Miniaturization eliminates detectable impacts of drones on bat activity

A new way to survey wildlife populations may be possible with advancements
in drones, or unmanned aerial vehicles (UAVs) that render aerial
technology more accessible and promote surveying in inapproachable
habitats. However, it remains unclear whether UAV disturbance deters
animals, which would make this method inaccurate for data collection and
hazardous to wildlife welfare. This study addresses the viability of UAV
use for wildlife research by measuring the effects of UAV flight on
acoustic bat detection and comparing bat activity in response to varying
UAV models. Depending on the way UAVs effect bat detection rate, it may be
possible to identify whether wildlife surveys should be done with UAVs and
the drone models best suited for this purpose. The results reveal that
larger and louder UAVs deterred significantly more bats, and the smallest
and quietest model had no effect on bat detection. Indeed, drone noise was
positively correlated with drone size, but drone size had little effect on
the range of frequencies emitted. While detecting bats with small and
quiet UAVs may be possible, complications still arise with acoustic
detection and the species-specific effects of drone flight. The
reliability of automatic identification with the acoustic detecting
software is limited, as over a quarter of detections were triggered by
non-bat noises yet still classified as bats (25.99%). Overall, using
drones for wildlife detection should be approached with caution, as this
study illustrates that some drones deter and disturb wild bats. If drones
are used in wildlife habitat, consider flying smaller and quieter models,
which are significantly less disturbing. Otherwise, large and loud drones
will likely deter more animals and skew the results of the survey.