Magazine article Geographical

British Otters Return to the River: During the 1960s, the Use of Organochlorine Pesticides in Farming Devastated Much of England's Otter Population. but in Recent Years These Charismatic Creatures Have Once Again Begun to Flourish

Magazine article Geographical

British Otters Return to the River: During the 1960s, the Use of Organochlorine Pesticides in Farming Devastated Much of England's Otter Population. but in Recent Years These Charismatic Creatures Have Once Again Begun to Flourish

Article excerpt

Under cover of darkness, a sinuous shape silently slips beneath the river's inky surface. A short while later it reappears--an otter, a small roach flapping weakly in its jaws. Droplets of water hang from its long whiskers, glittering in the faint moonlight as it crunches greedily on its catch.

A few decades ago, such a scene would have been a rare sight indeed in England. Now, however, an increasing number of the nation's rivers and streams are seeing the return of these semi-aquatic mammals.

Otters virtually disappeared during the 1960s when farmers began using organochlorine pesticides, which wiped out a huge swathe of wildlife across much of the Western world. Aldrin and dieldrin, used in seed dressings and sheep dips, were the main culprits, devastating the otter population across most of arable lowland England and greatly reducing numbers in the sheep-farming uplands. The chemicals were banned in the 1970s and otters have since been returning steadily to old haunts across the UK.

This rare piece of good conservation news comes courtesy of a recent survey by the Environment Agency (EA), the fourth in a series of otter studies since the late 1970s. The results reveal that more than a third of roughly 3,000 sites examined across England showed signs of otter presence, a five-fold increase on the depressing results of the first survey, conducted in 1977-79, in which less than six per cent of sites were positive.

"The otter is on the road to recovery," says EA's Andrew Crawford, the report's author. "Overall, the survey suggests a real and continued increase in otter range, which in turn reflects a considerable increase in population."

In the context of the previous studies, this report shows that from a low point in the 1970s, the otter population has expanded steadily from strongholds in Devon, Wales and Scotland. Today, a relatively small area of southern and southeastern England remains to be recolonised, something that will hopefully take place over the next 20 years. Forthcoming studies from Wales and Scotland are expected to show that the otter has almost fully recovered there.

But although the overall news is good, the otter's recovery hasn't been as extensive as had been predicted. Following a survey in the mid-1990s, it was calculated that by 2002, about half of examined sites would show otter signs. The actual figure is 34 per cent. Although Crawford believes the results are within the "limits of tolerance", he says there's still some way to go before we can say that the otter has fully recovered right across England. That is probably still several decades away, he says. "There are a few specific areas where the otter is failing to recover for no obvious reason, and what we need to do is identify the reasons and the solutions."

The lower reaches of the River Severn is one such area. "They reached the head of the navigable part of the Severn in about 1985, but since then have shown very little progress downstream," says Crawford. "Over that amount of time, otters have made huge progress in recolonising the upper reaches of the River Trent, so what is blocking progress on the Severn?"

One explanation is that shipping is to blame or, more specifically, the clearance of underwater obstacles to aid shipping. "In the 1960s and '70s," says Crawford, "underwater rocks and shoals were removed from many of Britain's rivers to aid navigation. As a result, there is nowhere for fish to hide, leaving them vulnerable to being swept off in strong currents and hence leaving no prey for the otters." Crawford emphasises that this is just one possible explanation, but adds, "The otters have just reached the heads of navigation on both the Trent and the Thames, so it will be interesting to see what happens at these places over the next few years."

There seems to be a general unease about whether otters are recovering at their optimal speed, or are being held back by some as-yet-unidentified factor. …

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