Abstract
Among spotted hyenas, Crocuta crocuta, neonatal aggression in twins is a well-known phenomenon and serves to establish intra-litter dominance soon after birth. As the stronger more aggressive cub presumably attains dominance over its twin, intra-litter dominance presents mothers with an ideal opportunity to assess individual cub fitness and, thereafter, to selectively favor one cub over the other. This study quantified maternal response to sibling conflict in 26 sets of twins born to 16 wild-living females to determine whether mothers of different social ranks exhibited favoritism towards sons or daughters, or in the case of same-sex twins, the dominant or subordinate cub. Maternal response to sibling conflict did not vary with litter sex composition, suggesting that mothers do not favor offspring of one sex over the other. All mothers intervened when their cubs fought and sometimes punished their cubs. Higher-ranking mothers more often punished both cubs, while lower-ranking mothers were more selective and punished the dominant cub. Where sibling aggression was most extreme, rather than favor the dominant sibling, mothers of all ranks made concessions to the subordinate cub that included procuring private nursing bouts for the subordinate and temporarily housing twins in separate dens, presumably to decrease sibling conflict. These findings represent a complex example of parent–offspring conflict and support both the insurance cub hypothesis and resource tracking hypothesis that mothers endeavor to keep all offspring alive for as long as possible in the event that the dominant sibling dies or that resources provide for the rearing of twins.



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Acknowledgments
I thank the Office of the President of Kenya for permission to conduct this research (OP/13/001/C689; KPP #253151) and the Kenya Wildlife Service, Narok County Council, and the Senior Warden of the Masai Mara National Reserve. Field research for the Mara Hyena Project was supported by National Science Foundation grant IBN-9306912. I received additional financial assistance from the National Institute of Mental Health grant MH-39917 and the Annie M. Alexander California MVZ Scholarship. Animal Use Protocols for animal handling were approved by the Animal Care and Use Committee. L. Frank, S. Glickman, E. Lacey, and W. Getz provided thoughtful input on this work. I thank M. Dahlheim and three anonymous reviewers for their helpful comments on an earlier draft of this manuscript.
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Communicated by A. Schulte-Hostedde
This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson and Fritz Trillmich).
An erratum to this article is available at http://dx.doi.org/10.1007/s00265-007-0447-6.
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White, P.P. Maternal response to neonatal sibling conflict in the spotted hyena, Crocuta crocuta . Behav Ecol Sociobiol 62, 353–361 (2008). https://doi.org/10.1007/s00265-007-0422-2
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DOI: https://doi.org/10.1007/s00265-007-0422-2