Structural changes in vegetation coincident with reseeding Elymus nutans can increase perceived predation risk of plateau pikas (Ochotona curzoniae)

The perceived predation risk of animals is often influenced by the structure and complexity of vegetation communities. Plateau pikas (Ochotona curzoniae) are considered a pest species in alpine meadows when their densities exceed a certain threshold. The changes in vegetation structure caused by reseeding Elymus nutans can reduce pika densities, which may result from the increased risk of predation for pikas. However, whether the changes in community structure caused by reseeding of E. nutans is sufficient to alter the perceived predation risk for pikas, remains unknown. In this study, we measured the running speed (spontaneous without stimulation), alert distance (AD) and vigilance to a potential human predator in E. nutans habitat and open habitat by video review to assess perceived predation risk for plateau pikas in the two habitat types. Our results showed that body mass and habitat type influenced the running speed, group size and the habitat type influenced AD, and habitat type and group size influenced vigilance. The running speed of pikas was 1.67 times faster in the E. nutans compared to in open habitat, the AD of pikas was 1.79 times longer in the open than in the E. nutans habitat, and pikas were more vigilant in E. nutans than pikas in open habitat. The shorter AD indicates pikas have poor visibility due to higher vegetation height. The faster running speed and higher vigilance suggest a higher perceived predation risk for pikas in E. nutans habitat. Therefore, we believe that structural changes in vegetation following reseeding of E. nutans can increase the perceived predation risk for pikas, and could be responsible for the decrease in the pika population densities in these areas.