Description.—The dusky shrew is similar in form of body to the cinereous shrew. The length of head and body is about 2-1/4 inches. The tail is about 2-1/2 inches. The upper parts are rusty or reddish brown. The underparts are brownish gray. The dusky shrew differs from the wandering shrew in possessing a slightly longer body and longer tail, but in eastern Washington the two species are almost indistinguishable.
Dusky shrews range from northern Alaska to southern New Mexico, and from the Rocky Mountains to the Pacific Ocean. Thirteen subspecies are recognized by [Jackson] (1928: 115), of which two occur in Washington.
Records of the dusky shrew are not available from the arid subdivision of the Transition or the Upper Sonoran life-zones. It occurs sparingly in the humid subdivision of the Transition and is common in the Canadian and Hudsonian life-zones.
The habitat of the dusky shrew is varied. Near Seattle, King County, several specimens were trapped in marshes where Sorex vagrans was abundant. Near Stevens Pass, King County, two were taken in a marsh; two others were trapped in a dry, coniferous forest; one was taken in a small bed of heather on a barren mountain top; and another was found dead in a pan of pancake batter in camp. Two specimens were trapped along a small stream at Dewey Lake, Mt. Rainier, Yakima County. Four specimens were caught in traps set in a talus slope on a dry hillside at the North Fork of the Quinault River, Jefferson County. Three others were trapped in dense, rain-forest thickets along the ocean at La Push, Jefferson County. These records indicate that the dusky shrew has a wider environmental range than other Washington shrews. Despite this wide range of tolerance the dusky shrew is common only locally, except in the Hudsonian Life-zone.
Little is known of the habits of dusky shrews but they seem to be as diurnal as they are nocturnal. At Wolf Bar, North Fork of the Quinault River, Jefferson County, a dusky shrew was seen on the packed-earth floor of an old trapper's cabin. A hat was carefully dropped over the live animal but, when the hat was lifted, the shrew was found dead. In an old cabin at Stevens Pass, King County, a dusky shrew was found dead one morning in a pan of flapjack batter prepared the evening before. As this pan was on a table about three feet from the floor, the shrew must have climbed to the table by way of the rough cabin wall, but how the animal managed to scale the side of the pan is a mystery.
[Slipp] (1942: 211) discovered the nest of a dusky shrew between Round Pass and Lake George, 4200 feet elevation, in Mt. Rainier National Park, on July 25, 1937. The nest was in a rotten fir log 20 inches in diameter. The nest, a ball of dry grass the size of a man's fist, had no central cavity or passages, the occupants "merely pushed through wherever they wished." Seven young shrews were found in and near the nest. Though the eyes of the young were still closed, they were able to creep about and squeal.
A specimen obtained 5 miles west-southwest of Guler, Skamania County, contained 4 embryos on July 10, 1939.