REPRODUCTIVE AND BEHAVIORAL BIOLOGY OF THE GRAY-TAILED VOLE

We describe the reproductive biology of the gray-tailed vole, Microtus canicaudus, and relate behavioral and morphological features to the m ating system. The breeding season extended from March through December , mean litter size was 4.4 young, and hip (scent) glands were prominen t in adult males and females throughout the breeding season. Juvenile dispersal was male-biased, and home ranges of opposite-sex relatives d id not overlap when juveniles became reproductively active. Gray-taile d voles were sexually dimorphic, and males had larger home ranges than did females, indicative of a polygynous or promiscuous mating system. However, males had relatively small testes, which is characteristics of monogamy or single-male harems. We conclude that the mating system of gray-tailed voles cannot be inferred from behavioral and morphologi cal correlates, as has been attempted for other species of Microtus.