Though currently thought to be extinct in Liechtenstein and Switzerland, it is now common in Latvia, along the coast of Norway, in the western regions of Spain and Portugal and across Great Britain and Ireland.

[1] It inhabits unpolluted bodies of fresh water such as lakes, streams, rivers, canals and ponds, as long as the food supply is adequate.

[11] In India, it is distributed in the Himalayan foothills, southern Western Ghats and the central Indian landscape.

[14] During the winter and in colder environments, it also feeds on amphibians,[15][16] worms, clams, crustaceans, insects, eggs, birds and sometimes small mammals, including young European beavers.

[19] As with various other mustelid species, otters are capable of overpowering and killing prey significantly larger than themselves, and are known to hunt large waterbirds such as adult greylag geese on occasion.

The Eurasian otter uses its feces, called spraints, to mark its territory and prioritize the use of resources to other group members.

Female otters become sexually mature between 18 and 24 months old and the average age of first breeding is found to be 2+1⁄2 years.

Though long thought to hunt using sight and touch only, evidence is emerging that they may also be able to smell underwater – possibly in a similar manner to the star-nosed mole.

[25][26] The extinct Japanese otter is sometimes considered a subspecies; recent studies have found it to fall outside the subspecific clades comprising L. lutra, so it has been reclassified as a distinct species, but significant uncertainty remains.

[27] The Eurasian otter declined across its range in the second half of the 20th century[28] primarily due to pollution from polychlorinated biphenyls and pesticides such as organochlorine.

A study conducted in 2001, examined whether or not the populations of Eurasian otters suffered from a lack of genetic variability.

The study examined the tissue on the teeth of the skulls and determined the genetic variability based on DNA analysis.