Wildlife Responses to Drone Noise: A Preliminary Approach for Quantifying Disturbance During Single- and Dual-Drone...

Drones are increasingly being deployed to study wildlife; however, growing evidence indicates that drone noise can alter animal behavior and confound ecological data. Few studies have quantified how acoustic exposure affects behavioral responses of wildlife. In this preliminary, descriptive study, we present a field-based approach that integrates in situ acoustic monitoring with behavioral scoring to document group-level disturbance patterns in free-ranging plains zebras. In Ol Pejeta Conservancy, Kenya, we monitored how flight altitude and single vs. dual drone configurations affected plains zebras (Equus quagga) in single-species and mixed-species contexts. We conducted these flights between 75 and 20 m altitude with two DJI quadcopter drones (Mavic 3Pro and 3T). Drone noise was characterized using a ground-level linear microphone array, and observers used a detailed ethogram to log vigilance and escape behaviors. Drone noise generally declined with increasing flight altitude, while dual-drone operations introduced a disproportionate increase in acoustic exposure. This increase was non-linear, reflecting overlapping rotor harmonics and an extended acoustic exposure window from two sequentially approaching platforms, rather than a simple doubling of noise. Bootstrapping of behavioral scores showed a directional effect, with dual-drone flights eliciting stronger disturbance responses on average, though these estimates should be interpreted cautiously given the small sample size. Behavioral responses appeared to vary with flight altitude and group composition, with greater disturbance recorded during dual-drone operations and in mixed-species assemblages. These findings suggest initial, context-specific behavioral indicators for plains zebras in open savannah conditions. Coupling in situ acoustic measurements with behavioral observations may enable a richer description of drone disturbance, though observed differences likely reflect responses to combined acoustic and visual cues rather than acoustic exposure in isolation. As a preliminary investigation, the results suggest this integrated approach can inform future field study design and evaluation of emerging configurations such as multi-drone flights, while underscoring the need for larger-sample validation across species and environments.