Mammal Species of the World
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Pacific coast of northern California and Oregon.
Biogeographic Regions: nearctic (Native )
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: Columbia River south through western Oregon to northwestern California (to about 100 km north of S.F. Bay); Pacific Ocean to summit of Cascade Range (Alexander and Verts 1992).
Dorsally, this species is chestnut brown, mixed with black. Its color gradually lightens on sides to buff-gray on belly. It has an indistinct reddish stripe along back. The tail is bicolored and roughly 1/2 the length of the head and body.
Range mass: 15 to 40 g.
Range length: 110 to 190 mm.
Other Physical Features: endothermic ; bilateral symmetry
Length: 17 cm
Size in North America
Range: 121-165 mm
Range: 15-40 g
Myodes californicus prefers forested riparian habitats and is often found at stream edges. Abundance is positively correlated to size of logs, depth of organic soil, diameter of standing trees and snag size. Overall, old-growth, naturally degenerate forests with moist soils, abundant ground cover and litter are the ideal habitat.
Range elevation: 0 to 1900 m.
Habitat Regions: temperate
Terrestrial Biomes: forest
Other Habitat Features: riparian
Habitat and Ecology
Decayed logs appear to be a critical component of suitable habitat, they use logs for cover (Tallmon and Mills 1994). Riparian areas are reported to be most favourable for reproduction, but uplands may have higher populations (see Alexander and Verts 1992). Sometimes found in manzanita brushlands in California. Logged and burned areas do not provide suitable habitat and may be temporarily inhabited (Alexander and Verts 1992). They nest underground in burrows (made by other animals), under logs, or under old leaves. In Oregon, home range size of four radio collared individuals was 606-3,418sqm (Tallmon and Mills 1994).
West of Cascade Range the voles breed throughout the year; populations in Cascade Range breed February-November (females pregnant or lactating mainly April-September). Gestation lasts 17-21 days. Litter size averages two to three (Maser et al. 1981, Alexander and Verts 1992). Individual females produce several litters per year. Western red-backed voles are active throughout the year. West of Cascade range, voles are active mostly at night; in the mountains, voles are active throughout the 24-hour cycle (Maser et al. 1981).
Their diet is dominated by fungal sporocarps (especially of hypogeous fungi) and lichens. Will sometimes eats green vegetation, grass, seeds, and insect larvae. May store fungi for later use. Forages mainly under cover. Predators include marten, short-tailed weasel, spotted skunk, bobcat, coyote, domestic cat and owls.
Comments: Coniferous and mixed forests (see Alexander and Verts 1992 for details). Apparently prefers dense forests with little ground cover, but with large-diameter rotten logs; generally in cool moist microhabitats in deep forest. Decayed logs appear to be a critical component of suitable habitat; uses logs for cover (Tallmon and Mills 1994). Riparian areas are reported to be most favorable for reproduction, but uplands may have higher populations (see Alexander and Verts 1992). Sometimes in manzanita brushlands in California. Logged and burned areas do not provide suitable habitat (may be temporarily inhabited) (Alexander and Verts 1992). Nests underground in burrows (made by other animals), under logs, or under old leaves.
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Interestingly, M. californicus seems to rely heavily on fungal sprorocarps (75 to 90% of diet). These voles appear to have physiological and morphological adaptations of their digestive sytems which allow them to digest to fibrous materials of EMF (ectomycorrhizal fungi) sporocarps more efficiently than their body size would suggest. Myodes californicus is also known to eat some lichens, green vegetation (late winter), seeds, twigs, and insects (and occasionally insect larvae). Foraging is mostly terrestrial, but they occassionally climb into trees and shrubs in search of food. There is some evidence that they cache fungi for later consumption.
Animal Foods: insects
Plant Foods: leaves; seeds, grains, and nuts; lichens
Foraging Behavior: stores or caches food
Primary Diet: mycophage
Comments: Diet dominated by fungal sporocarps (especially of hypogeous fungi) and lichens. Also sometimes eats green vegetation, grass, seeds, and insect larvae. May cache fungi for later use. Forages mainly under cover.
Ecosystem Impact: disperses seeds
Myodes californicus are an important prey base for the forest ecosystem. They are preyed upon by martens, weasels, skunks, owls (including Spotted Owls), and other carnivorous birds and mammals.
- American martens (Martes americana)
- long-tailed weasels (Mustela frenata)
- ermine (Mustela erminea)
- striped skunks (Mephitis mephitis)
- eastern spotted skunks (Spilogale putorius)
- spotted owls (Strix occidentalis)
- other raptors (Falconiformes)
Spilogale putorius gracilis
This list may not be complete but is based on published studies.
Known prey organisms
This list may not be complete but is based on published studies.
In Oregon, home range size of four radiocollared individuals was 606-3418 sq m (Tallmon and Mills 1994).
Limited data indicate a home range of up to several hectares. Disperses viable spores of mycorrhizal fungi and nitrogen-fixing bacteria (see Maser and Maser 1988). Predators include marten, short-tailed weasel, spotted skunk, bobcat, coyote, domestic cat, owls, etc.
Life History and Behavior
Perception Channels: tactile ; chemical
Comments: Active throughout the year. West of Cascade range: active mostly at night; in mountains: active throughout 24-hour cycle (Maser et al. 1981).
Myodes californicus construct lichen nests under logs and forest floor debris. Mating occurs from February to October and young are born from April to November (Alexander, 1999).
Breeding season: February to November
Range number of offspring: 2 to 6.
Average number of offspring: 3.
Average gestation period: 18 days.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Parental Investment: altricial ; female parental care
West of Cascade Range breeds throughout year; populations in Cascade Range breed February-November (females pregnant or lactating mainly April-September). Gestation lasts 17-21 days. Litter size averages 2-3 (Maser et al. 1981, Alexander and Verts 1992). Individuals females produce several litters/year.
Myodes californicus are adversely affected by habitat fragmentation (due to reduced sporocarp abundance in cleared fields). They are also known to avoid road verge habitats, prefering to remain towards the forest interior. Human development of land, therefore, can apply a significant and damaging effect on M. californicus abundance.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Relevance to Humans and Ecosystems
M. californicus feed primarily on the ectomycorrhizal fungi symbionts of trees and probably help disperse the fungal spores. These symbiotic relationships are believed to be essential for the health and growth of trees
Western red-backed vole
The western red-backed vole (Myodes californicus) is a species of vole in the family Cricetidae. It is found in California and Oregon in the United States and lives mainly in coniferous forest. The body color is chestnut brown, or brown mixed with a considerable quantity of black hair gradually lightening on the sides and grading into a buffy-gray belly, with an indistinct reddish stripe on the back and a bicolored tail about half as long as the head and body.
The western red-backed vole was initially described by C. Hart Merriam under its original scientific name Evotomys californicus. The type specimen was obtained at near Eureka, California. It was an adult male collected by Theodore Sherman Palmer on June 3, 1889.
|Basal length||21.8 mm (0.86 in)||23.3 mm (0.92 in)|
|Nasal length||7.2 mm (0.28 in)||7.5 mm (0.30 in)|
|Zygomatic breadth||13.3 mm (0.52 in)||14.2 mm (0.56 in)|
|Mastoid breadth||11.5 mm (0.45 in)||12.4 mm (0.49 in)|
|Upper molar alveolus||4.5 mm (0.18 in)||5.3 mm (0.21 in)|
The length of the western red-backed vole ranges from 121–165 mm (4.8–6.5 in) overall, with a tail between 34–56 mm (1.3–2.2 in), hindfoot 17–21 mm (0.67–0.83 in), and ear 10–14 mm (0.39–0.55 in). The height ranges between 0.75–0.87 inches (18–21 mm).
The species is closely related to the southern red-backed vole (Myodes gapperi), which lives to the north and east of the range of this species, and is redder, with a more sharply bicolored tail. They are differentiated based on a reddish stripe on the dorsum of the western red-backed vole. The western red-backed vole also has characteristic differences in the anatomy of the hard palate.
Distribution and habitat
It is found in northern California and western Oregon in the United States. The northern limit is defined by the Columbia River, with the range extending south to around 100 km (62 mi) north of the San Francisco Bay. The range extends from the summits of the Cascade Range in the east, to the Pacific Ocean. They live mainly in coniferous forest. They live in the Transition and Canadian life zones, described by Vernon Orlando Bailey in The mammals and life zones of Oregon.
Behavior and ecology
The western red-backed vole lives largely underground in an extensive system of burrows. It feeds rimarily on fruiting bodies of hypogeous fungi. These mycorrhizal fungi are the symbionts of the forest trees around it. Rhizopogon vinicolor is one such which is associated with the Douglas-fir (Pseudotsuga spp.). Fruiting of the fungus takes place in well decayed timber when the nutrients are becoming exhausted. Because the fruiting bodies are underground, the spores are not liberated into the air as in most fungal species. However, the spores are found in the vole's droppings and are deposited throughout its burrows, thus enabling the fungus to spread and form associations with uninfected trees. It has been found that in a clear-cut forest where all the dead wood and trimmings are removed, the mycorrhiza stops fruiting, the vole population dies out and newly planted trees fail to thrive. This is an example of a three way symbiosis. The vole gains food from the fungus and spreads its spores. The fungus gains photosynthetic products from the tree which benefits from the nutrients produced by the fungus.
The western red-backed vole, as a denizen of old-growth forests, it plays an important role as prey to a number of species. For the northern spotted owl, western red-backed voles are one of the top five prey species. The red tree vole, northern flying squirrel, and western red-backed vole constitute more than 75% of the spotted owls diet.
The diet of the vole varies depending on its environment. At higher elevations, they are exposed to a broader differential of climactic conditions. They eat a more varied diet under such conditions, compared to what they eat under more moderate conditions at lower elevations.
No fossil remains have been identified.
The species breeds between February and November on the slopes of the Cascade Range in north Oregon, as well as all year to the west of the Cascade Range, with 2–7 young per litter and a gestation period of around 18 days.
According to the IUCN, the species conservation status is of "least concern." The rationale is that no major threats are identified to this common animal with a widely distributed geographic range.
In areas where vole populations live in close proximity to industrial areas, voles are used as a biological indicator to monitor environmental contamination, especially persistent organic pollutants such as PCBs which build up in the vole's fatty tissues.
- Linzey, A.V. & NatureServe (Hammerson, G.) (2008). Myodes californicus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 30 June 2009. Database entry includes a brief justification of why this species is of least concern.
- Don E. Wilson; DeeAnn M. Reeder (2005). Mammal Species of the World: A Taxonomic and Geographic Reference. JHU Press. pp. 1022–. ISBN 978-0-8018-8221-0.
- Alexander, Lois F.; Verts, B. J. (10 December 1992). "Clethrionomys californicus". Mammalian Species (406): 1–6. Retrieved 14 December 2014.
- Hinton, Martin Alister Campbell (1926). Monograph of the voles and lemmings (Microtinae) living and extinct : . Department of Zoology. [Mammals] : Free Download & Streaming : Internet Archive. British Museum (Natural History) London. pp. 275–276. Retrieved 14 December 2014.
- United States. Dept. of the Interior (1991). Recovery plan for the northern spotted owl - draft. U.S. Dept. of the Interior. pp. 366–368.
- Schultz, Stewart T; Kellerman, Kathy; Megahan, John (1998). The Northwest coast : a natural history. Portland, OR: Timber Press. pp. 275–276. ISBN 0881924180.
Names and Taxonomy
Comments: The species-group taxa occidentalis and caurina, formerly included in this species when it was known as Clethrionomys occidentalis, are now included in Myodes gapperi (see Musser and Carleton, in Wilson and Reeder 1993, 2005). See Alexander and Verts (1992) for a brief taxonomic history.
See Musser and Carleton (in Wilson and Reeder 2005) for an extensive discussion of the basis for correcting the generic name from Clethrionomys to Myodes.