Common Shrew – Sorex araneus
Taxon: Insectivora
Habitat: Urban & gardens, deciduous woodland, grassland, mixed woodland, arable land
Description: Common shrews are tricoloured: dark brown on the back, pale brown at the sides and whitish underneath, dense velvety fur, with a long pointed nose, tiny eyes, small ears and red teeth.
Size: 48-80mm, tail 24-44mm; tail less than 3/4 length of head and body.
Weight: 5-14g
Lifespan: In comparison with mice, shrews have a very short life-span and it is uncommon for a shrew to live for more than 12 months.
Origin & Distribution: Native. The common shrew is found throughout mainland Britain and has also been introduced to many islands with the notable exception of Ireland, the Outer Hebrides, and Shetland. It is replaced on Jersey by the very similar French shrew (Sorex coronatus).
Diet: Their main food source is insects but they will also eat earthworms, small slugs and snails especially in damp areas.
General Ecology: The common shrew is a terrestrial species living almost anywhere and is most commonly found in hedgerows, scrubland, grassland and deciduous woodland. Since shrews must eat every 2-3 hours to survive they are often seen at the surface foraging for food, but live in burrows which may have been used previously by another animal. Shrews do not hibernate, but they do become less active in winter. Remarkably, their size shrinks in winter, so that they require less effort to move and so need less food, not only does the liver shrink but also the brain and the skull.
Shrews have a number of predators and are most commonly killed by tawny owls and barn owls, although weasels, foxes, stoats and kestrels have all been observed as predators. They are often found abandoned by the predator, particularly cats, since a liquid produced from glands on the skin is foul tasting. Shrews are noted for providing a home for a large number of parasites, normally transmitted to the shrew from its prey.
Breeding: Shrews are highly territorial animals and only socialise with one another in the mating season. Females have three or four litters of 5-7 young between May and September. Females are promiscuous and a litter may have two or three different fathers. Young shrews are occasionally observed following their mother in a ‘caravan’. Each shrew grasps the base of the tail of the preceding shrew so that the mother runs along with a line of young trailing behind. This behaviour is often associated with disturbance of the nest and may also be used to encourage the young to explore their environment.
Conservation Status: The common shrew is very widespread, the second most numerous British mammal. Living at densities of up to 50 per hectare in many woodlands and often over 20 per hectare in grasslands and other habitats, the most recent estimate puts the number of shrews in Britain at 41,700,000. Although there is no reason to fear their extinction, all shrews (including the common shrew) are protected under Schedule 6 of the Wildlife and Countryside Act (1981). Due to this protection, shrews may not be trapped without a licence and, when trapping for other small mammals, precautions are necessary to minimise the chances of death or damage to shrews. Information on trapping and the law is given in Live Trapping Small Mammals, a practical guide available from the Mammal Society.
