APPLYING GPS TO THE STUDY OF PRIMATE ECOLOGY - A USEFUL TOOL

Data on the spatiotemporal distribution of resources can be collected and plotted using GPS (global positioning system) and GIS (geographica l information system) technologies. By combining such data with inform ation on foraging and ranging behavior of nonhuman primates, one can a nalyze the influence of resource distribution on social organization a nd group cohesion. We investigated the abilities of a three-channel GP S receiver to collect location data under varying canopy densities in both temperate and tropical forests. Eighty randomly selected points w ere sampled in a beech-maple forest in northeast Ohio, USA; 65 points also were sampled at several tropical forests in Costa Rica and Trinid ad. At each point we attempted to obtain a GPS position fix; we also d etermined the speed of satellite acquisition and measured canopy densi ty using a spherical densiometer. The ability to obtain a reading diff ered greatly between the two forest types (chi(2) = 53.79, P < 0.001). Ninety-seven percent of all attempts were successful in the temperate forest, whereas only a 34% acquisition rate was obtained in the tropi cal forests. Logistic regression showed that the probability of obtain ing a reading in Neotropical forests was 75% but only when canopy cove r was less than 20%. Thus, these minimal-channel GPS units may be of l imited utility for behavioral ecologists working in closed-canopy Neot ropical forests. (C) 1998 Wiley-Liss, Inc.