Testing a New Passive Acoustic Recording Unit to Monitor Wolves

Abstract

As part of a broader trial of noninvasive methods to research wild wolves (Canis lupus) in Minnesota, USA, we explored whether wolves could be remotely monitored using a new, inexpensive, remotely deployable, noninvasive, passive acoustic recording device, the AudioMoth. We tested the efficacy of AudioMoths in detecting wolf howls and factors influencing detection by placing them at set distances from a captive wolf pack and compared those recordings with real-time, on-site howling data between 22 May and 17 June 2019. We identified 1,531 vocalizations grouped into 428 vocal events (236 solo howl series and 192 chorus howls). The on-site AudioMoth correctly recorded 100% of chorus and solo howls that were also documented in real-time. The remote array detected 49.5% of chorus and 11.9% of solo howls (≥1 unit detected the event). The closest remote AudioMoth (0.54 km, 0.33 mi) detected 37% of choruses and 8.9% of solo howls. Chorus howls (9.4%) were detected at the farthest unit (3.2 km, 2.0 mi). Favorable wind (carrying source howls to the remote units) and calm (no wind) conditions increased detectability and detection distance of chorus howls. Temperature was inversely related to detection. Given the detection distances we observed, AudioMoths are probably useful in studying specific sites during periods when wolves move less frequently (e.g., during late spring and summer at homesites or potentially during winter at kill sites of very large prey). AudioMoths would also be useful in a passive sampling array (e.g., occupancy studies), especially when used in concert with other methods such as camera-trapping. Additional research should be conducted in areas with different environmental variables (e.g., wind, temperature, habitat, topography) to determine performance under varying conditions and also when fitted with a parabolic dish.

Addressing Power Issues in Biologging: An Audio/Inertial Recorder Case Study

“…The more direct comparison we can make of our design is with the Audiomoth [ 16 ], a former academic development now sold under the Open Acoustic Devices brand. It is an audio only recorder, with similar architecture as the one herein presented, including a MEMS analog microphone which has been successfully involved in the recent application of passive acoustic monitoring [ 17 , 18 , 19 ]. SOLO is an open-source architecture based on low-cost embedded computer [ 11 ].…”

Can non-invasive methods replace radiocollar-based winter counts in a 50-year wolf study? Lessons learned from a three-winter trial

“…2012; Zemanova 2020), reliance on animal captures for information will likely become increasingly unnecessary. For example, the field of passive acoustic research of wild animals is rapidly advancing and pack counts of wild wolves may eventually be possible via chorus howl analysis (see Barber-Meyer et al . 2020 b ).…”

“…As non-invasive methods improve and expand, including advances in technology and statistical analysis (Long et al 2012;Zemanova 2020), reliance on animal captures for information will likely become increasingly unnecessary. For example, the field of passive acoustic research of wild animals is rapidly advancing and pack counts of wild wolves may eventually be possible via chorus howl analysis (see Barber-Meyer et al 2020b). Further, non-invasive genetic surveys represent a rapidly evolving area (e.g.…”

HydroMoth: Testing a prototype low‐cost acoustic recorder for aquatic environments

“…AudioMoth is already widely used by terrestrial biologists in a range of biomes (e.g. Barber‐Meyer et al, 2020; Revilla‐Martín et al, 2021; Sethi et al, 2020); this new prototype HydroMoth is the AudioMoth 1.2.0 device but with a modified case and firmware to make it compatible for long‐term underwater use.…”