23. The Prairie Vole (Microtus ochrogaster)
If I were to ask you to guess what the most abundant mammal inhabiting GPFWA is, you might first think of white-tailed deer. They seem to be abundant almost everywhere in Indiana. Perhaps the muskrat or the mink, a common predator-prey duo of the wetlands, would come to mind. All would be good conjectures. But, based upon the results of biodiversity surveys conducted at Goose Pond, the answer is – the prairie vole.
Recalling that nearly two thousand acres of grassland exists at Goose Pond FWA, the abundance of prairie voles is less surprising. After all, this is a species typical of the grasslands of the mid-United States. Even though over 90% of America’s tallgrass prairie has been lost, the little prairie vole has managed to do quite well by making use of pasture lands, reclaimed strip-mined land, oldfields, and idle croplands.
As with our other native “field mice”, the prairie vole is modest in size having a total length of around five inches and a weight of one or two ounces. The upper body hair is brownish with a mixture of black and yellow. The belly fur is a yellowish-brown or ochraceous thus its specific name ochrogaster. The genus name Microtus refers to their small ears.
Prairie voles are almost entirely herbivorous and feed on a variety of grasses and other plants such as clover and fleabane. They tend to cut tall plant stems, such as grasses, into sections and these may often be found lying in the surface runs they make through fields.
The reproductive potential of this species is high as is typical of many rodents. They begin to breed when only weeks old and can produce young throughout the year. The coldest winter months see a lower number of young born however. The gestation period of the prairie vole is only 21 days and the average litter size is four pups. Thus they have the potential to produce dozens of offspring during a year. Their lifespan rarely exceeds a year and a half to two years.
Prairie voles need this high reproductive potential as they are preyed upon by a host of predators. These include reptiles such as the prairie kingsnake, black racer, and black ratsnake. Avian predators are many and this is one of the reasons that GPFWA is popular among birders. At various times of the year one may find American kestrels, red-tailed hawks, northern harriers, rough-legged hawks, and short-eared owls on the hunt for voles. Mammalian predators include coyotes, bobcats, and weasels.
For such an abundant mammal, the prairie vole is easily overlooked at Goose Pond FWA. The next time you go for a walk there, take time to look downward too. If you are traipsing through grasses or other herbaceous vegetation, you are highly likely to encounter the little vole highways that have been cut through the grass. You might even be lucky enough to see one scurrying for cover. And let’s give them their due. Because of their position near the base of so many grassland food chains, prairie voles are inarguably one of the most important species on the entire property.
*Vole photo by Terry L. Castor in Indiana Mammals: a Field Guide by J.O. Whitaker, Jr.