Animal-borne accelerometers do not reliably identify social calls from tagged humpback whales

Abstract

Understanding which animal produces a sound is essential for animal communication studies and for estimating cue rates for passive acoustic monitoring. In marine environments, biologging tags are used to study vocal behaviour, but efficient underwater sound transmission makes it challenging to identify whether the call is produced by the tagged (focal) animal. In low-frequency baleen whales, animal-borne accelerometers on acoustic recording tags have recorded signals corresponding to vocalizations. Here, we test whether high sample rate accelerometers could estimate focal status with validation datasets in which all members of humpback whale feeding groups were tagged concurrently. Accelerometer signals were only rarely associated with known calls from the tagged animal (3%). In addition, high-amplitude calls from nearby conspecifics were occasionally associated with accelerometer signals, including nine calls present on the accelerometer of two tags simultaneously. Calls were present on the accelerometer only when the acoustic received level was high. Our results indicate that source level and accelerometer noise from movement limit the utility of identifying focal calls from accelerometers, but also highlight the risk of false detections for high-amplitude calls. Group-level tagging provides an alternative way to differentiate calls and investigate communication dynamics in baleen whale social groups.