Despite an exhaustive two-year search of caves and woods across Ireland, scientists have been unable to find an elusive bat species last seen seven years ago.
Researchers at the Centre for Irish Bat Research (CIBR) fear the Brandt's bat may have become extinct because its natural woodland habitat has been depleted. A wildlife ranger found a female Brandt's stuck to a freshly-painted fence in Glendalough in 2003 and biologists have been looking for more specimens ever since.
But despite an intensive two-year search, none can be found.
"Unfortunately, despite extensive field studies over two years we couldn't find a single Brandt's bat in Ireland," CIBR researcher Daniel Buckley said.
"We genetically screened all bats captured at roosts and in woodlands using forensic DNA methods. These results would suggest that Ireland has only nine resident bat species rather than 10."
Experts believe that the chopping down of native forests is a reason for the decline.
The research, published in the journal Acta Chiropterologica, puts forward a number of theories why roosts of Brandt's bats were not found.
"It is possible that this species is associated with semi-natural woodland, a scarce habitat in Ireland due to historical deforestation and as a consequence this species is very rare here," Dr Emma Boston said.
The bat is among just 26 species of native Irish mammals of which one, the grey wolf (canis lupus), is extinct.
The Red List of Irish land-based mammals says the black rat (rattus rattus) is 'vulnerable', while the Leisler's bat, otter and red squirrel are 'near threatened'.
Information on the Brandt's bat is 'deficient', the guide from the Department of the Environment says, noting that while Irish mammals are generally in good health they face threats, including the cutting down of forests, poor water quality and hunting.