Why the riverbank tells a story

British rivers and waterways are busy places, even when they look still. Otters have made a remarkable comeback across the UK, from lowland rivers like the Great Ouse to upland streams in Wales and Scotland. Yet these shy, nocturnal mammals are rarely seen. What you will find, if you know where to look, is a trail of signs. Learning to read spraint, prints and other clues turns an ordinary riverside walk into a quiet detective story. The best part? You do not need special equipment, just patience, a keen eye and a respect for the animals that made them.

Spraint: the otter's calling card

Spraint is the proper name for otter droppings, and it is the single most reliable sign you can find. Fresh spraint smells distinctly of fish, sometimes with a hint of hay or jasmine tea. That smell is not accidental: it carries chemical messages that mark territory and advertise the otter's presence to others. You will often find spraint on prominent objects — flat rocks, logs, bridge ledges and tussocks — where it is easily sniffed by passing otters. Look for dark, almost black deposits, two to five centimetres long. Fresh spraint is glossy and may contain fish bones, scales or fragments of crayfish shell. As it ages, it turns grey and crumbly. If you find several spraints in one spot, you have discovered a latrine, a regularly used marking site. Do not touch it: not only is it unsanitary, but disturbing it can upset the otter's routine.

Prints and tracks: reading the mud

Look for five-toed prints in soft mud beside fallen trees and under bridges. Otter prints are broad and rounded, about six to seven centimetres across, with a wide pad and five distinct toes. In wet mud, you may also see webbing between the toes, a clear giveaway. Compare them with dog prints, which have four toes and no webbing. Otter tracks often lead from the water to a spraint site or a resting place, and you might spot a tail drag mark between the prints. The best places to look are muddy banks, sandbanks and gravel bars, especially after rain has softened the ground. Check under bridges, where otters frequently travel and leave prints on ledges or in the mud below. Fallen trees are another favourite, providing both a crossing point and a natural sprainting platform.

Other riverside signs to watch for

Spraint and prints are just the beginning. Otters leave a range of other clues that tell you they are about.

• Slides: Smooth, muddy or grassy chutes running down a bank into the water. Otters use these for quick, playful entry. Look for claw marks in the mud and a well-worn path leading to the slide.
• Couches: Flattened patches of vegetation, often on islands or secluded banks, where otters rest during the day. They may be lined with moss or grass.
• Holts: Den entrances, usually under tree roots, rock crevices or in the riverbank itself. They are often hidden and may have a worn path leading to the water. Never disturb a holt.
• Feeding remains: Fish heads, bones, scales, crayfish claws or frog legs left on a flat rock or bank. Otters often eat their catch on a favourite perch, leaving a tell-tale mess.

How to look without disturbing

Otter signs are a privilege to find, but the animals themselves are protected by UK law. It is an offence to disturb them, so always observe from a distance and keep dogs on a lead near water. Early morning is the best time to look, before rain washes away tracks and spraint scent. Wear dull clothing, move slowly and use binoculars if you have them. Never touch spraint, and do not follow tracks into dense vegetation where you might disturb a resting otter. Remember that the otter is probably aware of you long before you see it. If you are lucky enough to spot one, enjoy the moment quietly and let it go about its business. The signs will still be there tomorrow, waiting to be read.