Foraging for animal prey by outdoor groups of Geoffroy’s marmosets (Callithrix geoffroyi)

I studied animal prey foraging by three outdoor groups of Geoffroy’s marmosets, Callithrix geoffroyi, over the course of two summers (June–August 1994; August–September, 1995. Marmosets are highly motivated to forage for animal prey, as demonstrated by the amount of time spent foraging for insects and small vertebrates even in the presence of provisioned, high-quality food. Like their wild congeners, the marmosets engaged in prolonged visual searches of selected areas while slowly locomoting. They seldom used their hands to manipulate substrates. The marmosets were startled proportionately more often while foraging for animal prey than would be predicted by their overall time budgets, and they regularly, if briefly, interrupted their search/locomote pattern with sweeping scans of the surroundings that may contribute to a vigilance function. While carrying infants, they almost never foraged. These results are consistent with the notion that marmosets may be particularly vulnerable to predation while searching for animal prey. Most of the data on marmoset and tamarin feeding ecology have focused on fruits and gums. My data underscore the need to understand better the role of animal prey in the behavioral ecology of callitrichids.