What do they look like?

The fur of least shrews is short, dense and velvety. In winter the upper fur is brown to black and the underside is white. In summer the fur is paler. Least shrews measure 67 to 103 mm long, of which 12 to 22 mm is the tail. The hind feet are 9 to 13 mm long. Least shrews weigh 4 to 6.5 grams.

Where in the world do they live?

Least shrews occur throughout the eastern half of the U.S. south of the Great Lakes, in eastern and parts of central Mexico, in all of Guatemala, in the southern half of Belize, throughout El Salvador, in most of Honduras and in the northwest corner of Nicaragua.

What kind of habitat do they need?

In the northern part of their range, least shrews prefer grassy, weedy or brushy fields. In Central America they are more commonly found in damp areas, often bordering streams or lakes.

How do they reproduce?

Little is known of the reproductive behavior of least shrews. In the northern parts of their range breeding probably occurs from March to November. In Florida and Central America breeding occurs throughout the year but peaks around the same time of year as in the north. Average litter size is five young with a range of one to nine. Pregnancy lasts 21 to 23 days. Young are born with small whiskers and claws, and they nurse for up to 20 to 23 days after birth. Females reach sexual maturity at 31 days and males reach sexual maturity at 36 days.

Like all female mammals, least shrew females provide their newborns with milk until they are independent and can eat solid food.

How long do they live?

One captive least shrew lived for 21 months. In the wild, they do not live nearly as long.

How do they behave?

Unlike most shrews, least shrews seem to be somewhat social. Nests of as many as 31 individuals have been reported. Nests are small (less than 200 mm in diameter) and are typically lined with loosely piled leaves. Nests are connected to the surface by runways or burrows. Least shrews use burrows constructed by other animals or natural cracks in the ground or in buildings. They also dig their own burrows and pairs of animals have been observed digging burrows cooperatively. Burrows constructed by least shrews are about 25mm in diameter. Although indivduals are active all day, activity peaks at night. Fighting has not been seen during encounters between least shrews, even when sharing the same piece of food.

How do they communicate with each other?

Least shrews give off a variety of high-pitched sounds, many of which seem to be involved in social behavior. Like all shrews, least shrews have sensitive whiskers and keen senses of smell and hearing.

What do they eat?

Least shrews eat a wide variety of invertebrates, including insects and bugs, earthworms, and snails and slugs. Plant material makes up a tiny portion of the diet. These animals seem to have a habit of opening the abdomens of grasshoppers and crickets and eating the internal organs.

What eats them and how do they avoid being eaten?

Predators of least shrews include owls, red foxes, skunks, house cats, and snakes.

How do they interact with us?

Where common, members of this species probably help control populations of harmful insects.

Are they endangered?

In the United States, least shrews are in no danger of extinction (populations in Michigan, at the northern limit of the range of this species, are considered to be threatened). Populations in Central America may be threatened by habitat destruction, but not enough information is available.

Contributors

Allison Poor (editor), University of Michigan: February, 2005.

David L. Fox (author), University of Michigan: June, 1999.

References

Hall, E. R. 1981. Mammals of North America. John Wiley, New York.

Nowak, R. N. 1991. Walker's Mammals of the World. The Johns Hopkins University Press, Baltimore, MD.

Silva, M. and Downing, J. A. 1995. CRC Handbook of Mammalian Body Masses. CRC Press, Boca Raton, FL.

Whitaker, John O., Jr. 1974. Cryptotis parva. Mammalian Species Accounts No. 43, pp. 1-8.

Kurta, A. 1995. Mammals of the Great Lakes Region. Ann Arbor: The University of Michigan Press.