Population Ecology of the Water Vole (Arvicola terrestris L.) in the West Siberia. I. Population Numbers, Coat Colour Polymorphism, and Reproductive Effort of Females.
V. I. EVSIKOV, G. G. NAZAROVA, V. G. ROGOV
Institute of Animal Systematic and Ecology Siberian Branch
of the Russian Academy of Sciences, Frunze Str., 11, Novosibirsk 630091, Russia)
Pages: 59-68
Abstract
Ovulation rate, embryo mortality, mean number of live embryos and sexual maturation rate depended significantly on the phase of water vole population dynamics. Female's reproductive capacity was the highest at the increase phase and the lowest at the decline phase. Embryo mortality and sexual maturation rate were affected pleotropically by the coat colour genes. The lower reproductive capacity of dark-brown over wintered voles at all phases of population cycle, except for the peak, was due to a higher incidence of resorption of entire litters compared to brown over wintered females. At the peak, reproductive characteristics of brown and dark-brown over wintered females did not differ. Young-of-the-year dark-brown females matured earlier than brown females at the peak and decline phases and, therefore, were more reproductively successful. Analysis of voles growth in captivity revealed that dark-brown voles grew faster than brown ones. In natural population, coat colour differences in body weight of over wintered individuals were phase-dependent. Dark-brown voles usually weighed more than brown voles in the peak and decline years. It is suggested that differences in female fertility, growth and sexual maturation rate between coat colour genotypes contribute to transformation of genetic structure and act as mechanisms maintaining coat polymorphism in cyclic water vole population.
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