Density-dependent regulation in populations of northern red-backed voles (Myodes Rutilus) in optimal and suboptimal habitats of southwest Siberia

In a population of red-backed voles (Myodes rutilus) that live in optimal habitats (mountain taiga of North-Eastern Altai), in the years of peak density, we have observed the total suppression of the sexual maturation of young animals, which is known to be the main mechanism of density regulation. The increase in the local density of voles is accompanied by an increase in glucocorticoids in the blood of mature and immature individuals of both sexes that indicates the important role of hypothalamic-pituitary-adrenal axis in density-dependent regulation. Another population of red-backed voles from southwest Siberia that live in suboptimal habitats (Novosibirsk city vicinity) had a significantly lower density. Here, the dynamics of demographic traits and endocrine status of the individuals did not correlate with the interannual fluctuations of abundance and density. Nonetheless, we cannot exclude the possibility that, under suboptimal conditions, the local density occasionally reaches values that are sufficient to induce self-regulation.