Does the telemetry technology matter? Comparing estimates of aquatic animal space-use generated from GPS-based and passive acoustic tracking

Underwater passive acoustic (PA) telemetry is becoming the preferred technology for investigating animal movement in aquatic systems; however, much of the current statistical tools for telemetry data were established from global positioning system (GPS)-based data. To understand the appropriateness of these tools for PA telemetry, we dual-tagged free-ranging aquatic animals that exist at the air-water interface (Crocodylus porosus, n=14). The location of each animal was simultaneously recorded over a 3-month period by fixed acoustic receivers and satellite positioning. Estimates of minimum travel distance and home range (HR) were then calculated from the PA and GPS datasets. The study revealed significant disparity between telemetry technologies in estimates of minimum travel distance and HR size. Of the five HR measures investigated, the linear distance measure produced the most comparable estimates of HR size and overlap. The kernel utilisation distribution with a reference smoothing parameter function and ad hoc function, however, produced comparable estimates when raw acoustic detections were grouped into periods when animals were within and between receiver detection fields. The study offers guidelines on how to improve the accuracy and precision of space-use estimates from PA telemetry, even in receiver arrangements with large areas of non-detection.