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The vocalizations monitored on the Navy PAM systems include a combination of broadband, tonal, pulsed, and sweeps, showcasing the wide variety of calls this species produces. Some whale species have consistent and highly recognizable call structure, for example the fin whale, which make them easy to identify in acoustic records. However, this is not the case for gray whales which produce more variable, less consistently structured, and ‘rough’ sounding signals. 

Examples of tonal and broadband calls are shown below. These types of calls, which are inconsistent with any other known baleen whale species in these regions in spectral and temporal content, were repeatedly and consistently detected in the western Pacific. These detections occurred in areas and times of year that are consistent with traditional breeding habitat of the critically endangered western gray whale population. 

Information provided by Marine Acoustics, Inc.