Comprehensive assessment of snow leopard distribution and population in the Indian Trans-Himalaya, Ladakh: Standardizing methods for evidence-based conservation.

Effective conservation of threatened species depends on accurate scientific assessment of their occurrence and population status. This information is often lacking or has poor scientific reliability for low-density carnivores, such as snow leopards (Panthera uncia) that inhabit remote and challenging habitats. We address prevalent sampling and study design limitations and evaluate the population and distribution of snow leopards and their prey using a double sampling approach across the Trans-Himalayan Ladakh (~59,000 km2), India. We used spatial data on the sign occurrence of snow leopards, collected by replicate sign surveys of 6,149 km to model occupancy and potential distribution. Regions representing varying occupancy were used to stratify density-estimation using spatially explicit capture-recapture by sampling 956 camera trap locations with an effort of 97,313 trap nights. Camera traps captured 26,130 images of 126 unique snow leopards identified by a pattern recognition program using their distinctive forehead pelage patterns. Low-elevation grassy and resource-rich regions, with moderate climatic conditions and complex terrain had higher presence of herbivores and consequently higher occupancy of snow leopards. Density of snow leopards was estimated at ~ 1 per 100 km2 with a large movement parameter (σ) of 4.09 (SE 0.15) km and detection at home-range centre (g0) of 0.003 (SE 0.0003). Snow leopard density reached up to 3.18 per 100 km2 and was driven by the distribution of their wild and domestic prey in suitable habitats. The snow leopards in Ladakh occupied 47,572 km2, holding globally highest extensive densities of snow leopards in Hemis National Park (2.073 ± 0.278 per 100 km²), Kargil (1.257 ± 0.480 per 100 km²), and Leh (1.029 ± 0.434 per 100 km²), and making one of the world's largest contiguous populations of 477 (CI 380-598) snow leopards. This population holds global significance as an important source of snow leopards, predominantly (61%) occurring in multi-use areas and closely linked with wild and domestic herbivores. We offer a robust and comprehensive method for large-scale population estimation of snow leopards, applicable globally. The co-occurrence of humans and wildlife across the landscape underscores the need for inclusive and evidence-based conservation planning, especially considering the impending large-scale infrastructural development and escalating global climatic changes.