Using Trail Cameras to Watch Nocturnal River Wildlife

There is a particular sort of quiet on a British riverbank at two in the morning. The water keeps up its low conversation with the gravel, a moorhen mutters somewhere upstream, and everything with fur is going about its business entirely unaware that you exist. That is precisely the point. A trail camera left quietly in the right place lets you see the river as it really is, rather than the sanitised daytime version with the dog walkers and the paddleboarders.

Why the Hours After Dark Matter Most

Most of our riverside mammals are creatures of the night, or at least of the twilight fringes either side of it. Otters, badgers, mink, foxes, water shrews, the occasional polecat in the western counties, hedgehogs working the towpath hedges, and bats stitching their way over the water at dusk. Daylight gives you kingfishers and herons and a great deal of nothing else. Darkness gives you the whole cast.

The good news is that these animals are habitually predictable. They use the same runs, the same crossing points, the same latrine stones, often within a few minutes of the same time each night. Once you have found one of those places, you have found a theatre.

Finding a Spot Worth Watching

A badger path is usually obvious once you know the look of it: a well-worn run perhaps 20–30cm wide, often with a low arch of nettles or a gap under a fence where the bottom wire is polished and pushed up. Look for snagged grey hairs on barbed wire and a cluster of shallow scrapes nearby, which is a latrine. Set the camera overlooking the narrowest point of the run, where the animal has to commit.

Otters leave spraint on flat-topped stones, fallen trunks and ledges beneath bridges, particularly where a tributary joins the main river or where a bank makes a natural pinch point. Fresh spraint is black and tarry, full of fish scales and tiny bones, and smells faintly of jasmine tea or new-mown hay. Also worth hunting for: five-toed prints in soft mud and smooth, worn slides down steep banks. Set your camera to cover the stone and a couple of metres of bank on either side, not just the stone itself.

Setting the Camera Low and Getting It Right

Most trail camera mistakes are height mistakes. A camera strapped at chest height on a riverbank photographs the backs of heads and a lot of empty water.

• Height: roughly 40–60cm from the ground. Badgers, otters and hedgehogs are low-slung animals; the lens should be near their eye level.
• Angle: tilt it down 10–15 degrees so the subject lands in the centre of the frame rather than marching off the bottom edge.
• Distance: two to four metres back from the path or spraint stone, far enough to get the whole animal in shot.
• Mounting: a stout post or a mature trunk. A slender sapling will sway in the wind and fill your card with blurry leaves.
• Illumination: choose a no-glow, or black, infrared model where you can afford one. Cheaper red-glow cameras emit a faint red light that many mammals can see, and a white flash is out of the question on a waterway, both for the animals and for anyone living nearby.
• Settings: a three-shot photo burst or a ten to twenty second video, a short trigger interval, and medium sensitivity so that swaying grass does not trigger hundreds of empty frames.

Reading What Comes Back

Otters move with a sinuous, low, bounding gait and show a thick tail tapering sharply from a broad base; you will often catch pairs, or a female with cubs. Badgers are unmistakable, rolling along with that banded face. Mink are smaller, uniform dark brown, and move in a businesslike bound. Foxes are easy. Water voles look like small, blunt-nosed barrels with short tails, swimming with the head up, whereas a brown rat has a pointed snout and a long, thin tail. The timestamp matters as much as the image: after a fortnight you will know your badger's schedule to within ten minutes.

The Dawn Check and Looking After the Kit

Check the camera at first light. Most nocturnal animals are heading for their beds by then, few people are about, and you are less likely to be noticed. Keep the visit brief and do not linger, however tempting it is to sit and watch a while.

• Swap the memory card and batteries in one go, so you never leave the camera open to the weather.
• Keep a silica gel sachet in the housing and check the rubber gasket for grit; condensation is the death of riverside cameras.
• Face the lens north or east so low morning sun does not flare across the sensor.
• Use lithium batteries in winter, as ordinary rechargeables fade badly in the cold.
• Lock the camera with a cable, tuck the strap out of sight, and avoid handling it with food-scented hands.

Watching Without Interfering

Badgers and their setts are protected in law, and otters are protected wherever they are found, including their holts. Never dig, block, or shine a light into a sett or a holt, and never bait an animal towards a road or a garden boundary just to get a better picture. Keep the exact location of a sett or a spraint site to yourself; share timestamps and species records rather than grid references, and pass your more interesting sightings to your county records centre.

Do talk to your neighbours, too. A quiet word with the landowner, the angling club and the farmer about what you are doing and why saves a great deal of suspicion later. Riverside living works best when the people along the bank and the wildlife in it manage to ignore one another politely, and a well-placed camera, checked at dawn and left alone, is the quietest way there is of being let in on the secret.