The British otter is also known as the European otter because of its vast geographical distribution. Lutra lutra has historically occupied a broad range from Ireland in the west to Japan in the east and the arctic north to the semi-desert of North Africa. Within this range there are 10 recognised subspecies. However today it is scarce or totally absent from many parts of this range as a result of the usual environmental problems namely hunting, habitat loss and pollution.
The British population is now increasing and one of the largest in Europe. They tend to be found along rivers, streams, lakes and marshes as well as around certain coastlines. Although they do swim and feed in the sea they are not sea otters. The genuine Sea Otter is a different species found off the west coast of North America.
The otter has a large territory that may be over 10 miles for a dog otter depending on the food supply and cover that it affords. Within this territory the otter will live in dens that are called holts. These are to be found mostly along river banks under rocks or amongst the root systems of trees for example. Otter habitat is not exclusive to dens, and it is also known in quiet undisturbed areas, for them to sleep above ground in what are known as couches, made from reeds or grass.
The otter is one of Britain's largest carnivores and a male otter may weigh over 15kg although females are somewhat lighter. They have short legs with a long tail and body, which leans forward when walking. This gives rise to the classic arched back outline of an otter travelling on land.
Mink are sometimes mistaken for otters, being the only other semi-aquatic mammal in the British Isles. Mink however, despite having a similar shape to otters are much smaller. They are smaller than a domestic cat and also have much darker, almost black fur and a fluffy tail. Recently with the many escapes and releases of mink from fur farms the feral mink has probably increased in number in many parts of the country with sightings often confused for wild otters. But having seen a British otter at the Sanctuary and read the facts about otters, visitors should not have any problem distinguishing between mink and otters.
Mink can be a threat to young otters but recent observations have indicated that adult otters will chase mink away from their territories.