Lutra lutra
AKA: Eurasian otter, river otter, Old World otter
The otter is a large semi-aquatic mammal with a long streamlined body, a long powerful cylindrical, tapering tail, short legs, and large webbed feet. They can measure up to c. 1.5m long and can weigh up to 12kg. They have a large flat head, and are brown in colour with a light brown/creamy-coloured chin and throat.
In the water, otters are agile swimmers, and on land can run surprisingly fast over short distances. They swim with just their head showing above the water, whereas mink swim with their heads and backs exposed. Otters live in dens which they make in tree root systems, holes in river banks or under rock formations. The dens are known as holts.
Otters breed all through the year and females have 2-3 cubs usually between May and August. Newborn cubs measure around 12cm long and can swim at 3 months. They are independent from their mothers at 10-12 months and start breeding at 2 years old.
What they eat
Otters eat fish (particularly eels), frogs, crustaceans (such as crayfish), small birds and eggs. Small mammals may also be taken.
Where and when to see them
Look near clean rivers, and wetlands with plenty of bank-side vegetation.
Generally, otters are quite elusive, with large ranges and are active at night (nocturnal), so it easier to see their field signs than the animals themselves.
They are active and breed all year round so look out for them and their field signs when walking near wetlands, rivers and coastlines.
!Take care near waterbodies!
View an otter 10km distribution map of Wales
Legal status
Protected in the UK under the Wildlife and Countryside Act, 1981. Priority Species under the UK Post-2010 Biodiversity Framework. European Protected Species under Annex IV of the European Habitats Directive. Listed as Near Threatened on the global IUCN Red List of Threatened Species.
Field signs
Footprints
Look at the edge of river banks, in gravel, sand, mud and snow. They have 5 toes, but sometimes only 4 toes appear in the print. The prints are large and round (5-7cm in width, 6-9cm in length) and may/may not have claw marks. Occasionally their tail may leave an impression in the substrate too.
Spraints (Droppings)
Spraints are left on prominent features such as rocks, logs, storm drains and bridge supports close to water. They can be variable in colour but are often greenish, grey-black. They contain fish scales, bones, crustacean shells, feathers or fur. They are sweet smelling, often likened to a cross between jasmine tea or laurel flowers and fresh fish. They are rounded and tarry.
Anal jelly
A clear (although can also be coloured) jelly-like substance that smells the same, and is deposited in similar areas as spraint. It is thought to be the mucus lining of the gut that protects the otter from sharp fish bones.
Similar species
American mink (Neovision vison)
American mink are non-native mammals that are now well established throughout the UK. They were originally kept on fur farms until they escaped or were intentionally freed in the 1950s. Unfortunately, it is a formidable predator and will feed on anything it can catch including ground-nesting birds and water voles.
It is a small sleek mammal with brown-black fur and narrow ferret-like face. It has a pointy nose, a distinctively pointed white chin and white throat (a ‘bib’).
Mink droppings (also called spraints or scat) are dark, often have a twisted, tapered appearance and contain fur, bones and feathers. They usually have a very bad odour.
Mink footprints often show claw impressions; the claws can often join with the toepad to create a teardrop shaped print.
Other links
Did you know?
A group of otters is called a romp.