or shrew mouse
) is a
classified in the order Soricomorpha
. True shrews are also not to be
confused with West Indies shrews
, or elephant shrews
belong to different orders.
Although its external appearance is generally that of a long-nosed
, a shrew is not a rodent
, as mice are, and not closely related to
rodents. Shrew feet have five toes; rodent feet have four, and
shrews have sharp, spike-like teeth, not the familiar gnawing front
incisor teeth of rodents.
Shrews are distributed almost worldwide: of the major tropical and
temperate land masses, only New Guinea, Australia, and New Zealand
do not have native shrews at all; in South
, shrews are relatively recent immigrants
are present only in the far north. In terms of species diversity,
the shrew family is the fourth most successful of the mammal
families, being rivalled only by the rodent
and the bat
. Shrews were among
the first placental mammal
originally evolved during the dawn age of
All shrews are comparatively small, most no more than mouse size.
The largest species is the House Shrew
) of tropical Asia which is about
15 cm long and weighs around 100 grams ; several are very
small, notably the Etruscan Shrew
) which at about 3.5 cm and 2 grams
is the smallest living terrestrial mammal.
In general, shrews are terrestrial creatures that forage for seeds,
insects, nuts, worms and a variety of other foods in leaf litter
and dense vegetation, but some specialise in climbing trees, living
underground, in the subniveal layer
even hunting in water. They have small eyes, and generally poor
, but have excellent senses
. They are very active animals, with
voracious appetites and unusually high metabolic rates
. Shrews must eat 80-90 % of
their own body weight in food daily.
They do not hibernate
, but are capable
of entering torpor
. In winter, many species
that drastically reduce the animal's body weight. Shrews can lose
between 30% and 50% of their body weight, shrinking the size of
bones, skull and internal organs.
Whereas rodents have gnawing incisors
grow throughout life, the teeth of shrews wear down throughout
life, a problem made more extreme by the fact that they lose their
before birth, and therefore
have only one set of teeth throughout their lifetime. Apart from
the first pair of incisors, which are long and sharp, and the
at the back of the
mouth, the teeth of shrews are small and peg-like, and may be
reduced in number. The dental formula
Shrews are fiercely territorial, driving off rivals, and only
coming together to mate. Many species dig burrows
for caching food and hiding from predators,
although this is not universal..
Female shrews can have up to ten litters a year, and the animals
only stop breeding in the winter in temperate zones, and breed all
year round in the tropics. Shrews have a gestation
period of 17–32 days. The female often
becomes pregnant within a day or so of giving birth, and lactates
during her pregnancy, weaning
one litter as the next is born. Shrews live
for between 12 and 30 months.
Shrews are unusual among mammals in a number of respects. Unlike
most mammals, some species of shrew are venomous
. Shrew venom is not conducted into
the wound by fangs, but grooves in the teeth. The venom contains
various compounds and the contents of the venom glands of the
American short-tailed shrew are sufficient to kill 200 mice by
intravenous injection. One chemical extracted from shrew venom may
be potentially useful in the treatment of blood pressure while
another compound may be useful in the treatment of neuromuscular
conditions and migraines.Also, along with the bats
and toothed whales
some species of shrew
. Unlike most other
mammals, shrews lack a zygomatic bone
(also called the jugal
), and therefore have an
incomplete zygomatic arch
Shrews hold nearly 10% of their mass in their brain, a relatively
high brain to body mass
terrestrial mammals known to echolocate are two genera (Sorex and Blarina) of shrews and the tenrecs of Madagascar.
These include the Vagrant Shrew
Common or Eurasian Shrew
), and the Northern Short-tailed Shrew
). The shrews emit series of ultrasonic
squeaks. The nature of shrew sounds unlike those of bats are low
amplitude, broadband, multi-harmonic and frequency modulated. They
contain no ‘echolocation clicks’ with reverberations and would seem
to be used for simple, close range spatial orientation. In contrast
to bats, shrews use echolocation only to investigate their habitat
rather than additionally to pinpoint food. Except for large and
thus strongly reflecting objects, such as a big stone or tree
trunk, theywill probably not be able to disentangle echo scenes,
but rather derive information on habitat type from the overallcall
reverberations. This might be comparable to human hearing whether
one calls into a beech forest or into a reverberant wine
There are 376 species of shrew in 26 genera, which are grouped into
three living subfamilies: Crocidurinae
(African white-toothed shrews) and
). In addition, the
family contains the extinct subfamilies Limnoecinae
(although Heterosoricinae is
also commonly considered a separate family).
- Piper, Ross
(2007), Extraordinary Animals: An Encyclopedia of Curious and
Unusual Animals, Greenwood Press.
- Brains of White Matter
- Thomas E. Tomasi, "Echolocation by the Short-Tailed Shrew
Blarina brevicauda", Journal of Mammalogy, Vol.
60, No. 4 (Nov., 1979), pp. 751–759.
- Siemers BM, Schauermann G, Turni H, von Merten S. (2009). Why
do shrews twitter? Communication or simple echo-based orientation.
Biol Lett. 5(5):593-6. PMID 19535367
- Buchler, E.R. 1973. The use of echolocation by the wandering
shrew, Sorex vagrans Baird. Diss. Abstr. Int. B. Sci. Eng. 33(7):
- Buchler, E.R. 1976. Experimental demonstration of echolocation
by the wandering shrew (Sorex vagrans). Anim. Behav. 24(4):
- Busnel, R.-G. (Ed.). 1963. Acoustic Behaviour of Animals.
Amsterdam: Elsevier Publishing Company.
- Forsman, K.A., Malmquist, M.G. 1988. Evidence for echolocation
in the common shrew, Sorex araneus. J. Zool., Lond. 216 (4):
- Gould, E. 1962. Evidence for echolocation in shrews.Ph.D.
Thesis, Tulane University.
- Gould, E., Negus, N., Novick, A. 1964. Evidence for
echolocation in shrews. J. Exp. Zool. 156: 19-38.
- Hutterer, R. 1976. Deskriptive und vergleichende
Verhaltensstudien an der Zwergspitzmaus, Sorex minutus L., und der
Waldspitzmaus, Sorex araneus L. (Soricidae - Insectivora -
Mammalia). Unpublished Ph.D. Thesis, Univ. Wien.
- Hutterer, R., Vogel., P. 1977. Abwehrlaute afrikanischer
Spitzmäuse der Gattung Crocidura Wagler, 1832 und ihre
systematische Bedeutung. Bonn. Zool. Beitr. 28(3/4): 218-227.
- Hutterer, R., Vogel, P., Frey, H., Genoud, M. 1979.
Vocalization of the shrews Suncus etruscus and Crocidura russula
during normothermia and torpor. Acta Theriol. 24(21): 267-271.
- Irwin, D.V., Baxter, R.M. 1980. Evidence against the use of
echolocation by Crocidura f. flavescens (Soricidae). Säugetierk.
Mitt. 28(4): 323.
- Kahmann, H., Ostermann, K. 1951. Wahrnehmen und Hervorbringen
hoher Töne bei kleinen Säugetieren. Experientia 7(7): 268-269.
- Köhler, D., Wallschläger, D. 1987. Über die Lautäußerungen der
Wasserspitzmaus, Neomys fodiens (Insectivora: Soricidae). Zool. Jb.
Physiol. 91: 89-99.
- Sales, G., Pye, D. 1974. Ultrasonic communication by animals.
- Tomasi, T.E. 1979. Echolocation by the short-tailed shrew
Blarina brevicauda. J. Mammalogy 60(4): 751-759.