INTRODUCTION

In widely different habitats and among taxonomically diverse groups, recent extinction rates are 100–1000 times their pre-human levels, with regions rich in endemics especially at risk (Wilson, 1988; Pimm et al., 1995). There is a strong recognition that many primate species are in jeopardy of extinction in the near future (Mittermeier, 1988; Rowe, 1996). Half of the 250 primate species are considered to be of conservation concern according to the Primate Specialist Group of the Species Survival Commission of the World Conservation Union (IUCN, 1996). It is an achievement for primate conservationists that we have not lost any species in this millennium, as other groups such as rodents, birds and reptiles have (Mittermeier, 1996). And primatologists should be congratulated that within the last decade more than 15 new primate species have been discovered or rediscovered (Meier et al., 1987; Simons, 1988; Hershkovitz, 1987, 1990; Meier & Albignac, 1991; Mittermeier et al., 1992; Ferrari & Lopes, 1992; Queiroz, 1992; Silva & Noronha, in press). But it is a sobering fact that 96 primate species are in the Critically Endangered or Endangered category and could disappear within the next 100 years (Rowe, 1996).

The inventory data and categories of threat developed by the Conservation Monitoring Center (IUCN) and The United States Endangered Species Act (USESA), (World Conservation Monitoring Centre, 1992; Rowe, 1996) are very useful in targeting primate species with high conservation priority. But the lists of endangered species alone have limited use in estimating causes and consequences of primate extinctions. Indeed, a major limitation of species counting in conservation biology is that ecological measures of biodiversity are not reducible to taxonomic measures (e.g., Fig. 18.1, Jernvall & Wright, 1998).