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Understanding the amount of space required by animals to fulfill their biological needs is essential for comprehending their behavior, their ecological role within their community, and for effective conservation planning and resource management. The space-use patterns of habituated primates often are studied by using handheld GPS devices, which provide detailed movement information that can link patterns of ranging and space-use to the behavioral decisions that generate these patterns. However, these data may not accurately represent an animal’s total movements, posing challenges when the desired inference is at the home range scale. To address this problem, we used a 13-year dataset from 11 groups of white-faced capuchins (Cebus capucinus imitator) to examine the impact of sampling elements, such as sample size, regularity, and temporal coverage, on home range estimation accuracy. We found that accurate home range estimation is feasible with relatively small absolute sample sizes and irregular sampling, as long as the data are collected over extended time periods. Also, concentrated sampling can lead to bias and overconfidence due to uncaptured variations in space use and underlying movement behaviors. Sampling protocols relying on handheld GPS for home range estimation are improved by maximizing independent location data distributed across time periods much longer than the target species’ home range crossing timescale.

 

Across multiple species of social mammals, a growing number of studies have found that individual sociality is associated with survival. In long-lived species, like primates, lifespan is one of the main components of fitness. We used 18 years of data from the Lomas Barbudal Monkey Project to quantify social integration in 11 capuchin (Cebus capucinus) groups and tested whether female survivorship was associated with females’ tendencies to interact with three types of partners: (1) all group members, (2) adult females, and (3) adult males. We found strong evidence that females who engaged more with other females in affiliative interactions and foraged in close proximity experienced increased survivorship. We found some weak evidence that females might also benefit from engaging in more support in agonistic contexts with other females. These benefits were evident in models that account for the females’ rank and group size. Female interactions with all group members also increased survival, but the estimates of the effects were more uncertain. In interactions with adult males, only females who provided more grooming to males survived longer. The results presented here suggest that social integration may result in survival-related benefits. Females might enjoy these benefits through exchanging grooming for other currencies, such as coalitionary support or tolerance.

 

Cultural evolution researchers still debate whether humans are unique among species in having social norms, i.e. moralized, group-specific, socially learned, shared understandings of the rules by which social life should be conducted, maintained via moral emotions that inspire impartial third parties to punish violators of these rules. I sought to establish what behaviors spark outrage in capuchins by recording the details of social context whenever a capuchin aggressed against or screamed at another monkey. Food theft, certain types of sexual interaction, and branch-breaking displays were situations that elicited outrage often enough to warrant documentation of which other monkeys witnessed these events, and how they responded. Three decades of long-term data on ten groups were used to measure degree of maternal kinship and relationship quality (using focal follow data and ad libitum data) between the bystander monkeys and the monkeys involved in the putative norm violation. This population fails to meet three of my operational criteria for social norms: (1) There is very little between-group variation in the patterning of social behaviors relevant to the putative social rules identified. (2) The rate at which third party bystanders aggress against putative norm violators is low (0.6-7.0%). (3) Using a logistic regression modeling framework, the most salient predictor of whether third party bystanders punish putative rule violators is the quality of bystanders’ relationships with those violators, suggesting that bystander behavior is driven more by grudge-holding against particular individuals with whom they have poor-quality relationships than by altruistic enforcement of a group-wide behavioral standard. 

Many white-faced capuchin monkey dyads in Lomas Barbudal, Costa Rica, practise idiosyncratic interaction sequences that are not part of the species-typical behavioural repertoire. These interactions often include uncomfortable or risky elements. These interactions exhibit the following characteristics commonly featured in definitions of rituals in humans: (i) they involve an unusual intensity of focus on the partner, (ii) the behaviours have no immediate utilitarian purpose, (iii) they sometimes involve ‘sacred objects’, (iv) the distribution of these behaviours suggests that they are invented and spread via social learning, and (v) many behaviours in these rituals are repurposed from other behavioural domains (e.g. extractive foraging). However, in contrast with some definitions of ritual, capuchin rituals are not overly rigid in their form, nor do the sequences have specific opening and closing actions. In our 9260 h of observation, ritual performance rate was uncorrelated with amount of time dyads spent in proximity but (modestly) associated with higher relationship quality and rate of coalition formation across dyads. Our results suggest that capuchin rituals serve a bond-testing rather than a bond-strengthening function. Ritual interactions are exclusively dyadic, and between-dyad consistency in form is low, casting doubt on the alternative hypothesis that they enhance group-wide solidarity. This article is part of the theme issue ‘Ritual renaissance: new insights into the most human of behaviours’. 

Natural selection has evidently mediated many species characteristics relevant to the evolution of learning, including longevity, length of the juvenile period, social organization, timing of cognitive and motor development, and age-related shifts in behavioural propensities such as activity level, flexibility in problem-solving and motivation to seek new information. Longitudinal studies of wild populations can document such changes in behavioural propensities, providing critical information about the contexts in which learning strategies develop, in environments similar to those in which learning strategies evolved. The Lomas Barbudal Monkey Project provides developmental data for the white-faced capuchin, Cebus capucinus , a species that has converged with humans regarding many life-history and behavioural characteristics. In this dataset, focused primarily on learned aspects of foraging behaviour, younger capuchins are more active overall, more curious and opportunistic, and more prone to inventing new investigative and foraging-related behaviours. Younger individuals more often seek social information by watching other foragers (especially older foragers). Younger individuals are more creative, playful and inventive, and less neophobic, exhibiting a wider range of behaviours when engaged in extractive foraging. Whereas adults more often stick with old solutions, younger individuals often incorporate recently acquired experience (both social and asocial) when foraging. This article is part of the theme issue ‘Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals'. 

The Challenge Hypothesis, designed originally to explain the patterning of competitive behavior and androgen levels in seasonally breeding birds, predicts that males will increase their androgen levels in order to become more competitive in reproductive contexts. Here we test predictions derived from the Challenge Hypothesis in white‐faced capuchin monkeys (Cebus capucinus), a species that has somewhat seasonal reproduction. We analyzed demographic and hormonal data collected over a 5.25‐year period, from 18 males in nine social groups living in or near Lomas Barbudal Biological Reserve, Costa Rica. Alpha males had higher androgen levels than subordinates. Contrary to our predictions, neither the number of breeding‐age males nor the number of potentially fertile females was obviously associated with androgen levels. Furthermore, male androgen levels were not significantly linked to social stability, as measured by stability of male group membership or recency of change in the alpha male position. Androgen levels changed seasonally, but not in a manner that had an obvious relationship to predictions from the Challenge Hypothesis: levels were generally at their lowest near the beginning of the conception season, but instead of peaking when reproductive opportunities were greatest, they were at their highest near the end of the conception season or shortly thereafter. This lack of correspondence to the timing of conceptions suggests that there may be ecological factors not yet identified that influence ifA levels. We expected that the presence of offspring who were young enough to be vulnerable to infanticide during an alpha male takeover might influence androgen levels, at least in the alpha male, but this variable did not significantly impact results.