The role of snow leopard predation in determine prey recruitment: a synthetic study of abiotic, bottom-up and top-down influences on the Tibetan Plateau

Ungulate populations could either be limited by resources (bottom-up control) or be regulated by predation (top-down control). Consequently, for ungulates and their predators, conservation strategies may need to differ depending on the predominance of either of these forces at any given time period. Livestock competition, snow leopard Panthera uncia predation, and snow disaster in winter are three main forces affecting recruitment of blue sheep Pseudois nayaur, the major wild prey of snow leopards on the Tibetan Plateau. To answer the question which of them is the dominant force regulating blue sheep population, we selected seven study sites representing a gradient of livestock grazing pressure on the Tibetan Plateau. Population structure of blue sheep after birth and after winter, livestock density, snow leopard density and other environmental variables were recorded. We used Generalized Linear Model to examine the potential roles of the three forces on blue sheep recruitment. Our results did not find any evidence of resource limitation/livestock competition. Snow leopard predation appeared to significantly decrease the young : female ratios both in summer and after winter. Low winter temperature decreased young : female ratio after winter. These results indicated that blue sheep populations in our study area were more predation-regulated than resource-limited. Conservation actions should be more targeted on maintaining the ecological function of snow leopards, rather than controlling livestock density.