The singing vole (Microtus miurus), is a medium-sized vole found in northwestern North America, including Alaska and northwestern Canada.
Physical characteristics
Singing voles have short ears, often concealed by their long fur, and a short tail. The fur is soft and dense, especially in winter. They vary in color from pale tawny to pale grey, with buff-colored patches running from the undersides of the ears along the flanks to the rump, and buff or ochre underparts. The fur is lightly ticked with black guard hairs, but these are so sparse that have little effect on the visible coloration of the animal. The fur is greyer in color during the winter. The paws have sharp, narrow claws, which are largely hidden by fur.
Adult singing voles range from in length, not counting the short, , tail. They can weigh anything from , depending on their exact age and recent diet. There is no significant difference in size or coloration between the two sexes. Male singing voles possess modified sebaceous glands on their flanks, which are used in scent marking; these glands have also been noted in some lactating females. The penis is relatively long and narrow, with a complex baculum.
Reproduction
Singing voles breed from May to September, and each female can give birth to up to three litters in a breeding season. Gestation lasts 21 days, and typically results in the birth of eight young, although litters of between 6 and 14 young have been reported.
Evolution
The oldest known fossils of singing voles date from the Ionian, around 300,000 years ago, and were found near Fairbanks. During the Ice Ages of the late Pleistocene, singing voles may have been much more widely distributed than today, and fossils have been reported from as far south as Iowa, which was then probably similar in climate to present-day Alaska. The closest living relative of the singing vole today is the insular vole, which is found only on two small islands off the west coast of Alaska, and probably diverged as those islands were cut off from the Beringia land bridge by rising sea levels.