Passive acoustic monitoring (PAM) has become an essential tool in conservation management for the critically endangered North Atlantic right whale (NARW). While PAM studies focused on detection of the commonly produced “upcall” call type have been instrumental in describing NARW presence across a variety of spatiotemporal scales, the ubiquitous production of upcalls makes it more difficult to determine the behavioral context of detected NARWs. Here we have examined an extensive 26-year dataset of NARW acoustic recordings ranging from the Canadian Bay of Fundy to the Southeastern United States to identify other common NARW call types and their associated behavioral context. Calls were grouped into discrete call types based on a contour feature analysis, then examined for context via visual observations and/or movement data from biologging tags. We identified two stereotyped mid-frequency call types, “downcalls” and “constant calls,” produced across regions during social surface active group behaviors. We propose that these call types could be used to identify periods where groups of NARWs are at or just below the surface. The implementation and analysis of these call types in acoustic monitoring would enhance the quality of data collected, allowing for identification of potential right whale aggregations through PAM studies.
Tennant et al. (Wed,) studied this question.