168 S. Hameed et al. Taxonomic accuracy plays a crucial role in understand-
ing species distribution ranges, population trends, threats and conservation efforts (Mace, 2004; Lewis & Maslin, 2015). The ambiguity in the taxonomic status of some Indian primate species arises from the fact that the majority of existing classification schemes rely on plastic morpho- logical traits, a situation that is further complicated by in- compatibility between various classification systems (Nag et al., 2011). Given these taxonomic uncertainties, the exact number of Indian primate species at risk of extinction re- mains unknown (Ashalakshmi et al., 2015). There have, however, been studies employing molecular techniques in an effort to resolve this issue (Karanth et al., 2008, 2010a; Osterholz et al., 2008; Wangchuk et al., 2008; Ashalakshmi et al., 2015). For example, studies based on molecular phylogeny and biogeography have led to the as- signment of the purple-faced langur Semnopithecus vetulus and Nilgiri langur Semnopithecus johnii to the genus Semnopithecus, rather than Trachypithecus (Karanth et al., 2008; Osterholz et al., 2008), and maintaining the species status of the tufted gray langur Semnopithecus priam (Blyth, 1844) and black-footed gray langur Semnopithecus hypoleucos (Blyth, 1841). A study using an integrative taxo- nomic approach confirmed species status for the Himalayan langur Semnopithecus schistaceus (also referred to as Nepal gray langur) but did not support dividing this taxon into multiple species or subspecies (Arekar et al., 2021). Similarly, a recent study ascertained the hoolock gibbon Hoolock hoolock as the only gibbon species in India (Trivedi et al., 2021), contrary to an earlier report of there being two species, the eastern Hoolock leuconedys and western Hoolock hoolock hoolock gibbons (Das et al., 2006). Taking these ambiguities into account, a recent study re-
ported 24 species of non-human primates in India, includ- ing two species of lorises, 10 species of langurs, 10 species of macaques and two species of small apes (Singh et al., 2020), of which 18 species are categorized as threatened on the IUCN Red List (IUCN, 2021). For many primate species in India, information on their current distribution is lack- ing, which impedes the assessment of their conservation status (Karanth et al., 2010b). Furthermore, with the excep- tion of a few recent studies, most surveys on Indian pri- mates have been methodologically outdated and geograph- ically limited (Singh et al., 2020). To improve our understanding of the conservation status
of Indian primates, we carried out a comprehensive review of the published literature, seeking to answer the following questions: (1)What do the data from recent studies indicate about population trends of Indian primates and the reasons for any observed changes? (2) How has the conservation status of Indian primates changed over time? (3) What are the reasons for such changes? (4) How do these changes vary amongst different species with respect to their habitats and the level of anthropogenic disturbance?
Methods
Weundertook a systematic reviewusing the search, apprais- al, synthesis and analysis (SALSA) approach (Grant & Booth, 2009). We followed methods described by Shrestha et al. (2022) and included research articles dedicated either fully or in part to the study of the population status of non- human primates in India (Fig. 1). To keep our findings rele- vant to current species conservation efforts, we limited our search to studies published during the past 2 decades (2000– 2021). We conducted a Boolean search across the Web of Science (Clarivate, Philidelphia, USA), Research Gate (ResearchGate, 2023), and Google Scholar (Google, 2023) platforms, using a combination of keywords related to the population and conservation status of Indian primates. To retrieve the relevant results, we used search operators such as AND, OR and NEAR in combination with species names and different keywords related to population status (Supplementary Table 1).Weretrieved a total of 105 research publications related to Indian primates, which we examined for the presence of search query terms in the title, abstract and keywords. After this initial selection process, 41 publica- tions accounting for 62 status reports, including multi- species studies, were retained for further analysis. For each research article in this sample (Supplementary Table 2), we recorded information on the population trend, year of sur- vey, main threats reported, study area location, protection status of the study area and survey methods used. In the case of species for which repeated surveys had been conducted in a given area, we considered only the results from the most recent study. Although various studies have attempted to resolve the taxonomic ambiguity among Indian primates, here we considered the species taxonomy as reported by the authors in the research articles. We retrieved information on all primate species present in India, irrespective of whether or not they are threatened. We conducted all data analyses in R 4.2.2 (R Core Team, 2013) and used ArcGIS Desktop 10.8 (Esri, Redlands, USA) to map the geographical areas covered by the analysed publications.
Results
Population status We included all primate species in India, along with their conservation status and the number of studies that we found for each species, in our review.We found the highest number of studies on the rhesus macaque Macaca mulatta, but there were no reports on the population status of some species, including several langurs (Table 1). We identified five population status categories (Fig. 2) based on author in- ference in the reviewed articles: declining, increasing, stable, small and recovering populations. Studies that were the first
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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