Abstract
AbstractThroughout the Himalaya, mountain ungulates are threatened by hunting for meat and body parts, habitat loss, and competition with livestock. Accurate population estimates are important for conservation management but most of the available methods to estimate ungulate densities are difficult to implement in mountainous terrain. Here, we tested the efficacy of the recent extension of the point transect method, using camera traps for estimating density of two mountain ungulates: the group-living Himalayan blue sheep or bharalPseudois nayaurand the solitary Himalayan musk deerMoschus leucogaster. We deployed camera traps in 2017–2018 for the bharal (summer: 21 locations; winter: 25) in the trans-Himalayan region (3,000–5,000 m) and in 2018–2019 for the musk deer (summer: 30 locations; winter: 28) in subalpine habitats (2,500–3,500 m) in the Upper Bhagirathi basin, Uttarakhand, India. Using distance sampling with camera traps, we estimated the bharal population to be 0.51 ± SE 0.1 individuals/km2(CV = 0.31) in summer and 0.64 ± SE 0.2 individuals/km2(CV = 0.37) in winter. For musk deer, the estimated density was 0.4 ± SE 0.1 individuals/km2(CV = 0.34) in summer and 0.1 ± SE 0.05 individuals/km2(CV = 0.48) in winter. The high variability in these estimates is probably a result of the topography of the landscape and the biology of the species. We discuss the potential application of distance sampling with camera traps to estimate the density of mountain ungulates in remote and rugged terrain, and the limitations of this method.
Highlights
Ungulates are an integral component of Himalayan mammalian fauna and play an essential role in shaping ecosystems by influencing vegetation structure (McNaughton, ; Bagchi & Ritchie, ) and as primary prey for large predators (Bagchi & Mishra, ; Sathyakumar et al, a)
We focused on the Himalayan blue sheep or bharal Pseudois nayaur and the Himalayan musk deer Moschus leucogaster, both of which are affected by anthropogenic impacts (Mishra et al, ; Bhattacharya & Sathyakumar, )
We took measurements using a calibration pole of known height at known distances from the camera, in the centre and along both sides of the camera’s field of view. This calibration was done for a total of camera traps, and we considered the measurements taken at these locations representative for others with similar topography and field of view
Summary
Ungulates are an integral component of Himalayan mammalian fauna and play an essential role in shaping ecosystems by influencing vegetation structure (McNaughton, ; Bagchi & Ritchie, ) and as primary prey for large predators (Bagchi & Mishra, ; Sathyakumar et al, a). Several studies on mountain ungulates have used an indirect index of abundance (e.g. Schaller et al, ; Sathyakumar, ; Bagchi & Mishra, ; McCarthy et al, ; Suryawanshi et al, ) as an alternative to absolute abundance. These estimates are less reliable and highly dependent on the assumption of constant detection probability throughout the survey period (Yoccoz et al, ). Small population sizes, cryptic and elusive behaviour, and patchy distribution of Himalayan ungulates limit the number of observations that can be made for a given survey effort (Singh & Milner-Gulland, ). Forest-dwelling mountain ungulates may have activity peaks at night (Cavallini, ; Bhattacharya et al, a) and are rarely detected during day-time surveys
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