Otter field signs and surveys

Otters are very charismatic mammals; they’re inquisitive and playful and can be found in many parts of Britain. However they’re secretive, shy and generally elusive creatures and the chances of seeing one in the wild is very rare. The population has undergone significant decline since the 1970’s due to habitat loss, water pollution and competition from invasive species such as Mink.

Freshwater otters have large territories with females potentially utilising up to 20km of watercourse, with males utilising up to 32km, with vegetation for cover, and plenty of food sources (fish, amphibians, invertebrates).  Given the size of an otter’s territory, you’re more likely to find field signs of an otter than the otter itself.

We’ve recently been carrying out otter surveys near Fort Augustus and as Ecologists it’s predominantly these field signs we’re looking for (although always with the hope of seeing an otter)! Common field signs include spraints (droppings), prints, and feeding remains. In addition you may find resting structures including couches and holts that the otters use. Couches are above ground rest sites in semi-enclosed areas (e.g. under overhanging river banks / tree root plates) whilst holts are subterranean structures only visible by their entrance.

Camera traps are useful tools once you’ve ascertained that otters are using an area, as they can be ‘on-guard’ 24/7 (they don’t require sleep!) and are unlikely to disturb the otters from an area. Should you be lucky enough to get footage they provide you with opportunities to determine how an area is being utilised by the otters, from which you can assess if the otters are merely passing through an area, or if it’s a significant feeding or resting spot.

Sometimes however, you can just get lucky when you’re out and about, here’s a video of an otter family on the Culroy Burn taken back in 2013 whilst surveying for invasive non-native species.

Otters, Field SignsEmma Downie