Boost for wildlife as resurgent otters kill marauding mink

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As in The Wind in the Willows, so in real life. Otters have come to the rescue of Britain's beleaguered water rats.

As in The Wind in the Willows, so in real life. Otters have come to the rescue of Britain's beleaguered water rats.

New research shows that soaring numbers of the much-loved mammals are dragging the water rat back from the brink of extinction by attacking its greatest enemy, just as the fictional character protected Ratty in the Wild Wood.

This time, the threat to the rats, more properly water voles (or Arvicola terrestris) comes not from stoats and weasels, but from a transatlantic terminator unknown to Mr Toad and his friends - the mink.

But after decades of massacring water voles, birds and other wildlife, the American mink are now getting a taste of their own medicine from the return of the killer otter.

Since the 1950s, when they first broke their way out of fur farms in the West Country - not far from where Kenneth Grahame wrote the first draft of his 90-year-old classic - the mink have spread rapidly throughout Britain, from East Anglia to the Highlands.

They have slaughtered terns, coots and moorhens. And, largely as a result of their predation, the numbers of water voles have slumped by 88 per cent in the 1990s alone, according to the Vincent Wildlife Trust, Britain's leading authority on the mammals.

Scientists once thought that they were also responsible for the decline of the otter, whose numbers crashed after 1957, just after the first mink escaped. But they later discovered that organochlorine pesticides, such as aldrin and deildren, first used the previous year, were to blame, and that the mink had merely taken up the ecological niche the otters vacated.

After the chemicals were banned in the mid 1960s, the otters began to recover: since 1977 their numbers have been doubling every seven years. As they rebounded they killed and ate mink - although fish are the mainstay of the otter's diet - so that it is now the escapees' turn to suffer a population crash.

"The mink population is decreasing everywhere now," says Don Jefferies, who has carried out a special survey for the Trust. "There is a close correlation between it and the otter's recovery. Both the decline and the recovery are good news for conservation."

The mink have suffered most where otters are most widespread - their numbers have plummeted by 91 per cent in Wales, for example. Even in the Thames area, where they have survived relatively well, their population is down by more than a quarter.

It all bears out the Otter's reassurance to a nervous Ratty in the Wild Wood. "It'll be alright, my fine fellow. If there's a head that needs to be punched, you can confidently rely on me to punch it."