Science Spotlight: Why Do Humpbacks Breach?

by Sukee Bennett

More than 40 feet long and weighing up to 40 tons, adult humpback whales (Megaptera novaeangliae) are formidable giants. But their immensity doesn’t hinder their athleticism—humpbacks are very active at the water’s surface. The whales slap their tails, flap their pectoral fins, and jump vertically out of the sea—a behavior called “breaching” that is rare among other cetaceans.

Scientists are unsure why humpbacks breach. The remarkable behavior might be a method of communication or a way to attract mates. Skyrocketing out of the water might also remove parasites, like barnacles, from the surface of the whale’s skin. Or perhaps humpbacks breach just for fun, scientists say.

“They’re definitely the most exuberant whale, the most playful and very curious,” says Nancy Black, a marine biologist with Monterey Bay Whale Watch. Pectoral and fluke flapping may enhance the ways humpbacks communicate, Black says.

Humpbacks have expansive pectoral flippers. Measuring one-third of their body length, they are proportionately the longest of any cetacean’s flippers. The evolutionary advantage is unknown, but scientists suggest it’s multi-faceted.

“Sometimes they use them like long arms. . . to bunch up schools of fish,” Black says. Mother whales also use their flippers to protect their calves from predators, while males use them to fend off competition during the winter breeding season.

Breeding males spar with their tubercles—bumpy protrusions on the front of each pectoral fin. The tubercles also make humpbacks more hydrodynamic when they swim and dive. Harvard University researchers have applied this adaptation to alternative energy—an example of “biomimicry” in technology. The scientists found that wind turbines with bumpy, tubercle-inspired blades generate more energy than traditionally smooth ones.

Note from the editors: Science Spotlights are a joint project of the UCSC Science Communication Program and Hilltromper. This article was published in May 2017.