Geographic distribution and abundance of woolly (Lagothrix cana) and spider (Ateles chamek) monkeys in southwestern Brazilian Amazonia.

Two species of frugivorous atelids, Ateles chamek and Lagothrix cana, occur in southwestern Brazilian Amazonia. Populations were surveyed at 36 sites in the state of Rondônia. Ateles chamek is widespread, but the distribution of L. cana is limited by a combination of riverine barriers and ecological factors, possibly including competition with A. chamek. Groups of L. cana were generally larger and more abundant than those of A. chamek, even in syntopy. The transitional forest that predominates in the extreme south of Rondônia (Hylea‐cerrado) is not a barrier to either species, with both species being tolerant of habitat disturbance when hunting pressure is low. Am. J. Primatol. 56:57–64, 2002. © 2002 Wiley‐Liss, Inc.