A comparison of unmanned aerial vehicles (drones) and manned helicopters for monitoring macropod populations

Context: Developments in the use of remote aircraft, or unmanned aerial systems (UAS), for ecological study have been rapid. Helicopter surveys have proven to be a reliable, repeatable method for broad-scale monitoring of harvested kangaroo populations in Australia’s rangelands, but the recent availability of long-range UAS may offer improvements in detectability and cost efficiency.Aims: We aimed to test the ability of a long-range UAS (Spylite, Bluebird Aero Systems Ltd, Kadima, Israel) to survey macropod populations at a landscape scale, and validate the results against those from the current best-practice helicopter surveys.Methods: Four 80-km transects in south-western Queensland were surveyed using a helicopter and UAS. Two observers, occupying the rear seats of the helicopter, recorded animals observed in distance classes perpendicular to either side of the aircraft. Continuous electro-optical (EO) or infrared (IR) video from the UAS were recorded for later processing. Animal densities were calculated using line-transect methods for both techniques. The efficiency and cost effectiveness of each survey technique were also assessed using the flight and data processing times.Key results: The encounter rate for macropods during the UAS was significantly lower compared with the helicopter survey, resulting in low estimates of macropod density (3.2 versus 53.8 animals km–2 respectively). The UAS technique recorded between 2.9 and 12.7% of the macropod density observed on each transect during the helicopter survey. The helicopter surveys were less expensive and more efficient and cost effective, requiring less flight and data processing time than the UAS surveys.Conclusions: Utilising long-range UAS to detect and count groups of wild animals for landscape-scale wildlife monitoring has potential, but improvements in detection and identification technology are needed to match or exceed the accuracy of the conventional aerial survey technique for kangaroos.Implications: Recent advances in camera technology and methodological refinements are encouraging for aerial survey of wildlife using UAS. However, significant improvements are required to survey for kangaroos and new technology should again be tested against current benchmarks