|Scientific Name:||Aplodontia rufa|
|Species Authority:||(Rafinesque, 1817)|
|Taxonomic Notes:||Helgen (in Wilson and Reeder 2005) applied the common name "Sewellel" to this species.|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Fellers, G.M., Lidicker Jr., W.Z., Linzey, A.V. & Nature Serve (Williams, D.F. & Hammerson, G.)|
|Reviewer(s):||Amori, G. (Small Nonvolant Mammal Red List Authority) & Chanson, J. (Global Mammal Assessment Team)|
Listed as Least Concern because it is a very widespread, common species, that is unlikely to be declining fast enough for listing in a more threatened category.
|Range Description:||The mountain beaver (Aplodontia rufa) occurs along the Pacific coast of western North America, from southwestern British Columbia, Canada, south to central California in the United States. It ranges from near Merritt, British Columbia, south along the Cascade, Olympic, Coast, and Siskiyou ranges to Rio Dell, California; Mt Shasta, California, southeastward through the Sierra Nevada of eastern California and west-central Nevada; Point Arena, Mendocino County, California; and near Pt. Reyes, Marin County, California (Carraway and Verts 1993).
The subspecies nigra has the most restricted distribution of all subspecies, it is known only from an area of 60 km² in the vicinity of Point Arena, Mendocino County, California. The subspecies phaea is known primarily from an area of approximately 285 km² within the Point Reyes National Seashore, Marin County, California, with a few populations occurring on privately owned land immediately adjacent to the Park.
Native:Canada (British Columbia); United States (California, Oregon, Washington)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Except for two small relictual populations in California, the mountain beaver is widespread and common in the Pacific Northwest. Global abundance estimates are from 10,000 to >1,000,000 individuals. For the subspecies nigra there are thought to be 10 populations within its known geographic range, totalling 100 individuals. Prior to a wildfire in 1995 that killed an estimated 98 percent of Reyes Point mountain beavers (subspecies phaea), the population was estimated at 5000 individuals.|
|Habitat and Ecology:||
In the main portion of their range, mountain beavers occur in moist forests and forest openings, where they prefer cool, moist environments such as overgrown thickets and seepage areas. They are most abundant near water courses in early to mid-seral stages vegetated by a tangle of secondary growth tree species, shrubs and forbs, and containing debris left from earlier forests (Carraway and Verts 1993). It prefers damp soils, digging networks of tunnels along stream banks. Tunnels generally are just below the ground surface, usually on north slopes in California, and on south slopes in British Columbia. It is primarily fossorial but can climb trees and swims well (but not arboreal or aquatic), and stays mostly underground in winter. Oval nests are constructed with leaves, twigs and grasses in a chamber that may be about two feet below the surface of the ground.
A. r. nigra occurs only in sheltered gulches, steep north facing slopes, and in a few old dune systems, where it requires soil conditions that allow easy excavation and abundant succulent plant food. A. r. phaea requires north-facing slopes with dense thickets of brush typically composed of coyote brush, sword fern, blackberry, and poison oak. Openings within Bishop pine forest with dense herbaceous understorey of sword fern and blackberries are also occupied (Carraway and Verts 1999).
Mountain beavers feed on a wide variety of vegetation. They consume ferns, forbs, and deciduous plants in summer and conifer foliage in fall/winter if other plants are unavailable (Banfield 1974). It forages mainly above the ground (Epple et al. 1993). They require free surface water or succulent vegetation on a daily basis and caches grasses and forbs for winter food. They are active during winter. Throughout the 24-hour day in summer, five to seven periods of activity alternate with periods of rest. They are more active at night than during daylight hours.
Mountain beavers have a low rate of reproduction and are monoestrous. Gestation lasts 28-30 days. One litter of two to four altricial young are born March-April, sometimes as late as early May in the north. Young are weaned in about six to eight weeks. Females are sexually mature in about two years; yearling females may ovulate but do not breed (Carraway and Verts 1993). A few live up to five to six years. They are usually solitary but may live in loose colonies. Population density estimates generally range from four to eight per hectare, but up to 15-20 per ha (Carraway and Verts 1993). The home range of ten adults radio tracked for three to 19 months was 0.03-0.20 ha, with a mean of 0.12 ha (Carraway and Verts 1993). Significant predators of mountain beavers include coyote and bobcat.
This species is common and considered a pest throughout much of its range in coastal areas of Northern California, Oregon, Washington and southern British Columbia. The areas inhabited are generally not visited frequently by humans. The mountain beaver is only rare in some relictual populations in California.
Threats to the disjunct subspecies nigra and phaea include wildfire, livestock grazing, expansion of exotic plant species, rodent control measures, alteration of natural stream flow, housing development, highway construction, predation by cats and dogs as well as the general uncertainties associated with small population sizes (Hafner et al. 1998).
|Conservation Actions:||In California relictual populations are protected in National Park Service land or through state endangered species listing. The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) have the mountain beaver listed as; Special Concern (01 Nov 2001). The subspecies nigra of northern California is protected nationally under the United States Endangered Species Act as of 1991.|
|Citation:||Fellers, G.M., Lidicker Jr., W.Z., Linzey, A.V. & Nature Serve (Williams, D.F. & Hammerson, G.) 2008. Aplodontia rufa. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 28 March 2015.|
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