Population density of Alactagulus pygmaeus in different years and regions varied from 2.5 to 38.0 animals per 1 hectare and correlated positively with the last year forage yield (r = 0,94). The numbers in spring were shown to depend on fluctuations of winter mortality (34.7-96.4%) which is not connected with fat accumulation in the pre-hibernation period (r = —0.25), but is directly determined by the dynamics of Alactagulus food resources (15.6-213.0 kg per 1 specimen) in the winter period (r = 0.71). The numbers of Alactagulus during the spring-summer period is actively adjusted and maintained to correspond with the available food resources. It was shown that there was a complex of trophically conditioned mechanisms owing to which the population density by autumn is adjusted to the level corresponding to the optimal utilization of the available resources and minimal winter mortality. Violation of such a correspondence due to overpopulation of a territory during years when migration are intensive is extremely inauspicious for the population. Such a violation was observed when food resource level fell to 15—23 kg per 1 specimen.
МЫЛЬНИКОВ А.П., КАРПОВ С.А.