Smoky Shrew (Sorex fumeus)

County List:

Rule:

Forested or Mixed Forested/Nonforested Landscapes

      (Northern Hardwoods (Pole or Sm Saw or Lg Saw or Uneven))
      or (Hemlock (Sm Saw or Lg Saw or Uneven))
      or (Mixed Northern Hardwoods (Sm Saw or Lg Saw or Uneven))
      or (Swamp Hardwoods (Sm Saw or Lg Saw or Uneven))
      or (Northern White Cedar (Sm Saw or Lg Saw or Uneven))
      or (Any Lowland Mixed (Sm Saw or Lg Saw or Uneven))
      or Treed Bog
   containing:
      Dead Down Woody Debris

Habitat List:

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Literature:

This insectivore occasionally occupies grassy areas, bogs, swamps, and talus slopes, but its preferred habitat is deciduous or evergreen woods. The forest floor in smoky shrew habitat is shaded and moist and contains moss-covered logs or rocks and an abundance of plant litter overlying loosely packed soil. The smoky shrew has a spotty distribution - abundant in some areas yet often absent in nearby, seemingly identical patches of woods. Also, it is scarce in areas where either the short-tailed shrew or the masked shrew are common.

It is similar to other shrews in preying on a variety of invertebrates, including adult insects, caterpillars, grubs, centipedes, spiders, and earthworms. Some vertebrates, such as salamanders occasionally fall prey to the smoky shrew and an additional 15% or so of the diet is vegetable matter.

Habitat: Damp, boulder-strewn upland woods (often beech or maple, birch and hemlock) with thick leaf mold. Typically near streams with moss-covered banks. Also uses clearcuts in coniferous woodlands.

Special Habitat Requirements: Loose damp leaf litter-does not burrow, uses runways of other small mammals in shady wooded areas.

Habitat Preferences: Cool, moist, shady boreal forest areas seem preferred by the smoky shrew within its rather restricted geographic range in eastern North America. The forest floor of favored habitat is underlain by black friable soils and covered with loose leaf mold. Characteristic also are growths of ferns, moss-covered logs and other litter (Hamilton 1940). Field observers have found smoky shrews most commonly in mature maple, birch, and hemlock woodlands. Despite more exacting environmental requirements than its common associate, the masked shrew, the smoky shrew has been found in such varied habitats as deep spruce forest under moss-covered logs on the Gaspe Peninsula, on a sparsely wooded hillside and in open woods in New York, in wet, dense cedar and subsequent successional stages in northern deciduous and boreal coniferous forest habitats in West Virginia, and in northern deciduous forest treated with aerial application of the herbicide 2,4,5-T, in West Virginia. In Michigan, the three smoky shrews obtained on Sugar Island were caught in pitfall traps set in open forest habitat (Master 1982). The substrate consisted of a thick layer of leaf mold with sand below. Understory was mostly open with scattered seedlings of maple and oak and broken and fragile ferns. Mature trees making up the park-like forest included sugar maple, and, to a lesser extent, striped maple, hemlock, and birch.

Density and Movements: In populations living in favorable areas in beech, maple, and hemlock forests. Hamilton estimated smoky shrews to number from 25 to 50 individuals per acre. In similar habitat in Ohio, Bole found 15 smoky shrews per acre. However, in habitats other than mature deciduous-coniferous forest, Bole noted that shrew populations were much more sparse, averaging less than one per acre.

Behavior: The occurrence for smoky shrews in cedar swamps, along shaded brooks, and in sphagnum bogs shows its affinity for saturated substrate and even surface water areas. Nests are secluded under logs or other forest floor debris.

Food Habits: In the warm moths, the great bulk of food selections by smoky shrews is provided by ground-inhabiting insects, their pupae and larvae. In the cold months, the diet is apt to be more varied with snails, earthworms, and other invertebrates taken, as available. Some vegetable matter appears in stomach contents in autumn.

Ecology and Behavior: Sorex fumeus inhabits primarily the cool, shaded floors of deciduous and coniferous forests. Microhabitats of S. fumeus commonly include thick leaf mold over friable soils, damp mossy-covered rocks, and old decaying logs and brush. In Canada, smoky shrews were reported from bogs and swamps, grassy areas, and talus slopes. In the United States S. fumeus is known to occupy bogs and swamps, talus slopes, stream banks, and grassy areas.

Sorex fumeus occurs primarily in shady damp woods, typically of a northern hardwood type. Seldom found in dry woodlands, it requires deep, loose leaf litter; nests are located in or under rotted logs or stumps. We found that S. fumeus used hardwood poletimber stands preferentially. However, none of the other species that favor moist sites displayed an affinity for pole timber stands.