9th June 2022

As part of my continuing quest to elucidate the importance of our beaches as foraging habitat for bats, I put two Anabat Express detectors overlooking the beach just west of the access at the Lhen bridge on 1st June. I’d got some intriguing results there in September 2020, including 1500 pipistrelle calls (common, soprano and social calls of both) over three nights, so I was interested to see if this was a general phenomenon.

Unhappily, I got nowhere near that number of recordings this time, although 140 common pipistrelle recordings in one night isn’t that bad, but I did get a much greater diversity of species, with a maximum of 28 Natterer’s and 21 Daubenton’s recordings on one of the detectors, with 31 of these on the first night.

I’ve had more Daubenton’s recordings before but nearly always over a quietly flowing river or pond and away from such classic localities I tend to only get one or two recordings per survey. I have had Daubenton’s at the coast before, notably at Cronk y Bing nature reserve, but only the odd recording so you always worry about mis-identification. Of course, numerous recordings could still only represent one, busy, bat but nevertheless it is unusual and leads you to ask what it was doing.

 I usually also only get one or two Natterer’s recordings. Apart from being a very quiet bat that “they” say can only be detected when it passes within 5m, I had also formed the opinion that this species hunts in a different way to pipistrelles, more or less carrying on in a straight line until it finds something and not flitting back and forth like pipistrelles or whiskered bats. That would account for its often singular appearance in the recordings.

But here they are, several blocks of consecutive recordings, only a minute or so apart, with a total of 22 recordings in the two hours after midnight. Even Ecobat, the Mammal Society’s online tool for assessing bat activity, says that for one location there was one night of high activity and one of moderate/high activity for Natterer’s, and that’s in comparison to surveys 30 days either side of mine and surveys within 200km2 of the survey location. Added to that, common pipistrelles exhibited three nights of high activity at both detectors and Leisler’s bats two, while soprano pips had one night of high/moderate activity at one location.

Finally, the timings of the first recordings are well outside the average emergence times for all five species recorded, indicating that they have travelled some distance to arrive at the beach.  This all seems to me to confirm that beaches are an important foraging ground for our bats but it remains to be discovered exactly what they are doing and, if they are feeding, what they are feeding on. Yet more surveys for the Bat Group to do.

Nick Pinder