The water vole — immortalised by Ratty in The Wind in the Willows — is making a comeback. Their numbers have doubled in the past nine years after falling rapidly throughout the 20th century, the Environment Agency said.

The decrease from an estimated seven million water voles in Britain in the early 1900s to 200,000 at the turn of the century has been put down to the destruction of habitat, the arrival of the American mink, trapping and persecution. But the latest figures show that there are now about 500,000.

When The Wind in the Willows by Kenneth Grahame was published in 1908 the animals were a common sight in waterways across the country. The biggest fall came after 1990, when there were still about 1.5 million.

The Environment Agency said that its efforts to undertake large-scale habitat restoration and mink control projects were helping to have a positive effect on numbers.

Water voles were granted full legal protection last year under the Wildlife and Countryside Act — making it illegal to kill or injure them intentionally, disturb their habitat or take them from the wild.

The agency said that in many of the areas where it had carried out work, in particular the Sussex coastal plain, the Somerset Levels and Snowdonia, water voles were beginning to spread. The study showed, however, that they were scarce in Devon and had died out in Cornwall.

About a hundred water voles bred from those in Somerset have been released in the Lower Axe Valley by East Devon District Council, in a project part funded by the Environment Agency. It is hoped that the voles, which have all been fitted with microchips to allow their progress to be monitored, will set up colonies on the River Axe and spread to its tributaries.

Alistair Driver, the Environment Agency’s national conservation manager and chairman of the UK water vole steering group, said: “We were encouraged to find in our recent survey that water vole populations may be turning the corner after their dramatic decline in the 1990s.

“We need to keep funding projects like these, along with mink control and habitat improvements, to make sure these enigmatic little creatures are not lost from the UK for ever.

“These reintroduction projects are designed to give the environment a helping hand, in the hope that water vole populations will sustain themselves in the future.”

The agency has spent more than £1 million since the Nineties on mink control, habitat improvement and captive breeding programmes.

In Scotland 600 water voles have been released into the Trossachs 25 years after they died out there. Katy Freeman, of the Forestry Commission, said: “It is great for biodiversity and the water voles will be a great draw for visitors to the area.”

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