Britain is home to three species of shrew, and two are likely to turn up in gardens.
The common shrew, Sorex araneus, is a chocolate brown colour on the back, paler on the flanks and near white on the under-parts, its short fur giving it a velvety appearance. It has a rounded head, tiny ears and a long pointed muzzle, which is constantly twitching and sniffing as the shrew searches for food.
The pygmy shrew, Sorex minutus, is the smallest mammal likely to turn up in a garden. The main distinguishing features between the pygmy and common shrews are the former’s smaller size, slightly longer tail in relation to body length, and a more domed head.
Although frequent in gardens, neither are seen very often, as they prefer to forage in dense cover, under long grass, brambles and debris. They are more usually heard, as shrews communicate with high pitched squeaks audible to humans.
Head and body length, 5-8cm (2-3in), tail 3.5-5cm (1 ¼-2in)
Head and body 4-6cm (1 ½-2 1/4in), tail 3-4.5cm (1 ¼-1 3/4in)
Both species are found across most of lowland Britain.
Both species of shrew are believed to be in decline, due to loss of suitable habitat, although exact numbers are unknown. Neither have any special protection at present.
The common shrew is primarily a woodland species, but is also found in hedgerows, scrub and long grass. The pygmy shrew can be found wherever there is sufficient cover in grassland, heath, and hedgerow, but it is less common in woodland.
Where to find them in the garden
Shrews build themselves nests, and these are likely to be under stones or logs, or even under the shed. Pygmy shrews are good climbers, and have been found in bird nest boxes, making use of an old nest. Both species will spend much of their time foraging in long grass, among leaf litter or under logs, but rarely coming out in the open.
Role in the garden
Both shrews eat a wide range of invertebrates. The common shrew will feed mainly on beetles, insect larvae, worms, slugs and snails, while the smaller pygmy shrew takes spiders, woodlice and smaller insects.
Shrews need large amounts of food to support their very high metabolic rate; a shrew can eat the equivalent of its own body weight in 24 hours. They also need to eat frequently, as they can starve to death in less than a day. So they are active day and night, constantly foraging, and resting for only a couple of hours at a time.
Owls and kestrels will often prey on shrews. Mammalian predators rarely take them as shrews have scent glands on their flanks, which mammals find distasteful (most birds have no sense of smell). Domestic cats will kill shrews, but not eat them for this reason.