Cryptotis parva
Least Shrew
Species 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. 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, D.L., 1996).
Distribution:
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.)
Reproduction:
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; Connecticut Dept. of Environmental
Protection, 2003).
Ecology and Behavior:
In more northern parts Cryptotis parva prefers nonwooded 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; 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, Bradley, and Brodie
1989, Least Shrew 2003, and Fergus, C., 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, S. 2000.)
Interesting Facts:
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, S. 2000 and Fox D.L., 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, Watson, and Newland, 2002).
Literature Cited:
Hall, S., Stenseth, N.C. 2000. Activity Patterns in Small Mammals- An
Ecological Approach. Springer-Verlag Berlin Heidelberg, Germany. P.243.
Formanowicz D.R., Bradley P.J., Brodie E.D. 1989. Food Hoarding by the Least
Shrew (Cryptotis parva): Intersexual and Prey Type Effects. American Midland
Naturalist 121-122: 26-33.
Goldstein, D.L., Watson, D., Calloway, P., Newland, S. 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. 2000.
Pennsylvania Game Commission. Least Shrew. 2002.
http://sites.state.pa.us/PA_Exec/PGC/shrew/least/profile.htm. 11/4/2003.
Fox D.L. Cryptotis parva (Least Shrew): Narrative
http://animaldiversity.ummz.umich.edu/accounts/cryptotis/c._parva$narrative.html.
11/3/2003.
Fergus, C. Shrews. http://sites.state.pa.us/PA_Exec/PGC/w_notes/shrews.htm.
11/4/2003.
Connecticut Department of Environmental Protection. Wildlife in ConnecticutEndangered and threatened Species Series. Least Shrew (Cryptotis parva). 1997.
http://dep.state.ct.us/burnatr/wildlife/factshts/leshrew.htm. 11/4/2003.
The Mammals of Texas- Online Edition. Least Shrew.
http://www.nsrl.ttu.edu/tmot /crypparv.htm. 11/3/2003.
The Pennsylvania Department of Conservation and Natural Resources. Least Shrew
(Cryptotis parva)
http://www.dcnr.state.pa.us/wrcf/lstshrew.htm. 11/3/2003.
Least Shrew (Cryptotis parva)
http://www.fcps.k12.va.us/StratfordLandingES/Ecology/mpages/leastshrew.htm.
Reference written by Gina Marie Bergman, Biol 378: Edited by Chris Yahnke.
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