1 Four types of sleeping sites were found with 11 different variant forms. Aotus nancymai was found in all forms of sleeping sites while A. vociferans was formed only in the five forms of type A sleeping sites. None of these sleeping sites showed signs of nestbuilding.
2 . Sleeping sites of Aotus offer protection, refuge, ease of routine, and circumstantial entry and exit, shelter, and sufficient space to lodge the family group.
3 A. nancymai sleeping sites were located in the under, lower, and middle stories of the forest below 25 m elevation, whereas A. vociferans slept also in the upper and emergent stories up to 37 m elevation. On the average, A. vociferans tended to use higher sleeping sites than A. nancymai.
4 Competitive interactions and cohabitation of sleeping sites between Aotus and other nocturnal mammals were common. 5. The principal sapwoodbearing trees that presented holes for Aotus sleeping sites were Eschweilera sp. (40.2%), Macrolobium acaciaefolium (12.0%), Campsiandra laurifolia (10.0%), and Calycophyllum spruceanum (9.0%).
