Northern short-tailed shrew

Description

Northern short-tailed shrew is the largest and most widespread shrew in eastern North America. It is the most common shrew in Minnesota. Its population fluctuates greatly, at times abundant, up to 12 per acre, at other times in the same area as few as 2 per acre.

Adults are 3″ to 4⅛″ in length from nose to tail, 4⅜″to 5½″ in length including the tail. They weigh from ⅝ to 1¼ ounces. Males are slightly larger than females, especially in skull size.

The coat (pelage) is dark gray, thick, short, soft, and velvety. It molts in October to November and February to July. The winter coat is slightly darker and may have a brownish cast. The summer coat is almost uniformly dark gray. The belly is lighter gray. Juveniles are paler than adults.

The body is stocky. The legs are short. The feet are relatively thick and broad. There are five toes on every foot. The tail is short, ⅝″ to 13 ⁄16″ long, about ¼ as long as the head and body together. It is covered with hair. Females have six mammae. Like all shrews, males have one scent gland, up to ½″ long, on each side between the fore and hind legs. On females these glands are less prominent or rudimentary. Unlike other shrews, they also have a scent gland in the groin area. This gland is up to 13 ⁄16″ long and ⅜″ wide and is active in both males and females.

The snout is long and sharply pointed. The ears are short and inconspicuous, mostly hidden by the fur. The eyes are tiny and barely apparent. The skull has 32 teeth that are at least in part chestnut-colored. The space between the incisors and molars is less than the width of the widest molar. Canine teeth are present. There are 6 upper and 2 lower incisors. The first upper incisor is greatly enlarged. A pair of glands on each side behind the lower jaw contain a poisonous venom. The venom is released through a duct below the lower incisors and is conducted into prey by way of a groove formed between the two teeth.

Giant mole shrew (Blarina brevicauda brevicauda), as the name suggests, is the largest subspecies, 5″ to 5½″in total length including the tail.

Manitoba short-tailed shrew (Blarina brevicauda manitobensis) is slightly smaller. The pelage is slightly darker.

Northern short-tailed shrew (Blarina brevicauda talpoides) is a medium-sized subspecies, about 45 ⁄16″ long.

Size

Total length: 4⅜″to 5½″

Head and body: 3″ to 4⅛″

Tail: ⅝″ to 13 ⁄16″

Sign

Shrew tracks are unlikely except in fresh snow. A shrew bounds (hops) like a squirrel. The two front feet land first, next to each other, then the back feet land next to each other and a little ahead of the front feet. The trail is similar to some species of mice but narrower, 1″ to 1¼″ in width.

Similar Species

Habitat

Almost all terrestrial, moist to moderately moist habitats with brushy cover or deep leaf litter, especially bogs and swamps, deciduous and coniferous woodlands, and grassy roadsides and fencerows in agricultural areas.

Ecology

Behavior

Northern short-tailed shrew is solitary and territorial. It marks its territory using scent glands and drives intruders away. Its home range varies by availability of prey but averages about 6 acres, overlapping that of its neighbors.

It spends most of its time underground. It is active day and night but mostly at night. It is a good burrower and constructs an elaborate tunnel system and nest, usually under a fallen log or stump. The nest is up to 8″ in diameter and is lined with the fur of meadow voles. It will sometimes use the tunnel of another species.

It has a poor sense of smell and very poor vision. It can navigate and detect objects in its environment using echolocation and and touch. Like bats, it emits a series of ultrasonic squeaks to detect its surroundings. Unlike bats, it does not use echolocation to locate prey. Its snout and whiskers are highly sensitive to touch.

Lifespan

2½ years

Life Cycle

In Minnesota, breeding season is from May to August or later. The female will have 2 to 4 litters each year. About 17 to 24 days after mating she gives birth to from 3 to 10, usually 4 to 6, young. The young leave the nest in 18 to 20 days. They reach sexual maturity at 60 days. Most probably die in their first year from predation and cold stress. Those that survive the first year may live up to 2½ years.

Food

Northern short-tailed shrew is a carnivore and invertivore. It eats mostly small vertebrates, including voles, mice, and other shrews; and invertebrates, including snails, earthworms, and beetles. It also eats a variety of plant materials and fungi. It may hoard food, especially snails, at least in winter. It eats up to three times its weight each day in winter, less in summer.

Toxicity

The venom allows the shrew to paralyze its prey and eat it at a later time. It is sufficiently strong to kill animals up to the shrew’s size, and to produce a very painful reaction in humans who handle the shrew.