Water voles are Britain’s largest voles, with fully grown adults reaching lengths of 20cm (plus a 12cm tail) and weighing up to 350g. They are charismatic little creatures with a round face, a blunt nose, a short furry tail and glossy dark brown or black fur. Water voles were popularised by the well-known character Ratty in Kenneth Grahame’s ‘Wind in the Willows’, who, despite his misleading name, is not a rat but a water vole.

In spite of their name, water voles are not particularly well-adapted to aquatic life. They have evolved to live alongside water to aid their escape from predators. Their characteristic ‘plop’ is the sound of them diving into the water to escape any would-be predator and to access the underwater entrance to their burrow. But they are clumsy swimmers, without the rudder-like tail or webbed feet evolved by other water-loving creatures.

Water voles live in burrows that they build by biting into the banks with their very strong, enamel-coated orange teeth. These burrows can be very complex and consist of nesting and nursing chambers, with two entrances, one on the bank and one underwater.

The breeding season begins in April and continues until October. Water voles are extremely successful breeders – they need to be to replenish the numbers lost during winter; when up to 80% of water voles perish, mainly as a result of starvation. Their babies (pups) leave the nest after three weeks and are themselves able to breed at 15 weeks old. One female water vole can have between five and six litters in a year, with between 3-5 pups per litter, meaning that one female water vole could have 25-30 babies in one breeding season – poor thing!

Water voles need to eat up to 80% of their own body weight every day in order to stay healthy. Their diet consists mainly of grasses and waterside plants, as well as twigs, bulbs, roots and fallen fruit. They aren’t too picky and have been recorded feeding on up to 220 different plants. Although they are described as herbivorous, a female feeding young will eat a dead water snail or fish if she comes across one, to boost her protein levels. 

Sadly, water voles are one of the UK’s fastest declining mammals. Up to 90% of the population has been lost since the 1970s; part of a longer-term decline stretching back to the Middle Ages. The reasons for this decline include habitat loss and fragmentation (their habitats being broken up into smaller, disconnected chunks).

It is well-known, however, that the American mink is the key driver behind the more recent decline of our water voles. Mink were introduced into the UK in the 1960s after fur farms were closed. Water voles are at the bottom of the food chain, and are eaten by otters, buzzards, owls, and foxes to name just a few! But these are all native animals and the water vole can cope with these natural predation pressures by breeding rapidly and escaping into their burrows. However, a female mink is slim enough to follow the water voles into their burrows and predate entire populations. 

Fortunately, it’s not too late for the water vole! Wildlife Trusts across Britain have been working to help water voles recover, restoring their habitats and even reintroducing them to areas where they were once lost. One excellent example of the Wildlife Trusts’ work for water voles is Northumberland Wildlife Trust’s Restoring Ratty project.

Restoring Ratty is a water vole re-introduction project based at Kielder Forest in Northumberland.

Voles were captured from sites in the North Pennines, North Yorkshire Moors and the Trossachs in order to create a wide genetic pool to breed from – with genetics similar to the water voles that would originally have been found in Kielder. To avoid impacting the donor populations, we only captured voles in the autumn that weighed less than 160g and would therefore be unlikely to survive the winter.

Following captive breeding, release sites were carefully chosen and the water voles were returned to the wild, with regular monitoring to make sure the voles were thriving. Between June 2017 and June 2020, seven separate releases took place, involving 1,762 water voles!

Restoring Ratty is made possible thanks to funding from the National Lottery Heritage Fund and the support of partners in Forestry England and Tyne Rivers Trust.