Population density of primates in a large fragment of the Brazilian Atlantic rainforest

We performed a line transect survey (352.4 km) of primates in the Serra de Paranapiacaba, at one of the largest relatively undisturbed fragments of the Atlantic rainforest of Southeastern Brazil (ca. 1400 km²), in August 1998. The brown capuchin, Cebus apella nigritus, was the most common species found in the area (20 groups, density estimate: 5.31 ± 2.05 individuals per km², mean ± SE). Nine groups of the brown howler monkey, Alouatta guariba clamitans, and eight of the woolly spider monkey, Brachyteles arachnoides arachnoides, were also recorded, with preliminary density estimates of 0.79 ± 0.40 and 2.33 ± 1.37 individuals per km², respectively. Density estimates for these species in other fragments of Atlantic rainforest are reviewed, showing that densities in Paranapiacaba are among the lowest reported. It is suggested that the higher densities reported for isolated populations in small forest patches (<50 km²) is related to the absence of main primate predators, the density compensation phenomenon and the ecological plasticity of some primate species. In contrast, local extinction in many small patches is probably related to hunting pressure. Given the important primate populations found in the Paranapiacaba fragment, conservation strategies for the studied species should give priority to effective protection of the largest remnant fragments from illegal hunting and deforestation, rather than translocation of individuals or captive breeding programs to introduce monkeys in small forest fragments vulnerable to hunting and of uncertain future.