These "open mikes" picked up the ballads of the fin whale, blue whale, humpback whale, minke whale, sei whale, and the rare North Atlantic right whale, said Christopher Clark, Bioacoustics Research Program at the Cornell Lab of Ornithology in Ithaca, New York.

The fin, humpback, right, and sei whales are on the U.S. endangered species list, meaning the federal government considers them to be "on the brink of extinction."

(See whale pictures.)

But what amazed the team the most was not the types of whales heard, but the sheer density of animals spread out over the entire study area, said Aaron Rice, science director of the bioacoustics lab.

For one thing, the scientists were struck by the "juxtaposition of