These ferocious little predators are most unusual amongst mammals in possessing venomous saliva. A mild toxin secreted into the saliva in the mouth helps to stun the prey. Even humans can feel the effects of this if bitten by a water shrew – a painful red rash appears at the site of the bite.
In addition to their venom, water shrews posses a second unusual weapon. They have iron deposits in the enamel of their teeth, making them more resistant to wear and tear. This is essential for the shrew’s survival; water shrews have voracious appetites and must catch and eat about half their own body weight in invertebrates every 24-hours to stay alive.
It is the largest of the British shrews, and the only one of our species adapted to life in the water. Stiff hairs border the feet and form a keel on the underside of the tail which aid in swimming.