Blarina brevicauda - Short-tailed Shrew

Physical Description:

Total Length 96-130 mm

Tail Length 18-32 mm

Weight 15-30 grams

Short-tailed shrew is the largest shrew in North America (Boonstra 2002).  It has a robust body with a dense, velvet coat.  The dorsal fur is darker brown/gray while the ventral fur is a lighter gray. The ears and eyes are small easily hidden by the fur.  Their snout is elongated and comes to a point (Kurta 1995). They have five unicusped teeth in the upper jaw, second and third incisors, and canine, normal premolar and minute molar (Jackson 1961).  Males display a somewhat sexual dimorphism, being larger than the females (Benedict 1999).

Distribution:

Short-tailed shrews range from south eastern Canada and north eastern U.S. south to Nebraska, Missouri, Kentucky, and Alabama (Whitaker 1996).  Short-tailed are abundant especially in the northern regions and can be found throughout Wisconsin.  They live in a variety of disturbed and undisturbed habitats such as grasslands, old fields, fencerow, marsh borders as well as deciduous and coniferous forest.  They prefer moist environments with more than 50% herbaceous cover (Boonstra 2002, Kurta 1995).

Reproduction:

Reproduction can occur year round but mostly takes place March through September, females giving birth earlier or later in the season.  Females can have up to three litters per year; gestation is 17-22 days (Whitaker 1996).  Average of 4-7 is born weighing less than one gram.  Young leave the nest at about 18-22 days and are weaned by day 25.   Females reach sexual maturity at 6 weeks and males reach sexual maturity at 12 weeks (Kurta 1995).

Behavior:

Short-tailed shrews tend to be solitary animals, densities range from 5-30/ha depending on the vegetation and cover (Kurta 1995).  They are the most fossorial of all the shrews, building underground nests and tunnel systems.  Two different nests are created, one for resting (160 mm long, and 203 mm wide) and the other for reproduction (150-250 mm long and 100-150 mm wide) (Merrit 1986).  The tunnel system is built with 2-3 exits along with various tunnels that are used for waste deposits and storage of extra food (Kurta 1995).

Short-tailed shrews are active for 5 minute bouts which add up to 4 hours each day in the early morning and 2-3 hours after sunset (Benedict 1999).  Since they are food hoarders and utilize higher energy sources they are able to stay active all year long even in the winter without communal living or physidontical heterothermy (Merrit 1986).

Diet:

Short-tailed shrews are voracious eaters with a high metabolic rate that requires them to consume over half their body weight in food (Boonstra 2002, Whitaker 1996).  They have a diverse diet including small amounts of seed and fungi but are mostly carnivorous preying on earthworms, millipedes, spiders, slugs, snakes and small vertebrates (Benedict 1999).  With the aid of venom produced by the sub maxillary glands they can even prey on smaller shrews, voles, mice, salamanders and snakes (Kurta 1995).  The venom functions as an immobilizing agent that puts its prey into a catatonic state.  This allows the short-tailed shrew to store its prey so it is fresh for a period of time after captured.  Thus insures predictable quick energy sources that will be readily available as a buffer against prey scarcity (Merrit 1986).  Because their eyes are rudimentary and can only sense light vs. dark, short-tails relay on their fine-tuned sense of touch and ability to echolocate to locate their food (Kurta 1995).

Remarks:

Short-tail shrews have been playing an important role in the ecosystem for many years, first appearing in the late Pliocene about 3 million years ago (Benedict 1999).  Because of their abundant population they provide food for many different carnivores such as the coyote, pine martin, badger, fisher, long-tailed weasel, mink and bobcat (Kurta 1995).  They also are responsible for keeping population checks on larch sawflies and other destructive insects  (Jackson 1961).

Literature Cited:

Benedict, R.A. 1999 Morphological and mitochondrial DNA variation in a hybrid zone between short-tailed (Blarnia) in Nebraska. Journal of Mammology 80:112-34.

Boonstra, R. 2002. Demography of short-tailed shrew populations living on PCB contaminated sites. University of Toronto. Ontario, Canada.

Brant, S.V. 2003. Phylogeography of the northern short-tailed shrew, Blarina brevicauda Insectivore: Soricidae): past fragmentation and postglacial recolonization. Molecular Ecology. 12:1435-49.

Jackson, H.H.T. 1961. Mammals of Wisconsin. The University of Wisconsin Press, Madison, Wisconsin. pp. 42-55.

Kurta, A. 1995. Shrews.  Mammals of The Great Lakes Region. University of Michigan Press, U.S.A. pp. 46-49.

Merritt, J.F. 1986. Winter survival adaptations of the short-tailed shrew (Blarnia b.) in Appalachian Montane forest. Journal of Mammology 67: 450-64.

Whitaker, J.O. 1996. Shrews.  National Audubon Society, Field Guide to Mammals.  Chanticlerr Press, Inc.  pp.  298-299

Reference written by Sheri Robb, Biol 378: Edited by Chris Yahnke and Jen Callahan. Page last updated  4-5-04.