Field Guide
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Water Shrew
Neomys fodiens
Not yet photographed by the community
Dives for aquatic prey; fringed hind feet aid swimming.
Species Profile
UK Biodiversity Action Plan priority species; widespread but declining due to river pollution and habitat loss; currently classified as Data Deficient on the IUCN Red List
- Lifespan
- 2–3 years in the wild
- Size & Weight
- 12–15 cm body length; 10–16 g
- Habitat
- Fast-flowing, clean streams and rivers with dense bankside vegetation and rocky substrates, occasionally found in ditches and canal systems.
- UK Distribution
- Found throughout much of mainland Britain north to central Scotland, though absent from Ireland and southern coastal areas; resident year-round.
- Diet
- Aquatic invertebrates including freshwater shrimp, insect larvae, small fish, and aquatic worms; hunts by diving and walking along the riverbed.
- Prey
- Freshwater shrimp (Gammarus), mayfly and caddisfly larvae, bloodworms, sticklebacks, water boatmen
- Predators
- Owls (particularly Barn Owls), herons, pike, cormorants, and foxes
- Mating Season
- April to August
- Breeding
- Two litters per year; 5–8 young per litter; gestation period approximately 21–22 days; young weaned at 4–6 weeks.
- Behaviour
- Highly aquatic and active both day and night; uses venomous saliva (toxic to small prey) to subdue invertebrates. Solitary and territorial, marking territory with scent glands. Can dive for up to 30 seconds and carries an air bubble in its fur for insulation.
- •The water shrew is one of only two venomous British mammals; its saliva contains toxins that paralyse small prey
- •It has fringes of stiff hairs on its hind feet and tail that act as rudders and paddles for swimming
- •The water shrew must eat approximately 80–90% of its body weight daily to maintain its high metabolism
- •It is one of the smallest carnivorous mammals in Britain and can hunt prey almost as large as itself
- •Its fur is unusual among shrews, being water-resistant and possessing an air-trapping undercoat for thermoregulation
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