Eating up to a whopping 2,500 kilograms (5,500 pounds) of food every day, one of the world’s largest animals has an equally large appetite to boot.
Humpback whales (Megaptera novaeangliae) off the northeastern coast of Canada’s Vancouver Island have found a way to make their food come to them. Known as “trap-feeding”, a humpback whale suspends itself at or just below the surface with its mouth open for at least four seconds, allowing surface water to pool in their mouth. Fish fleeing from dive-bombing seabirds mistake these “ponds” for a safe haven as the whale helps shepherd them along using its pectoral fins. The whale then snaps its jaw shut just in time for a healthy meal of krill, herring, and other small planktonic sea animals.
In 2011, two humpback whales were confirmed to use this “trap-feeding” strategy in this area. Just four years later, that number jumped to 16, suggesting this technique could be a “culturally transmitted foraging innovation that provides an energetically efficient method of feeding on small, diffuse prey patches.”
Molly Zaleski, a marine biologist who was not involved in the study, has been studying whales and marine ecosystems in neighboring Southeast Alaska and Prince William Sound for several years. She says that she has not observed whales doing this type of “trap-feeding” in Alaskan waters, but is excited to learn about this new technique nonetheless.
“I know other whales show learned feeding and foraging behaviors that are specific to certain areas,” said Zaleski to IFLScience. “For example, sperm whales seem to be teaching each other how and when to target longline vessels because they can pick sablefish off the line as an easy meal.”
Writing in Marine Mammal Science, the authors note that the ability of individual whales (and their broader populations) can depend on physiology, as well as their ability to respond to their external environment, like changing numbers, availability, distribution, or behavior of prey.
The bus-sized humpback whales are generalist predators known to partake in a variety of feeding behaviors, like the dramatic lunge-feeding strategy or fairy-tale-sounding bubble-feeding technique. This newly observed strategy could be in response to environmental pressures. Humpback whale populations off Canada’s west coast were severely depleted by commercial whaling until it was banned more than 40 years ago.
“Innovative foraging strategies arise when an individual invents a new feeding behavior or modifies a behavior that is already in use in a population. These new strategies can then be transferred to other individuals within the population, a process that can occur through social or asocial learning,” wrote the authors, adding that this type of learned behavior has been observed in other mammals, birds, and even fish.
Today, humpback whale populations continue to bounce back with some populations being delisted from the Endangered Species Act.