Margaret C. Crofoot

Communication is fundamental to sociality and can shape interactions that are critical for individual fitness. Vocal communication is particularly important for many group-living animals, as it all...

When individual preferences for collective outcomes diverge, cohesive animal groups often coalesce on the majority opinion. However, majority-based decision rules may be counterbalanced by other factors, particularly in heterogeneous groups with differentiated social relationships, and these factors could produce inequality in social influence. We used multi-sensor tracking collars to collect detailed and simultaneous data on the movements and vocalizations of almost all members of three wild white-nosed coati ( Nasua narica ) groups, and analyzed 2,401 individual decisions between conflicting travel directions that were indicated by acoustically signaling groupmates. Decision-making was shared: individuals favored directions that had majority support, and we found evidence that they used acoustic signals and movement cues to infer majority support. Individuals were also more likely to choose directions favored by closer kin and by groupmates in more frontward spatial positions. Although decisions were shared, influence was not equally distributed across individuals. Individuals who consistently formed majorities or occupied frontward spatial positions had higher influence over travel direction. By explicitly linking decisions by individual followers to emergent patterns of influence among potential leaders, our results suggest that influence is a complex product of higher-order interactions that are likely dependent on group demography and socio-spatial structure.

In most vertebrates, social play among peers is considered essential for behavioral development. Yet in solitary species bearing single offspring, opportunities for social play are inherently scarce. Whether mothers of such species actively facilitate play opportunities for their offspring, and at what cost, remains unknown. We used 15 years of behavioral and movement data (~30,000 observation hours) from 31 wild Bornean orangutan (Pongo pygmaeus wurmbii) mother-offspring pairs to test whether mothers adjust ranging behavior to increase their offspring's access to play with neighboring peers. Neighboring mothers with similarly aged offspring showed disproportionately high annual overlap in space use, independent of their relatedness or fruit availability. They intensified use of shared areas within existing range boundaries rather than shifting or expanding their ranges, indicating a fine-scaled ranging strategy. Mothers also incurred energetic costs; on days their offspring played with peers, mothers traveled farther and spent less time feeding. Travel distances were also elevated on the days before and after play, with mothers orienting movement toward play partners' core areas before play and back toward their own core areas after play. This suggests these encounters are planned and actively pursued over multiple days rather than arising by chance. These findings reveal that orangutan mothers incorporate their infants' social needs into daily ranging decisions, at a cost to their own energy budgets. This points toward an underappreciated form of maternal investment and illustrates how the social requirements of development can be met even near the solitary extreme of animal social organization.

For many group living species, vocal signals are a vital form of communication needed to coordinate social behaviours. Investigating these processes first requires a detailed description of the species' vocal repertoire. White-nosed coatis (Nasua narica), which forage and move together in forest habitats, are thought to rely on vocalisations to coordinate movements and maintain group cohesion. However, quantitative studies of their vocal repertoire are lacking. We examined the vocal repertoire of white-nosed coatis from wild populations in Panama and Arizona, USA, to gain a more comprehensive view of their calling behaviours. By combining traditional acoustic analyses with an unsupervised approach based on spectrogram structure, we characterised the diversity of calls in this species and described the temporal and structural features of their vocalisations. We identified 19 call types, with some of these calls emitted in multi-syllable call sequences or in fast succession. We found variability in call rates among group members, which may be driven by differences in social status within the group. In addition, our results indicate that white-nosed coatis likely have individually-recognisable vocalisations. This study provides a foundational description of the white-nosed coati vocal repertoire, laying the groundwork for future research on vocal communication in this species.

Many social animals exhibit fission-fusion dynamics, where group members split into subgroups and come back together. Studying these dynamics can reveal how individuals weigh the costs and benefits of sociality. Most studies infer the drivers of fission-fusion dynamics by examining subgroup association patterns, yet different underlying processes can produce similar patterns. Here we take a fundamentally different approach by focusing on subgrouping events themselves, where decision-making plays out in real time. Using multi-sensor tracking collars, we collected simultaneous movement and vocalisation data from all group members within two wild white-nosed coati groups. We developed analytical tools to extract and characterise fission and fusion events, thus establishing a framework for quantifying the spatiotemporal dynamics of these events and the use of vocalisations before, during, and after them. We found that fissions typically occurred when groups were initially stationary, indicating that splitting does not result from loss of coordination while moving. Subgrouping was associated with reduced aggression, yet aggressive vocalisations did not precede splits, supporting the hypothesis that subgrouping is a pre-emptive mechanism to manage within-group conflict. Contact calls in moving subgroups increased before fissions and fusions, indicating that vocal communication is key to the coordination of these collective movement decisions.

Larger animal groups are widely understood to require more space and expend more energy to mitigate the foraging costs of within-group competition. Yet between-group interactions and shifting resource distributions can obscure links between group size and behaviour, making responses to demographic change difficult to predict. Here, using 33 years of observational data from 12 neighbouring white-faced capuchin ( Cebus imitator ) groups in Costa Rica, combined with remotely sensed environmental data, we show that within- and between-group competition jointly shape space use, with their relative importance shifting with seasonal and interannual climate cycles. Larger groups compensated for reduced per capita foraging efficiency by expanding into less-exploited areas over longer timescales rather than increasing daily travel. Notably, this expansion disproportionately encroached on smaller neighbouring groups. In the dry season, resource confinement to riparian zones increased intergroup encounters and reduced overlap, with larger groups occupying the highest-quality areas. Climatic extremes linked to El Niño and La Niña exacerbated within-group foraging costs for large groups, whereas intermediate anomalies relaxed these constraints and amplified the benefits of between-group competitive ability. Our findings show that environmental variation shifts the trade-offs of within- and between-group competition, shaping how group-living animals adjust to changing social and ecological conditions.