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Cryptotis parva - Least Shrew

Physical Description:

Least Shrews are categorized as one of the smallest mammals, weighing in at 4-5 grams.  Overall length is 3 to 3 ½ inches long, with tail length ranging from ½ to ¾ inches.  The snout is long, pointed, and mole-like.  Ears and eyes are small.  Fur is short and velvety.  Underside of the least shrew is black to ash-gray in color, while the upper parts are more cinnamon-brown.  Overall color is paler in summer.  Dental Formula:  I 3/2, C 1/0, P 2/1, M 3/3 = 30 (Pennsylvania Department of Conservation and Natural Resources 2003, and Fox 1996).


Loss of habit, due to intensive agriculture, has caused the least shrew to become extirpated from the state of Wisconsin; however, this species occurs throughout most of the central eastern U.S. all the way down Florida and into Mexico and Central America.  Cryptotis parva is the only species in its genus found North of Mexico (Fox 1996.)


Least shrew nests are 2-to-5 inches wide and built in shallow burrows under rocks or logs.  Nests are typically made out of dried grass and leaves.    These organisms breed from March to November.  Average litter size is 5, ranging from 3 to 6 young per litter.  This species may have up to 3 litters per year.  After a gestation period assumed to be 15-23 days, young are born blind and without fur, and weigh only 0.3 grams. Small vibrissae and claws are apparent right away, while there is no evidence of teeth at birth. Both adults take part in caring for the young, which are weaned at 21days.  Sexual maturity is reached as early as 30 days in females and 36 days in males Life expectancy is less than 2 years (Fergus 2003 and Connecticut Dept. of Environmental Protection 2003).

Ecology and Behavior:

In more northern parts Cryptotis parva prefers non-wooded areas, or grassy fields.  Least shrews favor loose soils for digging burrows, although substrate type does not seem to affect presence of C. parva.  In Central America it located in damp areas, usually neighboring lakes or streams (Least Shrews 2003 and Fox 1996).

Least Shrews are foraging organisms, which dictates their known hoarding behaviors.  Hunger level and seasonal changes affect the degree of hoarding that takes place.  Shrews are considered insectivores, feeding primarily on various insects, insect larvae, earthworms, lizard tails, centipedes, snails, some plant material and carrion.  They are also known to attack larger animals like frogs.  In such cases the shrews would bite the leg of their prey, crippling it with its toxic saliva (Formanowicz and Brodie 1989, Least Shrew 2003, and Fergus 2003).

C. parva is a social animal.  These shrews take part in cooperative burrowing and are not known to show aggression toward one another.  Food is often shared. Activity in this species peaks at night, although individuals are active during the day.  Least shrews communicate by using a variety of high pitched sounds associated with social behavior (The Mammals of Texas –Online Edition 2003 and Hall 2000).


Individuals in C. parva have been known to aid in keeping down populations of damaging insects and pests because they are able to eat their own body weight in insects, everyday (Hall 2000 and Fox 1996).

The toxins in least shrews’ saliva enable them to efficiently kill prey for food or in defense (Least Shrew 2003).

Shrews are sometimes confused as rodents.  They are actually classified under the taxonomic order Insectivora.  The least shrew is one of the smallest mammals in North America (Pennsylvania Game Commission 2002).

Least shrews will at times invade bee hives, and after eating all the larvae are known to make a home of the hive (Least Shrew 2003).

Crptotis parva is one of the smallest mammals in North America; therefore, C. parva has assisted modern science because it works as great biological indicators of soil contamination in studies of industrial pollution (Goldstein et al.  2002).

Literature Cited:

Connecticut Department of Environmental Protection.  1997.  Wildlife in Connecticut-Endangered and threatened Species Series.  Least Shrew (Cryptotis parva). <>.  Accessed on Nov 4 2003.

Fergus, C.  Shrews.  <>.  Accessed  Nov 4 2003.

Formanowicz, D.R., P.J. Bradley, and E.D. Brodie.  1989.  Food Hoarding by the Least Shrew (Cryptotis parva):  Intersexual and Prey Type Effects.  American Midland Naturalist 121-122:  26-33.

Fox D.L.  Cryptotis parva (Least Shrew):  Narrative.  <$narrative.html>.  Accessed on Nov 3 2003.

Goldstein, D.L., et al.  2000.  Kidney Function in the Least Shrew (Cryptotis parva) and the effects of Cadmium on the Kidneys.  The F A S E B journal 14(4): A594.

Hall, S. and N.C. Stenseth.  2000.  Activity Patterns in Small Mammals- An Ecological Approach: 243.  

Least Shrew (Cryptotis parva).  <>.

Pennsylvania Game Commission.  2002.  Least Shrew. <>.  Accessed on 4 Nov 2003.

The Mammals of Texas- Online Edition.  Least Shrew.  < /crypparv.htm>.  Accessed on Nov 3 2003.

The Pennsylvania Department of Conservation and Natural Resources.  Least Shrew (Cryptotis parva).  <>.  Accessed on Nov 3 2003.

 Reference written by Gina Marie Bergman, Biol 378: Edited by Chris Yahnke.
Page last updated 4-23-03.

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