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Masked Shrew
Sorex cinereus
NatureServe conservation status
Global (G-rank): G5
State (S-rank): S3?
External links
General information
The masked shrew, Sorex cinereus, is widely distributed, occurring in Alaska, most of Canada, and much of the northern United States. In Utah, the species occurs primarily in mountainous areas, where it is most often found in moist habitats.
The masked shrew is a generalist feeder, eating insects, worms, other invertebrates, small vertebrates, and even seeds. Because of its high metabolic rate, the masked shrew must consume a great deal of food, often eating more than its body weight in food each day. The species mates from late spring to early fall. Gestation lasts approximately eighteen days, and females give birth to two or three litters of approximately seven young each year. The masked shrew is active both day and night throughout the year.
Phenology
Active throughout the day (and the year) to secure enough food to maintain high metabolic rate. Peak active period 0100-0200 (van Zyll de Jong 1983). Cloudy, rainy nights increase nocturnal activity.
Species range
Alaska to Labrador/Newfoundland, south to Washington, Utah, New Mexico, the Northern Great Plains, southern Indiana and Ohio, through the Appalachian Mountains to northern Georgia and western South Carolina, and on the east coast to New Jersey and northern Maryland (Laerm et al. 1995, Brimleyana 22:15-21; Whitaker 2004).
Habitat
Occupies most terrestrial habitats excluding areas with very little or no vegetation. Thick leaf litter in damp forests may represent favored habitat, although appears adaptable to major successional disturbances. In Nova Scotia, diet indicated that much foraging was done among wrack on beaches (Stewart et al. 1989). Nest sites are typically in shallow burrows or above ground in logs and stumps.
Food habits
A generalist, opportunistic invertivore. Eats primarily insects and other invertebrates, carrion, small vertebrates, occasionally seeds. Echolocation may be used for detecting prey (Gould et al. 1964). Consumes daily its own weight in food.
Ecology
Large annual fluctuations in population size. Density estimates range from 1-12 shrews per acre (Buckner 1966). Home range about 0.10 acre. Usually in scattered, locally abundant populations. Rarely lives past second summer.
Reproductive characteristics
Breeding season may last from March through September (there is evidence of mid-winter births in at least some years in Nova Scotia) (Stewart et al. 1989). Usually 2 litters, may be 3. Gestation lasts 18 days. Litter size is 2-10 (average around 7). Young are weaned in 3 weeks. Sexually mature in 20-26 weeks. Some young may breed in the year of their birth.
Threats or limiting factors
This and other generalist insectivores are not likely to be impacted negatively by selective insecticides such as BACILLUS THURINGIENSIS (Bellocq et al. 1992).
References
- Biotics Database. 2005. Utah Division of Wildlife Resources, NatureServe, and the network of Natural Heritage Programs and Conservation Data Centers.
- Burt, W. H. and R. P. Grossenheider. 1980. A field guide to the mammals. Houghton Mifflin Company, Boston. 289 pp.
