MEPS 330:269-284 (2007)  -  doi:10.3354/meps330269

Behavioral context of call production by eastern North Pacific blue whales

Erin M. Oleson1,*, John Calambokidis2, William C. Burgess3, Mark A. McDonald4, Carrie A. LeDuc5, John A. Hildebrand1

1University of California San Diego, Scripps Institution of Oceanography, 9500 Gilman Drive No. 0205, La Jolla, California 92093, USA
2Cascadia Research Collective, 21812 W 4th Avenue, Olympia, Washington 98501, USA
3Greeneridge Sciences, 4512 Via Huerto, Santa Barbara, California 93110, USA
4Whale Acoustics, 11430 Rist Canyon Road, Bellvue, Colorado 80512, USA
5NOAA Fisheries, Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, California 92037, USA

ABSTRACT: We assessed the behavioral context of calls produced by blue whales Balaenoptera musculus off the California coast based on acoustic, behavioral, and dive data obtained through acoustic recording tags, sex determination from tissue sampling, and coordinated visual and acoustic observations. Approximately one-third of 38 monitored blue whales vocalized, with sounds categorized into 3 types: (1) low-frequency pulsed A and tonal B calls, in either rhythmic repetitive song sequences or as intermittent, singular calls; (2) downswept D calls; and (3) highly variable amplitude- or frequency-modulated calls. Clear patterns of behavior, sex, and group size are evident for some call types. Only males were documented producing AB calls, with song produced by lone, traveling blue whales, and singular AB calls were more typically produced by whales in pairs; D calls were heard from both sexes during foraging, commonly from individuals within groups. The sex bias evident in AB callers suggests that these calls probably play a role in reproduction, even though the calls are produced year-round. All calls are produced at shallow depth, and calling whales spend more time at shallow depths than non-calling whales, suggesting that a cost may be incurred during D calling, as less time is spent feeding at deeper depths. This relationship between calling and depth may predict the traveling behavior of singing blue whales, as traveling whales do not typically dive to deep depths and therefore would experience little extra energetic cost related to the production of long repetitive song bouts while moving between foraging areas.

KEY WORDS: Blue whale · Acoustics · Suction-cup tag · Sex bias · Calls · Foraging

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