The American shrew mole, Neurotrichus gibbsii, is the smallest species within the Talpidae family, which includes all moles in North America. This tiny mammal, weighing approximately 10 grams, represents a unique evolutionary path between shrews and moles. The shrew mole is classified as semi-fossorial, meaning it has adapted to both life underground and foraging above the soil surface. This dual existence allows it to utilize habitats in ways that its larger, strictly subterranean relatives cannot.
Defining the North American Range
The distribution of the shrew mole is confined to a narrow strip along the western edge of North America, stretching from mid-California northward into southwestern British Columbia, Canada. This range is restricted to the temperate Pacific coast, demonstrating a strong association with the region’s maritime climate. Within the United States, populations are found throughout western California, Oregon, and Washington.
The Cascade and Sierra Nevada mountain ranges generally form the eastern boundary of its territory. While most sightings occur at lower elevations, the animal has been recorded at altitudes up to 2,500 meters.
Specific Environmental Requirements
The shrew mole selects environments with high moisture content and dense vegetative cover, typically favoring temperate rainforests and coniferous woodlands. Optimal locations include damp ravines, riparian zones, and forested areas with deep, loose soil rich in organic matter. The presence of Douglas-fir, redwood, and mixed conifer forests is strongly linked to its preferred habitat.
The animal thrives in areas that have a significant layer of leaf litter and decaying logs. This dense understory provides both cover from predators and a rich source of invertebrate prey, such as earthworms and insect larvae. While they prefer friable, well-drained soils, shrew moles can also be found in swampy or brushy areas, demonstrating flexibility as long as moisture is abundant.
The Subterranean Lifestyle
Unlike other North American moles, the shrew mole spends a considerable amount of time foraging on the surface, utilizing the leaf litter and undergrowth for protection and movement. This surface activity is balanced by a reliance on shallow, non-permanent tunnel systems for shelter and hunting. Their burrows are typically constructed right beneath the leaf litter and rarely extend deeper than 30 centimeters into the soil.
These tunnel networks are not as extensive or deep as those created by larger mole species, reflecting the shrew mole’s smaller size and semi-fossorial nature. They use these shallow tunnels and surface runways to patrol for prey, which they consume in large quantities due to their high metabolism. For rest, they construct sleeping nests of damp leaves, often located under logs, stumps, or within the dense leaf litter, rather than in deep underground chambers.