Acousticians abuse Darwin: Multipath propagation of seismic airgun signals and bowhead whale calls in the Arctic Ocean, with evolutionary implications.

Abstract

Evolutionary biologists have long noted that animals attempting long‐range communication often adjust their acoustic signals to compensate for or even exploit features of the acoustic propagation path. Here we present recordings of long‐range seismic exploration signals and bowhead whale calls detected on directional autonomous seafloor acoustic recorders deployed in the Beaufort Sea in 2008. Seismic signals that begin as broadband impulses geometrically disperse into FM downsweeps as they propagate over several kilometers range in shallow water waveguides parallel to the Alaskan coast, eventually becoming similar to bowhead FM sweeps in bandwidth and modulated structure, creating headaches for unfortunate scientists trying to create automated bowhead whale acoustic detectors. It is suggested that the similarity in structure between long‐range seismic signals and bowhead whales is not coincidental, but provides an enlightening example of how marine mammals, over evolutionary time scales, have optimized their acoustic signals to propagate long distances while retaining information. A broadband harmonic bowhead whale call is analyzed to examine the speculation. In general, stereotyped baleen whale calls might serve purposes beyond simple species identification in complex waveguide environments.