The Common Shrew Sorex aranaeus

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Recognition:Tricoloured, dark brown, pale brown, whitish, dense velvety fur, long pointed nose, tiny eyes, small ears and red teeth.Head/body length: 48-80mm, tail 24-44mm; tail less than 3/4 length of head and body.
Weight: 5-14g

General Ecology: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.

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. Their main food source is insects but they will also eat earthworms, small slugs and snails especially in damp areas.

Shrews are highly territorial animals and only socialise with one another in the mating season. Females have one litter of 5-7 young from May to September. 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. Shrews do not hibernate, but they do become less active in winter.

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. 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.

Conservation: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.

Frequent Questions:

How many types of shrew are there in Britain?
Five. These are divided into two groups, the red-toothed and white-toothed shrews. The red-toothed group is composed of the common shrew, the smaller pygmy shrew, and the water shrew. Lesser and greater white-toothed shrews are not found in mainland Britain. The lesser white-toothed shrew is found on the Isles of Scilly, Jersey and Sark, whilst the greater lives on Alderney, Guernsey and Herm.

Where can I see a shrew?

Shrews are not easily seen because they move very quickly, but they can often be heard, particularly in March and April when they meet to mate. They communicate by a series of high-pitched shrieks and chatters, which are particularly loud if the shrew is alarmed or angry. One of the shrews' main predators is the domestic cat. Thus, many peoples' first encounter with a shrew is when it is given to them as a present by the family pet.

How can I study shrews?

Shrews are very curious and will investigate any new objects they find. Because of this they can be easily captured in live traps, the most common of which is a Longworth trap. The Mammal Society runs a trap loan scheme for members. In order to trap shrews you must have a licence (from English Nature, the Countryside Council for Wales or Scottish Natural Heritage) and provide plenty of bait, (blow-fly larvae, cat or dog food) and straw bedding to ensure the shrews' survival.

Shrews are the most common mammals caught in discarded bottles and drink cans. Tipping out the contents of these containers may reveal parts of the shrew skeleton.

Another method used to find out if shrews are present in an area is hair- tubing. A series of tubes with two holes in the top can be placed at the soil surface with Sellotape covering the holes. An animal passing through the tube will leave a hair sample on the tape, which can then be identified using a hand- lens or microscope.

Further Information