Distribution and taxonomy of the Grey voles (Mammalia, Rodentia, subgenus Microtus) in Bulgaria

Grey voles (subgenus Microtus), widespread in Eurasia, may be important pests and could cause serious damage to agricultural grain fields. In Bulgaria two morphologically similar species are present (Microtus arvalis Pallas, 1778 and M. rossiaemeridionalis Ognev 1924), which are impossible to identify in the field. Despite their importance as pests, very little is known about their current status and distribution. Here we cotributed new data - based on karyological examination of 27 individuals of voles. We summarized all available information on the distribution of the voles – 20 published and 11 unpublished locations. Both species co-occurred together in north Bulgaria; in Thrace and the SE only M. rossiaemeridionalis is distributed. Microtus rossiaemeridionalis seems to occupy lower elevations, while in the mountain areas (above 1000 m) only M. arvalis is found, which corresponds well with the data from neighboring countries. The taxonomy of both species in Bulgaria is discussed.