A maternity roost, where females come together to have their pups, of Leisler’s bats was found near Newton Stewart in a plantation in Galloway Forest Park.
It is only the second such breeding site for the mammal ever found in Scotland.
Foresters say there are at least 27 females in the roost, which is in Norway spruce trees.
Three of the furry creatures, which were once known as hairy-armed bats, have been fitted with radio tags to allow their movements to be monitored.
The work is being carried out as part of the Scottish Leisler’s Bat Project.
Experts say the new find is a good sign for the rare bats, and shows Galloway’s plantation forests are playing an important part in helping the species to thrive.
The only other recorded find of a maternity roost was in 2012 in Culzean country park, where 40 adult females were found.
Gareth Ventress, environment forester with Forest Enterprise Scotland, an agency of the Forestry Commission, is involved in the project.
“Since 2010, a group of bat experts and volunteers have been trying to find out more about the rare Leisler’s bat in Scotland,” he said.
“At first we knew that bat boxes on the national forest estate were being used by Leisler’s bats in the Cree Valley and Glentrool area of Galloway. Unfortunately there was no evidence of breeding at all.
“Over the next few years research continued but it proved difficult to find any signs of breeding. In 2016 we did find a juvenile male Leisler’s in Galloway, which confirmed that there must be a roost nearby.
“The team decided to come back again this July and were successful in finding lactating Leisler’s bats with the help of sonic lures and specialist bat nets. We radio-tagged three adult female bats and were able to track them to their maternity roosts.
“We’re really pleased that our forests are providing a safe haven for this wonderful and rare bat.”
The Leisler’s is a mid-sized bat, measuring between 5cm and 7cm long with a wingspan of 26cm to 32cm.
It is one of just 10 bat species found in Scotland, all of which are found in Galloway Forest Park – which is also home to the only known Scottish roost for the Brandt’s bat.
Although widely distributed throughout the UK the Leisler’s bat is not common – especially in Scotland – and few maternity roosts have been located.
In Galloway the bat is found in several places using bat boxes.
The males will fly around a roost slowly calling for females to join his harem, which can contain up to nine females.