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Koops K, Akankwasa W, Camara HD, Fitzgerald M, Keir A, Mamy G, Matsuzawa T, Péter H, Vicent K, Zuberbühler K, Hobaiter C. Flexible grouping patterns in a western and eastern chimpanzee community. Am J Primatol 2024; 86:e23593. [PMID: 38247391 DOI: 10.1002/ajp.23593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 12/19/2023] [Accepted: 12/27/2023] [Indexed: 01/23/2024]
Abstract
Primate social organizations, or grouping patterns, vary significantly across species. Behavioral strategies that allow for flexibility in grouping patterns offer a means to reduce the costs of group living. Chimpanzees (Pan troglodytes) have a fission-fusion social system in which temporary subgroups ("parties") change in composition because of local socio-ecological conditions. Notably, western chimpanzees (P. t. verus) are described as showing a higher degree of bisexual bonding and association than eastern chimpanzees, and eastern female chimpanzees (P. t. schweinfurthii) are thought to be more solitary than western female chimpanzees. However, reported comparisons in sociality currently depend on a small number of study groups, particularly in western chimpanzees, and variation in methods. The inclusion of additional communities and direct comparison using the same methods are essential to assess whether reported subspecies differences in sociality hold in this behaviorally heterogeneous species. We explored whether sociality differs between two communities of chimpanzees using the same motion-triggered camera technology and definitions of social measures. We compare party size and composition (party type, sex ratio) between the western Gahtoy community in the Nimba Mountains (Guinea) and the eastern Waibira community in the Budongo Forest (Uganda). Once potential competition for resources such as food and mating opportunities were controlled for, subspecies did not substantially influence the number of individuals in a party. We found a higher sex-ratio, indicating more males in a party, in Waibira; this pattern was driven by a greater likelihood in Gahtoy to be in all-female parties. This finding is the opposite of what was expected for eastern chimpanzees, where female-only parties are predicted to be more common. Our results highlight the flexibility in chimpanzee sociality, and caution against subspecies level generalizations.
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Grants
- Newnham College, University of Cambridge
- Royal Zoological Society of Scotland
- Homerton College, University of Cambridge
- Gates Cambridge Trust
- #12002009 Ministry of Education, Culture, Sports, Science and Technology
- #16002001 Ministry of Education, Culture, Sports, Science and Technology
- #20002001 Ministry of Education, Culture, Sports, Science and Technology
- #24000001 Ministry of Education, Culture, Sports, Science and Technology
- #16H06 Ministry of Education, Culture, Sports, Science and Technology
- Stichting Lucie Burgers
- PCEFP3_186967 Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
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Affiliation(s)
- Kathelijne Koops
- Ape Behaviour & Ecology Group, Department of Evolutionary Anthropology, University of Zurich, Zurich, Switzerland
- Department of Archaeology, University of Cambridge, Cambridge, UK
| | | | | | | | - Alex Keir
- Department of Archaeology, University of Cambridge, Cambridge, UK
| | - Gnan Mamy
- Institute de Recherche Environnementale de Bossou, Bossou, Guinea
| | - Tetsuro Matsuzawa
- Division of Humanities and Social Sciences, California Institute of Technology, Pasadena, California, USA
- Department of Pedagogy, Chubu Gakuin University, Gifu, Japan
- College of Life Sciences, Northwest University, Xi'an, China
| | - Hella Péter
- School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Kizza Vicent
- Budongo Conservation Field Station, Masindi, Uganda
| | - Klaus Zuberbühler
- Budongo Conservation Field Station, Masindi, Uganda
- Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland
| | - Catherine Hobaiter
- Budongo Conservation Field Station, Masindi, Uganda
- Wild Minds Lab, School of Psychology & Neuroscience, University of St Andrews, St Andrews, UK
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2
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Lousa TC, Mendes FDC. Disputes over provisioned resources are no more intense between groups than within groups in free-ranging Sapajus libidinosus. Primates 2024; 65:61-68. [PMID: 37938471 DOI: 10.1007/s10329-023-01105-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 10/27/2023] [Indexed: 11/09/2023]
Abstract
Socioecological models predict that disputes between primate groups will be more intense than those within groups, given that the systematic loss of contests over a given resource will restrict the access of all of the members of that group to that resource. Higher levels of aggression are also expected for provisioned resources that have a more lucrative cost:benefit ratio. The levels of aggression in and between two free-ranging tufted capuchin monkey (Sapajus libidinosus) groups in the context of daily provisioning with bananas were evaluated. The aim of a complementary analysis was to identify possible predictors of the frequency of disputes at the site of the provisioned resource. The disputes were recorded using all-events sampling, while the social behaviour of the study groups was recorded by instantaneous scan sampling. The data were analysed using t-test, Mann-Whitney's U, and generalised linear modelling. Between-group disputes were no more intense than within-group events, and did not involve more individuals, or more adult females. The frequency of disputes increased as the number of individuals eating bananas increased. No evidence was found that disputes between groups were any more intense than those within groups. Dominance patterns may have affected these findings, by mediating intergroup disputes. An increase in the number of competitors affected the frequency of disputes at the site of the provisioned resource.
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Affiliation(s)
- Túlio Costa Lousa
- Department of Basic Psychological Processes, Institute of Psychology, University of Brasília, Brasília, DF, 70910-900, Brazil.
| | - Francisco D C Mendes
- Department of Basic Psychological Processes, Institute of Psychology, University of Brasília, Brasília, DF, 70910-900, Brazil
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3
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Non-aggressive inter-group interactions in wild Northern Gray gibbons (Hylobates funereus). Acta Ethol 2023. [DOI: 10.1007/s10211-023-00415-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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4
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Wirobski G, Range F, Graat EA, Palme R, Deschner T, Marshall-Pescini S. Similar behavioral but different endocrine responses to conspecific interactions in hand-raised wolves and dogs. iScience 2023; 26:105978. [PMID: 36756369 PMCID: PMC9900400 DOI: 10.1016/j.isci.2023.105978] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 10/28/2022] [Accepted: 01/11/2023] [Indexed: 01/15/2023] Open
Abstract
Domestication has altered dogs' conspecific social organization compared to their closest, non-domesticated relatives, gray wolves. Wolves live in packs whose survival depends on coordinated behavior, but dogs rely less on conspecifics, which predicts greater cohesiveness in wolf than dog packs. Endocrine correlates such as oxytocin and glucocorticoids modulate group cohesion resulting in species-specific differences in social interactions. We found that although wolves' and dogs' observable behavioral reactions to a territorial threat and separation from the pack were similar, hormonal responses differed. Wolves' but not dogs' oxytocin and glucocorticoid concentrations correlated positively with territorial behaviors and only wolves showed increased glucocorticoid concentrations after separation from their pack. Together, results suggest stronger emotional activation to threats to group integrity in wolves than dogs, in line with their socio-ecology.
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Affiliation(s)
- Gwendolyn Wirobski
- Domestication Lab, Konrad-Lorenz-Institute for Ethology, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria
- Corresponding author
| | - Friederike Range
- Domestication Lab, Konrad-Lorenz-Institute for Ethology, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria
| | - Evelien A.M. Graat
- Domestication Lab, Konrad-Lorenz-Institute for Ethology, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria
| | - Rupert Palme
- Unit of Physiology, Pathophysiology and Experimental Endocrinology, Department of Biomedical Sciences, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria
| | - Tobias Deschner
- Institute of Cognitive Science, Comparative BioCognition, University of Osnabrück, Artilleriestrasse 34, 49076, Osnabrück, Germany
| | - Sarah Marshall-Pescini
- Domestication Lab, Konrad-Lorenz-Institute for Ethology, University of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria
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Costa RFP, Romano V, Pereira AS, Hart JDA, MacIntosh A, Hayashi M. Mountain gorillas benefit from social distancing too: Close proximity from tourists affects gorillas' sociality. CONSERVATION SCIENCE AND PRACTICE 2022. [DOI: 10.1111/csp2.12859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Raquel F. P. Costa
- Research Department Japan Monkey Center Inuyama Aichi Japan
- Primate Cognition Research Group, Centre for Philosophy of Science of the University of Lisbon Lisbon Portugal
| | - Valéria Romano
- Université de Strasbourg, CNRS, IPHC UMR 7178 Strasbourg France
- IMBE, Aix Marseille Univ., Avignon Univ., CNRS, IRD Marseille France
| | - André S. Pereira
- Centre for Research in Animal Behaviour, University of Exeter Exeter UK
- Research Centre for Anthropology and Health, Department of Life Sciences University of Coimbra Coimbra Portugal
| | - Jordan D. A. Hart
- Centre for Research in Animal Behaviour, University of Exeter Exeter UK
| | - Andrew MacIntosh
- Inuyama Campus, Kyoto University Wildlife Research Center Inuyama Japan
- Institute for Liberal Arts and Sciences, Kyoto University Kyoto Japan
| | - Misato Hayashi
- Research Department Japan Monkey Center Inuyama Aichi Japan
- Chubu Gakuin University Kakamigahara Japan
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Puberty initiates a unique stage of social learning and development prior to adulthood: Insights from studies of adolescence in wild chimpanzees. Dev Cogn Neurosci 2022; 58:101176. [PMID: 36427434 PMCID: PMC9699942 DOI: 10.1016/j.dcn.2022.101176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 10/28/2022] [Accepted: 11/15/2022] [Indexed: 11/18/2022] Open
Abstract
In humans, puberty initiates a period of rapid growth, change, and formative neurobehavioral development. Brain and behavior changes during this maturational window contribute to opportunities for social learning. Here we provide new insights into adolescence as a unique period of social learning and development by describing field studies of our closest living relatives, chimpanzees. Like humans, chimpanzees have a multiyear juvenile life stage between weaning and puberty onset followed by a multiyear adolescent life stage after pubertal onset but prior to socially-recognized adulthood. As they develop increasing autonomy from caregivers, adolescent chimpanzees explore and develop many different types of social relationships with a wide range of individuals in a highly flexible social environment. We describe how adolescent social motivations and experiences differ from those of juveniles and adults and expose adolescents to high levels of uncertainty, risk, and vulnerability, as well as opportunities for adaptive social learning. We discuss how these adolescent learning experiences may be shaped by early life and in turn shape varied adult social outcomes. We outline how future chimpanzee field research can contribute in new ways to a more integrative interdisciplinary understanding of adolescence as a developmental window of adaptive social learning and resilience.
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Interrelationship among spatial cohesion, aggression rate, counter-aggression and female dominance in three lemur species. Behav Ecol Sociobiol 2022. [DOI: 10.1007/s00265-022-03241-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Abstract
How social and ecological factors are associated with variation in dominance style across species of animals has been studied frequently, but the underlying processes are often not addressed. Theoretical research indicates that stronger spatial cohesion among individuals in a group causes a higher frequency of fighting and, thus, through the self-reinforcing effects of winning and losing fights, a stronger differentiation of the dominance hierarchy and dominance of females over more males. Our aim in the present paper is to study whether the same interrelationship among processes may underlie differences in dominance style among three species of lemur that differ in their degree of despotism: Lemur catta, Propithecus verreauxi and Eulemur rufifrons. We investigated their agonistic interactions and spatial cohesion based on 2752 h of observational data of 20 wild groups of these three species. We determined dominance style using the proportion of counter-aggression, with a lower proportion indicating a more despotic dominance style. We found that stronger spatial cohesion among individuals is associated with a higher rate of aggression, stronger despotism and dominance of females over more males. The results of our study emphasise the general importance of spatial cohesion in determining dominance style.
Significance statement
Theoretical studies have shown that the spatial configuration of individuals in a group influences the dominance style. In an agent-based model, DomWorld, individuals are guided by simple rules of grouping and fighting and emergent patterns of behaviour switch between resembling those of despotic or egalitarian primates depending on the degree of cohesion in groups. Yet this link has seldom been studied empirically. We, therefore, examine the relevance of spatial cohesion on patterns of behaviour of individuals in groups of three species of lemur. We confirm the predictions from the model and show that stronger spatial cohesion results in more frequent aggression, a more despotic dominance style and stronger female dominance over males. In light of this, we urge future research of animal dominance to include measures of cohesion.
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Hobaiter C, Graham KE, Byrne RW. Are ape gestures like words? Outstanding issues in detecting similarities and differences between human language and ape gesture. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210301. [PMID: 35934962 PMCID: PMC9358316 DOI: 10.1098/rstb.2021.0301] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 05/24/2022] [Indexed: 12/30/2022] Open
Abstract
Opinion piece: ape gestures are made intentionally, inviting parallels with human language; but how similar are their gestures to words? Here we ask this in three ways, considering: flexibility and ambiguity, first- and second-order intentionality, and usage in interactive exchanges. Many gestures are used to achieve several, often very distinct, goals. Such apparent ambiguity in meaning is potentially disruptive for communication, but-as with human language-situational and interpersonal context may largely resolve the intended meaning. Our evidence for first-order intentional use of gesture is abundant, but how might we establish a case for the second-order intentional use critical to language? Finally, words are rarely used in tidy signal-response sequences but are exchanged in back-and-forth interaction. Do gestures share this property? In this paper, we examine these questions and set out ways in which they can be resolved, incorporating data from wild chimpanzees. This article is part of the theme issue 'Cognition, communication and social bonds in primates'.
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Affiliation(s)
- Catherine Hobaiter
- Origins of Mind Group, School of Psychology and Neuroscience, University of St Andrews, St Andrews KY16 9JP, UK
| | - Kirsty E. Graham
- Origins of Mind Group, School of Psychology and Neuroscience, University of St Andrews, St Andrews KY16 9JP, UK
| | - Richard W. Byrne
- Origins of Mind Group, School of Psychology and Neuroscience, University of St Andrews, St Andrews KY16 9JP, UK
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9
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Badihi G, Bodden K, Zuberbühler K, Samuni L, Hobaiter C. Flexibility in the social structure of male chimpanzees ( Pan troglodytes schweinfurthii) in the Budongo Forest, Uganda. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220904. [PMID: 36177197 PMCID: PMC9515636 DOI: 10.1098/rsos.220904] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 09/08/2022] [Indexed: 06/16/2023]
Abstract
Individuals of social species experience competitive costs and social benefits of group living. Substantial flexibility in humans' social structure and the combination of different types of social structure with fission-fusion dynamics allow us to live in extremely large groups-overcoming some of the costs of group living while capitalizing on the benefits. Non-human species also show a range of social strategies to deal with this trade-off. Chimpanzees are an archetypical fission-fusion species, using dynamic changes in day-to-day association to moderate the costs of within-group competition. Using 4 years of association data from two neighbouring communities of East African chimpanzees (Pan troglodytes schweinfurthii), we describe an unexplored level of flexibility in chimpanzee social structure. We show that males from the larger Waibira community (N = 24-31) exhibited additional structural levels of semi-stable core-periphery society, while males from the smaller Sonso community (N = 10-13) did not. This novel core-periphery pattern adds to previous results describing alternative modular social structure in other large communities of chimpanzees. Our data support the hypothesis that chimpanzees can incorporate a range of strategies in addition to fission-fusion to overcome costs of social living, and that their social structures may be closer to that of modern humans than previously described.
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Affiliation(s)
- Gal Badihi
- School of Psychology and Neuroscience, University of St Andrews, South Street, St Andrews KY16 9JP, UK
| | - Kelsey Bodden
- School of Psychology and Neuroscience, University of St Andrews, South Street, St Andrews KY16 9JP, UK
| | - Klaus Zuberbühler
- School of Psychology and Neuroscience, University of St Andrews, South Street, St Andrews KY16 9JP, UK
- School of Biology, University of Neuchâtel, Neuchâtel, Switzerland
- Budongo Conservation Field Station, Masindi, Uganda
| | - Liran Samuni
- School of Psychology and Neuroscience, University of St Andrews, South Street, St Andrews KY16 9JP, UK
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Catherine Hobaiter
- School of Psychology and Neuroscience, University of St Andrews, South Street, St Andrews KY16 9JP, UK
- Budongo Conservation Field Station, Masindi, Uganda
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Braga Goncalves I, Morris-Drake A, Kennedy P, Radford AN. Fitness consequences of outgroup conflict. eLife 2022; 11:e74550. [PMID: 35833830 PMCID: PMC9282852 DOI: 10.7554/elife.74550] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 06/27/2022] [Indexed: 12/13/2022] Open
Abstract
In social species across the animal kingdom, conspecific outsiders threaten the valuable resources of groups and their members. This outgroup conflict is recognised as a powerful selection pressure, but we argue that studies explicitly quantifying the fitness consequences need to be broader in scope: more attention should be paid to delayed, cumulative, and third-party fitness consequences, not just those arising immediately to group members involved in physical contests. In the first part of this review, we begin by documenting how single contests can have survival and reproductive consequences either immediately or with a delay. Then, we step beyond contests to describe fitness consequences that can also result from interactions with cues of rival presence and the general landscape of outgroup threat, and beyond single interactions to describe cumulative effects of territorial pressure and elevated outgroup-induced stress. Using examples from a range of taxa, we discuss which individuals are affected negatively and positively, considering both interaction participants and third-party group members of the same or the next generation. In the second part of the review, we provide suggestions about how to move forward. We highlight the importance of considering how different types of outgroup conflict can generate different selection pressures and of investigating variation in fitness consequences within and between species. We finish by discussing the value of theoretical modelling and long-term studies of natural populations, experimental manipulations, and meta-analyses to develop further our understanding of this crucial aspect of sociality.
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Affiliation(s)
| | - Amy Morris-Drake
- School of Biological Sciences, University of BristolBristolUnited Kingdom
| | - Patrick Kennedy
- School of Biological Sciences, University of BristolBristolUnited Kingdom
| | - Andrew N Radford
- School of Biological Sciences, University of BristolBristolUnited Kingdom
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11
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Harrison RA, van de Waal E. The unique potential of field research to understand primate social learning and cognition. Curr Opin Behav Sci 2022. [DOI: 10.1016/j.cobeha.2022.101132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Morris-Drake A, Kennedy P, Braga Goncalves I, Radford AN. Variation between species, populations, groups and individuals in the fitness consequences of out-group conflict. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210148. [PMID: 35369741 PMCID: PMC8977661 DOI: 10.1098/rstb.2021.0148] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 12/02/2021] [Indexed: 12/30/2022] Open
Abstract
Out-group conflict is rife in the natural world, occurring from primates to ants. Traditionally, research on this aspect of sociality has focused on the interactions between groups and their conspecific rivals, investigating contest function and characteristics, which group members participate and what determines who wins. In recent years, however, there has been increasing interest in the consequences of out-group conflict. In this review, we first set the scene by outlining the fitness consequences that can arise immediately to contest participants, as well as a broader range of delayed, cumulative and third-party effects of out-group conflict on survival and reproductive success. For the majority of the review, we then focus on variation in these fitness consequences of out-group conflict, describing known examples both between species and between populations, groups and individuals of the same species. Throughout, we suggest possible reasons for the variation, provide examples from a diverse array of taxa, and suggest what is needed to advance this burgeoning area of social evolution. This article is part of the theme issue 'Intergroup conflict across taxa'.
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Affiliation(s)
- Amy Morris-Drake
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Patrick Kennedy
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Ines Braga Goncalves
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Andrew N. Radford
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
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Lemoine SRT, Samuni L, Crockford C, Wittig RM. Parochial cooperation in wild chimpanzees: a model to explain the evolution of parochial altruism. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210149. [PMID: 35369746 PMCID: PMC8977654 DOI: 10.1098/rstb.2021.0149] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 01/24/2022] [Indexed: 12/18/2022] Open
Abstract
Parochial altruism, taking individual costs to benefit the in-group and harm the out-group, has been proposed as one of the mechanisms underlying the human ability of large-scale cooperation. How parochial altruism has evolved remains unclear. In this review paper, we formulate a parochial cooperation model in small-scale groups and examine the model in wild chimpanzees. As suggested for human parochial altruism, we review evidence that the oxytocinergic system and in-group cooperation and cohesion during out-group threat are integral parts of chimpanzee collective action during intergroup competition. We expand this model by suggesting that chimpanzee parochial cooperation is supported by the social structure of chimpanzee groups which enables repeated interaction history and established social ties between co-operators. We discuss in detail the role of the oxytocinergic system in supporting parochial cooperation, a pathway that appears integral already in chimpanzees. The reviewed evidence suggests that prerequisites of human parochial altruism were probably present in the last common ancestor between Pan and Homo. This article is part of the theme issue 'Intergroup conflict across taxa'.
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Affiliation(s)
- Sylvain R. T. Lemoine
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Department of Archaeology, University of Cambridge, Cambridge, UK
| | - Liran Samuni
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Catherine Crockford
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Institute of Cognitive Sciences Marc Jeannerod, UMR 5229, CNRS/University of Lyon, Bron, France
| | - Roman M. Wittig
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Institute of Cognitive Sciences Marc Jeannerod, UMR 5229, CNRS/University of Lyon, Bron, France
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14
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Bouchard A, Zuberbühler K. Male chimpanzees communicate to mediate competition and cooperation during feeding. Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.01.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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15
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Love thy neighbour: behavioural and endocrine correlates of male strategies during intergroup encounters in bonobos. Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.02.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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16
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Giuliano C, Stewart FA, Piel AK. Chimpanzee (Pan troglodytes schweinfurthii) grouping patterns in an open and dry savanna landscape, Issa Valley, western Tanzania. J Hum Evol 2022; 163:103137. [DOI: 10.1016/j.jhevol.2021.103137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 12/09/2021] [Accepted: 12/14/2021] [Indexed: 11/25/2022]
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17
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Graham KE, Badihi G, Safryghin A, Grund C, Hobaiter C. A socio-ecological perspective on the gestural communication of great ape species, individuals, and social units. ETHOL ECOL EVOL 2022; 34:235-259. [PMID: 35529671 PMCID: PMC9067943 DOI: 10.1080/03949370.2021.1988722] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Over the last 30 years, most research on non-human primate gestural communication has been produced by psychologists, which has shaped the questions asked and the methods used. These researchers have drawn on concepts from philosophy, linguistics, anthropology, and ethology, but despite these broad influences the field has neglected to situate gestures into the socio-ecological context in which the diverse species, individuals, and social-units exist. In this review, we present current knowledge about great ape gestural communication in terms of repertoires, meanings, and development. We fold this into a conversation about variation in other types of ape social behaviour to identify areas for future research on variation in gestural communication. Given the large variation in socio-ecological factors across species and social-units (and the individuals within these groups), we may expect to find different preferences for specific gesture types; different needs for communicating specific meanings; and different rates of encountering specific contexts. New tools, such as machine-learning based automated movement tracking, may allow us to uncover potential variation in the speed and form of gesture actions or parts of gesture actions. New multi-group multi-generational datasets provide the opportunity to apply analyses, such as Bayesian modelling, which allows us to examine these rich behavioural landscapes. Together, by expanding our questions and our methods, researchers may finally be able to study great ape gestures from the perspective of the apes themselves and explore what this gestural communication system reveals about apes’ thinking and experience of their world.
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Affiliation(s)
- Kirsty E. Graham
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
| | - Gal Badihi
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
| | - Alexandra Safryghin
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
| | - Charlotte Grund
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
| | - Catherine Hobaiter
- School of Psychology & Neuroscience, University of St Andrews, St Mary’s Quad, South St, St Andrews KY16 9JP, Scotland, UK
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18
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Morris-Drake A, Linden JF, Kern JM, Radford AN. Extended and cumulative effects of experimentally induced intergroup conflict in a cooperatively breeding mammal. Proc Biol Sci 2021; 288:20211743. [PMID: 34875195 PMCID: PMC8651417 DOI: 10.1098/rspb.2021.1743] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 11/17/2021] [Indexed: 12/05/2022] Open
Abstract
Conflict between rival groups is rife in nature. While recent work has begun exploring the behavioural consequences of this intergroup conflict, studies have primarily considered just the 1-2 h immediately after single interactions with rivals or their cues. Using a habituated population of wild dwarf mongooses (Helogale parvula), we conducted week-long manipulations to investigate longer-term impacts of intergroup conflict. Compared to a single presentation of control herbivore faeces, one rival-group faecal presentation (simulating a territorial intrusion) resulted in more within-group grooming the following day, beyond the likely period of conflict-induced stress. Repeated presentations of outsider cues led to further changes in baseline behaviour by the end of the week: compared to control weeks, mongooses spent less time foraging and foraged closer to their groupmates, even when there had been no recent simulated intrusion. Moreover, there was more baseline territorial scent-marking and a higher likelihood of group fissioning in intrusion weeks. Consequently, individuals gained less body mass at the end of weeks with repeated simulated intrusions. Our experimental findings provide evidence for longer-term, extended and cumulative, effects of an elevated intergroup threat, which may lead to fitness consequences and underpin this powerful selective pressure.
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Affiliation(s)
- Amy Morris-Drake
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Jennifer F. Linden
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Julie M. Kern
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
- School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia
| | - Andrew N. Radford
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
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19
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Heesen R, Zuberbühler K, Bangerter A, Iglesias K, Rossano F, Pajot A, Guéry JP, Genty E. Evidence of joint commitment in great apes' natural joint actions. ROYAL SOCIETY OPEN SCIENCE 2021; 8:211121. [PMID: 34909217 PMCID: PMC8652280 DOI: 10.1098/rsos.211121] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 11/08/2021] [Indexed: 05/20/2023]
Abstract
Human joint action seems special, as it is grounded in joint commitment-a sense of mutual obligation participants feel towards each other. Comparative research with humans and non-human great apes has typically investigated joint commitment by experimentally interrupting joint actions to study subjects' resumption strategies. However, such experimental interruptions are human-induced, and thus the question remains of how great apes naturally handle interruptions. Here, we focus on naturally occurring interruptions of joint actions, grooming and play, in bonobos and chimpanzees. Similar to humans, both species frequently resumed interrupted joint actions (and the previous behaviours, like grooming the same body part region or playing the same play type) with their previous partners and at the previous location. Yet, the probability of resumption attempts was unaffected by social bonds or rank. Our data suggest that great apes experience something akin to joint commitment, for which we discuss possible evolutionary origins.
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Affiliation(s)
- Raphaela Heesen
- Institute of Work and Organizational Psychology, University of Neuchâtel, Switzerland
- Department of Psychology, Durham University, UK
| | - Klaus Zuberbühler
- Institute of Biology, University of Neuchâtel, Switzerland
- School of Psychology and Neuroscience, University of St Andrews, Scotland
| | - Adrian Bangerter
- Institute of Work and Organizational Psychology, University of Neuchâtel, Switzerland
| | - Katia Iglesias
- School of Health Sciences (HEdS-FR), HES-SO University of Applied Sciences and Arts of WesternSwitzerland
| | - Federico Rossano
- Department of Cognitive Science, University of California, San Diego, CA, USA
| | - Aude Pajot
- Institute of Work and Organizational Psychology, University of Neuchâtel, Switzerland
| | | | - Emilie Genty
- Institute of Work and Organizational Psychology, University of Neuchâtel, Switzerland
- Institute of Biology, University of Neuchâtel, Switzerland
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20
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Brooks J, Yamamoto S. The founder sociality hypothesis. Ecol Evol 2021; 11:14392-14404. [PMID: 34765114 PMCID: PMC8571591 DOI: 10.1002/ece3.8143] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 08/26/2021] [Accepted: 09/01/2021] [Indexed: 11/12/2022] Open
Abstract
In this review, we propose that the social dynamics of founder populations in novel and newly available environments can have critical effects in shaping species' sociality and can produce long-lasting changes in social structure and behavior. For founder populations which expand into an underexploited niche separated from the parent population, the necessity of bond formation with strangers, lack of clear territories, and initial abundance of resources can lead to altered initial social dynamics to which subsequent generations adapt. We call this the founder sociality hypothesis. After specifying the theoretical reasoning and mechanism of effect, we focus on three particular cases where the social dynamics of founder populations may have a central role in explaining their modern behavioral ecology. In particular, we develop and review evidence for three predictions of the founder sociality hypothesis in territorial, mixed-sex group forming species: relatively stronger social bonds in the dispersing sex with relatively weaker bonds in the nondispersing sex, reduced territoriality, and increased social tolerance. We briefly touch on the implications for human evolution given our species' evolutionary history marked by frequent expansion and adaptation to novel environments. We conclude by proposing several experiments and models with testable predictions following from the founder sociality hypothesis.
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Affiliation(s)
- James Brooks
- Wildlife Research CenterKyoto UniversityKyotoJapan
| | - Shinya Yamamoto
- Wildlife Research CenterKyoto UniversityKyotoJapan
- Institute for Advanced StudyKyoto UniversityKyotoJapan
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21
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Lindshield S, Hernandez-Aguilar RA, Korstjens AH, Marchant LF, Narat V, Ndiaye PI, Ogawa H, Piel AK, Pruetz JD, Stewart FA, van Leeuwen KL, Wessling EG, Yoshikawa M. Chimpanzees (Pan troglodytes) in savanna landscapes. Evol Anthropol 2021; 30:399-420. [PMID: 34542218 DOI: 10.1002/evan.21924] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 12/17/2020] [Accepted: 07/29/2021] [Indexed: 12/22/2022]
Abstract
Chimpanzees (Pan troglodytes) are the only great apes that inhabit hot, dry, and open savannas. We review the environmental pressures of savannas on chimpanzees, such as food and water scarcity, and the evidence for chimpanzees' behavioral responses to these landscapes. In our analysis, savannas were generally associated with low chimpanzee population densities and large home ranges. In addition, thermoregulatory behaviors that likely reduce hyperthermia risk, such as cave use, were frequently observed in the hottest and driest savanna landscapes. We hypothesize that such responses are evidence of a "savanna landscape effect" in chimpanzees and offer pathways for future research to understand its evolutionary processes and mechanisms. We conclude by discussing the significance of research on savanna chimpanzees to modeling the evolution of early hominin traits and informing conservation programs for these endangered apes.
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Affiliation(s)
- Stacy Lindshield
- Department of Anthropology, Purdue University, West Lafayette, Indiana, USA
| | - R Adriana Hernandez-Aguilar
- Department of Social Psychology and Quantitative Psychology, Faculty of Psychology, University of Barcelona, Barcelona, Spain.,Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Amanda H Korstjens
- Life and Environmental Sciences Department, Bournemouth University, Talbot Campus, Poole, UK
| | | | - Victor Narat
- CNRS/MNHN/Paris Diderot, UMR 7206 Eco-anthropology, Paris, France
| | - Papa Ibnou Ndiaye
- Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, Dakar, Senegal
| | - Hideshi Ogawa
- School of International Liberal Studies, Chukyo University, Toyota, Aichi, Japan
| | - Alex K Piel
- Department of Anthropology, University College London, London, UK
| | - Jill D Pruetz
- Department of Anthropology, Texas State University, San Marcos, Texas, USA
| | - Fiona A Stewart
- Department of Anthropology, University College London, London, UK.,School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK
| | - Kelly L van Leeuwen
- Department of Life and Environmental Sciences, Bournemouth University, Talbot Campus, Poole, UK
| | - Erin G Wessling
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Midori Yoshikawa
- Department of Zoology, National Museum of Nature and Science, Ibaraki, Tokyo, Japan
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22
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Group-level cooperation in chimpanzees is shaped by strong social ties. Nat Commun 2021; 12:539. [PMID: 33483482 PMCID: PMC7822919 DOI: 10.1038/s41467-020-20709-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 12/07/2020] [Indexed: 01/30/2023] Open
Abstract
Humans maintain extensive social ties of varying preferences, providing a range of opportunities for beneficial cooperative exchange that may promote collective action and our unique capacity for large-scale cooperation. Similarly, non-human animals maintain differentiated social relationships that promote dyadic cooperative exchange, but their link to cooperative collective action is little known. Here, we investigate the influence of social relationship properties on male and female chimpanzee participations in a costly form of group action, intergroup encounters. We find that intergroup encounter participation increases with a greater number of other participants as well as when participants are maternal kin or social bond partners, and that these effects are independent from one another and from the likelihood to associate with certain partners. Together, strong social relationships between kin and non-kin facilitate group-level cooperation in one of our closest living relatives, suggesting that social bonds may be integral to the evolution of cooperation in our own species.
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23
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Better together? How intergroup associations affect energy balance and feeding behavior in wild bonobos. Behav Ecol Sociobiol 2020. [DOI: 10.1007/s00265-020-02943-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Abstract
When the benefits of interacting with out-group members exceed the associated costs, social groups may be expected to be tolerant towards each other. However, in many species exhibiting intergroup tolerance, the nature of benefits gained from intergroup encounters remains unclear. We investigated the potential costs and benefits associated with intergroup associations in bonobos, a species with varying degrees of intergroup tolerance, by testing whether these associations conferred energetic benefits to participants under different socioecological contexts and whether the consequences of these associations substantially differed from within-group competition. We used measures of socioecological factors (fruit abundance and group size), feeding and ranging behaviors, and a physiological marker of energy balance (urinary c-peptide of insulin) collected over a 19-month period from two neighboring wild communities in the Kokolopori Bonobo Reserve, Democratic Republic of the Congo. We found that intergroup associations were not related to individuals’ energy balance, but they were related to variations in individuals’ ranging and feeding behavior. Specifically, bonobos traveled longer distances, visited larger fruit patches, and increased the time spent feeding on fruits on days they associated with the neighboring group. These adaptations in feeding behavior may be strategies to offset the energetic costs of increased travel distances. In the absence of obvious energetic benefits and with clear strategies employed to offset energetic costs, it is likely that intergroup associations in bonobos provide benefits unrelated to energy acquisition, such as social benefits. Our study sheds light on the potential incentives promoting social networks to extend beyond and across groups in a tolerant species.
Significance statement
Intergroup encounters can be energetically costly due to increased competition over resources. Yet, some species associate with out-group individuals for extended periods of time when the benefits of participating in these associations exceed the potential costs. Bonobos, a species exhibiting intergroup tolerance, modified their feeding behavior during intergroup associations by feeding on larger fruit patches and increasing their time spent feeding on fruits, likely to offset energetic costs of increased travel distances. As results, individuals’ energy balance was not related with intergroup associations. The employment of such strategies in addition to the absence of clear energetic benefits suggests that intergroup associations in bonobos provide social rather than ecological benefits.
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Tkaczynski PJ, Mielke A, Samuni L, Preis A, Wittig RM, Crockford C. Long-term repeatability in social behaviour suggests stable social phenotypes in wild chimpanzees. ROYAL SOCIETY OPEN SCIENCE 2020; 7:200454. [PMID: 32968512 PMCID: PMC7481694 DOI: 10.1098/rsos.200454] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 07/09/2020] [Indexed: 05/07/2023]
Abstract
Consistent individual differences in social phenotypes have been observed in many animal species. Changes in demographics, dominance hierarchies or ecological factors, such as food availability or disease prevalence, are expected to influence decision-making processes regarding social interactions. Therefore, it should be expected that individuals show flexibility rather than stability in social behaviour over time to maximize the fitness benefits of social living. Understanding the processes that create and maintain social phenotypes requires data encompassing a range of socioecological settings and variation in intrinsic state or life-history stage or strategy. Using observational data spanning up to 19 years for some individuals, we demonstrate that multiple types of social behaviour are repeatable over the long term in wild chimpanzees, a long-lived species with complex fission-fusion societies. We controlled for temporal, ecological and demographic changes, limiting pseudo-repeatability. We conclude that chimpanzees living in natural ecological settings have relatively stable long-term social phenotypes over years that may be independent of life-history or reproductive strategies. Our results add to the growing body of the literature suggesting consistent individual differences in social tendencies are more likely the rule rather than the exception in group-living animals.
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Affiliation(s)
- Patrick J. Tkaczynski
- Department of Human Behaviour, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Alexander Mielke
- School of Anthropology and Museum Ethnography, University of Oxford, Oxford, UK
| | - Liran Samuni
- Department of Human Behaviour, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
| | - Anna Preis
- Wild Chimpanzee Foundation, Conakry, Guinea
| | - Roman M. Wittig
- Department of Human Behaviour, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
| | - Catherine Crockford
- Department of Human Behaviour, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
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25
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Fighting for what it’s worth: participation and outcome of inter-group encounters in a pair-living primate, the Javan gibbon (Hylobates moloch). Behav Ecol Sociobiol 2020. [DOI: 10.1007/s00265-020-02879-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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26
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Van Belle S, Grueter CC, Furuichi T. Dynamics of Intergroup Relationships in Primates: Introduction to the Special Issue. INT J PRIMATOL 2020. [DOI: 10.1007/s10764-020-00159-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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27
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Yi Y, Fichtel C, Kim E, Choe JC. Impacts of Intergroup Interactions on Intragroup Behavioral Changes in Javan Gibbons (Hylobates moloch). INT J PRIMATOL 2020. [DOI: 10.1007/s10764-019-00116-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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28
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Majolo B, deBortoli Vizioli A, Martínez-Íñigo L, Lehmann J. Effect of Group Size and Individual Characteristics on Intergroup Encounters in Primates. INT J PRIMATOL 2020. [DOI: 10.1007/s10764-019-00119-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
AbstractIntergroup encounters are common in nonhuman primates and can vary from affiliative to aggressive. We extracted data from the literature to test five different hypotheses: 1) where there are group size differences between opposing groups, whether the larger group is more likely to win an intergroup encounter than the smaller group; 2) whether the likelihood of a group engaging in aggressive intergroup encounters increases with group size; and 3–5) whether dominant, older individuals, and/or males are more likely to participate aggressively in intergroup encounters than subordinate, younger individuals and/or females. Our data set comprised 52 studies on 31 primate species (3 lemur species, 5 New World monkeys, 19 Old World monkeys, and 4 apes). We found that the larger group is more likely to win an encounter against a smaller group than vice versa. We found no significant relationship between group size and propensity to be aggressive during intergroup encounters. We found weak/no support for the effect of age, dominance rank, and sex on the frequency of aggression displayed toward outgroup individuals during intergroup encounters. Species- and population-specific differences in inter- and intragroup competition and in the degree of the unequal distribution of resources across group members may explain why age, dominance rank, and sex are not strong predictors of aggression during intergroup encounters.
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