Visitors to Kenai Fjords National Park in Alaska listened to the sound of humpback whales singing underwater moments before a whale breached the water’s surface to feed, as shown in this video posted by the National Park Service on July 3.The video, taken by a park ranger in Resurrection Bay, shows a microphone being held up to the output of a hydrophone that was placed in the water before a whale surfaces. “We don’t fully know what they are saying,” the park service said in its Facebook post. “There are a few hypotheses that it could be communication with others about the feeding or perhaps a way of manipulating their prey.” Credit: Kenai Fjords National Park via Storyful