English otters reclaim the riverbanks

Dramatic comeback for much loved mammal that nearly died out in the 1970s

by Alok Jha

It is raining again in the Trent valley. Just visible under the hood of his standard-issue environment agency waterproof, otter expert Andrew Crawford's face shows nothing but unbridled enthusiasm as he races around the muddy riverbanks on the hunt for signs that one of his favourite animals has moved back into the area.

And they are everywhere. Otter droppings, or spraints, litter the riverbank and the remains of toads - a favourite food for otters in spring - are all over the place. According to Mr Crawford, not for 50 years have there been such good opportunities for spotting one of these elusive animals in the wild.

The English otter is very much back. In the 1970s experts estimated that there were only "tens" of otters left in England. But after a survey by the environment agency and the Wildlife Trusts, with input from the water companies and English Nature, it is believed there could be up to 4,000 in the country.

While otters in Scotland and Wales continued to thrive in the mid 20th century, English otters were pushed to the edge of extinction by pollution and the destruction of riverside habitats. But the fourth otter survey, published today, has found that the area of England populated by otters has increased fivefold in the past 25 years.

One of the biggest increases has been in the Trent valley. "Ten years ago there were no otters in the Trent catchment," said Mr Crawford, who led the study. "Now [in] roughly 20 to 25% of the sites that we look at we find otters. It shows that otters are able to recolonise an area, if conditions are right, relatively rapidly."

Mr Crawford's report does not give a firm figure for the number of otters, but Allison Crofts, the biodiversity and habitats manager at the Wildlife Trusts, suggested a total of around 4,000, based on the new survey.

Getting an accurate figure is difficult because otters are nocturnal and try to avoid contact with humans. Instead, the researchers looked for evidence such as spraints - which experts insist smell of jasmine tea but, in truth, smell very strongly of fish - and footprints left in soft ground.

Spraints can tell researchers a lot about the health of the otter population and Mr Crawford has collected buckets of dung as part of his two-year survey.

It concludes that a fivefold increase in otter distribution cannot be directly translated into a fivefold increase in otter numbers. However, the significant increase in distribution seen in the survey does represent an increase in England's otter population.

Renaissance

The return of the otter has raised morale throughout the environmental community. "The fact that they literally did become extinct in the Midlands and for a big part of England in the 1960s and 70s and they have been able to recover gives us a sense of hope," said Nick Mott, the rivers and wetlands officer at the Wildlife Trusts in Staffordshire.

The English population of otters declined after the second world war as their river habitats were destroyed to make way for new farms, or rivers were dredged to reduce flooding.

Another factor was the widespread use of organochlorine pesticides organochlorine pesticides such as dieldrin and aldrin. These lingered in the environment long after they were used, for example, in sheep dips. They entered rivers and passed up the food chains from fish to otters and other fish-eating predators.

Over time, the chemicals are thought to have accumulated in the otters and caused either death or infertility. According to the environment agency, by the mid 1950s Britain's otters had been reduced to remnant populations in south-west England, East Anglia, Wales and Scotland.

The otter's comeback is a result of the efforts of several groups, including government agencies, nature conservationists and volunteers. Between them, they have raised the quality of the water in rivers, improved fish stocks and changed the way riverbanks are managed to make sure that otter habitats are not destroyed.

Organochlorines, for example, have been banned or their use largely restricted. As a result, their levels in waterways have declined and otters have been given a chance to recover.

The highways agency has also been enlisted to try to reduce the numbers of otters that are run over on the roads. Its latest project involves building ledges underneath road bridges. Otters can use these to travel along their riverbank territories safely without the need to dodge fast-moving traffic.

"That's going to get more and more important as otters move south and east into the more built-up areas around London," said Mr Crawford.

The agency is already fitting otter ledges underneath all new bridges. For example, the builders of the M6 toll road in Birmingham are spending £200,000 installing ledges under the 40 or so culverts beneath the road, to prevent otters being forced to battle it out above with vehicles.

Mr Crawford said that the next step was to try to improve surveying methods to get a clearer idea of otter numbers. The most promising way of doing this is to profile the DNA contained in spraints and the environment agency has already been carrying out some preliminary research into it.

"That's going to always be expensive and we'll only be able to do it in a restricted area," said Mr Crawford. "But it should open a lot of doors to us about how many otters there are and how widely they move."

·Only the Eurasian otter, Lutra lutra, is native to Britain. It is a member of the mammal family that includes weasels, stoats, badgers and mink. They can be found everywhere from Ireland to Japan

·They live solitary lives in narrow territories that stretch along riverbanks or marshes. These "home ranges" can be anything up to 9 miles long depending upon the quality of the habitat and the feeding resources within an area

·The home range will contain several resting sites where the otter can lie up when it is not out fishing for its food. These can take a variety of forms from underground dens, or holts, such as cavities in the roots of trees on the riverbank, piles of logs or caves. They will also rest overground on tall vegetation or scrub - these are usually called couches

·An adult will normally grow to well over a metre long and live for around three to four years, although considerably bigger and longer-lived animals have sometimes been found. Otters are carnivorous and will eat, on average 1kg of food a day. They mainly eat fish but will eat amphibians

·Otters can breed at any time of the year and the cubs, usually born three or four at a time, stay with their mothers for the first year of their lives to learn how to exploit their environment