Common otters feed mainly on fish, and the occasional water bird or frog may be taken (3). Up to 15 % of an individual's body weight in fish may be consumed daily (2). Common otters mark their large territories by depositing faeces ('spraints') in various prominent places (3). Breeding can occur throughout the year; two or three cubs are usually born in a den known as a holt, and 10 weeks later the cubs emerge above ground with their mother (3). Common otter mothers care for their offspring for about a year; it may take the cubs up to 18 months to learn to fish, and the mother helps this learning process by releasing live fish for the cubs to re-catch (2).