12 May 2003
otters reclaim the riverbanks
comeback for much loved mammal that nearly died out in the 1970s
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.
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.
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.
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.
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
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.
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.
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
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.
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.
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.
factor was the widespread use of 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
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.
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.
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.
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.
going to get more and more important as otters move south and east
into the more built-up areas around London," said Mr Crawford.
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.
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.
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
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
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
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
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
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