discoverwildlife.com BBC WILDLIFE 73As well as having
dense, water-repellent
fur and webbed feet,
otters can close
their ears and nose
underwaterOTTERS O
Populations are still fragile and
face a multitude of threats
picture looks positive as otters are more
often sighted in daylight and increasingly
close to urban and suburban areas. They’ve
been spotted beside a busy retail park
in Rugby, raiding dustbins in Newcastle,
visiting parks in Bristol. In Edinburgh, CCTV
cameras at Haymarket station recorded
an otter lolloping along the platform. It
would appear, we have an intelligent and
opportunistic predator finding ways to
survive wherever its basic needs for food
and shelter can be met. Hunting otters was
banned in 1981, and as generations of them
grew up without being directly threatened by
people they become less wary and more able
to peacefully co-exist.
Ecologists warn however, that the
animals’ more visible presence could be
due to them having to travel further and
hunt longer to find food. Eels, for example,
were once a primary food source for otters
in British rivers, but their populations have
crashed catastrophically. So otters may be
resorting to inadequate food sources in far
from ideal settings.
Otters are also particularly vulnerable to
disturbance as they need to feed and sleep
a lot, which means busy places and crowds
can be a problem. Even well-meaning wildlifewatchers and photographers can disrupt
otters’ natural behaviour.
Many scientists caution against
complacency when celebrating the return of
the otter. Populations are still fragile and face
a multitude of threats. Road deaths are still
high, entanglement in fishing gear continues,
and food sources are precarious as climate
change disrupts ecosystems in every habitat.
Above all, there’s growing alarm about the
quality of the UK’s rivers and freshwater
systems, including the accumulation of a new
generation of chemical pollutants.
Cardiff University’s Otter Project has
been carrying out post-mortems on UK
otters for nearly 30 years. The bodies of
4,000 otters have a disturbing story to tell,
as the history of pollutants in European
agricultural and industrial policy can be
read in their bones and tissues. Levels of
lead have fallen significantly, reflecting
declining emissions from car fuel, but can
still be detected in otters’ ribs. A 2021 study
showed that decades after they were banned,
substances such as DDT, dieldrin and PCBs
were detected in the livers of more than 80
per cent of otters surveyed. Though overall
levels of these chemicals are falling, in some
areas they’re above the toxic threshold andmany more suffered sub-lethal poisioning,
where the build-up of toxins affected their
physiology, behaviour and reproduction.
Residues washed into the rivers and began
to accumulate in the food chain, from
microorganisms to small fish to large fish,
then to fish-eating birds and mammals. As
top predators, otters were absorbing the
highest concentrations of these toxins.
It took time for the effects of these
chemicals to be understood and the extent
of the carnage to be acknowledged, but
eventually some of the worst pollutants
were banned and – slowly – their effects
diminished. As the pesticide load reduced,
water quality improved and many of
Europe’s rivers became fit for otters again.
A raft of conservation measures assisted
their resurgence, including legal protection,
habitat restoration and infrastructure,
such as fencing and otter underpasses for
busy roads. In a few places otters were
reintroduced, but mostly they made their
own way back from coastal strongholds.
Despite their absence from our
waterways for a generation, otters have
retained their popularity, partly due to their
aesthetic appeal – though they share a hint
of menace with their non-aquatic cousins
of the weasel family, there’s also a note of
teddy bear about them. In his memoir Ring
of Bright Water, Gavin Maxwell describes
an otter at play as “an animal that might
have been specifically designed to please a
child”. Their place in literature, including
Maxwell’s tales of his pet otters and Henry
Williamson’s fictional Tarka, has ensured an
enduring place for otters in our imaginations.
And so, as otters continued to spread
through the country, their return was greeted
with delight by the general public. Even rivers
historically known for high levels of industrial
pollution, such as Newcastle’s Tyne and
Sheffield’s Don, were boasting otters again. In
2011, the Environment Agency annnounced
that otters had returned to every county in
England. For once there was much-needed
good news, and it seemed a quintessential
success story of rewilding: restore the habitat
and the wild will return. Now, 10 years on, it’s
important to check how the otters are faring
and assess the prospects for these predators
and their watery world.O
tters are still mostly
elusive denizens of watery
edges and half-light, so
are notoriously difficult to
count. Survey methods are
contested and actual population numbers
are difficult to estimate. On the surface, the