The northern short-tailed shrew (Blarina brevicauda) ranges throughout the north- central and northeastern United States and into southern Canada (George et al., 1986). It eats insects, worms, snails, and other invertebrates and also may eat mice, voles, frogs, and other vertebrates (Robinson and Brodie, 1982). Because they prey on other vertebrates, shrews can concentrate DDT (and presumably other bioaccumulative chemicals) to levels 10 times higher than either Peromyscus and Clethrionomys (Dimond and Sherburne, 1969). Shrews are an important component of the diet of many owls (Palmer and Fowler, 1975; Burt and Grossenheider, 1980) and are also prey for other raptors, fox, weasels, and other carnivorous mammals (Buckner, 1966).

Short-tailed shrews are 8 to 10 cm in length with a 1.9 to 3.0 cm tail (Burt and Grossenheider, 1980). The short-tailed shrew is the largest member of the genus, with some weighing over 22 g (George et al., 1986; see table). Some studies have found little or no sexual dimorphism in size (Choate, 1972), while other reports show that males are slightly larger than females (George et al., 1986; Guilday, 1957).

Short-tailed shrews are active for about 16 percent of each 24-hour period (Martinsen, 1969).

They inhabit a wide variety of habitats and are common in areas with abundant vegetative cover (Miller and Getz, 1977), and need cool, moist habitats because of their high metabolic and water-loss rates (Randolph, 1973).

The short-tailed shrew is primarily carnivorous. Stomach analyses indicate that insects, earthworms, slugs, and snails can make up most of the shrew's food, while plants, fungi, millipedes, centipedes, arachnids, and small mammals also are consumed (Hamilton, 1941; Whitaker and Ferraro, 1963). Small mammals are consumed more when invertebrates are less available (Allen, 1938; Platt and Blakeley, 1973, cited in George et al., 1986). Shrews are able to prey on small vertebrates because they produce a poison secretion in their salivary glands that is transmitted during biting (Pearson, 1942, cited in Eadie, 1952). The short-tailed shrew stores food, especially in the autumn and winter (Hamilton, 1930; Martin, 1984).

"Northern Short-tailed Shrews have poisonous saliva. This enables them to kill mice and larger prey and paralyze invertebrates such as snails and store them alive for later eating. The shrews have very limited vision, and rely on a kind of echolocation, a series of ultrasonic ""clicks,"" to make their way around the tunnels and burrows they dig. They nest underground, lining their nests with vegetation and sometimes with fur. They do not hibernate. Their day is organized around highly active periods lasting about 4.5 minutes, followed by rest periods that last, on average, 24 minutes. Population densities can fluctuate greatly from year to year and even crash, requiring several years to recover. Winter mortality can be as high as 90 percent in some areas. Fossils of this species are known from the Pliocene, and fossils representing other, extinct species of the genus Blarina are even older."

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This species occurs throughout southern Canada, west to central Saskatchewan and east to south east Canada, and south to Arkansas and Georgia in the United States.

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.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Occurs throughout most of U.S. and southern Canada east of the Great Plains. See French (1981) for information on distribution in the southeastern U.S.

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.

Range mass: 18.0 to 30.0 g.

Average mass: 21.63 g.

Range length: 75.0 to 105.0 mm.

Sexual Dimorphism: male larger

Average basal metabolic rate: 0.344 W.

Length: 14 cm

Weight: 29 grams

Sexual Dimorphism: Males may be slightly larger than females.

Length:
Range: 118-139 mm

Weight:
Range: 18-30 g

See Carraway (1995) for a key to western North American soricids based primarily on dentaries.

Habitat and Ecology

Systems

• Terrestrial

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.

Habitat Regions: temperate

Terrestrial Biomes: chaparral ; forest ; scrub forest

Wetlands: marsh ; swamp ; bog

Comments: Most abundant in hardwood forests with deep leaf-litter and abundant food; avoids areas with little cover and extremes of temperature and moisture. Semifossorial; digs tunnels or uses existing ones. Constructs elaborate underground nest. Nests are placed under logs or stumps, or underground.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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.

Primary Diet: carnivore (Eats non-insect arthropods)

Comments: Eats earthworms, slugs, snails, insect larvae, millipedes, other invertebrates, and small vertebrates (especially mice in winter). May hoard food (especially snails).

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.

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.

Known Predators:

• owls (Strigiformes)
• snakes (Serpentes)
• hawks (Accipitridae)
• weasels (Mustela)
• red fox (Vulpes vulpes)
• coyotes (Canis latrans)

Blarina brevicauda is prey of:
Squamata
Strigiformes
Accipitridae
Mustela
Canis latrans
Vulpes vulpes

This list may not be complete but is based on published studies.

Blarina brevicauda preys on:
non-insect arthropods
Sorex cinereus

This list may not be complete but is based on published studies.

Home ranges can be more than twice the size of those of most shrews. Estimates of home range size average about 2.5 ha; ranges generally overlap (George et al. 1986). Population density estimates range from 1.6/ha to about 121/ha (George et al. 1986). In 14-year study in Illinois, displayed annual but not multiannual population fluctuations; annual peak occurred in July or in Oct. in different habitats; average minimum density about 1-6/ha in winter, average peak density about 10-20/ha in summer or early fall; none survived more than 10 months following first capture (Getz 1989).

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.

Communication Channels: acoustic ; chemical

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

Range lifespan

Status: wild: 3.0 (high) years.

Average lifespan

Status: wild: 2.5 years.

Maximum longevity: 2.2 years (captivity) Observations: In the wild, these animals have been estimated to live up to 2.5 years (Bernhard Grzimek 1990), which could be overestimated. In captivity, they do not appear to live more than 2.2 years (Richard Weigl 2005), though some anecdotes indicate a longer lifespan.

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. Gestation is 21-22 days and litter size is 3-10, although 5-7 pups is most common. The young leave the nest when 18-20 days old and are weaned several days later. Females reach sexual maturity at 6 weeks, while males mature at 12 weeks. The life span can be as long as 3 years, but it is usually much more brief.

Breeding interval: Female northern short-tailed shrews may have multiple litters throughout the warm months of the year, depending on food availability.

Breeding season: The breeding season lasts from March through September.

Range number of offspring: 3.0 to 10.0.

Average number of offspring: 6.0.

Range gestation period: 22.0 (high) days.

Range weaning age: 20.0 (low) days.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); induced ovulation ; fertilization ; viviparous

Average birth mass: 1.34 g.

Average number of offspring: 6.

Average age at sexual or reproductive maturity (male)

Sex: male: 65 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 46 days.

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.

Parental Investment: altricial ; female parental care

Breeds mainly early February or March through September; peaks may occur in spring and late summer or early fall. Gestation 3 weeks. Litter size: 3-10, average 4-6. Three or more litters per year. Weaned by 25 days. Sexually mature in 1-2 months. (Dapson 1968, George et al. 1986).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Species: 45
Species With Barcodes: 1

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.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Population

Population Trend

Major Threats

Conservation Actions

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.

Negative Impacts: injures humans (bites or stings)

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.

Positive Impacts: controls pest population

Comments: B. CAROLINENSIS SHERMANI may be an isolated subspecies of B. BREVICAUDA or a distinct species (George et al. 1986). Blarina brevicauda was regarded as conspecific with Carolinensis and B. HYLOPHAGA by Hall (1981). Blarina B. TELMALESTES was regarded as a distinct species by Hall (1981) but not by Jones et al. (1986) or in most other recent accounts.

Blarina brevicauda and B. HYLOPHAGA may hybridize in narrow contact zones, but genetic exchange appears to be limited (Benedict 1999).