Viewing Mountain Beavers
Mountain beavers are abundant and active year-round, yet they are seldom observed due to their subterranean existence. Although active on and off throughout a 24 hour period, they are only occasionally seen wandering around on the ground or climbing in trees during daylight hours. They find the majority of their food and water within 150 feet of their burrows.
Mountain beavers have various calls; the most frequent is a chattering produced by gnashing the tips of the lower and upper front teeth. This indicates irritation and at close range is best heeded, because mountain beavers have sharp teeth and can be swift, vicious biters if cornered
Active Burrow Systems
Active systems are most evident during the late spring and summer months when most of the digging and repairing is done. Look for newly excavated soil (sometimes called a "kick out") or freshly cut vegetation next to or within the entrance of a 6- to 8-inch diameter hole. The presence of a mountain beaver (or other mammals using its tunnel system) can be recognized by the worn appearance of the tunnel floor and a lack or scarcity of spiderwebs at tunnel entrances.
In addition, after foraging above ground, mountain beavers carry or drag cut vegetation, which may vary in length from a few inches to several feet, to the burrow. There the material is cut into short sections at the burrow entrance and carried into the burrow to be eaten, stored, or used as nesting material. "Haystacks" of drying vegetation may be found near their burrows.
To check for occupants, you can install a temporary obstruction in the tunnel entrance. Cut three or four small-diameter (¼-inch) wide, 18-inch long woody stems and insert them vertically at the exits of several burrows. If mountain beavers are present, the inserted stems will be pushed aside or clipped within a few days. Their musky odor may also be noticeable.
Feeding Sites
Look for signs of clipped twigs and branches and stripped bark on shrubs and trees.
Seedlings less than 1½ inch in diameter are most often eaten. These are usually clipped off at or close to ground level, making signs of activity difficult to locate and invisible when covered by soil, vegetation, or debris.
Multiple bites on the clipped plant can create a serrated edge, but more often a clean, slanted cut similar to those made by rabbits, hares, voles, and other rodents is evident.
On small trees and large seedlings, the side branches are frequently clipped off high in the tree, leaving 1- to 3-inch stubs. (To distinguish mountain beaver activity from that of porcupines, note that mountain beavers eat from the bottom up and porcupines eat from the top down.)
Feeding activity on the roots of trees may cause trees to lean at odd angles or develop a curved trunk. Eating roots and/or bark may also kill the trees. Often, the foliage of injured conifers remains green during the first year, but the needles turn reddish brown during a relatively brief defoliation period the following summer. The defoliated skeletons of these trees may remain standing and visible for many years, becoming excellent habitat for the birds and mammals that use such trees.
Tracks
Mountain beavers are generally slow-moving animals so they leave a trail of closely spaced tracks Look for tracks near active burrows. The imprints, in mud, show distinctively long and slender toes that are not apt to be confused with those of any other animals.
Droppings
Mountain beaver droppings are seldom seen because they are normally deposited inside the burrow system. If you find droppings, they are probably from another animal using the burrow.
This information was provided by the Washington State Department of Fish and Wildlife, Russell Link, and Michael Holmquist
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