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Social group of chimpanzees_LittleJaneFa
Publications: Publications

2021

Group-level variation in co-feeding tolerance between two sanctuary-housed communities of chimpanzees (Pan troglodytes)

van Leeuwen, E.J.C., Van Donink, S., Eens, M. & Stevens, J. M. G. (2021). Ethology, in press.

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To study social tolerance in two groups of chimpanzees, we used two established and one new group-level co-feeding assay. In conjunction, the assays exposed similar group differences in social tolerance compared to the previous study eight years ago, indicating stability in group-level social tolerance in chimpanzees. Furthermore, based on the consideration that resources may deplete at different rates across groups, which would consequently alter the need for tolerance differentially, we identified the new assay with non-depletable resources as more valid.

2021

Zoo-housed female chimpanzee adopts local female-specific tradition upon immigrating into a new group

Goldsborough, Z., Webb, C.E., de Waal, F. B. M., & van Leeuwen, E.J.C. (2021). Behaviour 158: 547–564


We identified for the first time a female-specific behavioural tradition in a group of chimpanzees in the form of a "crossed-arm walk" - a deliberately handicapped manner of locomotion without discernible function. Upon being introduced to this group, two immigrant females adopted different integration strategies whereby one female immediately copied the local crossed-arm walk tradition. Across time, the "conformist" female became better socially integrated than the non-conformist female, which provides but an indication that conformity upon immigration occurs in chimpanzees, and that behavioural matching may facilitate favourability not just in the human species.

2021

Chimpanzees behave prosocially in a group-specific manner

van Leeuwen, E. J. C., DeTroy, S.E., Kaufhold, S.P., Dubois, C., Schütte, S., Call, J., & Haun, D.B.M. (2021). Science Advances, 7: eabc7982


A field experiment in a large Zambian sanctuary (Chimfunshi Wildlife Orphanage) shows that chimpanzees may behave prosocially towards each other at personal (opportunity) cost. Strikingly, neighbouring groups differed substantially in their prosocial proclivities -- groups that proved high on experimentally tested co-feeding tolerance behaved prosocially more frequently, to more group members, and less selectively (i.e., non-nepotistic). Contrary to previous research, these findings show that chimpanzees should not be evaluated at the species level for their prosocial nature but warrant scrutiny of their group-specific inclinations.

2021

Cofeeding tolerance in chimpanzees depends on group composition: a longitudinal study across four communities

DeTroy, S. E., Ross, C., Cronin, K. A., Haun, D. B. M. & van Leeuwen, E. J. C. (2021). iScience, 24: 102453

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A longitudinal study on co-feeding tolerance in chimpanzees reveals that temporal and between-group variation can largely be explained by demographic variables like the number of young females and mothers with dependent offspring. Yet, data simulations show that not all variation can be attributed to the assessed demographic variables, leaving open the possibility that chimpanzees live in group-specific social climates co-determining social tolerance.

2021

Beyond social learning

Singh, M., Acerbi, A., Caldwell, C.A., Danchin, É., Isabel, G., Molleman, L., Scott-Philips, T., Tamariz, M., van den Berg, P., van Leeuwen, E.J.C., & Derex, M. (2021). Philosophical Transactions Royal Society-B, Volume 376, Issue 1828 (special issue)

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In this perspective paper we argue that cultural evolution - the change of culture over time - results from many mechanisms operating in concert. We posit that the emphasis on social learning has distracted scholars from appreciating both the full range of mechanisms contributing to cultural evolution and how interactions among those mechanisms and other factors affect the output of cultural evolution. We examine understudied mechanisms at play in the social transmission of information and call for a more inclusive program of investigation that probes multiple levels of organization, spanning the neural, cognitive-behavioural, and populational levels. We hereby focus on factors involved in three core topics of cultural evolution: the emergence of culture, the emergence of cumulative cultural evolution, and the design of cultural traits.

2021

Chimpanzees’ behavioural flexibility, social tolerance and use of tool-composites in a progressively challenging foraging problem

Harrison, R., van Leeuwen, E. J. C., & Whiten, A. (2021). iScience, 24: 102033

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Chimpanzees faced with an increasingly challenging foraging task innovated adequate tools to efficiently solve the task. Some chimpanzees combined tool techniques into "tool-composites" - a creative capacity enabling subsequent cumulative culture. Chimpanzees from the most socially tolerant group were most successful at the task, with indications of social learning guiding the transmission of adequate solutions, including the composite techniques.

2020

Social culture in bonobos

van Leeuwen, E. J. C., Staes, N., Verspeek, J., Hoppitt, W.J.E., & Stevens, J.M.G. (2020). Current Biology. 30: R261–R262

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Based on a large dataset of grooming interactions across six zoo-housed populations of bonobos, we found strong evidence for the cultural transmission of idiosyncratic grooming typologies (social scratching and groom-slapping) along proximity networks. Using Network-Based Diffusion Analyses, we identified the spread of the grooming conventions across the sampled zoos and found indications that translocated individuals, especially females, can influence local residents.

2020

Do chimpanzees (Pan troglodytes) console a bereaved mother?*

Goldsborough, Z., van Leeuwen, E. J. C., Kolff, K. W. T., De Waal, F. B. M., & Webb, C. E. (2020). Primates, 61: 20190695, pp. 93-102.

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In human societies, tending of the dying and the treatment of the bereaved are typically governed by empathetic behaviour, including increased targeted affiliation during and after such distressing events. A thorough investigation of what happens in a group of chimpanzees when a mother loses her offspring shows that chimpanzees may also temporarily direct increased and selective affiliation towards the bereaved mother. Immediately after the death of the newborn, but also in the months thereafter, group members responded to the mother with pronounced mouth- and body-kisses, grooming approaches and close proximity. These findings reveal the empathetic nature of chimpanzees in an understudied research field â€“ evolutionary thanatology. *recipient of social impact award

2019

Bonobo personality predicts friendship

Verspeek, J., Staes, N., van Leeuwen, E. J. C., Eens, M., & Stevens, J.M.G. (2019). Scientific Reports. 9: 19245

2019

Reply to Farine and Aplin: Chimpanzees choose their association and interaction partners

van Leeuwen, E. J. C., Cronin, K.A., & Haun, D.B.M. (2019). PNAS 116: 16676–16677.

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In response to a challenge of our original research findings in PNAS (Population-specific social dynamics in chimpanzees), we show that the challenge was based on erroneous premises and that extending our analyses with the advanced social network analysis technique further identifies the robust nature of our inferences - chimpanzees choose their interaction patterns and are influenced in navigating their social world by group-specific (demographic and/or cultural) characteristics.

2019

Why intergroup variation matters for understanding behavior

Kaufhold, S.P. & van Leeuwen, E. J. C. (2019). Biology Letters. 15: 20190695

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In this opinion piece, we argue that intra-specific variation in behavioural phenotypes, here specifically defined in terms of inter-group variation within the same species, warrants more scientific attention. If we are to identify species' behavioural reaction norms and conduct valid phylogenetic analyses with the aim to pinpoint key evolutionary transitions in behavioural capacities and expressions, we ought to extend the commonly applied single-group approach to a multi-group approach, especially in species with an evidenced capacity for cultural transmission.

2019

Copy-the-majority of instances or individuals? Two approaches to the majority and their consequences for conformist decision-making

Morgan, T.J.H., Acerbi, A., & van Leeuwen, E. J. C. (2019). PLoS One 14: e0210748

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Conformist decision-making entails individuals adopting the majority strategy (in terms of behaviour, beliefs, opinions, etc.). Here, the majority can be defined in terms of individuals (the wisdom of the crowd) or in instances (irrespective of whom exhibits the strategy or how often). Contrary to the asserted view that the two operationalisations can be grouped to study the same conformist behaviour, we show that in plausible scenarios the majority of individuals showcase different phenotypes for the observer than the majority of instances. We conclude that both approaches can be meaningfully different and should thus be studied as separate potential social learning biases in animals' decision-making processes.

2018

The development of human social learning across seven societies

van Leeuwen E. J. C., Cohen, E., Collier-Baker, E., Rapold, C.J., Schäfer, M., Schütte, S., & Haun, D.B.M. (2018). Nature Communications 9, Article number: 2076

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