Mountain Beaver: Aplodontidae

These animals spend much of their time along the banks of rivers and streams. They frequently wash themselves by dipping their front feet into the water and then scrubbing their body. These animals are strong swimmers.

Mountain beavers live alone or in small colonies. They may live in the same area as other mountain beavers that are sometimes referred to as colonies (groups). The concentration of these animals is most likely due to the fact that the colony sites make good habitats.

These animals have small home ranges, about 0.6 acres (0.25 hectares). Within this range mountain beavers build complex burrows with chambers for food storage, sleeping, and shelter. The burrows are long and close to the surface. The majority of a mountain beaver's time is spent in the underground burrows. They emerge only to forage or during the brief period of time when the young animals leave the nest to establish their own burrow sites. Other animals may also use their burrow system. The tunnels are cleaned and worked on regularly. If a tunnel is flooded by rain, the mountain beaver will swim in it.

Mountain beavers are primarily nocturnal, active at night. They are occasionally active for short periods of time during the daytime, especially in the autumn. When foraging for food, they seldom wander more than a few feet (meters) from their burrow. Although food is sometimes eaten above ground, it is generally brought to the burrow. It cuts off the plants desired and drags it to the mouth of the burrow. The food is placed over some logs or some rocks to wilt, then is either stored or eaten. It eats holding its food in its front feet like a raccoon.

While not a great climber, the mountain beaver climbs shrubs and small trees to cut off small limbs and twigs. It cuts off the branches as it climbs. Occasionally, it will let the small limbs and twigs drop to the ground. More typically, the mountain beaver will carry the wood down by climbing down the tree headfirst.

Mountain beavers do not hibernate (slow down their body temperature to conserve energy) and are active year round. In the cooler months they rarely appear above ground and at this time, eat supplies of stored food. In the winter when vegetation is sparse, the beavers will eat bark and small twigs.

Mountain beavers have a brief breeding season. Pregnant females have been collected from late February to early April. Gestation (length of pregnancy) typically lasts twenty-eight to thirty days. Females generally have one litter per year, bearing two or three offspring, and rarely four. Newborns' eyes are Mountain beavers spend most of their time in their complex burrows, which have chambers for food storage, sleeping, and shelter. The burrows are long and close to the surface. (Joseph Van Wormer/Bruce Coleman Inc. Reproduced by permission.) tightly closed and may not open fully until about fifty days later. After about eight weeks, offspring are nearly half-grown and able to leave the nest. Offspring reach sexual maturity late in the second year of life.