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Chimpanzee populations differ in ranging patterns and social systems. Taï chimpanzees are considered bisexually bonded, with males and females ranging similarly. East African female chimpanzees often range alone and occupy distinct neighbourhoods. Little attention has been paid to the process of spatial integration of immigrant females within the different social systems. In Taï South Group, a large-scale female transfer of 12 immigrants occurred between 2012 and 2015. We analyse the extent of spatial overlap and association between males and resident and immigrant females. Resident and immigrant females exhibited high levels of spatial overlap, which increased over time, without forming distinct neighbourhoods. All females spent little time alone, and immigrant females spent more time in mixed-sex parties than resident females, especially when they presented maximal sexual swellings. Our findings support the social passport hypothesis and a Bisexually Bonded Community Model for Taï chimpanzees, in which eventually immigrant females occupy a similar range as the community and resident females adapt their ranging patterns towards the initial range of immigrant females.
Examining variation in social behaviour and associated endocrine physiology across groups of the same species can help identify consistent hormone–behaviour interactions. We investigated differences in urinary oxytocin levels of individuals, of two neighbouring chimpanzee groups related to (a) socio-positive and -negative interaction frequencies, (b) within-group cooperation associated with between-group competition and (c) group-specific differences in urinary oxytocin reactivity of individuals in response to the same behavioural contexts. We found higher rates of cooperative group-level behaviours and larger relative party sizes in East Group males, while South Group males had higher non-directed aggression and copulation rates. Individuals of both groups showed consistent urinary oxytocin reactivity after the same behavioural contexts. However, East Group males had higher urinary oxytocin levels across contexts than South Group males, including higher baseline levels. Our results support the oxytocinergic system’s involvement in cooperation and gregariousness, and suggest an association between group-specific social dynamics and oxytocinergic profiles.
The social life of female chimpanzees (Pan troglodytes) differs between subspecies, with females in East African field sites often described as avoiding association to avoid competition, while females in Taï have been shown to be more gregarious, spending most of their time in close contact with each other, probably to avoid predation. This close association leads to increased levels of direct competition for resources, possibly increasing the benefit of having a higher dominance rank and challenging dominant group members. Female chimpanzees in Gombe have been shown to queue for rank rather than challenge others. Here, we show that female dyads in Taï do change their dominance rank at times, with at least six clear rank changes recorded in the Taï North and South communities. We discuss life events that could facilitate rank challenges. The increased flexibility in the female dominance hierarchy potentially adds a level of complexity not seen in East African chimpanzees.
In a competitive environment, helping others at a cost presents a puzzle. Nonetheless, altruistic behaviour has been associated with human success as a species. Adoption, the provision of alloparental care to an orphan by an individual other than the biological mother, is a potential altruistic act in both humans and chimpanzees. We investigated potential benefits of adoption (like kin selection, improved reputation, or recruitment of allies) in a chimpanzee community with high adoption rates and alloparental care by adult males, who typically provide no paternal care to offspring. The probability of an adult male providing care to an orphan was connected to the grooming relationship/bond between male and mother before her passing and was not influenced by orphan sex or relatedness. The probability of positively interacting with orphans was negatively affected by the number of female bystanders. Results suggest that male–orphan interactions are not solely driven by reputation, ally recruitment, or kin selection and highlight the link between highly prosocial behaviours and social closeness.
After decades of research, the origins of human speech remain little understood. One undoubted problem is that the vocal repertoires of humans’ closest living relatives, the apes, remain poorly described. Given that the evolution of language has left few fossils, many researchers interested in this question adopt a comparative approach, examining differences and consistencies between human and animal communication. However, comparisons will remain limited in the absence of a comprehensive analysis of the vocal repertoires of the other extant apes, especially of our two closest living relatives, the chimpanzee and bonobo. After years of observing and conducting field experiments with both western and eastern chimpanzees, I posit several reasons why a comprehensive analysis of the chimpanzee vocal repertoire has not yet been completed, in spite of 45 years of research, and what can be done to remedy this situation. I also tabulate cross-site consensus in call categorization, associated contexts of usage and potential call functions. I also note cross-site variation in presence and absence of vocalizations.
The Taï Chimpanzee Project (Taï National Park, Cote D'Ivoire) has yielded unprecedented insights into the nature of cooperation, cognition, and culture in our closest living relatives. Founded in 1979 by Christophe and Hedwige Boesch, the project has entered its 40th year of continuous research. Alongside other famous long-term chimpanzee study sites at Gombe and Mahale in East Africa, the tireless work of the team at Taï has contributed to the fields of behavioural ecology and anthropology, as well as improving public awareness of the urgent need to protect this already endangered species. Encompassing important research topics including chimpanzee ecology, reproductive behaviour, tool use, culture, communication, cognition and conservation, this book provides an engaging account of how Taï chimpanzees are adapted to African jungle life and how they have developed unique forms of cooperation with less violence, regular adoptions and complex cultural differences between groups.