A COLD, MECHANICAL clicking comes briefly from the bat detector’s built-in speaker. Could that really be an animal? Perhaps it’s something to do with the points on the nearby railway line. Then the signal is gone and the static surges back. I am standing on an unlit and overgrown path which runs alongside the Ravensbourne river in Catford.
On the previous evening I’d joined a London Wildlife Trust bat walk at their nature reserve off Sydenham Hill, but the star performers didn’t turn up. Tonight things go better. The bat flies back along the path, and so I make my first ever bat recording – a moment of pure pleasure. Here’s what the sonar of the Common Pipistrelle sounds like once it’s brought from its secret spirit world around 45 kilohertz to within the range of human hearing:
In my excitement I forgot to check the recording levels until near the end, and the background noise is high. But hopefully you’ll enjoy it anyway, and many thanks to Cheryl Tipp for lending me her bat detector.