Dusky shrews are found from Alaska, south through Canada and the western U.S. to Mexico.
This shrew is rust brown dorsally and lighter below and it has a pointed nose (like all shrews). The tail is not distinctly bi-colored. It is sometimes called the montane shrew, and once was thought to be the same species as the vagrant shrew. All shrews are small; the dusky shrew is 3.7 to 4.7 inches (95 to 119 mm) in total length, its tail is 1.5 to 1.9 inches (39 to 48 mm) and it weighs only 0.25 ounce (7 grams). Accurate identification of this shrew depends on an examination of the teeth in order to differentiate it from several other shrew species.
Found in various habitats, including damp meadows surrounded by coniferous forests, in grass among spruce/fir forests, in mid-elevation fir/larch forests, along streams and rivers in high prairie, on mossy banks of small streams, and in alpine tundra or sphagnum bogs. In Idaho, its distribution is similar to the vagrant shrew, but thought to be less dependent on water. May be present in pinyon-juniper and sagebrush communities in southern Idaho.
Feeds primarily on insects and other small invertebrates (worms, sowbugs, mollusks, etc.) Also consumes some vegetable matter.
It is active throughout the year as none of the shrews hibernate. Its mean home range has been estimated at 1227 m2 for non-breeders, and 4020 m2 for breeders. Individuals are apparently not territorial in breeding season, and may move widely. Most individuals probably do not live longer than 18 months. It is possible that the dusky shrew uses echolocation to navigate its environment. Researchers have found that this shrew can discriminate with echolocation, objects as small as 1.5 square inches at a distance of 8 inches. Dependence on echolocation increases in unfamiliar habitat, apparently to help them select suitable cover.
Breeding season extends from April-August. Average litter size is about 5 young, but may reach 7. Information on reproduction from different parts of range is needed.
|Unprotected nongame species|
Important State References:
Groves, C.R. 1994. A preliminary report: effects of timber harvest on small mammals and amphibians inhabiting old-growth coniferous forests on the Clearwater National Forest, Idaho. Idaho Dept. Fish & Game, Boise. 24pp.