Even the littlest creatures find refuge and play an important role in Montana's Centennial Valley
Few, if any, would believe this small rodent may be playing a key role in the study of monogamous relationships between adults, is charged with causing a fire which destroyed over 16,000 acres and 60 homes, and could be providing critical information regarding global warming. However, these are all credited to the common Vole.
After spending most of my life studiously avoiding the animals which scurry around at my feet, I was intrigued to meet a young lady who has spent her last three summers in the Centennial Valley studying what I carelessly considered varmints. Paula Spaeth, a fifth year PhD student at Stanford University, has braved long cold springs, rainy summers, and the discomfort of tent living to study two of the vole species which reside in the Valley. Basing her studies on DNA studies conducted by Elizabeth Hadly, a Stanford associate professor of biological sciences, Paula has attempted to gain a deeper understanding into the role voles play as environmental indicators of global warming. And, in the process, Paula has come to appreciate these often overlooked and generally disliked little animals.
According to Paula, there are 27 distinct species of voles in North America, 5 which reside here in the Centennial Valley. Voles are not unique to North America. The temperate and arctic zones of the Northern Hemisphere are full of voles. Amazingly there are over 60 species of voles in Europe and Asia, but only one of those species is also found in North America.
Voles, which belong to the genus Microtus, have also been called ‘meadow mice’ or ‘vole-mice’. Although the various species differ more greatly in their DNA than humans and orangutans, they only differ slightly in their physical characteristics. These differences are limited to the length of their tails, most obvious on the Long-Tailed Vole, and their foot pads. With this closeness of DNA one might expect them to cross breed between species, however, this assumption appears to be inaccurate.
The voles living here in the Centennial reside in 5 distinct zones. These are the pines, the aspens, the grasslands, the willows (lower grasslands), and the wet zones (almost aquatic). Each vole species vole appears to prefer a specific vegetation zone.
Although the bulk of their time is spent below ground, voles spend a considerable amount of their time above ground. With an estimated mortality rate of 88%, one can easily understand why they prefer heavy ground cover, primarily grasses, when out of the safety of the burrow system. Voles are considered great pests to many orchard owners and gardeners because, in some parts of the country, they have adapted well to living in groves of trees and in cultivated fields.
A vole’s diet consists of a variety of plants and animals including grasses, forbs, roots, bulbs, tubers, bark, snails, and insects. They play a necessarily role in ecosystem health by dispersing grass seeds (which helps maintain the diversity and variety of the grasslands), and by feeding predators.
Voles are probably the most important item in the food chain among secondary consumers. They provide a food source for several smaller mammals including: dogs, coyotes, cats, raccoons, skunks, weasels, Martens, and foxes. They are also preyed upon by snakes and Raptors including several species of owls and prairie falcons. As Paula said, “They are important yet invisible. They turn grass into foxes.” And, I might add, owls, coyotes, falcons, and so forth. Fortunately, for the future maintenance of the vole species, they have a very high rate of reproduction.
Ms. Spaeth considers voles to be a good indicator of climate and habitat change. In experiments which she has conducted, she has observed the interaction between two specific species - the Long-Tailed Vole and the Montane Vole. Although quite similar in appearance, the Long-Tailed Vole, as its name implies, has a distinctly longer tail than the Montane Vole.
Another difference between the two species is their reaction to deviations in their habitat. In her studies she has found the Long-Tailed Vole to be much more adaptable to change. Usually living in aspen stands in the Centennial Valley, the Long-Tailed Vole is quite content to move down into the grasslands occupied by the Montane Voles, if this species is removed.
In contrast, the Montane Voles do not move up into Long-Tailed Vole territory when that species is removed. This suggests the Montane Vole to be less adaptable to change than the Long-Tailed Vole. As a result, Ms. Spaeth believes a decline in the Montane Vole population could readily indicate improper management of the grasslands (such as overgrazing). It could also indicate global warming if the climate were to become hotter and drier thus creating less suitable Montane Vole habitat.
A loss of Montane Voles would not only effect Ms. Spaeth’s studies on global warming. Such a loss would also effect studies currently being carried out by scientists who are trying to determine why some human couples remain monogamous while others do not. These studies are being carried out on the Prairie Vole, which remains monogamous, and the Montane Vole, which is completely promiscuous. To date, researchers have isolated a couple of chemical reactions occurring to different degrees in the two vole species which they believe may hold the key.
However, the loss of a few voles might be a cause for celebration in New Mexico. Here a forest fire claimed over 16,000 acres and 60 homes, in addition to two lives. Some attribute the cause directly to the little vole. Apparently the Forest Service stopped the power company from clearing the trees from underneath the power lines which ran through Forest Service land. Their concern? Protecting the voles which were an important food source for the spotted owl. Thus they set the stage for disaster. All it took was an aspen tree falling across a power line and creating a live short for the fire to start. And, this because a small rodent decided to make its home under the power lines.
Even the little things in this world can have a large impact. Obviously the vole is no different. As I learned from my conversations with a very dedicated young lady - you can get attached to the little guys too. I can’t say I’m in danger of doing so, but I certainly appreciate these unique little creatures a great deal more than I did in the past.