Only one female per group breeds during a breeding season, although she may mate with more than one male in the group. Birth weight is usually 9 to 15% of the mother's weight, which is considerably higher than with other primates. All group members take some part in carrying the young, and surrender food morsels, particularly insects, to them and the breeding female. So far as it is known, this form of cooperative breeding is unique among primates. By 10 weeks the young are independent, and reach puberty at 12 to 18 months.