Blarina brevicauda
northern short-tailed shrew

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.

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.

Head and body length is 75-105 mm, tail length is 17-30 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 pelage is a shade paler than winter.

Blarina brevicauda is a robust-looking shrew, 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.

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

Short-tailed shrews are active year round, both day and night (although they are more nocturnal than diurnal). These shrews are the most fossorial of American shrews and are effective in tunneling through leaves, plant debris, and snow with their strong paws and cartilaginous 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.

Blarina brevicauda is not a sociable or gregarious mammal. In captivity, short-tailed shrews have been observed to live together peacefully if enough space is provided, but in the wild, the shrews are solitary and territorial. Territory size and stability are determined by prey density and tend to overlap slightly between members of opposite sexes during the breeding season. Shrews mark their territories with scent and will threaten and physically drive away any intruders.

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.

Short-tailed shrews are voracious eaters and must feed frequently, commonly in the early and late afternoon. It is estimated that they consume and metabolize as much as three times their weight in food per day. The diet of Blarina brevicauda consists mainly of invertebrates, small vertebrates, and plant material. B. brevicauda stores food for winter, including snails and beetles, and in captivity puts nutmeats, sunflower seeds, and other edibles into storage.

The submaxillary salivary glands of Blarina brevicauda produce a toxic material which is effective in subduing its prey. This enables it to prey upon animals much larger than itself, including salamanders, frogs, snakes, mice, birds, and other shrews.

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.

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.

The poison secreted from the submaxillary glands of Blarina brevicauda 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.

Due to its insectivorous nature and ravenous appetite, Blarina brevicauda often serves as an important check on insect crop pests, especially the larch sawfly. It also destroys snails and mice that damage crops and are pests to humans.

Blarina brevicauda is common through much of its range, especially in the areas surrounding the Great Lakes. As with many small mammals, its populations undergoes frequent fluctuations, the causes and effects of which are not well understood.