Patterns and determinants of monkey densities in Peru and Bolivia, with notes on distributions
- Cite this article as:
- Freese, C.H., Heltne, P.G., Napoleon, C.R. et al. Int J Primatol (1982) 3: 53. doi:10.1007/BF02693490
A comparative study of species assemblages and population densities was conducted on Amazonian monkey communities in 16 areas, ranging from 3°S latitude in northern Peru to 18°S latitude in southern Bolivia. The habitats ranged from several types of tropical rain forest in the more northern latitudes to dry, deciduous forest in the southernmost study area. The monkey populations of three of the study areas have historically received light hunting pressure; the rest have been moderately to heavily hunted. A transect census technique was used to estimate the relative and absolute densities of all diurnal monkey species except Cebuella pygmaea. The number of coexisting monkey species ranged from 4–6 in the southern areas to 12–14 in the northern areas. The reduction in species richness in central and southern areas of Bolivia is probably attributable to several inimical habitat factors. Predation by humans was found to be the single most important factor affecting monkey densities. Monkey densities, and especially biomasses, were much lower in areas not protected from hunting than in protected areas. Hunting did not affect all species equally. Larger-sized species are hunted more and have severely reduced numbers in unprotected areas, whereas the densities of smaller species are not noticeably diminished in unprotected areas. Large, herbivorous monkey species contributed the major proportion of the total monkey biomass in protected areas. The strong influence of hunting has largely obscured the effects of other factors on population densities.