Root voles in the study area
Our study was conducted at Haibei Alpine Meadow Ecosystem Research Station, Menyuan County, approximately 155 km north of Xining, the capital city of Qinghai province, People’s Republic of China (37°370´N, 101°120´E). The area is a secondary vegetation type meadow with a dense leaf layer. The major plant species include Elymus nutans, Poasp., Kobresia humilis, and Potentila fruticosa . The root vole is the most common rodent in the study area. Root-vole populations in this area fluctuate only seasonally, with the lowest levels occurring in early spring; multiyear cycles are weak or absent (Jiang et al., 1991). Root voles have a preference for dense vegetation (mainlyE. nutan s) (Liu et al., 1991; Bian et al., 1994). The average population size in the habitat ranges from 217 to 280 voles ha-1 in autumn (Bian et al., 1994), where grazing activities had a limited population density of approximately 400 voles ha-1 in autumn (Sun et al., 2002). The breeding season typically lasts from April to late October. Females have exclusive territoriality during the breeding season; males, conversely, have large area ranges that extensively overlap with those of other males (Sun et al., 1982). The lifetime of free-ranging individuals is < 1 year. Spring-born individuals attain sexual maturity in the year they are born; fall-born voles remain reproductively inactive during winter (Bian et al., 2015).