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northern short-tailed shrew

Blarina brevicauda

What do they look like?

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.

  • Sexual Dimorphism
  • male larger
  • Range mass
    18.0 to 30.0 g
    0.63 to 1.06 oz
  • Average mass
    21.63 g
    0.76 oz
  • Range length
    75.0 to 105.0 mm
    2.95 to 4.13 in
  • Average basal metabolic rate
    0.344 W
    AnAge

Where do they live?

Short-tailed shrews inhabit most of North America from southern Saskatchewan and Nova Scotia to central Nebraska and Georgia.

What kind of habitat do they need?

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.

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. They need enough plants to provide cover. In the winter, they often retreat into barns, cellars, and sheds.

  • These animals are found in the following types of habitat
  • temperate

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. 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, 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. 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 can't 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.

Northern short-tailed shrews shrews utter a variety of sounds (chirps, buzzes, twitters) when fighting with other individuals. They make a clicking sound 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. 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.

  • Primary Diet
  • carnivore
    • eats non-insect arthropods

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.

  • Ways that these animals might be a problem for humans
  • injures humans
    • bites or stings

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.

  • Ways that people benefit from these animals:
  • controls pest population

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 change frequently. Researchers are not sure what causes these changes.

Contributors

Liz Ballenger (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

carnivore

an animal that mainly eats meat

chaparral

mid-altitude coastal areas with mild, rainy winters and long, dry summers. Dominant plant types are dense, evergreen shrubs.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that generate their own body heat through metabolic processes.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

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).

 
University of Michigan Museum of ZoologyNational Science Foundation

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Ballenger, L. 2000. "Blarina brevicauda" (On-line), Animal Diversity Web. Accessed April 18, 2014 at http://www.biokids.umich.edu/accounts/Blarina_brevicauda/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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