The astonishing choreography of humpback whales feeding has been filmed via drone.
Humpbacks are baleen whales, so they feed on small fish and crustaceans, rather than on larger prey like toothed whales. During their feeding season in high latitude waters they eat up to two tonnes a day to bolster their body weight for the long migration to the mating grounds, where there is much less food. The estimated 1.5 million calories in this diet is equal to an average human's consumption over two years.
As we reported last week, humpback feeding behavior has been discovered to be remarkably complex, working together to corral prey in three dimensions in the depths. The surface teamwork seen here is in some ways easier, since the air means they don't need to block the escape routes of the fish they are feeding on in one direction, but the division of labor is exceptional.
The process seen here is called bubble-net feeding and has been known to involve groups as large as 20. It requires individual whales to take on specific roles. Several circle the prey, herding them together. One releases a string of bubbles from its blowhole to create a barrier through which the small fish cannot easily pass. Another creates a series of astonishingly loud noises. The fish react by forming into tight balls – presumably an adaptive response in the face of some predators, but one that just makes things easier for the whales.
The whales lunge from below, driving the fish to the surface, which allows the hunters to scarf up the fish, with a generous dose of water as well. To avoid taking in too much salt water the whales force their take out through the baleen plates, leaving the fish pressed against the baleen sieve so they can be licked off. Seagulls, aware that there will be scraps, hone in on groups of whales getting ready to hunt in this way.
The behavior has been seen many times, and it has been observed that the whales always surface in the same spots relative to other members of their feeding troupe. However, the footage below, taken by AkXpro in Prince William Sound, Alaska, represents a new level of clarity in observing the coordination involved.