Bats found in national park woodland have not been seen in Britain before

The rare alcathoe's bat is widespread in Europe, but it was thought that the English Channel had acted as a barrier, stopping the species establishing itself in this country.

But Prof John Altringham of Leeds University and Prof Roger Butlin of Sheffield University have found the tiny creature in a Forestry Commission woodland in North Yorkshire.

According to the academics the creature is only as big as the end of an adult's thumb. They say it could have been living in Britain for years but remained undetected.

Prof Altringham said: "Over a third of the UK's native land mammal species are bats, making them by far the biggest contributor to our mammalian diversity. This discovery takes the number of bat species established in the UK from 16 to 17.

"Most of the bats were captured as they entered underground 'swarming' sites, where bats gather to mate before going into hibernation."

Prof Butlin said a second colony of Alcathoe's bat had been discovered at a site in the South Downs in Sussex, which added further weight to the argument they had been in Britain for some time.

The newly-discovered species is very similar to other indigenous bats, meaning experts may have missed its existence for some years.

The Yorkshire discovery was made in the North York Moors National Park. Forestry Commission wildlife officer Brian Walker said: "We have some incredibly rich bat habitats in North Yorkshire."