American Water Shrew
The water shrew inhabits much of northern North America. In the East, it ranges from New England to North Carolina. It is found across Pennsylvania’s northern half, and south through the Appalachians.
Sorex palustris is the second largest Pennsylvania shrew (the short-tailed shrew is more robust). Overall length, 5.3 to 6.1 inches; tail, 2.4 to 3.5 inches; weight, 0.35 to 0.6 ounces. In winter, the pelt is brownish-black above (sometimes faintly grizzled with silver) and light gray below. In summer, the upperparts are browner and the underparts paler. The long tail is brownish-black above, paler below.
The water shrew inhabits heavily wooded areas and is adapted to a semi-aquatic life. The banks of cold, clear streams provide optimum habitat. Water shrews occupy small surface runways under bank overhangs, fallen logs and brushpiles. They also live in bogs and springs, and may shelter in a beaver lodge or muskrat house in winter. Nests are usually made of dry moss.
This shrew uses its big hind feet, fringed with short, stiff hairs, to paddle about under water. It can stay submerged about 15 seconds. Water cannot penetrate the shrew’s dense pelage, so the animal itself never gets wet. A water shrew can run short distances across the water’s surface, buoyed up by globules of air like a water bug. Water shrews locate aquatic prey by touch. They eat insects and other small invertebrates (both aquatic and terrestrial), small fish and fish eggs.
Little is known about the breeding habits of this secretive species. The gestation period is about three weeks, with 4 to 8 young born from late February to June. Females probably bear more than one litter each year. Water shrews tend to be nocturnal but are also active at dusk, on cloudy days, and in the shade on sunny days. Predators include weasels, mink, otters, hawks, owls, snakes and fish (smallmouth bass, trout and pickerel). Longevity is about 18 months.