Sorex
cinereus
(Masked
Shrew)
Range:
Occurs from Alaska/Canadian
Arctic tundra through Rockies, northern Great Plains, and Appalachians.
Description:
The masked shrew's head and neck are evenly grayish to brown above
and paler underneath. Its tail is fairly long and bicolored. Total length is
3.5 to 4.4 inches (87-110 mm), tail length is 1.4 to 1.6 inches (35 to 40 mm),
its weight is only 0.10 to 0.20 ounce (3-6 grams).
Habitat:
It seems to prefer coniferous forests and moist habitat
along streams and ponds.
Thick leaf litter in damp forests may also
represent favored habitat, although the species
appears adaptable to major successional disturbances. In Idaho, it can be found
in both wet and dry coniferous forests, and even occasionally
in sagebrush. In Wyoming they have been found from 3800 to 9450 feet.
Diet:
They eat insects and other invertebrates, carrion, small vertebrates, and,
occasionally, seeds. They consume their own weight in food each day.
Ecology:
This species
remains active throughout day (and year) to secure enough food to maintain a
high metabolic rate. They may use echolocation to detect prey. Its peak
activity period occurs from 0100-0200 hr. One study found that activity seemed
to correspond to weather, increasing when the temperature of the previous night
increased and decreasing when the temperature decreased. There is a big surge
in activity immediately after rain, especially if it occurs between 6:00 pm
and midnight. Their population size is subject to large annual fluctuations.
Density estimates range from 1 to 12 shrews per 0.4 ha.(1 acre). Home range
is about 0.04 ha (0.1 ac). They are usually found in scattered, locally abundant
populations. Individuals rarely live past second summer.
Reproduction:
Breeding season may last from March-September (in Nova Scotia, evidence
of mid-winter births exists for at least some years). Females produce 2 to 3
litters. Gestation lasts 18 days. Litter
size varies from 2 to 10 young, but averages 7. Young are weaned in 3 weeks, and reach
sexual maturity in 20 to 26 weeks.
Conservation:
 Status: |
 Unprotected
nongame species |
|
Global Rank: |
|
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State Rank: |
S4 |
Important State References:
Rickard, W.H. 1960. The distribution of small mammals in relation to climax
vegetation mosaic in eastern Washington and northern Idaho. Ecology 41: 99-106