Common shrew

The common shrew (Sorex araneus) is correctly named, given that it is one of the commonest mammals found in Great Britain. However, most people have never seen one, because it is a secretive animal that is most active at night. 

The common shrew is about 5-8 centimetres long and it weighs up to 12 grammes. It has silky dark brown fur that is lighter on the underside. 

Its habitat is woodland, hedgerows and grassland, where it spends much of its time hidden beneath vegetation or burrowing underground. When active, the common shrew spends most of its time searching for and eating its food, which consists of worms, insects, spiders and other small animals. It hunts by using its acute sense of smell. It needs to eat up to three times its own bodyweight every day in order to survive. 

The common shrew is too small to hibernate during the winter – it cannot store enough fat in its body to make this possible. However, it has evolved a survival mechanism by which it shrinks in size and reduces its body weight by up to 20%, thus reducing the amount of food it needs to find and eat. This shrinkage involves reductions in size of bones, including the skull, and internal organs. When Spring returns the lost weight is recovered. 

The common shrew breeds during the summer months, and a female can produce up to four litters during that time, each one containing up to seven young. Given that the normal lifespan of the common shrew is only 14 months, a female can only expect one breeding season during its life. 

By being active mainly at night the common shrew is itself prey for other nocturnal wildlife, particularly owls and foxes. However, the species is not endangered.

© John Welford