The effects of cattle ranching on a primate community in the central Amazon
According to the International Union for Conservation of Nature and Natural Resources (IUCN), 64% of primate species are declining in the wild and 49% face a significant risk of extinction. This crisis is largely the result of human activity, including logging, ranching, and hunting. In this study I examine the impacts of the anthropogenic habitat disturbances associated with cattle ranching on a primate community. Research was conducted at the preeminent site for the study of rain forest fragmentation, the Biological Dynamics of Forest Fragments Project, Manaus, Brazil. I surveyed 8 line transects totaling 13 km that sampled: 1) secondary forest on abandoned cattle pasture,2) selectively logged primary forest, and 3) undisturbed primary forest. Specifically, I tested for edge effects, niche partitioning, and interhabitat differences in population density. Primate presence in edge habitats was negatively related to the amount of fruit consumed, a relationship that was also apparent in the densities of individual species. Four species were more abundant in edge habitats: Alouatta macconnelli (folivore-frugivore), Chiropotes chiropotes (seed predator), Saguinus midas (generalist), and Sapajus apella (generalist); one was less abundant: Ateles paniscus (frugivore); and the last showed no edge-related pattern: Pithecia chrysocephala (seed predator). Niche partitioning was evident in diet and macrohabitat use. In addition, in primary forest there was partitioning along several microhabitat variables. In secondary forest, however, microhabitat partitioning was absent, possibly due to habitat constraints or low encounter rates. Body size was positively related to use of vertical strata in both habitats, hence a combination of body size and competition may drive vertical niche partitioning. Primate characteristics were not related to their presence in selectively logged or undisturbed primary forest, though body size was inversely related to presence in secondary forest. Only the two generalists (Saguinus and Sapajus) heavily utilized secondary forest. The two largest species, Ateles (frugivore) and Alouatta (folivore-frugivore), showed an equal preference for all primary forest (logged and undisturbed) over secondary forest. Chiropotes (seed predator) also preferred undisturbed primary forest while Pithecia (seed predator) was relatively uniformly distributed.