The Scented Signpost: What Otter Spraints Are

An otter spraint is much more than a dropping. It is a message left on a stone, a tussock, or a bridge ledge, carrying scent from the otter’s anal glands. Each spraint holds a chemical signature that can tell other otters who passed by, whether they were male or female, and sometimes whether they were ready to breed. In a British river, where otters are mostly nocturnal and secretive, these dark, oily deposits are often the clearest evidence that a animal is present.

Fresh spraints are usually black or dark brown, sometimes greenish, and often contain visible fish scales, bones, or eel vertebrae. They may be tarry and soft or more crumbly as they age. The scent is distinctive: many describe it as mown hay, fish oil, or a faintly sweet tea-like smell. Old spraints weather to a paler grey or white and can be mistaken for bird droppings, so look for the shape and the remains inside. A single spraint is a clue; a collection of them is a conversation.

Where to Look for Spraints on a British River

Otters like to leave their marks where they will be found. On lowland rivers, canals, and lochs, the best places are prominent, dry, and close to water. Think of them as noticeboards along a watery path.

• Bridges and culverts: check ledges, abutments, and the tops of stones just above the waterline. Search 10–20 metres either side, especially under the first arch.
• Boulders and fallen trees: flat-topped rocks, root plates, and half-submerged logs are classic spraint sites. Look for dark splats on top, not underneath.
• Confluences and weir pools: where tributaries meet or water slows, otters often pause, feed, and mark. Islands and gravel bars are worth a careful scan.
• Bank features: grassy tussocks, earth ledges, and the flat tops of eroded banks. In marshes, check raised hummocks and the edges of reed beds.
• Latrines: some spots are used repeatedly, building up a collection of spraints. These are gold dust for surveyors and often sit on a stone, a mound, or a path edge.

Go early in the morning, after a dry spell if possible, as heavy rain can wash signs away. Move slowly, keep to the bank, and avoid trampling vegetation. A torch helps under bridges, but never disturb an otter if you are lucky enough to see one.

Territory and Social Life Written in Scent

Otters are not strictly territorial in the way a robin defends a garden. Their home ranges overlap, especially between males and females, and spraints act as a polite but firm notice system. By marking regularly, an otter advertises its presence and reduces the need for costly fights. Spraints at the edge of a range may signal a boundary; those in the core may simply say “I am here.”

Patterns of sprainting change with the seasons, water levels, and food supply. A male otter may range over 20–40 kilometres of river, while a female with cubs uses a smaller area. When cubs are growing, a mother may spraint more often around a favoured holt or feeding pool. Juveniles dispersing through the countryside leave spraints in new places, which is how populations slowly recolonise catchments. A sudden cluster of fresh spraints can mark a shift in range after a drought, flood, or pollution incident. They are not a precise map, but they are a living diary of otter society.

Reading Diet from a Splat of Spraint

Because spraints contain indigestible remains, they offer a free sample of what an otter has been eating. You do not need a laboratory to notice the main clues, though careful analysis can reveal far more.

• Fish: scales, fin rays, and bones are common. Eel vertebrae look like small beads; salmon and trout scales are larger and more silvery. Bullhead, stone loach, minnow, roach, dace, chub, and pike all appear in British spraints.
• Amphibians: frog and toad bones turn up in spring, especially in ponds and marshy ditches.
• Crustaceans: pieces of crayfish shell, including the invasive signal crayfish, can be abundant in some catchments.
• Other prey: feathers, small mammal fur, and insect remains show that otters are opportunistic, though fish usually dominate.

Seasonal shifts matter. A spraint full of eel bones in summer tells a different story from one packed with frog remains in March. Over time, these clues reveal which stretches of river are important feeding grounds. They can also flag problems: if spraints contain few fish and more secondary prey, the river may be suffering from siltation, low oxygen, or a lack of spawning habitat.

Monitoring Otters: Practical Survey and Ethics

Spraints are the foundation of otter monitoring across the UK. Standard surveys walk fixed stretches of river, often around bridges and accessible banks, and record the presence or absence of spraints. Repeated over years, this simple method shows whether otters are expanding, declining, or holding steady. More detailed studies use spraint DNA to identify individuals, sex ratios, and even genetic health, all without catching a single otter.

If you want to survey your local patch, keep it simple and responsible. Record the date, grid reference, and what you found. Photograph spraints rather than collecting them unless you have the necessary permission. Otter spraints can be collected for scientific study, but check with the relevant statutory nature conservation body first, as otters are protected under the Wildlife and Countryside Act 1981. Never handle spraints with bare hands; use a stick and gloves, and wash afterwards. Keep disturbance to a minimum, especially near holts, and follow biosecurity rules to avoid spreading invasive plants or diseases between sites.

Countryside Stories in a Changing Landscape

Every spraint tells a small countryside story. A line of fresh marks under a old stone bridge may mean otters are using a restored stretch of river. A latrine beside a new wetland scrape shows that habitat creation is working. A lack of spraints after a pollution incident is a warning that a catchment needs help. For volunteers, river trusts, and wildlife recorders, these signs turn a quiet walk into a survey and a walk into a conversation with the landscape.

Otters have recovered remarkably in Britain since the pesticide problems of the twentieth century, and spraints are often the first sign that they have returned to a river, canal, or estuary. Look for them on your next waterside walk. You will not always find them, but when you do, you are reading a message left by one of our most elusive mammals — a message about food, territory, and the health of the water between the banks.