Humpback whales in Stephens Passage near Admiralty Island, Alaska, USA

The song of a humpback whale can last up to 20 minutes, though an individual humpback may go on singing for hours on end. Both male and female whales vocalize, but only the males sing. Since they have no vocal cords, the sounds are made when the whales force air through their nasal passages. Why they sing is the real mystery, with many theories still being explored. Some think it’s to attract a mate (though there’s little evidence to support this) while others suspect the sounds help with echolocation.

While the purpose of the song is unknown, it’s still amazing to hear recordings of the variety of sounds the humpbacks make. And it is known that they use specific noises to corral their prey into a tight mass that’s easy to swallow in a single gulp. Those prey are usually krill and herring, abundant in summer months in the cold waters of the Pacific, near Alaska. A great spot to see humpbacks during summer feeding season? Stephens Passage, a narrow channel in Southeast Alaska, where these five swimmers were photographed.