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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

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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. Young are born ings. Burrow systems usually cover a years’ use of the nest and burrow blind and hairless, weighing about 3/4 1/4 acre (0.1 ha) or more and may system. intersect with burrow systems of adja- ounce (20 g). They develop incisors at cent individuals. Each system is appar- In the spring and summer, mountain about 30 days and are weaned at about ently defended against neighboring beavers periodically remove molded 8 weeks. Young animals are often mountain beavers. When an animal and partially eaten vegetation from active in May. Females apparently do leaves a system or dies, the system is their food caches. Most soil excavation not bear young until 2 years of age. occurs during dry periods from spring often quickly reoccupied by another Territorial behavior usually limits to fall. Vegetation is cut year-round, mountain beaver. mountain beaver population densities but activity outside burrows and away to about 4 per acre (10/ha) although Each burrow system contains an un- from the nest is curtailed during sub- densities may be higher in some areas. derground dome-shaped chamber freezing temperatures. Portions of a Densities are generally higher in May with a nest, usually about 3 feet (1 m) burrow may not be used daily, but and June when young are still active below ground level (Fig. 5). Nests may active burrows in a burrow system are within burrow systems. In winter, vary from 1 to 9 feet (0.3 to 3 m) deep usually used at least weekly. and are entered by one or several average population densities in large entrances. Nest chambers are usually The habit of stacking cut vegetation at reforestation tracts (more than 100 about 2 feet (0.6 m) in diameter and 1 burrow openings has been considered acres [40 ha]) seldom exceed 2 animals to 2 feet (0.3 to 0.6 m) high. The dome a means to lower its moisture content per acre (5/ha). is hardened by packing the soil, before taking it into humid food caches

B-55 Several predators prey on mountain beavers. Above ground, the main predator, when present, is probably the bobcat (Felis rufus). Coyotes (Canis latrans) and great horned owls (Bubo virginianus) are other major large predators. In burrow systems, mink (Mustela vison) and long-tailed weasels (Mustela frenata) are the main preda- tors. Weasel predation is probably lim- ited to young or subadult animals less able to defend themselves. Mountain beavers appear relatively free of diseases and internal parasites. Animals in western Washington were checked as possible carriers of plague but were found negative. A large flea Fig. 6. Mountain beaver in feeding position. (Hystrichopsylla schefferi) unique to mountain beavers is common on the animals but is not known to be a prob- Fig. 7. Mountain beaver–girdled conifer tree. lem for humans. Mites (Acarina spp.) often infest the ear and eye region. Most stem-girdling damage is at the Damage to coniferous species is con- base of 3- to 6-inch (7- to 15-cm) diam- sidered detrimental to forest produc- Damage and Damage eter stems (Fig. 7). Girdling damage tion and can have long-term effects on Identification can be distinguished from that caused habitats. This damage to commercial by bears or porcupines in that moun- crops and other vegetation, however, Mountain beavers have damaged an tain beavers do not leave pieces of does provide diversity of cover for estimated 300,000 acres (120,000 ha) of bark scattered on the ground and they other wildlife. In one area on the commercial coniferous tree species in cut the bark smoothly along the edges. Olympic Peninsula in Washington, the western Washington and Oregon. Girdling damage to older stems is excessive damage to conifers by moun- Much of the affected land has the more difficult to distinguish, but it can tain beavers caused a manager to potential to produce timber values of be verified by examining burrows near change the area designation from over $10,000 an acre. The damage tree trunks where fresh girdling can be reforestation land to wildlife habitat. period extends to about 20 years after seen on the roots. planting. The major losses occur from Root girdling may occur at any age, Legal Status cutting tree seedlings during the first but small roots are usually cut instead year after planting (Fig. 6). Secondary Mountain beavers are generally con- of girdled. Trees with stems over 6 damage occurs during the next 5 years sidered unprotected nongame species. inches (15 cm) in diameter may die to surviving tree seedlings, followed Individuals wanting to control moun- due to extreme root girdling. Root gir- by stem girdling and root damage for tain beavers should consult their state dling may allow tree root pathogens to the next 10 to 20 years. Increased need fish and game agency to determine become established in individual trees for weed and brush control and occa- current regulations. A subspecies in and spread to other trees. It occurs in sional replanting costs add to the eco- California is considered endangered. winter and spring, and may occur in nomic losses caused by mountain Information on registered pesticides is other seasons. beavers. available from the state’s Department Mountain beaver damage in 10- to 15- of Agriculture. Damage to conifer seedlings is identi- year or older stands appears to be fied by angular rough cuts on stems increasing and is of great concern be- 1/4 to 3/4 inches (0.6 to 1.9 cm) in Damage Prevention and cause the crop trees are often selected diameter. Mountain beavers climb Control Methods at this time for precommercial thin- larger trees and cut stems near the tips. ning. Stem and root girdling may Exclusion Limbs are often cut a few inches from affect over 50% of the trees in a stand. the stem. Small trees are usually cut Small diameter plastic mesh seedling Managers cannot achieve proper spac- near ground level while others may be protectors (Fig. 8) will protect most ing in these damaged stands, and cut several feet up the stem. Seedling conifer seedlings. Most are effective damage may continue on trees left as damage occurs primarily in winter and until the seedlings grow taller than the crop trees. early spring, but often continues tube height. The relatively small (1-to throughout the year. 3-inch [2.5- to 7.6-cm]) diameter tubes

B-56 damage. Damage-resistant trees should be about 2 feet (0.6 m) tall and have 1/2-inch (1.3-cm) or larger diam- eter stems at the base. Trees should be planted away from burrow openings so that mountain beavers will find them less convenient to cut. Prescribed slash burning before plant- ing may reduce mountain beaver populations by reducing available forage and increasing predation. Extremely hot fires may cause some Fig. 8. Plastic mesh seedling protector. mortality, but most mountain beavers will remain protected in their burrows. do not protect much competing vege- Reduction in available forage after fire tation and also allow lateral branches may cause mountain beavers to travel to grow through the mesh. The farther from burrows and subject them advantage of plastic mesh protectors to higher levels of predation. Legal over some other control methods is restrictions or other practices that that they provide protection from a inhibit prescribed burning may favor variety of animals including deer mountain beaver populations. (Odocoileus spp.), hares (Lepus spp.), elk Mountain beaver burrow systems may (Cervus spp.), and voles (Microtus be destroyed by tractor scarification on Fig. 9. Application of powdered repellent to co- spp.). The cost of installation can be level or moderate slopes when done to nifer seedling. high, but can be reduced if done at the remove logging debris for replanting time of planting. Tree seedlings that or to convert brush fields to planta- Repellents become established and reach 30 tions. This method requires the use of inches (76 cm) or more in height are toothed land clearing blades to rip soil Coniferous seedlings subject to moun- less susceptible to damage. and destroy burrows. It seldom tain beaver damage may be treated Plastic mesh seedling protectors removes the deeper nest chambers but with repellents, but they require spe- photodegrade and deteriorate after can make the area unattractive to cial application procedures to assure several years. Although they expand mountain beavers. Avoid piling soil the plant stem is treated near the base with stem growth, they probably pro- and wood debris, both of which will (Fig. 9). The effectiveness of a repellent vide little protection from girdling of attract mountain beavers. Wood debris can be enhanced by conditioning the large diameter stems by mountain piles should be burned when possible mountain beavers to the repellent. beavers. and soil leveled. Treat cull seedlings with the same repellent and place them in active bur- Removal of nest chambers after popu- Wire mesh cages 1 to 3 feet (0.3 to 1 m) rows. This practice has caused moun- lation reduction will reduce reinvasion in diameter will protect individual tain beavers to avoid both treated and of the burrow systems by 50% or trees but are expensive and may be untreated planted seedlings for up to a more. Practical methods for locating climbed over and burrowed under. year after planting. The only repellent and removing nest chambers need fur- These cages also allow competing veg- that has been registered for mountain ther study. etation to be protected and often cause beavers in Washington and Oregon is poor tree growth. The wire used in Localized control of plants such as 36% Big Game Repellent Powder these cages may injure tree growth if sword fern, bracken fern, or salal may (BGR-P ), originally registered only for cages are tipped or come into contact reduce the attractiveness of an area to big game. Thiram (tetramethylthiuram with the tree stem. mountain beavers, but more study is disulfide) is another repellent regis- Cultural Methods necessary before methods can be rec- tered for hares, rabbits (Sylvilagus ommended. Use caution when apply- spp.), and big game that has been ef- Plant large tree seedlings to improve ing herbicides to avoid causing fective against mountain beavers. Re- survival of the trees in sites occupied increased feeding pressure on conifers pellents may be of most value where by mountain beavers. Larger stems are by suddenly removing the availability they cause a long-term avoidance. The less subject to being clipped at ground of other forage plants. In such situa- placement of repellent-treated cull tree level. Although large seedlings may be tions, tree seedlings may require pro- seedlings in burrows at time of plant- seriously damaged, enough foliage tection with plastic mesh seedling ing and treating significantly improves often remains after damage to provide protectors. repellent efficacy. for regrowth and survival after later

B-57 Toxicants A pelleted 0.31% strychnine bait (Boomer-Rid®) has been registered in Oregon for control of mountain beavers. Recent field tests in Washing- ton and Oregon, however, showed marginal efficacy in late winter with Boomer-Rid®. Pelleted bait is placed by hand inside main burrows, using about five baits each in 10 burrow openings in each system. The regis- tered label allows 1/2 to 1 1/2 pounds of bait per acre (0.6 to 1.7 kg/ha). The bait formulation contains waterproof- ing binders that tolerate wet burrow conditions. Experimental zinc phosphide-treated apple bait was poorly accepted by mountain beavers and was potentially hazardous to bait handlers. The treated bait was readily eaten by black- Fig. 10. Method for setting a kill trap in a mountain beaver burrow. tailed deer (Odocoileus hemionus colum- bianus) and could present a hazard. being girdled and undermined. Live is recent use. Set two or three traps in Baiting is severely restricted in areas trapping is seldom done in forest lands each active burrow system. All trap frequented by endangered species except for research purposes, but it is sites should be marked with flags and such as northern spotted owls (Strix used where there are urban damage mapped so they may be relocated; a occidentalis caurina), and bald eagles problems. crew of trappers should use several colors of flagging so that individuals (Haliaeetus leucocephalus). Kill trapping is normally done using can relocate their own traplines by unbaited Conibear® No. 110 traps set Fumigants color. Trapping in older stands of coni- in main burrows. Anchor traps with fers can be very difficult because traps Fumigants are generally ineffective three sticks, with either two in the are not easily relocated when branches because of the open, well-ventilated spring (Fig. 10) or with one in the hide the flagging. Mapping and flag- structure of the mountain beaver bur- spring and one at the far end of the ging travel routes in this type of habi- row systems. Aluminum phosphide jaws, in a vertical position with the tat may be necessary. The trap lines that was activated when mountain trigger hanging. The trap should take are usually checked after 1 day and beavers pulled pellets attached to veg- up most of the space in the burrow, again checked and pulled after about 5 etation into the nest area was only par- and when properly anchored, is days. Traps are usually reset during tially effective. The use of carbon readily entered by the mountain bea- the first check even where mountain monoxide gas cartridges and carbon vers. This trap is sometimes not imme- beavers are captured, because the sys- monoxide gas have been unsuccessful diately lethal because of the mountain tems may be quickly invaded by other in controlling mountain beavers. No beaver’s thick short neck. Stronger mountain beavers. If trapping is un- fumigants are registered for mountain double-spring traps may be more ef- successful, move traps to burrows beaver control. The use of smoke fective, but are more difficult to set in bombs or similar material is effective with fresh activity. During the breed- the limited burrow space. in locating the numerous openings in a ing season (January to March), male mountain beaver burrow system. Teams of trappers are normally used mountain beavers may be more com- when trapping large acreages. Indi- monly trapped than females because Trapping vidual trappers should be spaced of their greater activity. Mountain beavers are routinely kill about 30 to 50 feet (9.1 to 15.2 m) apart, During subfreezing temperatures, trapped for damage control on many depending on habitat conditions. Extra trapping should be postponed or trap- forest lands scheduled for planting. searching may be required in areas ping periods lengthened to include Trapping is usually done just prior to with many small drainages that may warmer periods when mountain bea- planting and repeated 1 or 2 years have many burrows. Active burrows vers are more active. Trapping during afterward. Trapping is also repeated have fresh soil and vegetation piled at periods of snow is also usually less when damage is found in established burrow entrances or in burrows. Bur- successful than during snow-free peri- plantations. Set kill traps in older rows can often be visually inspected ods because trap sites are difficult to stands where stems and roots are through openings to determine if there

B-58 locate and set, and animals are less where the potential crop value is high. by brush species. Sometimes, however, active. Well-stocked stands of Douglas-fir are the burrowing activity has caused usually commercially thinned once or damage to roads and trails. Forest Trapping may take nontarget species twice before final harvest, and often workers are periodically injured by such as weasels, spotted skunks produce timber values of thousands of falling into mountain beaver burrows. (Spilogale putorius), mink, squirrels dollars per acre. When mountain bea- (Tamiasciurus spp.), rabbits, and hares An economic study of Pacific North- vers prevent reforestation or cause that use the mountain beaver burrows. west forest animal damage indicates expenditures for protecting reforesta- Nontarget losses may be reduced by that damage control expenditures of tion, the value of the crops is reduced positioning the trap trigger near the about $150 per acre ($375/ha) are rea- or eliminated. A planned Douglas-fir side of the trap so that it is less likely to sonable on average-site Douglas-fir crop rotation period of 40 years on be tripped when small animals pass forest land. On higher quality land the good sites can be severely disrupted if through. expenditure for damage control can be at 15 years the crop is lost to damage higher, particularly where mountain Live trapping is recommended where by mountain beavers. Since mountain beavers cause heavy mortality in refor- domestic animals may enter the bur- beaver damage occurs on about estation areas. rows. Double-door wire mesh live 300,000 acres (120,000 ha) of commer- traps such as Tomahawk traps (6 x 6 x cial forest land, a conservative annual 24 inches [15 x 15 x 61 cm]) should be loss estimate of $100 per acre ($250/ Acknowledgments set nearly level in main burrows. Suit- ha) results in an annual loss of $30 mil- able vegetation should be placed lion. Losses to mountain beavers may I wish to thank numerous employees of USDA- inside and along the outside of the be $10,000 per acre ($24,700/ha) when APHIS, the USDA Forest Service, the USDI trap. Wrap the trap with black plastic damage causes failure of the timber Bureau of Land Management, the Washington and cover it with soil to protect ani- crop. Department of Natural Resources, the Oregon mals from the weather. Placement Department of Forestry, and many private forest Economic losses are caused by both industry companies for support of studies should assure that animals enter rather direct and indirect damage. Cutting of involving research into mountain beaver than go around the ends of the trap. damage control. I also wish to thank Kathryn planted tree seedlings is the most com- Traps must be checked once or twice Campbell for the illustrations drawn from mon damage. If it has been several daily, preferably in early morning and photos and descriptions by the author. years since planting, the site may need again in the late afternoon, to minimize brush control by machine, hand, or injury and stress to mountain beavers herbicide before replanting can be For Additional held in the live traps. Live-captured done. Damage to tree seedlings also mountain beavers should be placed in Information keeps the trees within a size range that dry burlap sacks and, if necessary, is susceptible to damage by hares, rab- euthanized with carbon dioxide. Borrecco, J. E. 1976. Vexar tubing as a means to bits, deer, and elk. If damage is not protect seedlings from wildlife damage. Shooting controlled, large areas may not be Weyerhaeuser For. Res. Tech. Rep. 4101/76/ adequately reforested. Trees that 36. 18 pp. Shooting is not a practical control escape early damage may be damaged Borrecco, J. E., and R. J. Anderson. 1980. method. later by girdling and undermining by Mountain beaver problems in the forests of Other Methods California, Oregon, and Washington. Proc. mountain beavers, causing a loss of Vertebr. Pest Conf. 9:135-142. Habitat manipulation by increasing or many years’ growth of commercially valuable species. Campbell, D. L. 1987. Potential for aversive decreasing favored vegetation has conditioning in forest animal damage been evaluated only indirectly. Where The mountain beaver currently has no control. Pages 117-118 in H. L. Black, ed. native forbs were seeded to reduce Proc. Symp. Anim. Damage Manage. Pacific commercial value. The pelt has no fur Northwest For. Spokane, Washington. deer damage to Douglas-fir planta- value and there is no market for the tions, mountain beaver damage did meat. The animal is of significant zoo- Campbell, D. L., and J. Evans. 1975. “Vexar” seedling protectors to reduce wildlife not significantly decrease or increase. logical and medical interest, however, damage to Douglas-fir. USDI Fish Wildl. In another area, where red huckleberry because of its limited range and Serv. Wildl. Leaflet. No. 508. 11 pp. was abundant and extensively cut, unique physiological characteristics. Campbell, D. L. and J. Evans. 1988. Recent mountain beaver damage to Douglas- Despite its limited range, however, the approaches to controlling mountain beavers fir was insignificant. overall populations of mountain bea- (Aplodontia rufa) in Pacific Northwest forests. vers have probably increased since Proc. Vertebr. Pest Conf. 13:183-187. Economics of Damage and timber harvesting began in the Pacific Campbell, D. L., J. Evans, and G. B. Hartman. Northwest. 1988. Evaluation of seedling protection Control materials in western Oregon. US Dep. Inter. The burrowing and vegetation cutting Bureau Land Manage. Tech. Note OR-5. Mountain beavers cause considerable activities of mountain beavers may 14 pp. economic damage to reforestation. improve soils and reduce competition Most of their habitat is in timberland

B-59 Campbell, D. L., J. D. Ocheltree, and M. G. Carey. 1988. Adaptation of mountain beaver (Aplodontia rufa) to removal of underground nests. Northwest Sci. 62(2):75. Engeman, R. M., D. L. Campbell, and J. Evans. 1991. An evaluation of two activity indicators for use in mountain beaver burrow systems. Wildl. Soc. Bull. 19:413-416. Evans, J. 1984. Mountain beaver. Pages 610-611 in P. MacDonald, ed. The encyclopedia of mammals. Facts on File Publ. New York. Evans, J. 1987. Mountain beaver damage and management. Pages 73-74 in H. L. Black, ed. Proc. Symp. Anim. Damage Manage. Pacific Northwest For. Spokane, Washington. Feldhamer, G. A. and J. A. Rochelle. 1982. Mountain beaver. Pages 167-175 in J. A. Chapman and G. A. Feldhamer, eds. Wild mammals of North America: biology, management, and economics. The Johns Hopkins Univ. Press, Baltimore. Hartwell, H. D. and L. E. Johnson. 1992. Mountain beaver tree injuries in relation to forest regeneration. DNR Res. Rep. State of Washington, Dept. Nat. Resour. Olympia. 49 pp. Hooven, E. F. 1977. The mountain beaver in Oregon: its life history and control. Res. Pap. 30. Oregon State Univ. Corvallis. 20 pp. Martin, P. 1971. Movements and activities of the mountain beaver (Aplodontia rufa). J. Mammal. 52:717-723. Motobu, D., J. Todd, and M. Jones. 1977. Trapping guidelines for mountain beaver, Weyerhaeuser For. Res. Rep. 042-4101/77/20. 28 pp.

Editors Scott E. Hygnstrom Robert M. Timm Gary E. Larson

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