Saguinus bicolor
Brazilian bare-faced tamarin

Usually only the dominant female in a social group will mate. Other females are unable to ovulate as long as the dominant female's pheromones are present. Although usually only the dominant female in a social group breeds, it is not known which males participate in breeding, and whether the species is polyandrous. It should be noted, however, that in other species of this genus, the dominant female has been observed copulating with more than one adult male, and given other similarities between all tamarins, it is likely that S. bicolor shows some degree of polyandry. (Goldizen, 1987; Nowak, 1999; Snowdon and Soini, 1988)

Eighty percent of births are twins, with litter weights ranging from 14.1 to 23.5% of the maternal weight. Within the genus Saguinus, it is common for the father as well as other members of the group to assist in the care, grooming, carrying, and feeding of young. (Goldizen, 1987; Nowak, 1999)

Generally, within the genus Saguinus, the young are born fully furred, but helpless. However, they are able to cling to their parents. The young are able to explore their environment on their own by about 21 days of age, but they continue to ride on their parents until they are 6 or 7 weeks old. Solid foods may be ingested by the young as early as 4 weeks of age, although nursing can continue much longer. (Nowak, 1999)

Females have an estrous cycle of approximately 15 days in this genus. Gestation lengths for these tamarins have been reported as around 140-150 days. Females reach reproductive maturity around 18 months of age, and males reach reproductive maturity around 2 years of age. It is reasonable to suspect that S. bicolor is similar to its congeners in these respects. (Nowak, 1999)

Parental care in tamarins is somewhat unique among primates, in that males provide a great deal of it. Both parents provide general care for their young, but the males usually carry them. Males transfer the young back to the mother every couple of hours to nurse. It is thought that the energetic demands of lactation and carrying such relatively heavy twin offspring are just too much for a single mother to manage. (Goldizen, 1987; Nowak, 1999; Price, Feistner, and Anna, 2001; Rowe, 1996)

From birth until 20 weeks of age, juveniles are given solid food by both parents, although fathers take the lead in providing such food for the young. Self-feeding is dominant after this period. (Goldizen, 1987; Nowak, 1999; Price, Feistner, and Anna, 2001; Rowe, 1996)

It is interesting to examine the communal care of offspring in tamarin species with regard to the polyandrous mating system noted in some species. It may be that this system has evolved because the energetic burden of reproduction in these small animals, which subsist mainly on high quality fruit and insect foods, is so very great. Because the young weigh so much, grow rapidly, and need a lot of milk, a mother is not able to carry the twins, and simultaneously obtain enough food to maintain both herself and her milk supply. In order to ensure that the offspring have a good chance of survival, a male may benefit by allowing another male to mate with a female (thereby reducing certainty of paternity) but providing an additional "father" to share the responsibilities of rearing the young. This may increase survivorship of the young tamarins. (Goldizen, 1987)

Nonreproductive individuals in tamarin social groups have also been seen to care for young, although at a lower frequency than parents. This sort of alloparental behavior may benefit the helpers by giving them valuable experience in the care of the young, and also in ensuring the survival of siblings or other close relatives. Although not specifically reported for S. bicolor, it is likely that some of this helping behavior occurs. (Goldizen, 1987)

Nancy Shefferly (editor), Animal Diversity Web Staff.

Rachel Kutschera (author), University of Wisconsin-Stevens Point. Chris Yahnke (editor, instructor), University of Wisconsin Stevens Point.