Water Shrew (Sorex palustris)

County List:

Rule:

Forested or Mixed Forested/Nonforested Landscapes

      (Any Lowland Conifer (Pole or Sm Saw or Lg Saw or Uneven))
      or (Mixed Lowland Conifer (Pole or Sm Saw or Lg Saw or Uneven))
      or Treed Bog
   containing:
      Dead Down Woody Debris
   adjacent to:
      (Marsh 2 or Sedge Meadow or Lowland Brush or Bog)
   adjacent to:
      (Lake or Pond or River)

Habitat List:

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Literature:

This species never strays far from open water. It occasionally resides near a sluggish stream, bog, or seasonal pond, but optimal habitat is a small, forest-lined stream with fast-flowing water, and plenty of cover provided by undercut banks, jumbled rocks, downed trees, and other debris.

The water shrew preys heavily upon aquatic larvae of certain insects, such as mayflies, stoneflies, caddisflies, and some of the true flies, and it also consumes leeches and snails. Terrestrial invertebrate prey includes crickets, slugs, and earthworms. This shrew also feeds to a lesser extent on vertebrate flesh, such as adult and larval salamanders, fish eggs, and even minnow-sized fish.

Habitat: Wet areas, especially grass-sedge marsh or shrub zones along ponds and streams in coniferous forest. Also at wooded shores with favorable cover in the form of crevices beneath boulders, tree roots, or overhanging banks.

Special Habitat Requirements: Herbaceous cover, body of cold water (bog, stream, lake)

Distribution: The water shrew occurs throughout the broad band of northern coniferous forest across North America, from the edge of the arctic tundra south to the states at the Canadian-American border except for those in the mid-continent plains.

Habitat Preferences: The water shrew, as its name implies, has a close affinity for water and is certainly the most aquatic of Michigan shrews. It has been found in moist situations along stone walls, along fence lines near cedar-spruce swamps, at bridge abutments, and on the wet forest floor, but especially at water's edge. Although it forages along swamps, bogs, and lakes, this shrew's favored habitat appears to be the edges of rock-filled and log-strewn cold-water streams bordered by woody vegetation.

Behavior: The nest may be as large as 4 inches in diameter and constructed of vegetation including sticks and leaves. Bankside burrows are used as retreats and perhaps places to hoard food. Water shrews often move along their own surface runways under the protective covering of bank overhangs, fallen logs, and debris. The animals are known to seek refuge in beaver and muskrat houses.

Food Habits: The water shrew's diet consists chiefly of invertebrates which frequent the water's edge, including the aquatic nymphs of caddis flies, mayflies, and stoneflies.

Ecology: Sorex palustris is rarely found far from water. Although it is typically found along edges of swift-flowing streams with rocks, logs, crevices, and overhanging banks, it also has been collected near slow-moving streams, dry ephemeral creek beds, and small springs. Extensive sampling of all habitat types in Manitoba produced 130 specimens, 92% of which were trapped in hydric habitats and 8% in mesic habitats. Some water shrews were collected in areas with herb, shrub, and tree cover, but most were trapped in grass-sedge marshes and willow-alder shrub zones along creeks and ponds; few water shrews were caught in wet habitats (such as sedge-moss or heather-moss bogs or tamarack swamps) that lacked open, moving water or did not support an abundant invertebrate fauna. Water shrews also are caught frequently in willow-grass or willow-sedge associations.

Clark found water shrews most common in habitats with approximately 75% ground cover. Such ground cover may be necessary to maintain high moisture levels in the microhabitat and to support abundant invertebrates and plant foods. In Manitoba, the local distributions of water shrews and beaver are similar; beaver dams increase the marsh-shrub edges of streams and create habitat with quite pools, running water, and moist humus.