Infant carrying in family groups of Goeldi's monkeys (Callimico goeldii)

Goeldi's monkey (Callimico goeldii) is closely related to marmosets and tam arins. Like marmosets and tamarins, C. goeldii lives in family groups, and fathers and older offspring (helpers) participate in infant carrying. In co ntrast to the typical twin births in marmosets and tamarins, C. goeldii has only single offspring, and paternal carrying is delayed. We studied infant carrying following 26 births in eight groups of C. goeldii, testing hypoth eses proposed in the literature on infant carrying in marmosets and tamarin s. The infant; was carried exclusively by the mother for the first 26.3 day s after birth. Afterwards other group members participated in infant carryi ng. Whereas the C. goeldii mother is always the main carrier, the father do es not always carry more than helpers. In contrast to other callitrichids, age and sex of sibling helpers was not found to have an effect on the parti cipation in infant carrying. The participation in infant carrying in Callim ico indicated intraindividual consistency, i.e., the amount of infant carry ing per formed by fathers and helpers following one birth correlated signif icantly with the amount of infant carrying of the same individuals followin g the next birth. We found a significant negative correlation between paren tal infant carrying and group size, indicating that helpers really do help, sharing the carrying burden with their parents. This is attributed to a cl ear trend for a reduction in maternal carrying in the presence of helpers, whereas fathers did not benefit from helpers. We conclude that the infant-c arrying pattern in C. goeldii is different from the infant-carrying pattern in marmosets and tamarins. The main differences were that the mother inste ad of the father is the main carrier, and that there is a clear time delay between infant birth and when the father and helpers participate in infant carrying. (C) 2001 Wiley-Liss, Inc.