Feisty Furballs

Brian Pike takes a close-up look at our native shrews and voles

ice are familiar creatures, especially to country dwellers –they are, after all, the small mammals most likely to sneak into our houses in search of food and shelter. Shrews and voles, by contrast, keep themselves to themselves, and are consequently shrouded in mystery.

Many of us aren’t entirely sure how to distinguish between the three different groups of animals, so let’s start by separating the mice from the rest. Think of the classic cartoon Mickey Mouse – big eyes, big ears and long tail – and you’ve got the basic recipe for a mouse, be it a house mouse, field mouse or harvest mouse. Shrews and voles have none of these traits. Their eyes and ears are small, and their tails are short.

So now all we need to do is distinguish shrews from voles, which is easy enough. Voles have blunt noses and shrews have long, pointy ones.

Although superficially similar, shrews and voles have very different lifestyles. Our three native shrews – the pygmy shrew, the common shrew and the water shrew – are all primarily carnivorous, whereas voles are almost exclusively vegetarian.

A deadly bite and metal teeth: the weird world of shrews

Tiny they may be, but shrews are ferocious predators – and, arguably, Britain’s oddest mammals. For one thing they have a poisonous bite. It’s their saliva that carries the venom, and it is transferred to their victim via razor-sharp, grooved teeth. A shrew bite poses no threat to humans, but if you’re a worm, a slug or a woodlouse it’s a very different story.

Shrews live life in the fast lane. They have a phenomenally high metabolic rate: a pygmy shrew’s heart beats more than 1,000 times per minute. Its owner is active night and day, sleeping only in short bursts. Pygmy shrews simply can’t afford to take things easy because they need to consume more than their own body weight’s worth of food every day to survive.

Thanks to their supercharged lifestyle, our native shrews possess another surprising feature: red teeth. This unusual colouration is due to iron deposits that help reinforce the animals’ dental enamel and ensure their teeth don’t wear out too fast. Yes, that’s right, shrews have metal gnashers!

As the name suggests, the pygmy shrew is the smallest of our native shrews, a sharpnosed, grey-brown creature with a body measuring around 5cm long and a 3cm tail. The average pygmy shrew weighs around 4 grams – about the same as a 5p piece.

Slightly bigger, at around 6.5cm with a 3.5cm tail, the velvety grey-brown common shrew weighs roughly as much as a pound coin. Like the pygmy shrew it can be found in a wide range of different environments: arable land, grassy places, gardens and woodland.

Biggest of the bunch, at around 10cm plus a 7cm tail, is the water shrew, which is notably different both in terms of colour scheme and habitat. The water shrew’s velvety fur is jet black on top and white underneath. It’s a semiaquatic animal, seldom found far from the streams, rivers, ponds or ditches into which it dives in pursuit of aquatic insects, shrimp, water snails, small fish, frogs and newts.

Because of its specialised habitat, and also because of continuing pollution of watercourses, the water shrew is less common than our other two species of shrew, although not so rare as to have triggered concern amongst conservation groups.

Cute and cosy plant munchers: our native voles

Compared to shrews, with their fatal bite, fast-forward metabolism and iron teeth, voles – which are close relatives of hamsters and lemmings – are pretty middle-of-theroad mammals.

Both the field vole and the bank vole can be found in rural and suburban gardens and in the countryside at large. Field voles favour grassland, heathland and moorland whereas bank voles are more at home in hedgerows and woodland. However, their ranges frequently overlap, so where you find an animal isn’t necessarily a guide as to which species it is.

Bank voles tend to be chestnut brown whereas field voles are usually greyish brown, but the most reliable way to distinguish them is by the length of the tail. Bank voles have significantly longer tails – about half the length of the animal’s body as opposed to the stubbier tails of field voles, which are usually less than a third as long as the animal’s body.

OPPOSITE Water shrew on a mossy bank

TOP Young bank vole

BOTTOM LEFT Common shrew foraging

BOTTOM RIGHT Baby water voles feeding

Field voles feed predominantly on grass shoots and mosses — hence their preference for open grassy habitats — whereas bank voles have a diet that includes plant roots, seeds, nuts, berries and fungi.

Field and bank voles are amongst our commonest mammals, and an important food source for owls, kestrels, stoats and weasels. By contrast, the plump and photogenic water vole, our largest native vole, has suffered a catastrophic decline in numbers over the course of the last half century, having disappeared from around 95% of its former habitat.

This has been due in part to pollution and the remodelling of watercourses, and in part to predation by the American mink that escaped – or were released – from fur farms during the 1960s and have now established themselves in the wild.

Since 2008 water voles and their habitat have had full legal protection under the Wildlife & Countryside Act. Without this legislation and the active intervention of various conservation organisations they would almost undoubtedly have become extinct in the UK.

One local nature reserve that is championing the water vole is Foxglove Covert in Catterick Garrison (foxglovecovert.org.uk). Reserve staff regularly monitor the site to ensure that it isn’t invaded by mink, and thanks to their vigilance water voles are regularly spotted chowing down on the apples provided on the reserve’s floating vole-feeding platforms.

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