Common Shrew

This article is about the European shrew species. For the mammal known as the Common Shrew in parts of North America, see Cinereus Shrew.

Common Shrew[1]
Common Shrew (Sorex araneus)
Conservation status
Least Concern (IUCN 3.1)[2]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Soricomorpha
Family:	Soricidae
Genus:	Sorex
Species:	S. araneus
Binomial name
Sorex araneus Linnaeus, 1758
Common Shrew range

The Common Shrew or Eurasian Shrew, Sorex araneus, is the most common shrew, and one of the most common mammals, throughout Northern Europe, including Great Britain, but excluding Ireland. It is 55–82 millimetres (2.2–3.2 in) long and weighs 5–12 grams (0.2–0.4 oz), and has velvety dark brown fur with a pale underside. Juvenile shrews have lighter fur until their first moult. The Common Shrew has small eyes, a pointed, mobile snout, and red-tipped teeth. It has a life span of approximately 23 months.

Shrews are active day and night, but mostly after dark. They are active most of the time, resting for only a few minutes between burst of activity.

Territory

The Common Shrew is found in the woodlands, grasslands, and hedgelands of Britain, Scandinavia, and Eastern Europe. Each shrew establishes a home range of 370–630 square metres (440–750 sq yd). Males extend these boundaries only during breeding season, to find females. The Common Shrew is extremely territorial and becomes aggressive when another shrew enters its home range. It makes its nest underground or under dense vegetation.^[3]

Diet

The shrew's carnivorous and insectivorous diet consists mostly of insects, slugs, spiders, small mice and worms. Shrews need to consume 200-300% of their body weight each day in order to survive. A shrew must eat every two to three hours to achieve this goal. This means that a shrew may starve if it finds no food for as little as 5 hours. They do not hibernate in the winter months because their bodies are too small to hold sufficient fat reserves.^{[citation needed]}

Shrews have poor eyesight, but use their excellent sense of smell and good hearing to locate food. Using these senses, a shrew can locate prey up to 12 centimetres (5 in) deep in the soil.^{[citation needed]}

Breeding

The Common Shrew breeding season lasts from April to September, but peaks during the summer months. After a gestation period of 24 to 25 days, a female gives birth to a litter of five to seven baby shrews. A female usually rears two to four litters each year. The young are weaned and independent by 22 to 25 days.^[4]

Breeding is the only time that shrews do not prefer to be solitary. Young shrews often form a caravan behind the mother, each carrying the tail of the sibling in front with its mouth.

Chromosomal polymorphism

The chromosome number (karyotype) of Sorex araneus varies from one individual to another. This is an example of chromosomal polymorphism;^[5] the variability occurs as a result of chromosome fusions or disassociations.^[6]

Protection and population

Common & Eurasian Pygmy Shrews (genus Sorex), size comparison

The Common Shrew is not an endangered species, but in Great Britain it, like other shrews, is protected from certain methods of killing by the Wildlife and Countryside Act of 1981.^[7]

In Britain, shrews can be found at densities up to one per 200 square metres (240 sq yd) in woodlands. The population is controlled by many predators including owls, weasels, stoats, and foxes. A liquid produced by glands on the skin make shrews taste rather unpleasant to domestic cats.^[3]

There has been a recent decline in common shrew populations due to increased use of herbicides.^{[citation needed]}

References

1. ^ Hutterer, Rainer (16 November 2005). Wilson, Don E., and Reeder, DeeAnn M.. ed. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press, 2 vols. (2142 pp.). pp. 283. ISBN 978-0-8018-8221-0. OCLC 62265494. http://www.bucknell.edu/msw3. 
2. ^ Insectivore Specialist Group (1996). Sorex araneus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 12 May 2006. Database entry includes a brief justification of why this species is of least concern
3. ^ ^{a b} British Wildlife. London: Collins. 2002. p. 402. ISBN 0 00 713716 8. 
4. ^ "BBC Science and Nature: Animals". http://www.bbc.co.uk/nature/wildfacts/factfiles/260.shtml. Retrieved 11 September 2009. 
5. ^ Polymorphism: when two or more clearly different phenotypes exist in the same interbreeding population of a species. Ford E.B. 1975. Ecological genetics, 4th ed.
6. ^ White M.J.D. 1973. The chromosomes. Chapman & Hall, London. p169
7. ^ Wildlife and Countryside Act 1981 S11, Sch 6

External links

• ARKive on the Common Shrew
• BBC information on the Common Shrew