SLEEPING HABITS OF TAMARINS, SAGUINUS-MYSTAX AND SAGUINUS-FUSCICOLLIS(MAMMALIA, PRIMATES, CALLITRICHIDAE), IN NORTH-EASTERN PERA

The sleeping habits of moustached tamarins, Saguinus mystax, and saddl e-back tamarins, Saguinus fuscicollis, were studied in northeastern Pe ru. Five types of sleeping sites were distinguished: 1) Jessenia batau a palms; 2) tree hollows; 3) dense tangles of vegetation; 4) crotches; 5) open horizontal branches. Both tamarin species used Jessenia-palms most frequently. Tree hollows ranked second in the saddle-back tamari ns, but were never used by moustached tamarins. Sleeping sites of mous tached tamarins were located significantly higher than those of saddle -back tamarins. Jessenia-palms used by moustached tamarins were signif icantly higher than palms from a random transect sample, but this was not the case for Jessenia-palms used by saddle-back tamarins. For both species, concealment seems to be more important than height above gro und. The maximum number of subsequent nights spent in the same sleepin g site was two in moustached tamarins and six in saddle-back tamarins. The two tamarin species did not compete for sleeping sites. While the general pattern of sleeping site selection conforms to hypotheses pre dicting safety from predators as a major factor, differences between t he two tamarin species reflect general niche differences between them. Most sleeping sites are located in exclusively used parts of the home range. Moustached tamarins generally use sleeping sites that are clos e to the last feeding site of the afternoon. The distance between simu ltaneously used sleeping sites of moustached and saddle-back tamarins are generally close together, which helps to minimize time spent out o f interspecific association.