University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln The Handbook: Prevention and Control of Wildlife Damage Management, Internet Center Wildlife Damage for July 1994 Mountain Beavers Dan L. Campbell USDA-APHIS-Animal Damage Control, Olympia, WA Follow this and additional works at: https://digitalcommons.unl.edu/icwdmhandbook Part of the Environmental Sciences Commons Campbell, Dan L., "Mountain Beavers" (1994). The Handbook: Prevention and Control of Wildlife Damage. 14. https://digitalcommons.unl.edu/icwdmhandbook/14 This Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in The Handbook: Prevention and Control of Wildlife Damage by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Dan L. Campbell Project Leader Olympia Field Station MOUNTAIN BEAVERS Denver Wildlife Research Center USDA-APHIS- Animal Damage Control Olympia, Washington 98512 Fig. 1. Mountain beaver, Aplodontia rufa Damage Prevention and Repellents Identification Control Methods 36% Big Game Repellent Powder has The mountain beaver (Aplodontia rufa, been registered for mountain beaver Exclusion Fig. 1) is a medium-sized rodent in the in Washington and Oregon. family Aplodontiadae. There are no Use plastic mesh seedling protectors Toxicants other species in the family. Average on small tree seedlings. Wire mesh adults weigh 2.3 pounds (1,050 g) and cages are somewhat effective, but A pelleted strychnine alkaloid bait was range from 1.8 to 3.5 pounds (800 to large diameter cages are expensive registered in Oregon but may be 1,600 g). Average overall length is 13.5 and allow animals to enter them. discontinued. inches (34 cm), including a rudimen- Exclusion from large areas with buried Fumigants tary tail about 1 inch (2.5 cm) long. The body is stout and compact. The head is fencing is impractical for most sites. None are registered. relatively large and wide and blends Cultural Methods/Habitat Trapping into a large neck with no depression Modification where it joins the shoulders. The eyes No. 110 Conibear® traps placed in and ears are relatively small and the Plant large tree seedlings that will main burrows are effective but may cheeks have long silver “whiskers.” tolerate minor damage. take nontarget animals using The hind feet are about 2 inches (5 cm) burrows, including predators. Burn or remove slash to reduce cover. long and slightly longer than the front Tractor scarification of sites will Welded-wire, double-door live traps feet (Fig. 2). Mountain beavers often destroy burrow systems. are effective and selective, but are balance on their hind feet while feed- primarily useful for research studies ing. The front feet are developed for Remove underground nests to reduce and removal of animals in urban/ grasping and climbing. reinvasion. residential situations. Adults are grayish brown or reddish Frightening Shooting brown. The underfur on the back and sides is charcoal with brown tips; Not applicable. Not applicable. guard hair is dark brown or black with PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994 Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska - Lincoln United States Department of Agriculture Animal and Plant Health Inspection Service Animal Damage Control B-53 Great Plains Agricultural Council Wildlife Committee Mountains and in the coast range of understory of sword fern (Polystichum Washington and Oregon than else- munitum), a preferred food of moun- where. In the southern limit of its tain beavers. Stands of bracken fern range, populations are more scattered (Pteridium aquilinum) are also favored but sometimes locally abundant. by mountain beavers. Preferred shrub habitats include salmonberry (Rubus Habitat spectabilis), huckleberry (Vaccinium parvifolium), salal (Gaultheria shallon), Mountain beaver habitat is characteris- and Oregon grape (Berberis nervosa). tically dominated by coastal Douglas- Small trees often found cut by moun- fir (Pseudotsuga menziesii) and western tain beavers include vine maple (Acer hemlock (Tsuga heterophylla). Within circinatum) and cascara (Rhamnus this zone, mountain beavers often purshiana). These species are often favor moist ravines and wooded or intermingled with 30 or more other brushy hillsides or flats that are not plant species including forbs, grasses, subjected to continuous flooding. and sedges. Although frequently found near small streams, they are not limited to those Food Habits sites except in more arid regions. The food habits of mountain beavers Active burrows may carry water run- are closely tied to the dominant vege- off after heavy rains, but mountain tation in their habitat. Sword fern and beavers will vacate burrow systems bracken fern are preferred when avail- that become flooded. Mountain bea- able. Douglas-fir, hemlock, western vers do not require free water; they red cedar (Thuja plicata), and red alder obtain adequate moisture from the are all commercial tree species that are vegetation they eat. cut and eaten by mountain beavers. Mountain beavers occupy mature for- Other species found in their habitat are ests usually in openings or in thinned either eaten or used for construction of stands where there is substantial veg- nests. Most feeding occurs above Fig. 2. Mountain beaver feet are developed for etation in the understory. They usually ground within 50 feet (15.2 m) of bur- burrowing and climbing. leave stands where the canopy has rows, although occasionally mountain closed and ground vegetation has beavers may travel several hundred become sparse. Preferred habitats in feet from burrows. They routinely silver tips. Ventrally, the underfur is forested sites are often dominated by climb shrubs and trees 8 feet (2.4 m) or gray with few guard hairs. A whitish red alder (Alnus rubra), which the ani- higher to cut off branches up to 3/4 spot of bare skin is present at the base mals promote by preferentially feeding inch (1.9 cm) in diameter, where they of the ears. The feet are lightly furred on conifers and other vegetation. leave cut stubs of branches on trees. on top and bare on the soles. Young These sites are often dominated by an Mountain beavers also girdle the base animals are generally darker than of tree stems and will feed on stems up adults. Males have a baculum (a bone to 6 inches (15 cm) in diameter, as well about 1 inch [2.5 cm] long in the penis). as the root systems of large trees. The Mature females generally have a patch bark is found in the stomach contents of dark-colored underfur around each of animals collected in midwinter. of the six nipples. Woody stems are often girdled and cut into about 6-inch (15-cm) lengths. Food Range and/or nest items are often stacked at burrow entrances (Fig. 4) but are Mountain beavers are found in the sometimes carried directly to food Pacific coastal region from southern caches or nests. Plant material is occa- British Columbia to northern Califor- sionally eaten outside the burrow but nia (Fig. 3). They range westward from is usually eaten at the food cache, in the Cascade Mountains and south- nests, or in the burrow. Mountain ward into the Sierras. Numbers are beavers practice coprophagy (con- higher and populations are more sumption of feces) and select soft over continuous in the coastal Olympic hard pellets. Fig. 3. Approximate range of mountain beavers in North America. B-54 Fig. 4. Sword fern and Douglas-fir piled at the entrance of a mountain beaver burrow. General Biology, Reproduction, and Fig. 5. Cross section of part of a mountain beaver burrow system including food cache, nest, and Behavior fecal chamber. Mountain beavers dig extensive indi- apparently with the front feet, causing or relatively dry nest chambers. Moun- vidual burrow systems that generally the ceiling to become a hardened shell. tain beavers, however, do not always are 1/2 to 6 feet (0.2 to 1.8 m) deep Water entering from above travels stack cut vegetation and often cut it with 10 to 30 exit or entrance holes that along this shell to the edges or floor of during periods of continuous rainfall are usually left open. The ground sur- the chamber. The floor is often covered and high humidity. Occasionally there face often caves in where burrows are with 1 to 2 inches (2 to 5 cm) of coarse may be 20 or 30 fern fronds or several shallow. There are many exit burrows sticks to facilitate drainage. On top of tree seedlings stacked at burrow open- forming T-shaped junctions with a the sticks is a variety of dry vegetation ings. The animals usually are quick to main burrow. These exits may be hori- that closely surrounds a sleeping carry away small bundles of sword zontal or even vertical. Burrows are mountain beaver. A nest may consist fern that they have placed inside the often found under old logs and are of several cubic feet of dry and nearly burrow opening. Some items such as sometimes on the surface in logging dry vegetation. The burrow system grasses and trailing blackberry vines debris. Mountain beavers seldom also includes smaller chambers or wid- are cut but are seldom stacked at make obvious trails through vegeta- ened burrows used as food caches. A openings. tion. Most activity is at night and sur- fecal chamber, usually present within a Little is known about mountain beaver face travel is usually near their few yards (1 to 3 m) of the nest cham- behavior during the breeding season. burrows. Sometimes they are seen ber, is packed with fecal pellets. Fecal Breeding activity occurs mainly from during daylight in dense surface vege- deposit chambers may be larger than January to March with gestation last- tation several feet from burrow open- the nest chamber, representing many ing about 30 days.