Occupancy, Coat Colour Pattern and Social Organization of Mixed-species and Mixed-morphotype Groups of Nilgiri langur (Semnopithecus johnii) and Tufted Grey langur (Semnopithecus priam)

A mixed-species group is formed due to an increase in close association among individuals of different species. Such groups also possibility of having diversity in size, phenotypic similarities and differences, and contrasting morphologies compared to the original species. We studied inter-individual variations in external morphology and social structure in mixed-species groups of Nilgiri langur (NL, Semnopithecus johnii) and tufted grey langur (HL, Semnopithecus priam) between 300 and 800 m in the Anamalai Tiger Reserve, Western Ghats in India. The study reports the largest number of mixed morphotypes in a population having a higher abundance of dark grey morphs at lower altitudes, light brown morphs in the mid altitudes and more dark brown morphs at higher altitudes. The group size of mixed species was mostly multi-male and multi-female and larger than the NL and HL groups. Our study provides a framework to determine their inter-specific interactions and reproductive strategies which are necessary in overlapping ranges.