One of the most aquatic of all shrews, this species occurs throughout Alaska and Canada. It extends south into high, mountainous regions of the United States, most notably along the Rockies, where climatic conditions are similar to those found further north. This shrew is often found in or close to water. It also lives in damp conifer forests.
Males of this large shrew species tend to be longer than females. The thick fur traps a layer of air around the body to keep the animal warm while diving in cold water.
Water shrews live alone and are known to hunt for insects. Most of their prey are the aquatic youngsters of insects such as crane flies and caddis flies. While under water, the shrews detect the movements of prey using whiskers on their snouts. They grab the food with their forefeet or mouth. In captivity, water shrews have been seen feeding once every ten minutes. In the wild, they will die if they go without food for about three hours.
Distribution: Northern North America.
Habitat: Near streams and other fresh-water habitats.
Size: 8 cm (3 in); 8 - 18 g (0.3 - 0.6 oz).
Maturity: 1 year.
Breeding: 2 - 3 litters of 3 - 10 young produced in spring and summer.
Life span: 18 months.
Eurasian Water Shrew
These small mammals are highly unusual, possessing a venomous saliva used to overcome prey, although they present no danger to people.
The Eurasian water shrew is found across Europe and Asia. The western limit of its range is Britain. It does not live in Ireland.
Eurasian water shrews live in burrows and occupy distinct territories. Most water shrews live close to fresh water, defending a small area of bank in which their burrow is located. Some members of this species live farther away from flowing water, in damp areas such as hedgerows.
The shrews live alone. They hunt at all times of the day and night, mostly in water. The tail has a keel of hairs, which helps with swimming. The shrew's fur traps a blanket of air as the animal submerges, which prevents the little mammal from losing body heat too quickly.
The Eurasian water shrew is the largest shrew species in Britain. The species is one of the red-toothed shrews. Red-coloured iron compounds coat the tips of its teeth, which makes them more hard-wearing. This is the result of iron deposits, which help strengthen the teeth.
They have prodigious appetites, thanks to their high metabolic rate, and they must eat about half their body weight every day. They catch prey in their mouths and stun it with mildly venomous saliva. Only a handful of other mammals deploy venom. They are vulnerable to many predators, including birds of prey.
Water shrews breed during the summer. Each female is capable of producing several litters in that time. A typical litter contains about five or six young, although twice this number is possible. The young are weaned after 40 days. Females born early enough can breed in their first year.
Distribution: Ranges across most of northern Europe into Asia, reaching the Pacific coast, and south into north Korea. Found in close proximity to fresh water.
Habitat: Freshwater streams and ponds.
Weight: About 15 g (0.53 oz).
Length: 17.5 cm (7 in) overall; the tail is about three-quarters of the body length.
Maturity: By 3.5 months.
Gestation Period: 20 days; 2 - 3 litters a year, born in a nest of grass.
Breeding: Average 5 - 6, range 3 - 12; weaning occurs at 42 days.
Food: Invertebrates caught in water and on land; may also hunt small fish.
Lifespan: Up to 18 months.
Very dark upperparts and white underparts.
Air is trapped in the fur, which gives the shrew buoyancy, but makes it harder to dive.
Eyes and ears
The eyes are very small, as are the which are largely hidden by fur.
The snout is very long with a pink tip on the nose.
Bristles are present on the underside of the tail and on the paws, helping the shrew to swim more easily.
Tibetan Water Shrew
There are several species of shrew that are at home in water. All of these have silky fur that repels water, long tails and fringes of stiff hairs along the edges of their feet, toes, fingers and tails that help them swim. In smaller species, these hairs allow the shrews to run across the surface of the water for short distances, supported by the surface tension.
The Tibetan water shrew is the only species of shrew to have webbed feet. It also has disc-like pads that may help it keep its footing on slippery wet stones. This shrew lives in a burrow dug in a stream bank.
The Tibetan water shrew has a long dark coloured tail with several fringes of short, stiff white hairs that shine with rainbow iridescence when wet.
Most aquatic shrews forage by making repeated dives in the same spot, each dive lasting usually less than 20 seconds. After each dive, they shake their fur dry. If no prey is found, they move along the stream lm (3 ft) or so and dive in a new position. The Tibetan water shrew has sharp teeth that seem to be specialized for catching fish, which are its main prey.
Distribution: Tibet, south-central China, Nepal and northern Burma.
Habitat: Mountain forest streams.
Food: Small fish and aquatic invertebrates.
Size: 9 - 13 cm (3.5 - 5 in); 25 - 45 g (0.05 - 0.09 lb).
Maturity: 6 months.
Life span: Unknown.