1Department of Anthropology, New Mexico State University, 2Department of Biology, New Mexico State University
Friday All day, Plaza Level
An unusual mating sequence was observed for black handed spider monkeys in a wild population at La Milpa, northern Belize. Mating in free-ranging and wild populations of the black handed spider monkey (Ateles geoffroyi) usually occurs in private, with the couple separated from the social group, in a dorso-ventral position, and lasts 17 minutes (Campbell 2005).
On March 23, 2011 we observed a large group of spider monkeys (at least 15 individuals) travelling and feeding. After approximately 15 minutes of feeding, an aggregation of males suddenly formed around a female. At least six male spider monkeys attempted to mate with the female in quick succession. They were hanging and attempting ventral-ventral mating. Each male appeared to spend approximately 5 minutes in potential mating position, but copulation could not be verified. Males were not aggressive with each other, but did hang onto one another, causing each other to drop to lower branches from which they would quickly climb back up to the female. The female did not vocalize or attempt to run away, as was observed during the forced copulation of spider monkey female in the wild (Gibson et al., 2008). Instead the female seemed to be receptive to the aggregation of males.
Similar mating aggregations were previously observed for woolly spider monkeys (Brachyteles arachnoides), the females of which copulated with multiple males in quick succession, with no copulation lasting longer than 4 minutes (Milton 1985). Implications for potential sperm competition between male spider monkeys are discussed.