Heterogeneity Of Rodent Populations During Terminal Phases Of Density Dynamics
Abstract
S.A. ÃÂyakushko
The population structure of populations of two vole species (Myodes glareolus Schreber, 1780 and Microtus subterraneus de Selys-Longchamps, 1836) were analyzed towards the peaks and depressions of their dynamics of density. Field researches were conducted throughout the first half of summer during 2000-2013. The sample was more than 800 individuals. Reactions of populations of rodents to changes of living conditions during dynamics of the population are provided with speciesspecific reorganizations of sex and age structure. On the basis of allocation of functional and physiological groups, comparison of their contribution to changes of density of populations is carried out. Specifics of this approach consist that at allocation of such groups as criterion the similarity of a functional condition of individuals connected with features of growth, development and unity of a reproductive state is accepted. Changes of living conditions during dynamics of population density, cause realization of species-specific population reactions are being show. In population of a bank vole delay of intensity of reproduction in years of density peaks is reached due to preservation of a considerable share of the wintered individuals. It is followed by simplification of age structure and change of a sex ratio towards prevalence of females. The analysis of coefficients of a reproduction shows that the wintered individuals provide 1/3 population increase. In years of the low density of an intensification of reproduction the maximum realization of biotic potential of young animals promotes. Also as the buffer a large number of individuals who will enter at reproduction the next year remains. In population of pine vole the priority mechanism of regulation of reproduction is the effective date variation in a reproduction of bulk of representatives of spring and summer generation. In the conditions of an overpopulation (density peak) the share of animals who don't breed is maximum and exceeds quantity of breeding almost twice. The wintered individuals aren't enough and they don't provide such essential contribution to a reproduction as at a bank vole. In depression phases the quantity of the breeding voles of the current year of birth more than twice increases, they provide the further growth of population.<