Tennis balls won't just be be flying around Centre Court at Wimbledon - but also at Slimbridge Wetland Centre in Gloucestershire, where harvest mice have taken up residence.
Conservationists hope the old balls will make perfect nest houses to boost numbers living at the centre.
They have been put in an area of the centre for mammals called Back From The Brink.
Wildfowl and Wetlands Trust mammal manager John Crooks said: "We are hoping it will be a case of game, set and mouse.
"I have cut small penny-sized holes in the balls and put straw inside and they seem to be taking very well to them.
"We have about 30 in our collection here and we are hoping that the tennis balls will make them feel secure so that they breed well this year."
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