Aerial VHF tracking of wildlife using an unmanned aerial vehicle (UAV): comparing efficiency of yellow-eyed penguin (Megadyptes antipodes) nest location methods

Context. Locating cryptic animals is an important aspect of many wildlife management programs and research studies. However, this process can be inefficient, time-consuming and expensive. Unmanned aerial vehicles (UAVs), unmanned aircraft systems (UASs) or drones fitted with a camera are increasingly being used for counting and monitoring wildlife; however, these are often not suitable for cryptic species. Very high-frequency (VHF) radio-tracking is commonplace; however, single-channel VHF receivers mean that animals must be tracked individually, or scanning receivers must be used; but this raises the possibility of signals being missed. Aims. We aimed to test the effectiveness of aerial VHF tracking using a multi-channel receiver for locating wildlife. Methods. We tracked wildlife fitted with VHF transmitters operating on individual frequencies, by means of a UAV with a multi-channel VHF receiver to simultaneously monitor all frequencies. This offered distinct advantages over traditional single-channel scanning receivers. To test and compare this novel method, yellow-eyed penguins (Megadyptes antipodes) were located on nests hidden under vegetation on Enderby Island in the New Zealand subantarctic, using manual ground searching, unassisted ground VHF tracking, as well as using location flights by the UAV Drone Ranger system. Key results. The UAV system allowed for faster nest location than did all other methods, with a higher cumulative success (number of nests found each day) and lower search effort required (person hours per nest). Conclusions. Aerial VHF tracking can greatly extend the search range and minimise search effort compared with ground VHF tracking or manual searching. Implications. This technology has applications for locating and tracking a wide range of wildlife, particularly cryptic species that may be difficult to find using other methods.