Abstract: Rare, elusive predators offer few sightings, hindering research with small sample sizes and lack of experimentation. While predators may be elusive, their prey are more readily observed. Prey respond to the presence of a predator, and these fear responses may have population- and community-level consequences. Anti-predator behaviors, such as vigilance, allow us to sidestep the difficulty of direct field studies of large predators by studying them indirectly. Here we used a behavioral indicator, the vigilance behavior of the Himalayan tahr, the snow leopard’s main local prey, to reveal the distribution and habitat use of snow leopards in the Mt. Everest region of Nepal. We combined techniques of conventional field biology with concepts of foraging theory to study prey behavior in order to obtain insights into the predator’s ecology. The Himalayan tahr’s vigilance behavior correlates with the distribution of snow leopard signs. Tahr actually led us to six sightings of snow leopards. We conclude that behavioral indicators provided by prey offer a valuable tool for studying and monitoring stealthy and rare carnivores.

Abstract: Twenty-five years ago, the snow leopard Uncia uncia, an endangered large cat, was eliminated from what is now Sagarmatha National Park (SNP). Heavy hunting pressure depleted that area of most medium-large mammals, before it became a park. After three decades of protection, the cessation of hunting and the recovery of wild ungulate populations, snow leopards have recently returned (four individuals). We have documented the effects of the return of the snow leopard on the population of its main wild prey, the Himalayan tahr Hemitragus jemlahicus, a 'near-threatened' caprin. Signs of snow leopard presence were recorded and scats were collected along a fixed trail (130 km) to assess the presence and food habits of the snow leopard in the Park, from 2004 to 2006. Himalayan tahr, the staple of the diet, had a relative occurrence of 48% in summer and 37% in autumn, compared with the next most frequent prey, musk deer Moschus chrysogaster (summer: 20%; autumn: 15%) and cattle (summer: 15%; autumn: 27%). In early summer, the birth rate of tahr (young-to-female ratio: 0.8-0.9) was high. The decrease of this ratio to 0.1-0.2 in autumn implied that summer predation concentrated on young tahr, eventually altering the population by removing the kid cohort. Small populations of wild Caprinae, for example the Himalayan tahr population in SNP, are sensitive to stochastic predation events and may be led to almost local extinction. If predation on livestock keeps growing, together with the decrease of Himalayan tahr, retaliatory killing of snow leopards by local people may be expected, and the snow leopard could again be at risk of local extinction. Restoration of biodiversity through the return of a large predator has to be monitored carefully, especially in areas affected by humans, where the lack of important environmental components, for example key prey species, may make the return of a predator a challenging event.