Common shrew  (Sorex araneus)

The common shrew, one of Britain's most abundant mammals has a long, flexible snout, tiny ears and small eyes typical of most shrews (2). The fur is dark brown on the back, with paler brown flanks and a pale belly (1). Juveniles have lighter fur until they undergo their first moult, after which their winter coat grows (3). This species is a 'red-toothed shrew'; iron is deposited in the enamel of the crowns of the teeth, making them more resistant to wear-and-tear (3). The Latin name araneus means 'spider'; this refers to the old belief that shrews were poisonous, like spiders.

Distributed throughout mainland Britain, as well as on many offshore islands. The common shrew also occurs throughout most of Europe but is absent from Ireland and the Mediterranean (5).

Inhabits a huge variety of habitats where there is good vegetation cover, including 'edge' habitats such as road verges (5).

Shrews are well known for their voracious appetites (3); the common shrew has to eat every 2-3 hours and needs to consume 80 to 90% of their body weight in food in 24-hours (3). They feed on most terrestrial insects, but will also take worms, slugs and snails (2). The common shrew is more active during the night, at dusk, and at dawn, and intersperses bursts of activity with rest periods (3). Shrews do not hibernate, as they are too small to store fat reserves sufficient to see them through the winter (3). This solitary species is territorial (2), but during the breeding season males set off in search of females. His advances may stimulate scuffles and high-pitched squeaks from unreceptive females (3). Mating begins in March, and 1-2 (sometimes 3 or 4) litters are produced in a year, each one consisting of 6-7 young (5). By 16 days of age the young begin to emerge from the nest, they can occasionally be seen following their mother around in a 'caravan', usually after the nest has been disturbed. The young grab the tail of the shrew in front of it, so the mother takes the lead and her offspring follow in a train (3). Juveniles breed in the year after their birth, but occasionally those born early in the year can breed between July and September that year (5). Common shrews live for 14-19 months, and mortality rates are high; main predators include owls, birds of prey, foxes, cats and stoats and weasels (5). Shrews belonging to the genus Sorex are known to produce ultrasound, which may be used as a primitive form of echolocation (5).

In farmland areas, this species is likely to be affected by pesticides, either through secondary contamination through their prey or by direct exposure (5). Decreases in prey availability can greatly affect survival as shrews have such high metabolic rates (5). The decline in hedgerows, field boundaries and other features that provide important habitats for shrews resulting from agricultural changes may also affect shrews (5).

All shrews are protected under schedule 6 of the Wildlife and Countryside Act 1981; under this act it is illegal to trap shrews without a licence (3).

For more on this species see the Mammal Society fact sheet, available at:
http://www.abdn.ac.uk/mammal/common_shrew.shtml

and Churchfield, S. (1988) Shrews of the British Isles. Shire Natural History Series No 30. Shire Publications, Princes Risborough.

For more on the conservation of Britain's mammals see:

Macdonald, D.W., and Tattershall, F.T. (2001). Britain's mammals- the challenge for conservation. The Wildlife Conservation research unit, Oxford University. Available at:
www.wildcru.org

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