Tuesday, April 29, 2014

Meadow Voles

by Doug Reeves, assistant chief, DNR Wildlife Division

As I was walking along a small rivulet adjacent to a field recently, something darted across the little stream so quickly that – even though I glanced as fast as I could – all I saw was a small wake the animal left. Then it darted quickly down the edge of the stream and off into the grass. At that point I was able to identify it as a meadow vole.

meadow voleMeadow voles, or meadow "mice" as I have often heard them called, are the base of the food chain in many grassland-dominated areas. Theirs is a very important function in that regard, and to say that they multiply like rabbits is putting it mildly, when conditions are right. Several species of hawks and owls, shrikes, red and gray fox, coyote, bobcat, weasels, mink and several species of snakes all find meadow voles a menu favorite. So they have to produce like crazy for the population to persist! But they have many other traits and behaviors that are worthy of admiration.

As their name implies, meadow voles live in grassland areas. They seem to like moist, grassy areas best and are frequently near water along marsh edges or streams. They are herbivores, eating grasses and forbs, but they can sometimes be seen cleaning up sunflowers and other seeds under bird feeders. Last summer we had a few meadow voles doing just that. One was either albino or piebald, the only such creature I have ever seen. We saw it for several weeks, which surprised me since so many things seek to eat voles, and that one stood out against the background of the short grass and soil. It would seem to have been more easily detected than its normally colored companions. The normal coloration for meadow voles is almost black.

Meadow voles are active all year. During winter they create trails in the grass under the snow. When the snow melts, their trails are readily evident, and as the snow is leaving you can sometimes see a vole running on those trails between patches of snow. For people who have manicured lawns, the voles' activity might be irritating, but for those of us who don’t put a premium on keeping a weed-free, closely cropped lawn, it is kind of cool to see their trails in the spring and realize how much life was going on under the snow. Meadow voles are also the creatures that leave a single round hole in the snow where they appear to come up for a bit of sun and fresh air during winter. Sometimes in snow a foot or more deep you will find a hole with a couple droppings next to it as you snowshoe across a field or marsh. Occasionally one of those holes has wing marks around it and a drop of blood, indicating that a predatory bird was successful at ambushing the vole, but most often the vole just goes back down the hole and on with its business. In summer, they live at, and even below, ground level, sometimes using mole runs as their highways. That keeps them out of sight of aerial predators.

Meadow voles make nests out of grass. They look like small haystacks a little bigger than a softball and are often found at the base of a clump of brush, under or adjacent to a log, or in a group of grass-covered rocks. Baby voles are born naked, with unopened eyes, and they grow up in these nests, then spread out and find their own place to live. Mortality is high, and the average life span of a vole is probably weeks or months rather than years. During wetter years they are particularly productive, but during dry years they do not produce as many young or as frequently. Field studies have shown that northern harriers (a.k.a marsh hawks) and barn owls, where they occur, are also much more productive in years when meadow vole numbers are high. They keep the food chain cranking!

Meadow voles are short-legged, short tailed, pudgy little creatures, but they are remarkably fast when they need to get to safety. I am frequently amazed that they can move so quickly. Most sightings are very brief, lasting only a couple of seconds or less, but sometimes when I am just relaxing along the edge of a field I get the opportunity to watch them collect grass or move about at a less hurried pace. It is then that I contemplate what a difference those little critters make in our world and yet how few people realize their ecological importance.


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Photo courtesy of Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor.