Long-Term Depression and Recovery of a Local Population of the Common Vole (Microtus arvalis, Cricetidae, Rodentia) in the Southeastern Part of Tver Oblast

Recovery of a local population of the common vole (Microtus arvalis arvalis) after a nine-year absence from the area of a research station near the village of Bakanovo, Staritskii district, Tver oblast, Russia is described. The species identity before the depression and after the restoration was established based on karyotype studies. The absence of the species from 2011 to 2019 was confirmed by data from long-term (>10 days) annual capture–mark–recapture sessions: with a maximum interval between the captures of resident voles (m + 3SD) of 2.8 + 3.0 days, the animals could be detected with 99% probability within six days. Additional surveys of the territory showed the absence of this species from the immediate (about 1 km) vicinity as well. The population restoration began in areas from which no voles had previously been found as residents; in all cases, adult females were among the first immigrants. Apparently, we observed both local extinction and subsequent recolonization of the territory. A quantitative predominance of females was observed in the population as a whole, both before and after the depression. During the recolonization, a higher proportion of adults, including females, was revealed compared to that in the local population before the extinction of common voles.