Estimating relative abundance and habitat use of Himalayan Blue Sheep Pseudois nayaur in Gangotri National Park, Western Himalaya, India

Abstract

Himalayan Blue sheep Pseudois nayaur is the most abundant wild ungulate in the Gangotri National Park in Western Himalaya, India. We conducted surveys from April 2008-November 2008, to estimate relative abundance, population structure and habitat use of the blue sheep in Gangotri National Park, Uttarakhand, India. We used 11 hill trails to estimate abundance parameters in Gangotri National Park. Sampling area ranges from an altitude of 2,600-5,000 m a.s.l. in Gangotri and Nilang valley of Gangotri National Park. We recorded a total of 120 groups (1,184 individuals) with an average encounter rate (individuals/km, SE [plus or minus]) of 9.07 (SE [plus or minus] 1.65), across three seasons viz, spring, summer and autumn. Blue sheep group sizes ranged from 1 to 65 individuals and the average group size was 9.87 (SE [plus or minus] 1.24). We classified 302 males, 518 females and 137 yawns (<2 years) also with 227 unidentified individuals (19%) during the study period. Blue sheep observed largely using grassland habitats and smooth undulating slopes of medium steepness (41[degree]-50[degree] (39.17%) and 31[degree]-40[degree] (31.66%)), largely on southerly aspects within the elevation range of 3,000-4,000 m most frequently in all seasons. When not in broken landforms, the blue sheep maintained proximity (<170m) to such features suggesting their importance as escape covers from predators. Blue sheep in Gangotri valley appeared to be habituated to human presence, as many of the groups were found to be unmindful of the movement of large number of pilgrims during April-October, a religious practice that has been going on for centuries. Livestock grazing, large tourism activities, poaching, developmental activities and military activities have been identified as threats for the conservation and management of blue sheep populations in the protected area.