Water voles fighting back in Sussex
22 April 2014 Last updated at 07:45 BST
The water vole is one of Britain's fastest declining mammals, but it seems like it's fighting back in the Sussex countryside.
Things like habitat loss, changing weather and predators mean that numbers of creatures are falling.
In Sussex last year, the water voles' habitat was changed dramatically when sea defences were knocked down and a new nature reserve was created.
A research team is keeping an eye on the area's water vole population - and it looks like the animals are surviving and have moved into their new home.
Watch Ricky's report.