Why Are Humpback Whales Making Bubbles?

Reseachers arre baffled on why humpback whales produce bubbles that create a spectacle that often draws tourists from around the world.

Now, a new study published in Marine Mammal Science explores rare instances when humpbacks (Megaptera novaeangliae) create dramatic, doughnut-shaped vortex bubbles that look like a rolling underwater smoke ring.

Researchers at the University of California, Davis, and their colleagues at other institutions—including the SETI Institute, which is known for focusing on the search for extraterrestrial intelligence (SETI) but is also interested in nonhuman intelligences on Earth —were looking for examples of whales’ general bubble behavior when they uncovered a striking video taken by videographer Dan Knaub in 1988. In the footage, a humpback called "Thorn" blows 19 bubble structures—including 11 rings—over a 10-minute period.

"We were just gobsmacked—like, 'What the hell is going on?'" says Fred Sharpe, a whale biologist at U.C. Davis. "For a team that’s interested in assisting astrobiologists parse unusual signals coming from deep space, it just fell real neatly into our paradigm.... It’s so bizarre."

Sharpe and his colleagues soon found more examples on social media and from other researchers. Study co-author Jodi Frediani, a wildlife photographer who is also at U.C. Davis, even noticed a telltale circle in a photograph a friend showed during a presentation about humpback whales. With this phenomenon on her mind, she says, "I went, 'Gee, there's a bubble ring!'"

For the study, the team recorded 12 events across the North and South Pacific and North Atlantic Oceans in which 11 individual humpbacks were seen blowing bubble rings. The researchers described 39 rings in total. "It’s not a lot in the world of whales but enough—and in multiple oceans," Frediani says.

"It’s a really fun paper," says Syracuse University biologist Susan E. Parks, who studies bubble-net feeding in humpbacks and wasn’t involved in the new study.

"It reads like a detective story that’s trying to piece together information about something that’s not widely studied and happens rarely." Parks hasn’t observed any bubble rings herself—as far as she knows, she says, "I may have seen them before and never really thought anything of them."

Despite compiling so many examples of the rings, Sharpe still doesn’t know what to think about their purpose. "My guess is that this is what it’s going to feel like when we first make contact with aliens," he says.

The researchers speculate that the behavior could be playful. One whale would blow a bubble ring and then swim through it or "do a spy hop right through the middle of it," Frediani says—when performing such a spy hop, the whale would peep its head vertically above the surface, right through the bubble ring. Or perhaps the animals’ behavior could respresent curiosity toward humans: of the 12 recorded events, nine involved whales that approached the human observers more closely before they blew rings.