ORIGINAL ARTICLE Andrew J. Plumptre Æ Debby Cox Counting primates for conservation: primate surveys in Uganda Received: 6 September 2004 / Accepted: 26 February 2005 / Published online: 13 August 2005 Ó Japan Monkey Centre and Springer-Verlag 2005 Abstract Primate census techniques have been devel- oped over the past 35–40 years yet there is still some confusion and great variation in the methods used. This precludes comparisons between sites where different techniques have been used. This paper discusses the variations between the methods that seem to be prac- ticed currently and then describes a census of primates in the forests of western Uganda. Primate density and biomass varied greatly between forests as well as within forests and this is probably related to food availability. Chimpanzee (Pan troglodytes) density was strongly correlated with nest encounter rates from reconnais- sance walks in the forest. This result can be used to estimate chimpanzee density in forests where it is diffi- cult to survey this species (e.g., due to security reasons). A total of 4,980 chimpanzee was estimated for Uganda which is higher than previously guessed, but still of conservation concern. Only four forests had more than 500 individuals which gives concern for long-term pop- ulation viability. Keywords Biomass Æ Chimpanzee Æ Primate census Æ Tropical forest Æ Uganda Introduction Primate censusing techniques have been developed since the late 1960s. Currently, there is general agreement that line transect surveys are the most efficient method for surveying most forest species, but there are still several different propositions as to what data should be col- lected and how they should be analyzed (Ghiglieri 1984; Tutin and Fernandez 1984; Whitesides et al. 1988; Hashimoto 1995; Plumptre and Reynolds 1996; Struhsaker 1997). Different methods will give different results and there is a need to develop uniform methods that are repeated over time if we are to successfully monitor primate populations for conservation purposes. Monitoring using line transect techniques does lead to relatively high standard errors and coefficients of vari- ation (Plumptre 2000) which makes it difficult to detect population changes unless these are of the order of 25–30%. Using different censusing techniques intro- duces additional sources of unknown error and as such makes it practically impossible to monitor populations. Counting primates is useful for conservation in several ways. It provides: 1. A baseline density or total number that can be monitored in the future 2. An assessment of the importance of different habitats for primate conservation 3. An assessment of changes in numbers since a previ- ous census period 4. An assessment of population trends if censuses are carried out frequently enough. Each of these can help conservation managers decide where to intervene to best conserve a species and also assess whether their conservation actions are truly working to conserve a species. Methods Primate census techniques Direct counts versus line transects Two types of counts that involve direct sightings exist. The first is a ‘‘complete’’ count of all animals. Examples of this include the gorilla (Gorilla beringei) counts in the Virunga Volcanoes and Bwindi Impenetrable national A.J. Plumptre (&) Wildlife Conservation Society, PO Box 7487, Kampala, Uganda E-mail: aplumptre@wcs.org D. Cox Jane Goodall Institute, Entebbe, Uganda Primates (2006) 47: 65–73 DOI 10.1007/s10329-005-0146-8