30 Days Wild 2018 – Day 1 – Bat Walk

Yes, 30 Days Wild has come round again. June seems to have slightly snuck up on me, hence no build-up to it this year. But I’ll be aiming once again for daily posts right through the month.

River Foss, New Earswick June 2016

For Day 1 I handily had a bat walk booked. I’ve been wondering for ages about the bats near my house, as they are clearly bigger than pipistrelles, our most common bat. So I hoped to shed a little light on this.

The walk was arranged by Community Action for Nature (CAN), a local conservation group working in New Earswick. They do some excellent work along the Foss improving habitats for nature, and have been supported by the Two Ridings Community Foundation to acquire some bat detectors.

The detectors work by being set to a specific frequency that corresponds to the ultrasonic echolocation calls of a particular species. They then convert that to an audible level for human hearing, allowing you to hear the noises they are making.

Screenshot of detector registering a Common Pipistrelle

We met at 20:30 and for the first hour or so there was little bat action – a bit too light yet. Happily we were still walking and talking with good people who love nature, so it was hardly wasted time. But then, at the North end of the village, a bat was spotted both by eye, and picked up on the detectors. My visual ID would have said ‘pipistrelle’, and this was confirmed by the detectors. In fact it was a common pipistrelle, Pipistrellus pipistrellus.

The bats were hunting along the fringes of the wood, and over the water, and putting on a good show as they swooped and dived, at times just feet from our faces and at head height. Great to watch.

Later that evening as the walk drew to a close we also picked up another species, the soprano pipistrelle, Pipistrellus pygmaeus. For a long time these were seen as the same species, but in 1999 they were divided based on their echolocation calls. Subsequent studies have found further differences.

Most interesting, for me, was that we recorded a third species, Pipistrellus nathusii. Nathusius’ pipistrelle. This is a rarer species in the UK, for a long time thought to only be here as an occasional migrant. But it is now known to be breeding in several sites. It’s possible that, rather than being rare, they have traditionally been lumped in with common pipistrelles and therefore under-recorded.

Of course, with all three being pipistrelles that doesn’t help me with my mystery bats, and sadly nothing showed up that gave me any insight there. However, they had picked up a possible Leisler’s bat a few nights previously, and that is a much better fit for my sightings. They’ve kindly lent me a detector, so hopefully we can confirm this next time they are out.

It was a fun two-and-a-half hours out looking/listening for the bats, and it’s hard to describe the thrill of the little box clicking into activity. Something you must try for yourself.

Nathusius’ pipistrelle


All images of scans kindly supplied with permission from Sarah at CAN.

I highly recommend joining them for a walk, or giving up a Saturday morning to join their volunteer sessions.

The Nathusius’ pipistrelle image is from Markus Nolf under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.

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I welcome thoughts, comments and questions, so please feel free to share anything at all. Thanks, David

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