174 S. Hameed et al.
Species coverage, temporal and spatial distribution of the studies
FIG. 4 Different primate survey methods used in the studies included in our analysis.
prior to our review (2016–2021), targeting only 27%(n = 7) of the 26 Indian primate species. There has been great dis- parity in the distribution of population status studies across Indian primate species over the years. A few species, includ- ing rhesus macaques, bonnet macaques Macaca radiata and eastern hoolock gibbons, have received more attention from researchers than others, with the tufted gray langur, black-footed gray langur and southern pig-tailed macaque Macaca nemestrina being studied the least.
The population status studies on Indian primates conducted since 2010 have diversified in terms of species coverage (Fig. 5). In terms of geographical coverage,.60% of the re- ports represent surveys conducted in theWestern Ghats and north-eastern Himalayas (Fig. 6), and 34% of studies were conducted in non-protected areas. Unlike the studies con- ducted in non-protected areas, which showed stable, in- creasing or declining population trends, all reports (66%) conducted exclusively in protected areas reported declining population trends, except in the Chakrashila Wildlife Sanctuary, Assam (Chetry et al., 2020). In contrast, one study conducted in the upper Brahmaputra Valley of north- eastern India reported increasing population trends within and decreasing trends outside protected areas. Focused on the overall population abundance of six primate species, this study reported a 251% increase of the population within protected areas for all six species, but a dramatic decline outside protected areas caused by rapid, severe habitat loss resulting in small habitat fragments and disruption of canopy continuity (Sharma et al., 2012).
Discussion
The overall trend in the population status of Indian primates mirrors the global pattern, with a population decline in 75% of primate species worldwide (Estrada et al., 2017). This declining trend in the population of Indian primates has persisted for decades, with 70% of species categorized as
FIG. 5 (a) Temporal distribution of the number of publications on the population status of Indian primates and (b) total number of primate species surveyed for their population over time.
Oryx, 2024, 58(2), 167–178 © The Author(s), 2023. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323000716
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