Distribution, social organization, and management of Semnopithecus johnii: An umbrella species of fragmented landscape of the Western Ghats

Abstract

Due to the threats posed by changes in land-use patterns to many species, it is necessary to have a proper description of the distribution of a range-limited species. We aimed to assess the spatial distribution and social organization of Nilgiri langurs, and to model the potential distribution of mixed-species groups of Nilgiri and Hanuman langurs (Semnopithecus priam or S. hypoleucos). We used our database of systematic surveys from 1994 to 2021 as well as the available literature. Nilgiri langurs are found in five regions in the Western Ghats: Nilgiri-Brahmagiri, Siruvani, Anamalai- Parambikulam, Cardamom Hills, and Periyar-Agastyamalai, each with many fragmented sub-populations. They live in mixed-sex groups ranging from 2 to 27 individuals with a mean group size of 9.10 ± 5.54SD and a few all-male bands. The groups with one or two males, several adult females, and immature individuals is a typical trait of the Asian colobine social organization. The potential distribution of mixed-species groups of Nilgiri and Hanuman langurs indicates that they are found on the eastern slopes of the Western Ghats between 500 and 800 m a.s.l, which is a transition zone of evergreen to dry forest landscapes. A detailed description of one of the populations is presented as a case study of fragmentation where the results revealed strategies to manage populations in such landscapes. Since most habitats, especially the rainforest regions, in the Western Ghats, are highly fragmented impacting many species, the results of this study may serve as a model for wildlife management in the Western Ghats.