Northern short-tailed shrews are 75 to 105 mm long from their head to the base of their tail. The 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 fur.
Northern short-tailed shrews are 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 inhabit most of 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. They construct their nests in tunnels or under logs and rocks. They also construct elaborate runways under leaves, dirt, and snow.
Northern short-tailed shrews are most commonly found in damp brushy woodlands, bushy bogs and marshes, and weedy and bushy borders of fields. They are also common in cultivated fields, in flower and vegetable gardens, fence rows, and beside country roads. They need enough plants to provide cover. In the winter, they often retreat into barns, cellars, and sheds.
Little information is available regarding the mating systems of northern short-tailed shrews.
Northern short-tailed shrews build elaborate mating nests out of shredded grass or leaves. The nests are 150 to 250 mm long by approximately 150 mm wide and are 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 usually have 2 litters in a year, although they sometimes have 3. Pregnancy lasts 21 to 22 days. Although 3 to 10 shrew pups may be born in a littler, between 5 and 7 young is most common. Young short-tailed shrews leave the nest at 18 to 20 days of age and are weaned several days later. Females reach adulthood at 6 weeks of age, 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, young northern short-tailed shrews leave the nest and all parental care ends.
Northern short-tailed shrews can live as long as 3 years, but most probably die in their first year or before they reach adulthood.
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. They 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, short-tailed shrews are solitary and territorial. Territory size and stability are determined by how much prey is available in the area.
Home ranges of northern short-tailed shrews can be twice the size of those of other shrews. Their home range is on average 2.5 ha. Although they are solitary and territorial in the wild, home ranges tend to overlap. Territory size and stability are determined by how much prey is available in the area.
Northern short-tailed shrews, especially males, release a musky odor from scent glands on their belly and sides. They may use this to mark their territories with scent. However, some researchers think this is unlikely because northern short-tailed shrews have a poor sense of smell. These researchers think the musky secretion may instead scare away predators because of its foul taste.
Northern short-tailed shrews have poor vision. It is possible they can only detect light from dark, but cannot see objects. 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 clicks and then listen for the returning echoes. (Ultrasonic means outside the range of human hearing). By decoding these echoes, shrews can perceive their environment without sight. Similar to other shrews, northern short-tailed shrews also have a highly developed sense of touch, particularly in the snout and vibrissae.
Northern short-tailed shrews shrews make a variety of sounds (chirps, buzzes, twitters) when fighting with other individuals. They make a clicking sound during courtship.
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. Shrews living 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 like snakes and spiders do. Instead, they chew the venom into the prey until the prey is subdued.
Northern short-tailed shrews are preyed upon by owls, hawks, snakes, weasels, red fox, coyotes, and occasionally pickerel, trout, and sunfish when they venture near water. Northern short-tailed shrews are aggressive, and they 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 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.
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.
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 change frequently. Researchers are not sure what causes these changes.
Tanya Dewey (editor), University of Michigan-Ann Arbor, George Hammond (editor), Animal Diversity Web Staff, John Berini (editor), Animal Diversity Web Staff, Gail McCormick (editor), Animal Diversity Web Staff.
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