Abstract

GOFFARD, Denisse A.; ARROYO-RODRIGUEZ, Víctor  and  AGUIRRE, Luís F.. Populations of howler monkeys (Alouatta sara) in four sites of Santa Cruz, Bolivia. Mastozool. neotrop. [online]. 2008, vol.15, n.2, pp.285-295. ISSN 0327-9383.

The Bolivian red howler monkey (Alouatta sara) is endemic to central Bolivia, and probably one of the least studied species of the genus. In this paper we present the first report on the populations of A. sara located in four different study areas of central Santa Cruz, Bolivia: The Ocorutú Sanctuary (a 172 ha reserve that is well conserved and protected), and three cattle ranches which suffer from differing degrees of anthropogenic pressure. In total, we sampled 619 ha of tropical rain forest, and we encountered 143 individuals (total density = 23.1 ind./km²) from 23 troops and two solitary adult males. The number of individuals, number of troops, and density were higher in Ocorotú Refuge (51 ind., 8 troops, 44 ind./km²) than in the altered sites (ranges = 19 to 44 ind., 4 to 6 troops, 10 to 33 ind./km²), with poaching being the main factor that could explain this population pattern. Nevertheless, social organization was similar between sites, with troops formed of 2 to 12 individuals (average troop size = 6.2 individuals), most of them with a single male (n = 15, 65%), and no troops with more than two males. Although two of these four populations seem to be expanding, their long-term persistence will depend on management plans carried out by the owners of the cattle ranchers.

Keywords : Density; Habitat perturbation; Howler monkeys; Social organization.

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