Comparison of noninvasive genetic and camera-trapping techniques for surveying snow leopards

The endangered snow leopard (Panthera uncia) is widely but sparsely distributed throughout the mountainous regions of central Asia. Detailed information on the status and abundance of the snow leopard is limited because of the logistical challenges faced when working in the rugged terrain it occupies, along with its secretive nature. Camera-trapping and noninvasive genetic techniques have been used successfully to survey this fetid. We compared noninvasive genetic and camera-trapping snow leopard surveys in the Gobi Desert of Mongolia. We collected 180 putative snow leopard scats from 3 sites during an 8-day period along 37.74 km of transects. We then conducted a 65-day photographic survey at I of these sites, approximately 2 months after scat collection. In the site where both techniques were used noninvasive genetics detected 5 individuals in only 2 days of fieldwork compared to 7 individuals observed in the 65-day camera-trapping session. Estimates of population size from noninvasive genetics ranged between 16 and 19 snow leopards in the 314.3-km(2) area surveyed, yielding densities of 4.9-5.9 individuals/100 km(2). In comparison, the population estimate from the 65-day photographic survey was 4 individuals (adults only) within the 264-km(2) area, for a density estimate of 1.5 snow leopards/100 km(2). Higher density estimates from the noninvasive genetic survey were due partly to an inability to determine age and exclude subadults, reduced spatial distribution of sampling points as a consequence of collecting scats along linear transects, and deposition of scats by multiple snow leopards on common sites. Resulting differences could inflate abundance estimated from noninvasive genetic surveys and prevent direct comparison of densities derived from the 2 approaches unless appropriate adjustments are made to the study design.