Food sharing patterns in three species of callitrichid monkeys (Callithrix jacchus, Leontopithecus chrysomelas, Saguinus midas): Individual and species differences.

Food sharing (FS) in cooperatively breeding callitrichids is unusual among nonhuman primates because they regularly share significant amounts of preferred food with immatures and engage in proactive FS. However, it is still unclear which classes of individuals (males or females, breeders or helpers) engage most in FS, and whether differences exist among callitrichid species. In the first part of this study, we characterized general FS patterns in common marmosets (Callithrix jacchus). We found substantial adult-immature FS, and female breeders shared the least with immatures. This conflicts with previously published studies, where data were collected with the prevailing standard method of providing a food bowl to the entire group. In the second part, a comparison of our access-bias-free method and the standard method suggested that previous findings are likely the result of access bias. In the third part, we investigated species differences in adult-adult FS among common marmosets, golden-headed lion tamarins (Leontopithecus chrysomelas), and red-handed tamarins (Saguinus midas). As common marmosets show lower levels of interdependence within groups, we expected more adult-adult FS in tamarins compared with marmosets. Adult-adult FS was indeed more prevalent in tamarins and not exclusively directed from male breeders to female breeders. Therefore, our results suggest that adult-adult FS in marmosets mostly reflects the high energetic demands of female breeders, whereas in the more interdependent tamarins, it may be used to reinforce cooperative bonds between adult group members.