ECOLOGY/EVOLUTION

Second Banana

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Science  15 Jul 2005:
Vol. 309, Issue 5733, pp. 357
DOI: 10.1126/science.309.5733.357c

The mountain gorilla is one of our closest living relatives, surviving in the wild as a population of perhaps no more than a few hundred individuals. Despite the gorillas' extreme rarity, their wariness of humans, and the remoteness of their habitat, an understanding of their ecology and behavior is slowly emerging through decades of patient observation.

In the latest example of such work, Bradley et al. investigated patterns of dominance and reproduction in wild populations of the mountain gorilla in Rwanda over a 15-year period, with a particular focus on how reproduction is apportioned between the adult males. In groups with two adult silverback males, genotypic analyses revealed that the dominant male was responsible for 85% of paternity. The subordinate male is typically unrelated to the dominant, having joined the group after migrating from another. When combined with the genetic data, behavioral observations suggested that the most likely explanation for the dominant male's lack of a reproductive monopoly is that he is unable to prevent the subordinate from having access to the females. This is an example of the “tug-of-war” model of reproductive skew in animal societies, as opposed to the “concessions” model, where the dominant male permits limited matings by subordinates—a situation that is more likely when the males are related to one another. — AMS

Proc. Natl. Acad. Sci. U.S.A. 102, 9418 (2005).

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