title: 'Adoption' by maternal siblings in wild chimpanzees.
abstract: The adoption of unrelated orphaned infants is something chimpanzees and humans have in common. Providing parental care has fitness implications for both the adopter and orphan, and cases of adoption have thus been cited as evidence for a shared origin of an altruistic behaviour. We provide new data on adoptions in the free-living Sonso chimpanzee community in Uganda, together with an analysis of published data from other long-term field sites. As a default pattern, we find that orphan chimpanzees do not become adopted by adult group members but wherever possible associate with each other, usually as maternal sibling pairs. This occurs even if both partners are still immature, with older individuals effectively becoming 'child household heads'. Adoption of orphans by unrelated individuals does occur but usually only if no maternal siblings or other relatives are present and only after significant delays. In conclusion, following the loss of their mother, orphaned chimpanzees preferentially associate along pre-existing social bonds, which are typically strongest amongst maternal siblings.
authors.affiliation: Centre for Social Learning and Cognitive Evolution and Scottish Primate Research Group, School of Psychology and Neuroscience, University of St Andrews, St Andrews, Scotland; Budongo Conservation Field Station, Masindi, Uganda.
authors.forename: Catherine
authors.initials: C
authors.lastname: Hobaiter
authors.affiliation: Department of Psychology, University of York, York, United Kingdom; Institute Jean Nicod, Ecole Normale Supérieure, Pavillon Jardin, Paris, France; Budongo Conservation Field Station, Masindi, Uganda.
authors.forename: Anne Marijke
authors.initials: AM
authors.lastname: Schel
authors.affiliation: Department of Anthropology, Boston University, Boston, Massachusetts, United States of America; Department of Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
authors.forename: Kevin
authors.initials: K
authors.lastname: Langergraber
authors.affiliation: Centre for Social Learning and Cognitive Evolution and Scottish Primate Research Group, School of Psychology and Neuroscience, University of St Andrews, St Andrews, Scotland; Department of Comparative Cognition, Institute of Biology, University of Neuchatel, Neuchâtel, Switzerland; Budongo Conservation Field Station, Masindi, Uganda.
authors.forename: Klaus
authors.initials: K
authors.lastname: Zuberbühler
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D005260:Female; D002679:Pan troglodytes / Q000502:physiology*
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