Reproductive strategies of cotton-top tamarins

The reproductive strategies of cotton-top tamarins (Saguinus oedipus) were investigated over a 2.5-year period in a captive breeding colony. Groups ranged in size from two to 14. The care of 21 infant tamarins was investigated over the first 12 weeks of life. Infants in larger families received more care than those in smaller families; singleton infants were carried more than twins. Parents provided more care than older siblings (helpers); older helpers provided more care than younger helpers. Individual contributions to care, particularly of fathers, declined as group size increased. There was evidence that tamarins competed to carry infants, and that some individuals attempted to restrict carrying by others. Tamarins carrying infants spent significantly less time feeding, foraging and moving than they did when not carrying, due partly to a decrease in general mobility, and partly to an increase in the time they spent concealed, presumably to avoid predation. The behaviour of five breeding pairs was observed for approximately 12 weeks before and 12 weeks after birth. During lactation, breeding females increased their feeding and foraging times to levels up to twice as high as those seen in pregnancy. There was evidence that breeding females attempted to encourage males to stay nearby to help with infant care by increasing grooming, and proceptive and receptive behaviour, shortly before postpartum. However, females were most attractive to males during the first weeks postpartum. Males mounted females significantly more often when carrying infants, suggesting that they might be using infants as part of a courtship strategy. Observations of a polyandrous group showed that the female had no preferred sexual partner. All three males in the group mated with her, and did not interfere in one another's copulations. A daughter in another group became pregnant and gave birth to a stillborn infant.There was no evidence of aggression between her and her parents.The possible benefit to be gained from a communal rearing system by both breeding and helping tamarins are discussed, and some predictions put forward to guide further research