The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


The Bruce effect in a wild primate

EILA K. ROBERTS1, AMY LU1,2, THORE J. BERGMAN1,3 and JACINTA C. BEEHNER1,4.

1Department of Psychology, University of Michigan, 2Anthropology, New York Consortium of Evolutionary Primatology, 3Ecology and Evolutionary Biology, University of Michigan, 4Anthropology, University of Michigan

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Female rodents are known to terminate pregnancies after exposure to unfamiliar males ("Bruce effect"). Although laboratory support abounds, direct evidence for a Bruce effect under naturalconditions is lacking, and no study has yet demonstrated a fitness advantage for females. Here, we report a strong Bruce effect in a wild primate, the gelada (Theropithecus gelada). Female geladasterminate 80% of pregnancies in the weeks after a dominant male is replaced. Further, data on interbirth intervals suggest that pregnancy termination offers fitness benefits for females whoseoffspring would otherwise be susceptible to infanticide. Taken together, data support the hypothesis that the Bruce effect is an adaptive strategy for females of some species.

Supported by the National Science Foundation (BCS-0824592 to EKR, BCS-0715179 to JCB), the Wildlife Conservation Society (SSF 67250 to JCB), the National Geographic Society (8100-06 to JCB), the Leakey Foundation, and the University of Michigan.

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