The water shrew (Neomys fodiens) is Britain's largest shrew and an indicator of high-quality freshwater habitats. It is rarely seen but widely distributed in clean-water streams and rivers, where its welfare depends on aquatic invertebrate prey and undisturbed bank vegetation.
Water shrews in polluted streams experience disrupted foraging: invertebrate community collapse from pesticide runoff eliminates their primary prey. Detergent pollution disrupts fur waterproofing, impairing thermoregulation and swimming ability in cold water. Their extremely high metabolic rate means starvation can occur within hours of food shortage. Otter population recovery (a conservation success) has increased water shrew predation pressure, creating complex multi-species welfare dynamics. Bankside vegetation management — leaving undisturbed margins along stream banks — protects water shrew territories from disturbance and maintains the invertebrate communities they depend on.