Whales, the biggest animals on the planet, are also among the hardest to find. They spend most of their time submerged and unseen. But not unheard: Whales are noisy animals that flood the oceans with songs, clicks, moans, and calls. And Purnima Ratilal from Northeastern University has developed a way of listening in on these calls to instantly detect, find, and classify whales, over 100,000 square kilometers of ocean—an area the size of Virginia or Iceland.

“The conventional method for studying marine mammals is to go out on a boat, dangle a hydrophone [an underwater microphone] off the side, and listen for the sounds the animals make,” she says. “Or you do visual surveys, focused on one or two species and just a handful of individuals at a time.” By contrast, her technique uses 160 hydrophones to simultaneously map the presence of at least eight whale species, without ever needing to see a single fin.

The Atlantic