A METHOD FOR CENSUSING THE GREATER WHITE-NOSED MONKEY IN NORTHEASTERNGABON USING THE POPULATION-DENSITY GRADIENT IN RELATION TO ROADS

This paper-presents a method for estimating monkey numbers in a large area of forest where there is a gradient of monkey densities. The meth od is illustrated using data collected in the northeastern forests of Gabon during an earlier project. These forests:are sparsely populated and there are few roads. The density of Cercopithecus nictitans increa ses with distance from the nearest road. A geographic information syst em (GIS) divided the forest into bands of increasing distance from the nearest road. The number of monkeys in each band is the product of th e monkey density in that band and the area of the band. Summing across bands gives the population estimate; the standard error can be estima ted by bootstrapping. The optimum sample size can be estimated by simu lation. Combining estimates of the density-gradient with a GIS is a co st-effective method of censusing primates in extensive forests.