Field Event Reports

Saturday 10th September 2016: Bat Hunt at Radley Lakes

Courtesy: Earth Trust

Leader: Ben Carpenter

Having gathered at the end of Barton Lane at 7:15 pm, we set off along the Sustrans Track, the old Bunk Line, towards Radley Lakes. We were ably led by Ben Carpenter, our guide for the evening. Four bat detectors belonging to the Society and Green Team were distributed to the attendees.

Ben provided us with a wealth of bat informative, showing us dried bodies of some species - the Pipistrelle so surprisingly small. Recordings of echolocation calls and sonograms were demonstrated on his smart phone.

On our way the ‘slapping’ sounds of Common Pipistrelle at 45kHz and the ‘chip-chop’ of Noctule at around 20 kHz were heard on detectors. Reaching Thrupp Lake we walked along the east side, stopping at gaps between the trees with views of the lake. Each time swarms of Soprano Pipistrelles (identified by their 55 kHz echolocation calls) were seen and heard. We ducked instinctively as they flew straight at us, swerving at the last moment. It was twilight and around 8 pm, when a shadowy hawk glided past, close to the lake surface. Ben identified it as Hobby, evidently on a bat hunt too, hoping for a meaty alternative to its usual diet of dragonflies.

Later in complete darkness, on the west side of the lake, Ben shone his torch across the water, picking out a Daubenton’s Bat flying close to the surface, flashing its white underside as it swerved.

Many times an acceleration in echolocation call frequency was heard as bats approached an insect prey, demonstrating the abundance of insect life around the lake.

We returned satisfied with a successful and enjoyable bat hunt

David Guyoncourt

Species identified:

Common and Soprano Pipistrelles, Noctule, Daubenton’s Bat, and a predatory Hobby.