Initiation of feeding by four sympatric Neotropical primates (Ateles belzebuth, Lagothrix lagotricha poeppigii, Plecturocebus (Callicebus) discolor, and Pithecia aequatorialis) in Amazonian Ecuador: Relationships to photic and ecological factors.

We examined photic and ecological factors related to initiation of feeding by four sympatric primates in the rain forest of Amazonian Ecuador. With rare exceptions, morning activities of all taxa began only after the onset of nautical twilight, which occurred 47-48 min before sunrise. The larger spider and woolly monkeys, Ateles belzebuth and Lagothrix lagotricha poeppigii, left their sleeping trees before sunrise about half the time, while the smaller sakis and titi monkeys, Pithecia aequatorialis and Plecturocebus (formerly Callicebus) discolor, did not emerge until sunrise or later.