Nature Notes: Meadow Vole
Every spring when the snow on our lawn finally melts, we find a series of tunnels in the dormant grass, along with some woven nests. If we are unlucky, we also find damage to our ornamental and fruit trees, with the bark chewed at the base of the trunk and on exposed roots. The likely culprit? One of Nature’s most prolific creatures and a key player in the animal kingdom’s food chain.
Sometimes referred to as a meadow or field mouse, the meadow vole is a rodent, but not a mouse. It is one of 60 or more species in the Microtus family, specifically M. pennsylvanicus. With a chunkier, more compact body than most mice, the tail is only one third of the vole’s body length, while a mouse’s tail is often longer than its body. The vole’s body is only three to five inches long, and it weighs less than two ounces at maturity. Adults sport a dense coat varying from tan to dark brown, with black tipped guard hairs, gray under body and short ears.
Meadow voles have a huge range in North America, from Alaska down to New Mexico and all the way across the continent to Georgia and northern Canada. Within that range, they favor marsh and grass land habitats, but under pressure will adapt to other terrain. Wherever they are found, voles provide a critical source of food to a wide range of predators including fox, coyotes, raptors, weasels, snakes, herons and even house cats on the prowl. Some owls have been found to depend upon voles for up to 85 percent of their diet.
Given the number of predators on their trail, it won’t surprise you to learn that meadow voles are some of the most fecund breeders around. In a short life span of roughly one year, meadow vole females may produce up to five litters (one female in captivity was documented to produce 17 litters and 83 pups in one year!). Breeding can occur year round, with females maturing on average in 35 days, and a gestation period of about 21 days. A litter is typically four to six pups and they are weaned after three weeks. Given this production rate, the vole population can average 150 per acre in good conditions, but peak populations have been documented in the thousands per acre.
Given their size, and energy needs, meadow voles are voracious eaters, needing food every two to three hours to fuel their rapid metabolism. While their preferred foods are grasses and forbs, meadow voles have been known to dine on mushrooms, berries, snails, insects and even carrion if necessary to survive. In agricultural areas, voles can cause significant damage to clover, hayfields and other crops that offer them nutrition and cover from predation. If sufficient food is available, a vole will consume up to half its weight. In late summer and autumn, voles will store seeds, bulbs and tubers for winter consumption.
Meadow voles are not given to long periods of sleep, driven by the need to feed, breed and survive in a competitive environment. They are active day and night and do not hibernate – voles are too small to store sufficient energy reserves. In ideal habitat, voles construct a network of tunnels in soft soil and surface runways in grassy areas, the tunnels being about 1.5 inches in width with multiple openings. Nests are made of woven grasses and generally located underground or below rocks and logs.
Humans generally have little interaction with meadow voles, other than trying to prevent damage to crops, trees and favored garden plants. Pesticides and poisons have limited effect on voles. The best way to control damage to plants is by regular mowing, by keeping mulch back from tree trunks, and by using small mesh fencing buried in the ground to prevent voles from digging under it. Meadow voles have been shown in some cases to be carriers for disease organisms for plague and tularemia, so any handling of voles should be done with protective clothing.
These tiny creatures are not often visible to us, but they play an important role in the natural balance. Their digging helps to aerate the soil, and they recycle nutrients from the plant materials they eat. In their droppings, they spread the spores of fungi that are beneficial for plant growth. Without the huge numbers of voles that exist in our meadows and grassy areas, there would be far fewer owls and foxes to make life in the woods and fields so interesting.
P.S. Special thanks to Tulle Frazer for sending along excellent reference material.