Territory: the otter is a shy, solitary animal and needs a large territory. One male has a territory of up to 40km of clean, undisturbed riverbank. It regularly patrols the territory, marking it here and there with droppings called 'spraints'. These have a scent which tells other otters that the territory is already occupied. Female otters also spraint to mark territory. Female otters with cubs live in holt which is often away from the riverbank and well hidden in a smaller territory within the male's territory, who is usually the cubs' father.
Daily Life: otters are mainly nocturnal and hunt in open, marshy places, rivers, lakes, seashores and estuaries. They will often travel a long way overland, from one river system to another, in search of food. However, the majority of the UK's otters are now found on our wilder coasts. They are strong, agile swimmers and catch fish by chasing them underwater. They grip the prey with sharp teeth and powerful jaws, carrying the catch ashore to eat it. An adult otter needs to eat 20 per cent of its body weight in food every day - about 2.5kg.
In undisturbed areas an otter often spends part of the day playing away from water, near to a 'lying up' den, which is usually under riverside tree roots.
An otter grooms itself frequently and this keeps its coat sleek and waterproof. The coat's long, stiff guard hairs are covered with oil to repel water. The thick underfur traps an insulating layer of air and the skin never gets wet.
Breeding: otters breed throughout the year. The dog and bitch live separate lives, meeting only for mating. Usually there are two or more females living in a male's territory and when they are receptive, he will mate with all of them. They find each other by scent and by whistling. The two often playfully chase each other and pretend to fight.
The gestation period is about 62 days and during this time the bitch builds a holt, an underground burrow, often under the roots of a waterside tree. In Scotland, where otters frequent seashores and lochs, the holt may be in a more open space such as a rocky cairn. The holt is lined with grass or moss and this is where a litter of two or three cubs is born. At birth they are about 12cm in length and are covered in very fine grey fur; their eyes open when they are four or five weeks old. The cubs are helpless for the first 6 weeks of their lives, relying entirely on their mother's milk. The mother drives the father away as soon as the cubs are born and he plays no part in their upbringing. Coastal otters need access to freshwater pools to wash the salt off their fur - otherwise this affects the insulation that the fur provides.
The cubs develop an adult waterproof coat at two or three months and this is when their mother teaches them to swim. To begin with they are often reluctant to go into the water and may have to be pushed in! An otter family is very playful and enjoys sliding games, using a steep snowy or muddy river bank to toboggan down on their chests, forepaws tucked in! The young soon become proficient underwater hunters and the family splits up when the cubs are about a year old. They may stay on in the mother's territory for a few more months and then leave to look for territories of their own.Read More: Otters and Humans