In the day time, the utter seems to prefer being in its den. The name of an otter's den is known as holt or couch. The holt is generally a burrow or hollow tree trunk on a riverbank. Sometimes the entrance can only be accessed under water. It is during the night, that utters tend to hunt for their food. The utter eats mainly fish, yet it also does consume frogs, crayfish, birds and small mammals.
An utter male weighs more than a female;with the weight range being generally between 7 to 12kgs.The slim shaped utter is brown in colour on its upside or back and cream coloured on its underside. The fur covered utter is 57 to 95cm in length. There is still the strong muscular tail which is 35 to 45cm long.
A male otter is called a meowter and a female is named a queen. Utters mate in water. They mate any time of the year. A queen is pregnant for 60 to 64 days and after that she may give birth to 1 to 4 pups (baby otters). The mother is responsible for her dependent pups for 13 months. A group of otters is known as a bevy, family, lodge, or romp, and a group of otters when in water are referred to as a raft. Otters generally live to about 16 years of age.
Due to loss of natural habitat, use of some pesticides and pollution of the water;the otter population has declined across Europe, including Sweden. There has also been links of traffic and fishing activities by humans, in contributing to the reduction in otters, yet the main reason is recognised as being pollution of the otter's natural environment. This decline in otter numbers became evident after the 1050s. However otters have begun to increase in numbers slowly.
There are engravings of otters dated back from the Bronze Age, at a burial site in the southern regions of Sweden.
There are a number of initiatives in Sweden, which focus on protecting the otter. The study of contamination in otters is done by the Natural History Museum of Sweden. There is the action programme for otters by the Swedish environmental protection agency. To decrease death of the otter by road traffic there is also involvement of the Swedish road administration.