This video says about itself:
Counting bats as they emerge from a roost. Lesser Horseshoe (Rhinolophus hipposideros).From the BBC:
Rare bats take to new villa roostGreater horseshoe bat: here.One of the rarest bats in Europe has begun colonising a new summer roost, created four years ago at an historic Roman site in Gloucestershire.
The lesser horseshoe bat has finally set up home in the roof of the visitor centre at Chedworth Roman Villa.
The project is part of a National Trust initiative to encourage and support the UK’s declining bat population.
And here.
