Gulf of Alaska fin whale calling behavior studied with acoustic tracking

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A pair of fin whales (Balaenoptera physalus) were concurrently tracked in the Gulf of Alaska from their 40-Hz calls recorded on an array of passive acoustic monitoring instruments. Calls were produced during movement of the whales along convergent tracks, but following a close-approach (~500 m) between the whales, there was no extended period of close proximity. Call frequency, swim speed, and root-mean-square (rms) source sound pressure levels (SL) were different between the two animals. One whale called more frequently, more often, at a higher frequency and with higher SL, but had slower swim speeds than the other whale.