Population assessment of the Endangered Kashmir Gray Langur (Semnopithecus ajax, Pocock 1928) using the double-observer method.

Primates are among the most threatened taxa globally, therefore, there is a need to estimate and monitor their populations. Kashmir Gray Langur Semnopithecus ajax is an endangered species for which there is no population estimate. We used double-observer method to estimate its population size in the Kashmir region of North-Western Himalaya. We walked 1284 km across 31 survey blocks spanning all three divisions of Kashmir viz., North, Central, and South Kashmir, covering an area of 411 km 2 . We counted a minimum of 1367 individual langurs from 27 groups. The detection probability for observer 1 (0.719) and observer 2 (0.656) resulted in a population estimate of 1496 (95% confidence interval [CI] 1367-1899) across 30 groups (with a mean group size of 51), giving a density estimate of 3.64 (3.33-4.62) langurs/km². We found double-observer surveys to be suitable for the population estimation of langurs, and we make recommendations on how to effectively conduct primate surveys, especially in mountainous ecosystems. Our records extend the species distribution range beyond stated by the International Union for Conservation of Nature. Our findings also highlight that the Kashmir Himalaya is a stronghold of the species, where conservation efforts should focus.