Seeing red

Mike Dilger is underground in Cheddar Caves looking for bats with Roger Martindale, a leading bat expert. They are using red lights for filming because bats are most sensitive to white light and the red light doesn't disturb them. The bats are Britain's most charismatic species, the lesser horseshoe. Unlike other British bats they 'free-hang', so can hang from the roof like pieces of fruit. They twirl round while hanging - like little disco balls - and echolocate to identify prey items on the ground. The bats are in a small crevice, chatting to each other and echolocating, which Roger and Mike can hear with the aid of a bat detector. The public can't come in here as you need a bat license, but you can still see some bats if you visit the public caves. They don't sleep all day, but get restless about lunchtime and fly about. At night they fly into Cheddar Gorge and nearby woodland and pasture.