Strange sounds in the night

Did you know last weekend was 'European Bat Weekend', organised by the splendidly-named Eurobats? No, me neither.

Despite this oversight, I'm pleased to say that I've enjoyed some bats lately.

You've probably read about Hope Farm, the RSPB's farm not far from Cambridge. It's where we're working to find ways to improve the lot of farmland birds alongside running a profitable business. Part of the work includes surveying the farm's wildlife, and I went along to help find some bats.

After a cuppa in the farmhouse kitchen we equipped ourselves with state-of-the-art detectors brought along by our friends at the Bat Conservation Trust and headed off into the fields.

We hadn't even left the yard when we picked up our first bat! It was inside one of the barns but our trusty detector picked up the sonar it was throwing out.

Wet slaps?

Finding a bat in the dark is an interesting experience. They're small, speedy and aren't audible to the human ear. That's why you need a bat detector. Basically - I think! - they work by picking up the sonar squeaked out by the bat, and kind of slowing it down and playing it back at a frequency that we humans can hear.

You might think that it would sound like 'eeep! eeep! eeep!' but the weird noises emitted by the detector are best described as 'wet slaps'! Or clunks. Very odd...

Anyway, we walked a set route through the fields, past the hedges and round the trees of Hope Farm. As the sun set beautifully, we picked up two common pipistrelles - which make noises at 45 Khz - flying out of a copse. Against an orange sky, the tiny bats flew up and down a stretch of hedgerow, clearly hoovering up the moths and small insects emerging from the vegetation.

What a privilege to see these beautiful animals in action. I was inspired. After our evening's surveying, I borrowed a detector and tried it out in my garden. There was the sound of grasshoppers, and then a tawny owl hooting. No bats? I had to wait.

Eventually patience paid off... after 20 minutes' wait, there were clicks, clunks and slaps from the detector and I knew that there was a pipistrelle feeding right above my head! I wonder if they roost in the tree at the bottom of the garden, or in my roof...?

Have you seen bats in your garden, or been bat surveying? I'd love to hear about it!