Demography, habitat use and activity budget of a wild group of black-faced black spider monkeys (Ateles chamek) in Las Piedras, south-eastern Perú

Abstract

Spider monkeys are one of the main seed-dispersal agents in the Amazonian ecosystem and therefore help regenerate the rainforest. The black-faced black spider monkey (Ateles chamek) is internationally recognized as Endangered, and its range is limited to Peru, Bolivia and Brazil. Spider monkeys are a difficult genus to study and little is known about their populations in the wild. Here we present the results of a study on demography, habitat use, activity budget and preliminary notes on ranging pattern and diet of a wild group of A. chamek studied in a floodplain forest in south-eastern Peru. The group (in total eight to nine individuals) had a home range of approximately 1.6 km2 (160 hectares) with a daily path length of approximately 1,200 m. The group was encountered at canopy levels above 20 m in height 75.2% of the time and rarely descended to lower forest levels. There was a weak but significant positive correlation between the number of encounters with individuals of the study group and the number of feeding trees in an area (R2 = 0.38, N = 93, P > 0.001). The majority of their diet consisted of fruits, followed by leaves. Resting accounted for 41.9% of their activity budget, with foraging accounting for 30% and traveling 23.8%. Most findings of this study are consistent with other studies on the species, but we found that the group size in our study was unusually small. However, this did not seem to have an influence on home range size or activity budget.