A Batty Way to Spend an Evening?
After a rather wet day we were delighted that Saturday evening was calm and dry so that our walk with Harriet Baber from the South Bucks & Berks Bat Group could go ahead. Fifteen friends joined us to explore Fox Hill woods after dusk looking for signs of bats.
Harriet explained why bats are so special – for example, they are one of only 4 genera of animals that have independently evolved the power of flight (the others being insects, pterosaurs and birds). Bats are also incredibly long-lived for their size – although about the same size as a mouse which might live 1-2 years, a bat can live for 20 years or more! Through a quirk of evolution bats don’t age in the same way that other mammals do, having an ability to repair their DNA and to avoid the shortening of their chromosomes that normally result in tumours and other age-related illnesses.
An example of a rare Nathusius’ Pipistrelle
It is well known that bats use echolocation to detect their prey and find their way around. However the sounds that they make are beyond most people’s hearing range, so Harriet had brought along some bat detectors which reduce their high frequency squeaks down to a level that we can hear.
On our route through the woods we stopped a couple of times and listened with our bat detectors pointed hopefully into the trees and up into the sky. After a short while we were rewarded with several bats flitting around. Based on the frequency set on our detectors (35-45Hz) these were most likely pipistrelle bats (although which of the 3 UK species we could not be sure). They seemed to be emerging from local roosts to feed in the larger clearings and in breaks in the canopy near the bike jumps. After circling round a couple times they would then drop back into the trees to rest. With the detectors we could also hear the clicks speed up into a raspberry-like noise as the bat homed in on its insect prey.
A Noctule bat was detected when we pointed our detectors at the tree line along the pylon line.
As the light began to fade we ended up on the pylon line, mostly tracking pipistrelles in and out of the trees but Harriet also spotted a solitary noctule which is one of our larger native species. Bats can travel at around 12 mph and so are capable of travelling some distance in the course of an evening. Despite their use of echolocation for feeding they do have quite good eyesight, using visual clues such as hedges, roads, railways and, yes, pylon lines for navigation between areas. Our pylon line may well be a “bat corridor” between different roosting sites.
Everyone enjoyed their evening walk in the woods and learning more about these mysterious little creatures. We are extremely grateful to Harriet for providing her time and expertise and hope that it will encourage you to take a moment to watch out for bats in and around the woods on a summer evening.