- Lifespan
- 5–10 years in the wild; up to 13 years in captivity
- Size & Weight
- 32–40 cm body length; 0.5–0.9 kg
- Habitat
- Semi-aquatic mammal found near freshwater bodies including rivers, streams, lakes, marshes, and wetlands with good vegetation cover.
- UK Distribution
- Established feral populations throughout much of mainland Britain and parts of Ireland, particularly in East Anglia, southern England, and Wales; present year-round as a resident species.
- Diet
- Carnivorous; hunts small mammals, birds, fish, frogs, and aquatic invertebrates; occasionally takes rabbits and poultry.
- Prey
- Water voles, shrews, fish (especially eels and trout), frogs, coots, moorhens, crayfish, aquatic insects
- Predators
- Birds of prey (especially golden eagles and sea eagles in Scotland), foxes, otters, and larger mammals; eggs and young vulnerable to corvids and herons
- Mating Season
- March to April
- Breeding
- Gestation period 42–45 days; litter size 3–7 kits (average 5); single brood per year; kits born in burrows or dense vegetation; weaned at 5 weeks.
- Behaviour
- Solitary and territorial, highly aquatic and agile swimmers with partially webbed feet. Primarily nocturnal and crepuscular; males have larger territories than females and may engage in scent-marking to defend range.