Developmental changes in food transfers in cotton-top tamarins (Saguinus oedipus)

We investigated the development of food transfer and independent feeding in cotton-top tamarin (Saguinus oedipus) families. We studied the relationship between infant-directed vocalizations and food transfers on the development of independent feeding in infants. We experimentally tested ten infants (eight twins and two singletons) three times a week for 17 weeks from before weaning through 20 weeks. Food transfers and vocalizations made during tests were recorded and analyzed to determine (1) the role of vocalizations (C- and D- chirps and D-chirp series) in food acquisition, (2) the relationship between food transfers and individual food acquisition, and (3) whether, owing to energetic costs of nursing and carrying twins, food is transferred to twins sooner than to singletons. Infants were more successful in acquiring food via begging when adults produced repeated vocalizations than when adults did not vocalize. Adults emitted more food-related vocalizations in rapid series when in the presence of infants, whereas during feeding in the absence of infants only single unit vocalizations were produced. Begging occurred frequently. Changes over infant age were not significant when all infants were included in analysis. However, when twin data were analyzed alone, begging success changed significantly over months, with successful begging peaking in month 3 (week 12). Begging success rate did not differ between twins and singletons, although twins fed independently sooner and at a higher rate than did singletons.