Wildlife watch: the water shrew

On first sighting of a water shrew its very dark, velvety coat can look confusingly like a small mole. Although water shrews are smaller than moles they are bigger than other species of shrew and are at home on both land and water.

The water shrew is well adapted to its semi-aquatic lifestyle. It has a water repellent coat and stiff hairs around its feet and tail which act like paddles to give it extra propulsion through the water. Indeed, when in the water these shrews paddle around like mad: they have a fast heart beat, a high metabolic rate and a huge appetite.

Dietry habits of the water shrew

Unusually, water shrews have a mildly poisonous saliva which enables them to tackle quite large prey, indeed these shrews are fearless hunters. Their typical aquatic prey include caddis fly larvae, freshwater shrimps, water skaters, small fish, tadpoles and water beetles though they also hunt on land where they take worms, larvae and beetles.

With such small bodies shrews cannot afford the risk of hibernation, they need to remain active all year round finding food regularly to stay alive, they need to consume about 50% of their body weight each day.

Breeding habits of the water shrew

Water shrews usually produce two litters per year, between April and September. Each litter may contain between 3 and 15 young, though 6 is average, and each youngster is weaned in about a month. Their life expectancy is short; the longest likely lifespan is only about a year and a half, though high mortality means that the average is much lower.

When to see water shrews

We know from records of shrews that most people only ever see them when they have been killed and brought in by their cats. Cats often choose not to eat shrews because they produce unpleasant, oily substances from scent glands which make them distasteful to predators.

Water shrews are widespread in Britain but rarely are they easy to spot. It is during autumn that I have had most of my own sightings and many of these have been away from water courses. In late summer many of the new generation of water shrews spread out from the place of their birth in search of new breeding areas and it is then that they are more likely to be seen.

Read our tips for creating a wildlife-friendly garden.