In comparison with the Neotropical big cats, jaguar (Panthera onca L.) and puma (Felis concolor L.), medium and small felids are poorly studied. Furthermore, studying wild felids in forest habitats is extremely difficult using direct methods given that most species are principally nocturnal and secretive (Gittleman 1996). Indirect methods are therefore particularly important, e.g. radio-telemetry (Emmons 1987, 1988; Konecny 1989, Ludlow & Sunquist 1987) or camera trapping (Maffei et al. 2002, Trolle & Kéry 2003). Using systematic camera trap surveys, we compare the population density of ocelots (Felis pardalis L.) across five Bolivian dry-forest sites with different habitat types and/or annual rainfall regimes (Table 1). We hypothesize that ocelot densities will decline as rainfall declines. In addition, we estimate the population of ocelots in the 34 400-km2 Kaa-Iya del Gran Chaco National Park. Finally, we describe and evaluate additional ecological information provided by camera trapping: activity patterns relative to seasonality and moon phase, sex ratios, ranging patterns and relative abundance compared with sympatric felids.