Factors affecting the rates of food calls given by red-bellied tamarins

Abstract

Food calls have been identified in a number of avian and mammalian species. Most investigations of the proximate elicitors of food calls have focused on palatability, quantity or divisibility of the food. Proposed, but mostly untested, functions of food calling have typically centred around the benefits associated with sharing food or attracting conspecifics to the food site. In two experiments involving five groups of captive red-bellied tamarins, Saguinus labiatus, rates of food calling were quantified in conjunction with four variables: quantity of food, food preference, food exchange, and visual contact with groupmates upon discovery of the food source. In agreement with other studies of food calling, calling rates increased when the food was particularly palatable, and when it was presented in large quantities. Food exchanges were not associated with food calling. There was also a social-location effect: when the food was discovered while the finder was temporarily out of visual contact with its groupmates, rates were higher than when groupmates were visible, even when the quantity of food was very small, and hence not ‘sharable’. These results suggest that red-bellied tamarin food calls are not entirely governed by opportunities or inclinations to share food, nor are they solely a function of arousal in the presence of large amounts of preferred food. Red-bellied tamarin food calls may be functionally analogous to those of house sparrows, Passer domesticus, which recruit flockmates to the vicinity of the caller. To the extent that a species is dependent on intra-group cohesion for critical daily activities and protection, food calls may benefit the caller by drawing its allies near, even if calling increases feeding competition.