Rare bats whose roost in a 16th century thatched barn has been designated as a nature reserve are to be tracked by a team of national "bat detectors".
There are eight known British colonies of Barbastelle bat
The Barbastelle bats were fitted with radio transmitters so National Trust and Natural England teams can monitor their flight over Norfolk's night sky.
Paston Great Barn is one of only a handful of roosts known in the UK.
Keith Zealand, of Sheringham Park, said the project aims to uncover more of the endangered creatures' breeding grounds.
Mr Zealand said: "Norfolk is extremely important for Barbastelle bats and until about five years ago the only maternity colony known in the UK was at Paston Great Barn national nature reserve in the north-east of the county.
"Since then, a handful of additional breeding groups have been found, but there must still be more out there just waiting to be discovered."
The project will run from May to September, with volunteers trained to track the bats' locations and habits throughout the night.
The Barbastelle bat is considered rare and declining around Europe due to lack of habitat and human disturbance.
Ash Murray, from Natural England who, with the National Trust, are funding the project, said: "We were carrying out some detailed surveys at Paston Great Barn NNR and wanted to get to know how the Barbastelles are using the surrounding landscape.
"It was natural that we teamed up with the National Trust to pool our resources, get more people involved and hopefully uncover more about these secretive creatures.
Mr Zealand added: "We have confirmed recordings of bats at Felbrigg and Sheringham in the early evening.
"There could be Barbastelle discoveries around the corner."