Tervo, Outi M.2; Christoffersen, Mads F.2; Simon, Malene3; Miller, Lee A.4; Jensen, Frants H.5; Parks, Susan E.6; Madsen, Professor Peter Teglberg7
1 Department of Bioscience - Zoophysiology, Department of Bioscience, Science and Technology, Aarhus University2 Arctic Station, University of Copenhagen, Qeqertarsuaq3 Greenland Climate Research Centre, Greenland Institute of Natural Resources, Nuuk4 Institute of Biology, University of Southern Denmark, Odense M5 Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts6 Department of Biology, Syracuse University, Syracuse, New York7 Department of Bioscience - Zoophysiology, Department of Bioscience, Science and Technology, Aarhus University
The low frequency, powerful vocalizations of blue and fin whales may potentially be detected by conspecifics across entire ocean basins. In contrast, humpback and bowhead whales produce equally loud, but more complex broadband vocalizations composed of higher frequencies that suffer from higher attenuation. Here we evaluate the active space of high-pitched song notes of bowhead whales (Balaena mysticetus) in Western Greenland using measurements of song source levels and ambient noise. Four independent GPS-synchronized hydrophones were deployed through holes in the ice to localize vocalizing bowhead whales, estimate source levels and measure ambient noise. The song had a mean apparent source level of 185 ± 2 dB rms re 1µPa and a high mean centroid frequency of 444 ± 48 Hz. Using measured ambient noise levels in the area and Arctic sound spreading models, the estimated active space of these song notes is between 40 and 130 km, an order of magnitude smaller than the estimated active space of low frequency blue and fin whale songs produced at similar source levels and for similar noise conditions. We propose that bowhead whales spatially compensate for their smaller communication range through mating aggregations that co-evolved with broadband song to form a complex and dynamic acoustically mediated sexual display.