Two bats from one of the world's most endangered species are now roosting in a former Ministry of Defence (MoD) bunker on a firing range.
There are thought to be 4,000 greater horseshoe bats in the UK
Military chiefs have even carried out work on the buildings in Lulworth Cove, Dorset, to shield the greater horseshoe bats from light and draughts.
The creatures are one of the UK's rarest species and numbers are reported to be in dramatic decline.
The uncultivated range provides a rich source of insects for them to feed on.
Secretary of State for Defence John Reid said: "We need to maintain and sustain the MoD's land to the highest standards in every respect today, to meet the training and operational needs for the servicemen and women of tomorrow.
"But as an organisation that uses rural land we are also very aware of our responsibility to nurture and conserve the environment where we work.
"Lulworth's bats are just one of many success stories that reflect how the MoD goes the extra mile to preserve and protect the environment and its inhabitants."
Intensive farming practices have resulted in the deaths of thousands of the greater horseshoe bats over the decades.
Cora Taylor, Range Warden for Babcock Defence Services, who are contracted by the MoD to manage the Lulworth Cove ranges, said: "We are now leaving them in peace over Christmas and crossing our fingers that the bats will start a family in the New Year."