Nate spent the whole afternoon and most of the evening trying to analyze spectrograms of whale-song recordings, correlate behavior patterns, and then chart the corresponding patterns of interaction. The problem was figuring out what actually defined interaction for eighty-thousand-pound animal? Were animals interacting when they were five hundred yards away? A thousand? A mile, ten miles? The song was certainly audible for miles; the low, subsonic frequencies could travel literally thousands of miles in deep ocean basins.