Otter

 
The elusive otter is one of our top predators, feeding mainly on fish (particularly eels and salmonids), waterbirds, amphibians and crustaceans.
Otters have stocky legs, a long, streamlined body, and a broad muzzle with prominent, sensitive whiskers. They are perfectly adapted to a semi-aquatic life. They have webbed feet, dense fur to keep them warm, and can close their ears and nose when underwater. Otters can see as well under water as they can above it, allowing them to hunt for fish. 
Otters have their cubs in underground burrows, known as 'holts'. Excellent and lithe swimmers, the young are in the water by 10 weeks of age. 
Seeing the signs of otters is far easier than seeing the animals themselves. Along riverbanks and waterways, look for five-toed footprints (about 6-7cm long) and droppings or 'spraints'. Otters leave spraints in prominent places, such as fallen trees, weirs and bridges, as 'scented messages', helping them to find mates and defend territories. They contain visible fish bones and have a distinctive, pleasant smell, reminiscent of jasmine tea!
Road traffic accidents; drowning in fish and lobster traps; and pollution such as oil and PCBs.
They are fully protected in the UK under Schedule 5 of the Wildlife and Countryside Act 1981.