GROWTH, DEVELOPMENT, AND REPRODUCTIVE PATTERNS IN THE JAPANESE FIELD VOLE, MICROTUS-MONTEBELLI

We describe characteristics related to the reproductive biology-of the Japanese field vole, Microtus montebelli. In comparison with the othe r species of Microtus examined to date, Japanese held voles grew more rapidly and exhibited the most male-biased sexual dimorphism, with mal es having relatively small testes, indicative of a polygynous mating s ystem. Thus, we conclude that this species is polygynous, possibly wit h the type of facultatively monogamous mating in which species show so cial patterns that combine elements of several systems.