By Alex Kirby
BBC News Online environment correspondent
Researchers have found five colonies of rare bats in woodland on the Isle of Wight, off the southern English coast.
Very few Barbastelle maternity roosts are known
They discovered two colonies of the Barbastelle bat, thought to number only about 5,000 individuals across the UK.
The People's Trust for Endangered Species says its team also discovered three colonies of another species listed as endangered, Bechstein's bat.
There are believed to be no more than 1,500 Bechstein's bats in the country, and PTES is very pleased by the finds.
Dr Valerie Keeble, chief executive of PTES, which owns the site, described the findings as "truly exciting and of great conservation significance".
She said: "It is wonderful news that we have successfully identified these new roosts, four of which are actually on our reserve and one in woodland close by.
"As far as we can tell, the bats seem to be entirely dependent on these woodlands for feeding and roosting, and it is encouraging for us to know that our management of the woods for the last 12 years seems to have been just right for these rare species."
The researchers found one male and one maternity roost for the Barbastelles, and three maternity roosts for the Bechstein's bats.
All were in Briddlesford woods, where nine of the 16 UK bat species have been recorded.
Both species, which can live for 25-30 years, produce just one young annually, and the females roost together to give birth.
The researchers were led by Ian Davidson-Watts, who said: "With such a unique assemblage of bats present at one site, Briddlesford has really proved to be a site of extraordinary national and international conservation significance.
Caught and followed
"The Barbastelle maternity colony, one of only eight known in the UK, is a first for the Isle of Wight." The survey was funded by English Nature jointly with PTES.
Mr Davidson-Watts told BBC News Online: "We found the bats with ultrasonic detectors picking up their echo-location signals, which are outside the range of our hearing system.
"We used soft mist nets to catch the bats then attached very small transmitters to them, weighing less than half a gram, with surgical glue that had been tested on humans.
"Using radio telemetry, we were able to track them back to their roosts. Barbastelles tend to roost under bark, but we were surprised to find the maternity roosts were often in woodpecker holes in ash trees.
"These are probably the rarest mammals in the UK, and they're declining because we're losing our ancient woodlands."
Images copyright and courtesy of Ian Davidson-Watts.