The role of accelerometer hardware limitations in focal caller identification from acoustic recording tags attached to mysticetes.

Abstract

Multi-sensor acoustic tags have revolutionized our understanding of the behavior of large whales. One limitation, however, is the inability to reliably distinguish calls produced by the tagged whale from those produced by other nearby whales. One proposed solution has been to detect calls using both hydrophone and accelerometer data to identify signals produced by the tagged animal. Some high-amplitude low-frequency calls can be detected with accelerometers, but the success in using this approach with all calls within and across species is variable. Here, we provide guidance on the role of the physics of sound propagation and the tag hardware's accelerometer capabilities for successful application of this method with examples from tag data collected from fin whales (Balaenoptera physalus), blue whales (B. musculus), and southern right whales (Eubalaena australis). Of 1190 high amplitude calls believed to likely be from the tagged animal, only 517 were also detected on the accelerometer. Reasons for lack of detection were primarily the frequency of the signal lying outside the usable frequency detection range of the accelerometer on the tag, indicating selection of appropriate hardware capabilities are critical for this approach.