Sibling species of Microtus arvalis and Microtus rossiaemeridionalis in north-eastern Moscow district

Distribution, numbers, demographic structure and reproductive potentialities of Microtus arvalis and M. rossiaemeridionalis in nature and in agricultural landscapes were studied in 1992-1996. In eight biotopes 1097 specimens of common vole were examined. In the territory studied sibling species were found to differ in biotopic distribution and reproduction. M. rossiaemeridionalis preferred urban areas, M. arvalis inhabited the territories less exposed to human activity. M. rossiaemeridionalis litters are of larger size than those in M. arvalis. Analyzing asymmetry and excess and t-test revealed in M. rossiaemeridionalis a tendency to increase fertility (in areas under anthropogenic impact), whereas in M. arvalis the fertility is stable enough. The last fact testifies that M. rossiaemeridionalis is more adapted to antropogenic impact than M. arvalis.