Recently, many studies have been conducted on manual laterality in chimpanzees. Nevertheless, whether nonhuman primates exhibit population-level handedness remains a topic of considerable debate. One of the behaviors studied has been bimanual coordinated actions. Although recent studies have highlighted that captive chimpanzees show handedness at population level for these tasks, some authors have questioned the validity and consistency of these results. The first reason has been the humanization of the samples. The second one has been that the results refer to animals in American biomedical centers and the studies were conducted by the same team [WD Hopkins et al.]. This article aims to assess the laterality in bimanual coordination (tube task) activities in animals housed in an intermediate environment (Chimfunshi, Zambia). This has been conducted by replicating previous studies on similar samples (Mona Foundation, Spain), and then by extending the results to chimpanzees housed in intermediate settings. Individuals were evaluated through four experimental sessions (tests). Results indicated that 86% of the Chimfunshi sample was lateralized (48% RH, 38% LH). Furthermore, the sample showed population-level right-handedness in the mean handedness index, in Test 1, Test 2, and the first half of the study (Test 112). Rearing experience did not have an influence on handpreference. Taken together, the two sample (intermediate settings: Chimfunshi and Mona) results indicate a clear right-handedness. In conclusion, this replication and extension shows that (1) the Mona and Chimfunshi chimpanzees are right-handed in certain conditions, (2) the results are consistent with those obtained by Hopkins in captive settings, (3) the humanization of the samples does not affect manual laterality, (4) females are right-handed at population-level, but not males, and (5) these results reinforce the fact that the complexity of the task plays a dominant role in the expression of hand laterality among chimpanzees.

Facilities housing captive animals are full of staff who, every day, interact with the animals under their care. The expertise and familiarity of staff can be used to monitor animal welfare by means of questionnaires. It was the goal of our study to examine the association between chimpanzee (Pan troglodytes) welfare, happiness, and personality. To these ends we collected two waves of welfare and subjective well-being ratings of 18 chimpanzees housed at the Edinburgh Zoo and one set of ratings of 13 chimpanzees housed at Fundació Mona. Ratings were made on a welfare questionnaire that included 12 items related to stress, psychological stimulation, and behavioural indicators of negative and positive welfare states, and a 4-item subjective well-being questionnaire. In addition, ratings were made on the 54-item Hominoid Personality Questionnaire and an abbreviated version of this scale consisting of 37 antonym pairs. We used generalizability theory to test whether welfare ratings generalized across items, raters, chimpanzees, and time. We then assessed the validity of the welfare and subjective well-being questionnaires by examining their associations with behaviour. Finally, we tested whether the welfare and subjective well-being ratings were associated with personality. Welfare ratings generalized across items, raters, chimpanzees, and time. Principal components analysis and regularized exploratory factor analysis indicated that ten welfare items and all four subjective well-being items formed a single dimension (welfareSWB).LASSO regression found that lower welfareSWB was associated with regurgitation, coprophagy, urophagy, and decreased proximity to nearest neighbour. A linear model that adjusted for age, sex, and facility, indicated that higher Extraversion and lower Neuroticism were related to higher welfareSWB. Welfare ratings were reliable and associated with subjective well-being and personality, demonstrating that staff ratings are a valid and potentially valuable tool for chimpanzee welfare assessment.

Researchers have shown renewed interest in the study of manual lateralization in chimpanzees. Currently there is no consensus confirming the presence or absence of manual dominance at a species level, mainly for populations in the wild and in semicaptivity. We aimed to evaluate the manual laterality in a group of chimpanzees in an intermediate setting (semicaptivity) via 2 tasks: one simple and unimanual (simple reaching) and the other complex and bimanual (tube task). We replicated the same experiments from Hopkins in a new and different sample of chimpanzees. In simple reaching, the hand is used to gather food and the type of grip and the posture are evaluated. The tube task assesses the hand used to extract food from the tube and the method of extraction (digital or instrumental). Through the handedness index we observed that the subjects show clear and strong individual preferences for both tasks (100% lateralized subjects in the tube task; 86% in simple reaching), although we did not detect population preferences for any of the tasks. However, considering both tasks jointly (multiple evaluation), it was possible to detect, for the first time, skilled manual dominance at a group level in semicaptive Int chimpanzees in one multitask index and borderline significance in a second multitask index.

Short-term memory is implicated in a range of cognitive abilities and is critical for understanding primate cognitive evolution. To investigate the effects of phylogeny, ecology and sociality on short-term memory, we tested the largest and most diverse primate sample to date (421 non-human primates across 41 species) in an experimental delayed-response task. Our results confirm previous findings that longer delays decrease memory performance across species and taxa. Our analyses demonstrate a considerable contribution of phylogeny over ecological and social factors on the distribution of short-term memory performance in primates; closely related species had more similar short-term memory abilities. Overall, individuals in the branch of Hominoidea performed better compared to Cercopithecoidea, who in turn performed above Platyrrhini and Strepsirrhini. Interdependencies between phylogeny and socioecology of a given species presented an obstacle to disentangling the effects of each of these factors on the evolution of short-term memory capacity. However, this study offers an important step forward in understanding the interspecies and individual variation in short-term memory ability by providing the first phylogenetic reconstruction of this trait’s evolutionary history. The dataset constitutes a unique resource for studying the evolution of primate cognition and the role of short-term memory in other cognitive abilities.

Abstracts Primates are at times used as performers in circuses, advertisements, films, and as pets. Most of these animals are socially isolated from their peers. They exhibit behavioral problems and lack important skills for living in a group environment. One of the main challenges primate rescue centers face is creating groups to socialize rescued individuals and promote the development of species-typical behaviors. We monitored a group of 15 chimpanzees (Pan troglodytes) housed at Fundació Mona, a primate rescue and rehabilitation centre, for 8 yr. The aim of the study was to study the rehabilitation process and to establish variables that may influence the behavioral recovery of the chimpanzees. We used scan sampling to assess behavior and two welfare indices over the study period. Our results show that both desirable behaviors and welfare indices increased over time, while nondesirable behaviors decreased. We found no differences between pet and performer chimpanzees, but captive-born subjects recovered better than wild-born. We also established that chimpanzees that were younger at the onset of rehabilitation reached higher levels of social and behavioral competence than those that were older. We conclude that both social group housing and opportunities for the development of species-typical behaviors have a positive effect on the welfare and rehabilitation of performer and pet chimpanzees, but that their previous history influences rehabilitation. Int J Primatol

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We evaluate a sanctuary chimpanzee sample (N = 11) using two adapted human assessment instruments: the Five-Factor Model (FFM) and Eysenck's PsychoticismExtraversion-Neuroticism (PEN) model. The former has been widely used in studies of animal personality, whereas the latter has never been used to assess chimpanzees. We asked familiar keepers and scientists (N = 28) to rate 38 (FFM) and 12 (PEN) personality items. The personality surveys showed reliability in all of the items for both instruments. These were then analyzed in a principal component analysis and a regularized exploratory factor analysis, which revealed four and three components, respectively. The results indicate that both questionnaires show a clear factor structure, with characteristic factors not just for the species, but also for the sample type. However, due to its brevity, the PEN may be more suitable for assessing personality in a sanctuary, where employees do not have much time to devote to the evaluation process. In summary, both models are sensitive enough to evaluate the personality of a group of chimpanzees housed in a sanctuary.

The long-term effects of early life adversities on social capacities have been documented in humans and wild-caught former laboratory chimpanzees (Pan troglodytes). However, former pet and entertainment chimpanzees have received little attention to date. This study aimed to investigate the long-term effects of early life experience on 18 former pet and entertainment chimpanzees, based on social grooming data collected at a primate rescue centre over a 12year period. Moreover, we also focused on the possible short-term effects that alterations to group composition might have on grooming patterns. For this purpose, we compared stable and unstable periods (i.e. where alterations to group composition occurred). We used two individual social network measures to analyse the grooming activity and the distribution of grooming among group mates for each individual. We could show that wild-caught chimpanzees were significantly more selective regarding their grooming partners and spent less time grooming when compared to their captive born companions. We also found that individuals who were predominantly housed without conspecifics during infancy spent less time grooming compared to those who were predominantly housed with conspecifics during infancy. Furthermore, we found that alterations to the group composition had short-term effects on the distribution of social grooming from a more equal distribution during periods with a stable group composition towards a more unequal and selective distribution during unstable periods. Thus, we conclude that the social grooming networks of former pet and entertainment chimpanzees are shaped not only by long-term effects such as early life experience, but also by short-term effects such as alterations to group composition. Remarkably, we found not only captive born chimpanzees but also wild-caught individuals to adjust their grooming to socially challenging situations by modifying their grooming distribution in a similar way.