How to Spot Otters Along a Quiet British Riverbank

Why a Quiet Riverbank Is the Best Place to Start

The Eurasian otter has made a remarkable return to British rivers since the dark days of the 1970s, and there is now a fair chance that otters are living within a few miles of wherever you are reading this. That does not mean you will simply see one. They are secretive, largely nocturnal animals with territories that can run for many miles of water, and a single otter may pass through a particular stretch only once a fortnight.

The trick is not to go hunting for an otter so much as to learn the signs they leave behind, and then to put yourself in the right place at the right time. Start with a quiet stretch — somewhere with no riverside footpath, no busy road within earshot, and no regular disturbance from dogs, boats or anglers. Otters are creatures of habit and will use the same crossing points, sprainting stones and resting places for years, provided nobody bothers them.

Reading the Bank: Spraints, Footprints and Slides

Long before you see an otter, the bank will tell you whether one is about. Learn these four field signs and you can read a stretch of water in minutes.

• Spraints. Otter droppings are left in conspicuously obvious places — on a flat boulder midstream, a ledge beneath a bridge, a fallen alder trunk, the top of a cattle drink. Fresh ones are dark and tarry; older ones grey and crumbly. They smell faintly of hay, fish and jasmine tea. Because spraints mark territory, they tend to sit at boundaries and at the entrances to favoured stretches.
• Footprints. In soft silt or mud at the water's edge, look for broad five-toed prints up to about seven centimetres across, often with webbing visible between the toes and a drag mark where the tail has swept through. Mink prints are smaller, more star-shaped and never webbed.
• Slides. Where the bank is steep or muddy, otters wear smooth polished chutes down to the water, sometimes several side by side. A slide is often the clearest hint that a holt is close by.
• Runs and couches. Flattened tunnels through bankside vegetation, and patches of trampled reeds or grass where an otter has rested. Look for fish scales and bones nearby.

Finding a Holt Without Disturbing It

A holt is an otter's den, and finding one is a privilege rather than a trophy. They are usually tucked among the roots of a mature alder, crack willow or sycamore, under a bridge arch or an undercut bank, or within a rock pile or reed bed. The entrance is often partly submerged or sits just above the waterline, with a slide leading down and a well-worn run through the grass.

If you find one, back off quietly. Do not approach, do not shine a torch inside, and keep dogs on leads and well away from the water. A disturbed holt may be abandoned altogether, and between late winter and summer it may hold cubs. Watch instead from the opposite bank or from thirty or forty metres upstream, with binoculars.

The Best Hours: Dawn, Dusk and the Quiet Months

Timing matters more than anything else. Otters are most active in the two or three hours around first light and around sunset, and that window is when nearly every good sighting happens. In summer, with long daylight hours, dawn is by far the most productive; you want to be in position before the sun clears the treeline, which in June means around half past four in the morning. In winter, when mornings are dark, late afternoon and dusk are better, and otters will occasionally be abroad in the middle of the day.

Conditions worth seeking out:

• Overcast, mild and drizzly weather, which seems to make otters less cautious and gives you softer light to watch in.
• Low, calm water after a spell of settled weather, when a hunting otter's wake shows clearly on the surface.
• The hours either side of high water on tidal rivers, when fish are pushed into fishable shallows.
• Riffles, pool tails and weir pools, where fish congregate and otters do most of their hunting.

Fieldcraft: How to Watch Without Being Seen

Approach slowly and keep low. Stay off the skyline, crouch behind a bush or a fallen trunk, and wear dull colours. A pair of 8x42 binoculars is ideal. Walk a short distance, then stop and stand still for several minutes, scanning the water twenty or thirty metres ahead rather than staring at your own feet. An otter travelling downstream can cover a mile while you are looking at the mud.

Watch for a V-shaped wake with no bird attached, a sudden boil in a pool as a fish is chased, a loud sharp whistle, or splashing and rolling at the surface. Take a notebook and record dates, water levels and any sightings — over a season or two you will build a picture of where your local otters travel and when.

Living Beside Otters: Small Kindnesses That Make a Difference

If you garden or keep land beside a river, a few modest habits will help enormously. Leave a rough unfenced margin of nettles, sedge and bramble rather than strimming to the water's edge, and avoid cutting banks between March and August. Keep log piles and leave fallen trees in place where they are safe to do so. Keep garden chemicals well away from the water, keep dogs out of sensitive stretches, and avoid night-time spotlights near a holt.

An otter needs somewhere in the region of a kilogram of fish a day, so a healthy river is one with plenty of cover, clean water and natural banks. Give it that, add patience and a quiet dawn, and the reward — a dark shape rolling in the shallows, whiskers first — is worth every early alarm.