, Volume 17, Issue 4, pp 733-747
Date: 01 Jan 2008

Conservation implications of low encounter rates of five nocturnal primate species (Nycticebus spp.) in Asia

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Abstract

Five species of slow lorises were once considered to comprise a single strongly polymorphic species, Nycticebus coucang, ranging throughout South and Southeast Asia. The cryptic nature of these nocturnal primates has led to a lack of understanding of their distribution patterns and abundance. In short surveys, often few if any lorises are detected, meaning that the few available density estimates are from long-term studies. Based on new research in Sebangau National Park, Borneo, and compilation of survey data from other areas, we provide the first comparative abundance estimates for all five slow loris species: N. coucang occurred in significantly higher abundances (median encounter rate 0.80/km: n = 15), than N. bengalensis (0.26/km; n = 12), or N. javanicus (0.11/km: n = 2), N. menagensis (0.02/km: n = 3), and N. pygmaeus (0.13/km: n = 4). Abundance estimates in Sebangau (0.19/km) did not increase with increasing survey effort, but for all species and studies combined, study duration was positively correlated with abundance estimates. We did not find a relation between abundance and body mass, nor between abundance and latitude. Long-term studies are more likely to be conducted at sites where the species of interest is particularly plentiful. The data suggest that slow lorises occur at low abundances throughout much of their range, and some in larger social groups than previously assumed. We recommend taking into account the species’ heterogeneous distribution (potentially requiring larger survey effort), their social structure, the use of red lights as opposed to white lights whilst surveying, and to make use of their vocalisations when surveying slow lorises.