Why Otters Are Returning to British Waterways

Otters have been part of our rivers for thousands of years, but by the 1970s they had vanished from much of England and Wales. Persistent pesticides accumulating in the food chain, polluted water and the loss of quiet, overgrown banks pushed them back to a few strongholds in Scotland and the West Country. Since then, tighter controls on the worst chemicals, cleaner rivers and full legal protection have helped them creep back — along canals, chalk streams, industrial rivers and even urban stretches that would once have been written off.

That recovery is still fragile and very patchy. Otters are slow to spread, they need a lot of food and they need banks that nobody has tidied to death. If you live beside water, or even a few streets away from a brook that runs into one, you are part of the corridor that decides whether they stay.

Clean Water Comes First

An otter eats roughly a tenth of its body weight in fish, eels, crayfish and amphibians every day, so a stream has to be genuinely productive before it can support one. That means water quality at the small scale, not just the big river downstream.

• Check your drains. Misconnected rainwater pipes, leaking septic tanks and cracked soakaways send sewage and detergent straight to the brook. A single leaking tank can strip a stretch of river of the invertebrates everything else depends on.
• Keep nutrients out. Phosphates from detergents, dishwasher tablets and garden fertiliser feed algae, which starves water of oxygen. Choose phosphate-free products and never wash a car on a driveway that drains to a stream.
• Bin the dog waste. It is a serious nutrient and bacteria source in watercourses. Bag it and take it home if there is no bin.
• Report pollution quickly. Discoloured water, a smell of sewage or a sudden fish kill should go to the Environment Agency's pollution hotline straight away, with a grid reference and photographs if you can take them safely.

Plant Native and Let the Bank Grow Wilder

A good otter bank is messy in the best sense. Native trees such as alder, willow, hawthorn, hazel and blackthorn send roots down that bind the soil and, over the years, create the undercut root plates and hollows that make perfect holts. Below them, soft marginal plants — meadowsweet, purple loosestrife, sedges, water mint, reed canary grass — give cover for frogs, small fish and the insects that feed them.

If you have a garden running down to water, leave a rough, tussocky buffer strip of at least two to three metres unmown between the lawn and the bank. Rough grass slows surface runoff, traps silt and filters out the nutrients and pesticides you would rather not lose to the river. Add a log pile, keep a few fallen branches in the shallows and resist the urge to strim to the water's edge. These small features are exactly what a female otter looks for when she is choosing somewhere to raise cubs.

Keep the Banks Undisturbed

Otters are shy, largely nocturnal and extraordinarily good at going unnoticed. A holt can sit beneath a busy footpath for years without anyone realising. Disturbance is often the difference between a stretch that is used and one that is only passed through.

• Keep dogs out of the water along quiet reaches, particularly between March and September when cubs are small and dependent.
• Cut back vegetation above the bank top only, and leave the waterline alone until late autumn.
• Avoid floodlighting the bank at night. If you want to watch, sit still, stay low, keep downwind and use a red filter on a torch — then move on after a few minutes.
• Never leave food out to attract otters. It draws in rats and foxes, and it teaches a naturally wary animal to associate people with an easy meal.

What to Avoid Near a Stream

Almost everything applied to a garden eventually travels downhill. Slug pellets containing metaldehyde have had their outdoor use withdrawn in Great Britain for good reason, but it is still worth reading the label on any pesticide and choosing only products approved for use near water. Never rinse a sprayer or pour a bucket down a drain — the drain almost certainly leads to a brook.

Dog flea and worm treatments deserve a mention too. Some active ingredients are highly toxic to aquatic invertebrates, and a swimming dog sheds them straight into the water. If your dog spends time in rivers or canals, ask your vet about alternatives with a lower aquatic risk. Ponds and boggy corners do not need chemical treatments at all; a healthy population of frogs, hedgehogs and ground beetles does far more for slugs than any pellet.

Watching, Recording and Reporting

You do not need to see an otter to know one is about. Look for spraint on flat rocks, boulders and bridge ledges — dark, tarry and often faintly jasmine-like — plus five-toed footprints with visible webbing in soft mud, and well-worn runs through bankside vegetation.

Send your records to your local wildlife trust, county mammal group or records centre. Six-figure grid references are ideal, along with the date, the time, what you found and any photograph. Do be discreet about the precise location of a holt or a regular sighting of cubs, and share it with recorders rather than on open forums. Quiet, clean, well-planted and undisturbed — that is all an otter really asks of a British riverbank, and most of it is within reach of the people who live beside one.