What do they look like?

Northern short-tailed shrews are 75 to 105 mm long from their head to the base of their tail, tail length ranges from 17 to 30 mm. Males are slightly larger than females, especially in the skulls. The fur is velvety and soft, and the color almost uniformly slate gray, with the underparts being only slightly paler. Summer fur color is a shade paler than winter. Northern short-tailed shrews are robust, nearly the size of a meadow mouse; the snout is shorter and heavier than that of other shrews, the tail is short, the eyes small, and the ears are almost completely hidden by the fur.

Where in the world do they live?

Northern short-tailed shrews are only native in the Nearctic region. They inhabit most of east central North America from southern Saskatchewan and Nova Scotia in Canada to central Nebraska and Georgia in the United States.

What kind of habitat do they need?

Northern short-tailed shrews are found in nearly all terrestrial habitats. However, their populations are most dense in damp brushy woodlands, bushy bogs and marshes, and weedy and bushy borders of fields. These shrews are also common in cultivated fields, in flower and vegetable gardens, fence rows, and beside country roads. In the winter, they often retreat into barns, cellars and sheds. They need only sufficient vegetation to provide cover. They are slow to rehabit areas of forest burns. Northern short-tailed shrews construct elaborate runways under leaves, dirt, and snow and construct theirnests in tunnels or under logs and rocks.

How do they reproduce?

Elaborate mating nests, 150-250 mm long by 150-150 mm wide, are built out of shredded grass or leaves and placed in tunnels or under logs and rocks. The breeding season extends from early spring to early fall (March-September), although some scattered reproductive activity may occur throughout the entire year. Females may have up to 3 litters per year, although 2 is more usual. Pregnancy lasts 21-22 days and litter size is 3 to 10, although 5 to 7 pups is most common. The young leave the nest when 18 to 20 days old and are weaned several days later. Females reach adulthood at 6 weeks, while males become adults at 12 weeks.

Females care for their young in the nest for 18 to 20 days. After weaning, at 25 days old, the young leave their mother's nest and all parental care ends.

How long do they live?

Northern short-tailed shrews can live as long as 3 years, but most probably die in their first year or before they reach adulthood.

How do they behave?

Northern short-tailed shrews are active year round, both day and night (although they are more nocturnal than diurnal). Of all the American shrews, Northern short-tailed shrews are the best at burrowing and are very good at tunneling through leaves, plant debris, and snow with their strong paws and tough snouts. They construct elaborate runways and nests but have also been known to use the tunnels of mice and moles. Although most of their time is spent on or under the ground, short-tailed shrews are also effective climbers and have been observed climbing nearly 2 meters up a tree trunk to obtain suet from a bird feeder. Northern short-tailed shrews are not sociable or gregarious mammals. In captivity, short-tailed shrews have been observed to live together peacefully if enough space is provided but in the wild, these shrews are solitary and territorial. Territory size and stability are determined by how much prey is available in the area.

How do they communicate with each other?

Northern short-tailed shrews, especially males, exude a musky odor from scent glands on their belly and sides. They may use this to mark their territories with scent, though some researchers think this is unlikely because Northern short-tailed shrews have a poor sense of smell. This musky secretion may instead be used to deter predators because of its foul taste. Northern short-tailed shrews also have poor vision, perhaps only being able to detect light and dark. They use a form of echolocation, similar to what bats and whales use, to detect and distinguish among objects in the environment. They send out a series of ultrasonic (outside of the human hearing range) clicks and then listen for the returning echoes. By decoding these echoes they can perceive their environment without sight. Northern short-tailed shrews utter a variety of sounds (chirps, buzzes, twitters) in their aggressive interactions with other individuals, and a clicking sound is used during courtship.

What do they eat?

Northern short-tailed shrews are voracious eaters and must feed frequently. It is estimated that they consume as much as three times their weight in food per day. They have to eat more in the winter than in the summer in order to keep their bodies warm. The diet of these shrews consists mainly of invertebrates, such as earthworms, millipedes, spiders, and insects. Small vertebrates and plant material are eaten as well. They store food for winter, including snails and beetles, and in captivity put nutmeats, sunflower seeds, and other edibles into storage. The salivary glands of northern short-tailed shrews produce venom that is effective in immobilizing prey. This enables them to prey upon animals much larger than they are, including salamanders, frogs, snakes, mice, birds, and other shrews. Northern short-tailed shrews cannot inject this venom into their prey, as can snakes and spiders, instead they chew the venom into the prey until the prey is subdued.

What eats them and how do they avoid being eaten?

Northern short-tailed shrews are aggressive and will threaten and physically drive away any intruders. They escape predation by remaining hidden in the cover of vegetation or under the soil or snow during foraging expeditions from their nest. They may also make themselves distasteful by exuding a musky odor from glands on their belly and sides. Many mammal predators, such as weasels and foxes, may refuse to eat northern short-tailed shrews because of their foul taste.

What roles do they have in the ecosystem?

Northern short-tailed shrews are highly abundant in many of the habitats in which they live. Because of this and the fact that they eat large quantities of invertebrates, they have a profound effect on invertebrate abundance. They are also an important prey species, especially for owls.

Do they cause problems?

The venom secreted from the salivary glands of Northern short-tailed shrews can cause pain that lasts for several days in a human who is bitten. However, bites are rare, and usually occur when someone attempts to handle a shrew.

How do they interact with us?

Because they eat large quantities of invertebrates, Northern short-tailed shrews can be important in controlling crop pests, especially the larch sawfly. They also destroy snails and mice that damage crops and are pests to humans.

Are they endangered?

Northern short-tailed shrews are common through much of their range, especially in the areas surrounding the Great Lakes. As with many small mammals, their populations undergo frequent fluctuations, the causes of which are not well understood.

Contributors

Liz Ballenger (author), University of Michigan: October, 2000.

References

Hamilton, W.J. and J.O. Whitaker, Jr. 1979. Mammals of the Eastern United States. Cornell University Press, Ithaca, NY. pp. 48-51.

Jackson, H.H.T. 1961. Mammals of Wisconsin. The University of Wisconsin Press, Madison, Wisconsin. pp. 42-55.

Nowak, R.M. and J.L Paradiso. 1983. Walker's Mammals of the World. 4th edition. John Hopkins University Press, Baltimore, MD.

Rue, L.L. 1967. Pictorial guide to the mammals of North America. Thomas Y. Crowell Company, New York. pp. 15-17.

"Animal Life Histories Database" (On-line).