Animal lovers are being asked to look out for Britain's most endangered mammal, the water vole.
British Waterways, in charge of the UK's canals and rivers, is launching a survey of water voles and other wildlife on its property.
The animal is in danger because its habitat is vanishing, and it's being threatened by American mink, which have recently arrived in Britain.
The group says knowing where voles live is vital if we are to protect them.
Water vole facts
Live in burrows on river banks
Are hunted by stoats, owls, herons, large fish, foxes and cats
Their homes are threatened by farming methods
Their greatest threat is the American mink
If we know where they live, then we can do more to protect their habitat.
But if you do go vole-spotting, you should be careful that you don't mix them up with brown rats.
Voles have small hidden ears, silky brown fur, a blunt nose and a short furry tail, whereas brown rats have big ears, grey-brown fur, a pointed nose and a long, pink, hairless tail.
Water voles also feed on vegetation while rats eat lots of different things.
To find out more, click on the link to the top right of this story.