The water shrew is Britain's largest shrew and an expert aquatic hunter, whose welfare depends on clean, productive waterways and the availability of aquatic invertebrate prey.
Water shrew welfare is inseparable from river water quality and invertebrate abundance. A water shrew in a clean, invertebrate-rich stream can meet its enormous energetic needs with efficient foraging in a small territory. The same animal in a degraded, sediment-laden waterway with reduced invertebrate prey must range further and work harder, with real welfare costs in terms of energetic stress. As with dippers and otters, the water shrew is a welfare indicator species: its presence in good condition signals healthy riverine ecology. Water quality improvement advocacy benefits the water shrew and the entire community of aquatic specialists it represents.