The water shrew (Neomys fodiens) is Britain's largest native shrew and a specialist of clean, fast-flowing waterways. Rarely seen but widely distributed, water shrews are indicators of good water quality and riparian habitat health. Their welfare is inseparable from the health of their aquatic environment.
Water shrews have dense, waterproof fur with silver-white undersides, and stiff hairs on their feet that trap air bubbles for buoyancy. They are capable swimmers and divers, hunting aquatic invertebrates, small fish, and amphibians along water margins. Uniquely among British mammals, water shrews possess venomous saliva that helps subdue prey larger than themselves. They are extremely active, requiring continuous feeding to maintain their high metabolic rate.
Water shrews require: clean, well-oxygenated water with abundant aquatic invertebrate prey, dense bankside vegetation for cover and nesting, and undisturbed bank structures for burrow creation. They are highly sensitive to water qualityâpollution events that reduce invertebrate communities eliminate shrew prey and habitat simultaneously. Agricultural intensification, river management, and bank clearance all degrade water shrew habitat.
Cat predation near waterways is a significant mortality cause. Secondarily, poisoning through the food chainâbioaccumulation of pesticides in aquatic invertebratesâaffects shrews consuming contaminated prey. Pollution events causing sudden prey loss force shrews to starve rapidly due to their high metabolic demands.
Riparian habitat managementâmaintaining bankside vegetation, reducing pesticide use adjacent to waterways, and supporting water quality through reduced agricultural runoffâdirectly supports water shrew welfare. The Species on the Edge program has highlighted water shrews as conservation priorities in certain regions.
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