Livestock grazing impacts on plateau pika (Ochotona curzoniae) vary by species identity

Abstract

Livestock and small burrowing mammals are potential ecosystem engineers and major drivers of ecosystem processes. Small mammals, often considered competitors with livestock, have been reported to increase in recent years and have been identified for their negative impacts on ecosystem services such as plant production and soil carbon sequestration. However, these increases and impacts by small mammals have rarely been studied with respect to how they may be influenced by livestock grazing. Here we experimentally manipulated large enclosures on the alpine grassland of Qinghai-Tibetan plateau, each with different livestock assemblages: yak (Bos grunniens), Tibetan sheep (Ovis aries), mixed populations of yak and sheep, and a control plot containing no livestock to study the potential impacts of livestock on the dominant small mammalian herbivore in the region, the plateau pikas (Ochotona curzoniae). We found that during the period of peak vegetative growth all pika populations in livestock experimental plots increased compared with those in the control plots. Additionally, pika populations and active pika burrow density increased more in experimental plots containing yaks compared with the sheep-only experimental plots. These results provide evidence that livestock grazing can increase the risk of pika outbreaks, which has led to this species being classified as a pest and subject to widespread control measures. We suggest explicitly incorporating livestock species identity in addition to grazing intensity and duration into management considerations to ensure maintenance of native biodiversity and long-term sustainability on the alpine grasslands of the Qinghai-Tibetan plateau.