Studying mate choice using inertial measurement units: a validation study with treefrogs

Investigations of mate choice continue to address fundamental questions about the mechanisms and evolution of animal behaviour. A common behavioural assay used to study acoustically guided mate choice with playback experiments is phonotaxis, a typically robust response in which a chooser approaches acoustic signals, such as courtship songs or mating calls. Robust empirical studies of phonotaxis often require substantial laboratory facilities, such as a dedicated and sound-treated room or enclosure, in which the acoustic environment is controlled and in which animals are freely able to move about. The financial and space resources required to outfit a research laboratory to investigate phonotaxis may be sufficiently prohibitive such that some researchers are excluded from undertaking bioacoustic behavioural research. Here, we validate a new device designed to measure animal movements related to phonotaxis using an inertial measurement unit (IMU). The device is small and portable; it can be constructed for less than $300 USD (£ 238 GBP); and the build instructions and code for operation are freely available. In a series of four experiments with treefrogs, we demonstrate using the device that an IMU-based approach to measuring animal movement can replicate a broad range of findings from traditional phonotaxis experiments on species recognition and sexual selection. We conclude by discussing several possible uses for IMU-based measurements of phonotaxis.