The mountain beaver,
endemic to California and the Pacific Northwest, is considered the most
primitive living rodent species. In open forest areas, large holes,
often with clipped sword fern or forbs neatly arrayed around them, are
indicative that mountain beavers may be present.
Mountain beavers are voracious. When the animals forage on seedlings,
the seedlings may show retarded growth or deformities, or may die. Though
ferns and salal are preferred foods, bark and twigs of trees are readily
taken when other forage is limited. Douglas-fir does not appear to be
a highly preferred food, yet establishment of Douglas-fir seedlings
is often difficult in areas with mountain beaver. In most areas, damage
by mountain beaver is limited to seedlings less than 1.5 inches in diameter.
However, larger trees can suffer basal barking and undermining of roots.
For a species that has been around for so long, very little is actually
known about the its basic ecology. Thus, the NWRC field station
is conducting studies to expand current understanding of this rodent.
At the station, researchers have the ability to house mountain beavers
in large outdoor habitat pens in which vegetation and populations can
Scientists have conducted a series of trials to determine the influence
of available forage and population pressure on seedling damage, in addition
to conducting standard cafeteria tests to determine mountain beaver
food preference. In the cafeteria trials, ferns, salal, cat’s
ear, and salmonberry were highly preferred foods over Douglas-fir and
western red cedar. Results from the habitat study showed that mountain
beaver in pens without preferred forage damaged more seedlings than
in pens with preferred forage. Population pressure did not have an effect
on damage because mountain beaver moved to areas where there was preferred
Field station scientists are currently conducting several studies
to understand mountain beaver movements and dispersal patterns under
varying vegetational characteristics (how far they can disperse to reinvade
areas, is important for forest managers). Home range size for adult
mountain beaver was previously reported as 0.08 to 0.5 acres with an
average home range size of 0.03 acres (0.07 ha). Several factors can
affect home range size including population density, available forage,
available cover, and available water. To understand which of these factors
may affect movements, scientists captured and radio collared 41 mountain
beavers. Although most previous literature supported a nocturnal activity
pattern for the mountain beaver, our data show that mountain beavers
are active throughout a 24-hour period. Home range sizes differed between
study sites and were substantially larger than previously reported.—from
an average of 1.17 ha (± 0.24) to 4.16 ha (± 3.23). Preliminary
results suggest that the difference in home range sizes between the
two areas is a result of available forage. In the absence of available
preferred food, mountain beavers may travel considerable distances,
as shown in this study, to forage on available plants (e.g., seedlings).
Predation on the study sites was high (40%). Bobcats, coyotes, and
raptors are the main aboveground predators, and an unknown species,
likely a mink or spotted skunk, the belowground predator. In addition
to the observed home ranges that were larger than previously reported,
we have found that mountain beaver can disperse over 0.5 km to establish
Seedling protection from mountain beaver damage has been limited to
barriers, although these have met with limited success. Trapping is
the most productive means to reduce mountain beaver populations, and
hence, damage to new seedlings. With current information gained from
mountain beaver movements and preference for food resources, alternative
nonlethal methods to reduce damage may be implemented. For instance,
managing for an alternate winter food source may help reduce the amount
of damage by mountain beaver to newly planted seedlings.
*the above discussion is summarized from the following article
by Wendy M. Arjo. Click on the link to see the full-text of the article.
ARJO, W. M. 2003. Mountain beaver: the little rodent with a large
appetite. Western Forester 48(4):10-11. 156K
Additional NWRC Resources
W. M., AND D. L. NOLTE. 2004. Assessing the efficacy of registered underground
baiting products for mountain beaver (Aplodontia rufa) control.
Crop Protection 23:425-430. 609K
W. M., D. L. NOLTE, J. L. HARPER, AND B. A. KIMBALL. 2004. The effects
of lactation on seedling damage by mountain beaver. Proceedings of the
Vertebrate Pest Conference 21:163-168. 449K
W. M., D. L. NOLTE, T. M. PRIMUS, AND D. J. KOHLER. 2004. Assessing
the efficacy of chlorophacinone for mountain beaver (Aplodontia
rufa) control. Proceedings of the Vertebrate Pest Conference 21:158-162.
EPPLE, G, J. R. MASON, E. ARONOV, D. L. NOLTE, R. A. HARTZ, R. KALOOSTIAN,
D. CAMPBELL, AND A. B. SMITH III. 1995. Feeding responses to predator-based
repellents in the mountain beaver (Aplodontia rufa). Ecological
Applications 5(4): 1163–1170.
CAMPBELL, D. L. 1994. Mountain beavers. Pages B53–B60 in
S. E. Hygnstrom, R. M. Timm, and G .E. Larson, editors. Prevention and
control of wildlife damage. University of Nebraska Cooperative Extension,
U.S. Department of Agriculture–Animal and Plant Health Inspection
Service–Animal Damage Control, and Great Plains Agricultural Council–Wildlife
Committee. Lincoln, Nebraska.
EPPLE, G., J. R. MASON, D. L. NOLTE, AND D. L. CAMPBELL. 1993. Effects
of predator odors on feeding in the mountain beaver (Aplodontia
rufa). Journal of Mammalogy 74:715- 722.
CAMPBELL, D. L., J. P. FARLEY, AND R. M. ENGEMAN . 1992. Field efficacy
evaluation of pelleted strychnine baits for control of mountain beavers
(Aplodontia rufa). Proceedings of the Vertebrate Pest Conference
Impacts on Forest Resources Research Project
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