Blue whales: An acoustic library helps us find what we can’t see

Reverberating through the ice shelves and gyres of the Southern Ocean are the undersongs of the largest animal that has ever lived on this planet, the Antarctic blue whale. Telling tales of the hunt for krill, of navigation and seduction, these tunes can carry for hundreds of miles.

And the world is listening: Moored around Antarctica is a loose ring of passive acoustic monitoring devices, or PAMs, deployed by various academic institutions. Released by oceanographic research vessels, the devices sink to the seafloor where they record a remote and often hostile realm that is practically out of reach of scientists. After about a year, a returning ship plays a coded message that trips a wireless trigger and frees the PAM recording to the surface.

“The idea here