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Sorex cinereus; aka common shrew
The second smallest shrew in the world, behind the pygmy shrew, adult masked shrews average just under 4 inches in total length, including a tail of up to almost 2 inches, and weigh less than an ounce. The slender, cylindrical body has short, velvety, directionless fur that is brown above and grayish-white below; the fur tends to be darker overall in winter. The long, tapered head ends in a flexible, tubular snout, with the narrow nostrils located on the outer edges of the tip. The small external ears are barely visible or are completely hidden by the fur. The eyes are tiny, the tail scantily haired, and the limbs short.
Distribution and Habitat
The most widely distributed shrew in North America, the masked shrew is found throughout the northern United States, most of Canada, and Alaska. It occupies a diversity of habitats, with the most common being open and closed forests, meadows, river banks, lake shores, and willow thickets. Habitat suitability depends on the availability of water, and the highest population densities can be found in moist environments. Masked shrews also do well in disturbed habitats such as those disturbed by fire or logging.
Habits and Behaviors
Although not strictly nocturnal, the masked shrew is most active after dark. Clouds and rain increase nocturnal movement. It tends to stay under cover and is therefore rarely seen. Active year round, it will even tunnel through snow to explore the surface.
Masked shrews consume a variety of invertebrates including insect larvae, ants, beetles, crickets, grasshoppers, spiders, harvestmen, centipedes, slugs, snails, as well as some seeds and fungi.
Breeding season extends from April to November. Two to ten young are born after a gestation of 19-22 days. Fine hairs develop at about 10 days, the eyes open at 17-18 days, weaning begins about day 20, and the young leave the nest around day 30. A female may have up to 3 litters in one year. The average life span of a masked shrew is less than 14 months.
This page was last updated on March 13, 2017.