory consisted of flipping and eye-poking. Self-sucking, hair-plucking, threat-biting, and withdrawn remained as individual behaviours. We encourage laboratories to replicate the validation of these subcategories first, and for scientists working with other species to validate their ethograms before using them in welfare assessments.

Stress behaviors in captive robust capuchins: Effects of humidity, visitors, management and sex

Wild robust capuchins (Sapajus spp.) are omnivorous neotropical primates that live in relatively large groups in extensive home and daily ranges with activity budgets dominated by traveling, foraging, and object manipulation, meaning that enclosed spaces can result in significant deprivation. Space restriction, manipulation by caretakers, and the chronic presence of visitors, can disrupt the animals' welfare, altering their normal activities and inducing stress behaviors. We aimed to study the behavioral repertoire, activity budget, and frequency of stress behaviors (stereotypes and self-directed behaviors) between two captive groups of robust capuchins in a public zoo in Foz do Iguaçu, Brazil, to understand how much their behavioral homeostasis has been affected. More specifically, we assessed the effect of environmental variables (temperature, relative air humidity, number of visitors, and food management) and sex on the frequency of stress behaviors. Capuchins showed a high frequency of stress behaviors, which represented around 10% of their activity budget (though the frequencies were unevenly distributed among the individuals), and traveling was positively correlated with stereotypes. We found that high relative air humidity appears to induce more stereotypes, high numbers of visitors appear to increase self-directed and vigilance behaviors and reduce stereotypes, food management can increase both kinds of stress behaviors, and females demonstrated more frequent stress behaviors than males, but individual variation may play a role. Capuchins in the group with a greater space restriction showed more stereotypes, while those in the group with more individuals showed more self-directed behaviors. Our study shows that the stress behaviors performed by the capuchins are complex and it is difficult to determine a single cause, because many traits could be involved. Despite that, this study enlightens us to direct some approaches to help these animals to meet their ecological and social needs, mitigating their stress.

The neurobiology of environmentally induced stereotypic behaviours in captive animals: assessing the basal ganglia pathways and cortico-striatal-thalamo-cortical circuitry hypotheses

The neurobiology of environmentally induced stereotypic behaviours (SBs) (e.g., pacing in zoo carnivores, crib-biting in horses, tail chasing in dogs) is hypothesized to involve altered functioning within the basal ganglia (‘Basal Ganglia (BG) Pathways Hypotheses’) and/or between the basal ganglia and cortex (‘Cortico-Striatal-Thalamo-Cortical (CSTC) Circuits Hypotheses’). We review four decades of relevant studies, critically assessing support for both hypotheses. Currently no BG Pathways or CSTC Circuits hypothesis is fully supported. While some results are partially consistent with some hypotheses (decreased subthalamic nucleus activity in deer mice and C58 mice); others (nucleus accumbens activity in mink and C57 mice) seem to reflect individual differences in SB, but not environmental effects. Yet others can be tentatively rejected: neither elevated striatal dopamine nor the cortico-striatal connection of the sensorimotor circuit seem to be involved for most species studied to date. Further research is now important for understanding the impact of captivity on animals’ functioning.

Coping Style and Early Life Vocalizations in the Common Marmoset (Callithrix jacchus)

Coping styles describe behavioral differences during stressful or challenging situations. Coping styles are stable over time but little is known about early life manifestation and development of these behavioral differences. We aimed to investigate if differences in the way marmosets produce vocalizations at an early age are related to their coping style in the future. We studied 14 common marmosets (Callithrix jacchus) from three social groups housed at the marmoset colony at Universidad Autónoma de Madrid. We recorded the vocalizations of each marmoset in isolation at 15–17 days of age, analyzing latency to vocalize and calling rate of phee and tsik calls. To measure coping style, we introduced a novel stimulus to the group cages when infants were 3 months old and recorded exploration, headcocking, and approaches to the stimulus. The results showed negative relationships between the latency of phee call (a long-range contact call) at 15–17 days and frequency of exploration and approach to the novel stimulus at 3 months, although both correlations fall above the cut-off points for the false discovery rate. Marmosets that gave long-range calls sooner at 15–17 days of age also showed more exploratory behaviors at 3 months. The results also showed group differences in exploration at 3 months, and twins were more similar to each other than to other infants in the sample. There were no group differences in early vocalizations and no sex differences in any variable. These findings suggest that coping style is stable from as early as 15–17 days after birth and suggest that the group can influence exploration in marmosets.

A longitudinal assessment of behavioral development in wild capuchins: Personality is not established in the first 3 years

Animal personality is defined as consistent individual differences across time and situations, but little is known about how or when those differences are established during development. Likewise, several studies described the personality structure of adult capuchin monkeys, without assessing the ontogeny of these personality traits. We analyzed the behavioral repertoire of 12 wild infants (9 males, 3 females) yellow-breasted capuchin monkeys (Sapajus xanthosternos), in Una Biological Reserve (Bahia, Brazil). Each infant was observed and filmed weekly from birth until 36 months, through daily focal sampling. We analyzed the behavior of each individual in 10 developmental points. By means of component reduction (principal component analysis), we obtained four behavioral traits: Sociability, Anxiety, Openness, and Activity. We investigated whether there were developmental effects on those traits by fitting regression models for the effect of time on behavioral traits, controlling for monkey identity, sex, and cohort. Sociability (decreasing) and Anxiety (increasing) changed significantly along development. By means of repeatability analysis, we did not find intra-individual consistency across time in those traits, so we cannot discriminate stable personality traits in early ontogeny. Our results show that the personality structure of capuchin monkeys is not established during early development, in agreement with the literature on human personality.

Acute effects of ayahuasca in a juvenile non-human primate model of depression

OBJECTIVE

The incidence rate of major depression in adolescents reaches approximately 14%. This disorder is usually recurrent, without remission of symptoms even after pharmacological treatment, and persists throughout adult life. Since the effects of antidepressants take approximately 2 weeks to begin, new pharmacological therapies are under continuous exploration. Recent evidence suggests that psychedelics could produce rapid antidepressant effects. In this study, we evaluated the potential antidepressant effects of ayahuasca in a juvenile non-human primate model of depression.

METHODS

While living with their families, juvenile marmosets (8 males; 7 females) were observed on alternate days for four weeks during a baseline phase. This was followed by 8 weeks of an induced depressive state protocol, the social isolated context (IC), in which the animals were monitored in the first and last weeks. Subsequently, five males and four females were randomly selected for treatment, first with a single administration of saline vehicle (1.67 mL/300 g of body weight, via gavage), followed by a single dose of ayahuasca (1.67 mL/300 g of body weight, via gavage). Both phases lasted 1 week and the animals were monitored daily. A third week of sampling was called the tardive-pharmacological effects phase. In all phases the marmosets were assessed for behavior, fecal cortisol levels, and body weight.

RESULTS

After IC, the animals presented typical hypocortisolemia, but cortisol recovered to baseline levels 24 h after an acute dose of ayahuasca; this recovery was not observed in vehicle-treated animals. Additionally, in males, ayahuasca, but not the vehicle, reduced scratching, a stereotypic behavior, and increased feeding. Ayahuasca treatment also improved body weight to baseline levels in both sexes. The ayahuasca-induced behavioral response had long-term effects (14 days). Thus, in this translational juvenile animal model of depression, ayahuasca presented beneficial effects.

CONCLUSIONS

These results can contribute to the validation of ayahuasca as an antidepressant drug and encourage new studies on psychedelic drugs as a tool for treating mood disorders, including for adolescents with early-onset depression.

Coping Styles in the Domestic Cat (Felis silvestris catus) and Implications for Cat Welfare

Identifying coping styles in cats may lead to improved health and welfare. The aims of this study were to (1) identify individual differences in response to acute confinement, and (2) to assess the predictability of guardian-rated personality traits on behavior. Adult cats (n = 55) were singly housed in enriched cages and behavioral observations were recorded for three days. On day 3, familiar and unfamiliar person approach tests were conducted. Fecal glucocorticoid metabolites (FGM) were quantified from voided samples. A questionnaire assessing personality traits and sickness behaviors was completed by each guardian. Analysis identified two clusters-cats in Cluster 1 (n = 22) were described as shy, calm, mellow, and timid; cats in Cluster 2 (n = 33) were described as active, playful, curious, and easygoing. Multilevel mixed-effects GLM revealed significant differences between the clusters including food intake (C1 > C2, p < 0.0001), affiliative/maintenance behaviors (C2 > C1, p < 0.0001), vocalization (C2 > C1, p < 0.0001), hide (C1 > C2, p < 0.0001), perch (C2 > C1, p < 0.0001), and latency to approach a familiar (C1 > C2, p < 0.0001) and unfamiliar (C1 > C2, p = 0.013) person. No statistically significant differences in FGM concentrations were identified (cluster p = 0.28; day p = 0.16, interaction p = 0.26). Guardian-rated personality traits agreed with the response of the cats when confined to a cage, suggesting that domestic cats have different coping styles. Identifying individual differences in response to stressful events or environments may provide caretakers with important information leading to improved welfare.