Wildlife writer Jane Adams introduces the sweet, invisible and venomous predator with ultrasonic powers that seems to swim cloaked in mercury
Hidden away in the Dorset countryside lives a small, furry creature you have probably never seen. It has velvety black fur on its upper body, a silvery-white belly and a long, pointed nose with sensitive whiskers for feeling for prey. Its body is about ten centimetres long, its tail three-quarters of that again, and its hind feet are partly webbed and covered in stiff hairs to help it swim.
Over the years, I’ve learnt all sorts of facts about this little mammal. I know it lives next to slow-moving unpolluted streams, in ponds and in water meadows. It nests in banks, with connecting tunnels close to the water. It’s on the move day and night in short frenetic bursts and it has an incredibly high metabolism. It’s also an excellent swimmer, catching aquatic insects, small fish, amphibians, snails, worms and even newts. I know all these things … and yet I have never seen one: the elusive water shrew.
There’s something special, quirky even, about the water shrew. When I’m near freshwater, I am always on the lookout for the slightest glimpse of one. I’ve seen plenty of common and pygmy shrews, with their similar pointy noses to see and carnivorous diets, but they are smaller, less secretive and more numerous than the water shrew. They’re also not as interesting (to me at least) as their weird watery cousins.
So why the fascination?
First, water shrews paralyse their prey with a venomous bite: they then store food, like worms, alive, to be eaten later.
They also use ultrasonic clicks (echolocation) – sounds higher than humans could ever hear – to navigate and communicate. It’s an adaptation usually seen in bats and dolphins – it’s unusual in small mammals.
Lastly, they trap air bubbles in their fur when swimming to help with buoyancy. I’m told it gives them a ghostly outline when seen from above, as if wearing body armour made out of liquid mercury … now that I would love to see.
So, I’ll keep visiting the little stream in the meadow at the back of the village church. I’ll stand for hours on the rickety bridge.
And one day I’ll see one.
I’ve only been waiting 20 years … I guess that’s the appeal of watching wildlife. You never quite know when something special will just appear.
