Humpback whales need to eat a lot every day. Some even use their flippers to help snag a big mouthful of fish. Now, aerial footage has captured details of this hunting tactic for the first time.
Humpbacks (Megaptera novaeangliae) often feed by lunging with their mouths open to catch any fish in their path. Sometimes, the whales will first swim upward in a spiral and blow bubbles underwater. This creates a circular “net” of bubbles that makes it harder for fish to escape. “But there’s so much you can’t see while you’re looking at these animals, standing on a boat,” says Madison Kosma. She is a whale biologist at the University of Alaska Fairbanks.
To get a better view of whales chowing down off the Alaskan coast, her team flew a drone. The researchers also held a video camera attached to a pole over floating salmon hatcheries. That’s near to where these whales were feeding.
The team noticed that two whales used the fins on each side of their bodies to herd fish inside the bubble nets. This hunting tactic is called pectoral herding. But the whales had their own way of herding fish.
One whale splashed a flipper at weak parts of the bubble net to make it stronger. Then the whale lunged upward to capture fish. This is called horizontal pectoral herding.
The second whale also made a bubble net. But instead of splashing, the whale put its flippers up like a referee signaling a touchdown during a football game. It then swam up through the center of the bubble net. The raised flippers helped guide fish into the whale’s mouth. This is called vertical pectoral herding.
Though the whales had different herding styles, they did have one thing in common, the scientists say. Both sometimes tilted their flippers to expose the white undersides to the sun. This reflected sunlight. And fish swam away from the flash of light, back toward the whales’ mouths.
Kosma’s team reported its findings October 16 in Royal Society Open Science.
This herding behavior isn’t just a fluke, the scientists think. The team observed herding in only a few whales feeding near salmon hatcheries. But Kosma suspects other dining humpbacks use their flippers in similar ways.