Masked Shrew (Sorex cinereus)

County List:

Rule:

Forested or Mixed Forested/Nonforested Landscapes

      (Any Forested Upland Except Conifer Plantations (Any Size Class))
      or (Any Forested Lowland (Any Size Class))
      or Sedge Meadow
      or Lowland Brush
      or Bog
      or Treed Bog
   containing:
      (Dead Down Woody Debris or Rock)

Habitat List:

view size class definitions

Literature:

Preferred habitat is moist woodlands containing abundant plant cover, thick leaf litter, and decaying logs. However, the masked shrew tolerates a wide range of conditions, and one often finds it in overgrown fields, alder thickets, cedar swamps, weedy fencerows, grassy marshes, and even sphagnum bogs. It is least common in dry upland areas and exposed fields.

A masked shrew rests periodically in a nest fashioned from leaves and grass and hidden inside a half-rotted log or beneath a rock.

In the wild, a masked shrew consumes just about any type of terrestrial invertebrate that it stumbles across. The most common foods are caterpillars and grubs, but adult insects, especially beetles and crickets, are frequently on the menu as well. Other important prey items include slugs, snails, spiders, and to a lesser extent, earthworms and centipedes.

Habitat: Damp deciduous and coniferous woodlands with grasses, rocks, logs, or stumps for cover; bogs and other moist areas. Less often in open country with abundant moisture or in dry woods. Kirkland found them in clearcuts in West Virginia.

Special Habitat Requirements: High humidity (moist sites), ground cover (especially leaves, rotten logs, herbaceous vegetation).

Habitat Preferences: The masked shrew successfully inhabits all terrestrial environments in Michigan, with the possible exception of newly plowed fields. This diminutive mammal appears as much at home amid heavy leaf litter in mature woodlands as in grassy cover of fallow fields, in well-drained uplands or in moist swamp and waterway borders. There is no evidence that shrew populations increase due to major successional disturbances, even after the burning of swamp conifer cover (Verme and Ozoga, 1981). Many masked shrews are caught by house cats in densely settled urban areas (Toner 1956).

Density and Movements: Most Michigan population estimates have been made in the Upper Peninsula. In Marquette County, Manville (1949) found approximately four masked shrews per acre in northern white-cedar swamp and three per acre in black spruce habitat. In Alger County, Verme (1958) found populations of similar size in white cedar mixed with balsam fir, black spruce, tamarack, and swamp hardwoods. At the McCormick Experimental Forest in Baraga and Marquette counties, Haveman (1973) estimated that masked shrews occurred at the rate of 11 per acre in spruce swamp, nine per acre in mature hardwoods; six per acre in bog habitat; and four per acre in spruce barrens. In a subsequent study in the same area, Anderson (1977) found a considerably higher population of 93 masked shrews per acre in mature hardwoods. These density figures are for warm season populations.

Behavior: The focal point of activity is presumably the nest which is generally constructed of grasses and leaves in a secluded place. Usual sites are in stumps, under logs, or in shallow burrows.

Food Habits: Whitaker and Mumford (1972) noted at least 26 categories of food in stomachs of 50 masked shrews captured in Indiana. Numerous small and obscure groups of insects are listed along with larval stages of moths and butterflies, crickets, adult and larval stages of beetles, and leaf hoppers. Also found in noticeable quantities were earthworms, spiders, slugs, centipedes, phalangids, and snails. Mouse flesh, seeds and other vegetable materials were at a minimum. Hamilton (1930) and Schmidt (1931) counted insects (mostly adult beetles, ants, and larval forms of flies, moths, and butterflies, and wasps) in stomachs of 62 masked shrews taken in summer. In pit traps, masked shrews attacked and partly ate such trapped associates as other shrews, meadow jumping mice, meadow voles, and woodland voles. Two stomachs contained mammalian hair; two others contained remains of salamanders.

Stomachs of masked shrews taken in various habitats in the McCormick Experimental Forest in Baraga and Marquette counties contained Diptera (pupae and adults), Coeloptera, Hymenoptera, Lepidoptera, spiders, annelid worms, unidentified mammalian hair, and other material.

Sorex cinereus is the most widely distributed shrew in North America, occupying all moist woodlands within its range. Logs, stumps and ground covers that help to maintain humidity are associated with this shrew. Microhabitat characteristics that increase soil moisture are probably key components in habitat occupancy of S. cinereus.