Cutting costs in response to predatory threat by Geoffroy's marmosets (Callithrix geoffroyi)

Ideally, prey should respond to their predators efficiently, without over- or underreacting to the threat. This may be particularly important for small-bodied species for whom metabolic demands are high and predatory risk is great. In the current study, two family groups of Callithrix geoffroyi living outside in a rural setting at the Center for Reproduction of Endangered Species, San Diego Wild Animal Park, were observed before, during, and after ten presentations of a great horned owl model. The owl was mounted on a post on a nearby hillside, simulating a situation in which a real but nonimminent threat is posed. As controls, a model of a crow and a cloth bag were also presented, each for ten trials. During the 10 min presentations of the owl, rates of play and foraging decreased, and rates of locomotion and vigilant looking increased from baseline rates. Data on occupation of the best viewing area suggest that the marmosets shared the job of monitoring a potential threat. After the owl was removed, behavior quickly returned to baseline rates, with the exception of looking at the place where the owl had been, and play. Neither the bag nor the crow generated significant differences from the baseline condition that preceded it. Marmosets may reduce the costs of antipredator behavior by appropriately assessing the degree of risk and by quickly resuming important activities once a potential threat has passed.