Effect of the enclosure on carriers' body weight loss in the cotton-top tamarin (Saguinus oedipus)

Infant carrying in cotton-top tamarins is a costly activity that results in weight loss by the fathers and helpers. However, to date, measures of carrying costs have been obtained in small indoor enclosures. We studied body weight changes in adult and subadult individuals from eight large groups (n > 5) for 9 weeks after the birth of infants. Four groups were housed in large indoor/outdoor enclosures (42 m(2) x 3.3 m high), and four were housed in small indoor enclosures (12 m(2) x 2.4 m high). All of the individuals were weighed regularly at least three times a week. Reproductive males lost more weight in the big indoor/outdoor enclosures (mean=6.51%) than in the small indoor ones, as did male adult helpers (mean=5.59%) and female adult helpers (mean=4.4%). Still-growing subadult individuals also lost weight in the big indoor/outdoor enclosures (mean=3.17%), although the differences did not reach significance (P=0.07). These results support the hypothesis that cotton-top tamarins living in more natural settings experience higher weight loss than those housed under less-natural conditions.