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

A Vandenbergh effect in wild geladas?


1Psychology, University of Michigan, 2New York Consortium of Evolutionary Primatology, 3Anthropology, University of Illinois at Urbana Champaign, 4Anthropology, University of Michigan

Friday 8:30-8:45, Galleria South Add to calendar

In 1967, John Vandenbergh conducted a series of remarkable experiments demonstrating that female mice mature significantly earlier when housed with an unrelated adult male as compared to being housed alone (Vandenbergh 1967). This “Vandenbergh effect” is thought to be one way that females can optimize the timing of maturation in response to environmental and social conditions. Intriguingly, a handful of cases from primate studies (including several from humans) offer tentative support for male-mediated maturation. However, whether female maturation is systematically accelerated by exposure to novel males remains untested in natural primate populations. Here, we investigated whether the onset of sexual maturation in wild female geladas (Theropithecus gelada) is sensitive to the social environment – particularly with respect to the arrival of unrelated males. Geladas are particularly relevant subjects for this research because gelada society features polygynous social groups (i.e., reproductive units) with frequent male replacement, and genetic data indicate that females mate exclusively with males in their unit. We examined the timing of all female maturations across 6 years of data from 21 distinct units. Our data indicate that the arrival of novel males triggers maturation for female geladas – a possible Vandenbergh effect. Furthermore, young females residing in groups with unrelated males reached maturation at a younger age compared to those residing in groups with only their fathers. Taken together, these data suggest that the Vandenbergh effect is a salient factor influencing sexual development in female geladas.

Supported by the University of Michigan (to JCB), the National Science Foundation (BCS-0715179 to JCB), National Geographic (to JCB), the Leakey Foundation (to JCB), and the Wildlife Conservation Society (to AL & JCB).

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