Last year, we deployed 100 AudioMoth dev recorders in France main land to record birds and bats in different public forest. Here is a feedback on how it went.

We used AudioMoth dev recorders in their dev cases with 3 Ansmann NiMH 10000 mAh D cells batteries and one SanDisk Extreme 512GB. They were set facing North at 1.5m on a wooden pole narrower than the recorder case. The sites were all enclosed forest plot to reduce theft.

The recorders were set with a duty cycle of 1/15min day and night. From sunrise to sunset, the sampling rate was at 44kHz and was then set to 250kHz during the night. This automatic switch was possible thanks to a custom firmware (Thanks again Alex). This switch was precise thanks to the location given by the AudioMoth chime app upon installation and its tracking of day length variation during the year.

The installation phase took two month and a half, from early April to mid June 2025. The recorders were then recovered around November. The average recording duration of the recorders recovered with empty batteries is 180 days, which results in around 17 000 files for approximatively 300GB per recorder. After compression in FLAC, we stored a total of 14TB of recordings.

After 6 months outdoor, 18 acoustic vents needed to be changed, 20 switches were broken (but are cheap and easy to replace) and 3 cases were damaged with only one being repaired so far.

The main issues we faced were:

• When first setting the time, date and location on the recorders using the AudioMoth web app, it took quite a long time to set each coordinates right, a query would be faster and more precise.

• Because of movement during transport, the batteries could become dislodged, losing the time and location previously set. The AudioMoth chime app is easy to used but sometimes it was someone else who had to use it or the issue was not seen fast enough causing the recorder to wait several days for the signal, losing lots of battery capacity. We will try to reduce the possibility of dislodgement when shaken using semi rigid foam.

For future development, we plan to:

• Have at least 15 plots equip with a solar panel (10W 6V), a LiPo battery (5000mAh, 3.7V) and a solar charger module. This would allow for year long deployment and Winter recordings, as only the SD card would need to be change every so often.

• Have those same 15 plots able to record a few full nights of Summer to share with Vigie-Chiro citizen science monitoring program.

All in all, it worked great and the AudioMoth dev in a relevant tool for large scale wildlife monitoring :)