Bats at Clodock Mill

Clodock Mill is home to a nursery colony of Lesser Horseshoe Bats. The bats, which are all females, arrive in the spring. During the day they hang upside-down from the ceiling, sometimes clustering together in a ball if the weather is cold. They are already pregnant when they arrive, having mated the previous autumn. Each gives birth to a single baby in the early summer. When the babies are still small, they hang on to their mothers’ fur and feed on milk like any other mammals. Their mothers are able to fly with the babies hanging on. After 3 or 4 weeks the babies can fly on their own.

Ten years ago there were only 12 bats in the mill. Now there are over a hundred. We don’t know where the males live, but presumably they are not far away. As autumn draws on the bats mate and then leave the mill to hibernate throughout the winter in caves or tunnels.

Bats are usually only active during the night. They hunt insects, such as moths, beetles and flies, by echo-location. They emit high-pitched bursts of ultrasonic sound and use their large ears to listen to the echoes bouncing off their surroundings and anything else flying nearby. Their calls are normally too high to be heard by people. The Lesser Horseshoe Bat makes a sort of warble at around 110 kHz. That is about 5 times higher than the highest range of human hearing, but we can listen to them with a bat detector, which plays back their calls at an audible frequency.

Other bats living around the mill include Pipistrelles, Noctules and Long-eared Bats. All bats in Britain are protected by law. It is illegal to harm them in any way or even to disturb them.