Bioacoustics audio logging device - recording bat activity

[BDennis]

Not really photography related..but this might be of interest to some here.

After seeing some bats in our garden at dusk for some time now I got interested in finding more about them. This summer, I managed to get a cheap full spectrum audio logging device called an AudioMoth to log the bat calls through the night. The basic device was about £60 but I spent about £100 after adding a waterproof case and shipping. This device can be configured to gather audio data between dusk and dawn and I get a load of 55 second duration WAV files about 15Gb of data total on an SD card from the device. I then analyse these files with some Python computer scripting in my Mac to find the files which might contain bat calls (it looks for peaks at frequencies between 40Khz - 60Khz). I submit some of this data to a British Trust for Ornithology site (yes, they’re also interested in bats!) online (BTO Acoustic Pipeline) and their system does some species ID on the files and sends me the results (it is a citizen science project run by BTO). The bats we get are mostly Common Pipistrelle but I’ve had some others crop up in the recordings. It has been an ongoing project and it will be interesting to see how long the bats stay active into the winter.

I have a video here of some of the bat calls slowed down with the spectrograms of the calls if anyone is interested:

[MJ224]

Well done. We have a local bat walk, and I recorded Pipistrells from the Bat box. Nowhere near as good as yours tho'

[BDennis]

Thanks. I would like to go on a bat walk some time. Some friends did one locally run by the chap who works on the grounds for the local golf course and they really enjoyed it. They have loads of wildlife there and he somehow has time to manage nest boxes for birds and monitor trail cams to find Otters and things. I didn't know much about bats before so it has sparked some interest for me!

[MJ224]

Not that many around at this time of year. You may see the odd one or two if the weather is warm, but they are now beginning to hide up for the winter. They do come out occasionally even in winter. Next spring, if that ever arrives, will be the time to see them in numbers..

[Phill D]

Fascinating stuff Bill, is it possible to ID other sounds as well as bats?

[BDennis]

The BTO system I mentioned can ID various types of crickets (bush crickets etc) and also some rodents (shrews, mice, rats I think). Surprisingly they don’t do any ID for birds, it just marks it as “bird”! For birds you can submit audio files to Cornell Labs online or using their app and it will give it a go but I got some odd results with that - they don’t ask for the location so it gets skewed to birds from the USA if it is not one of the common UK garden birds. Apart from that you can look at the frequency spectrogram and manually ID some birds like wrens which are easy or just listen to those ones! The thing to do with more time and software knowledge would be to program a machine learning system and train it with known subject material, I think that is what BTO have done although they surprisingly have not added birds yet.