Bubble-net feeding isn’t a new behavior in the Juneau area (it was described by Dr. Charles Jurasz in the 1970s). But for decades, it still felt rare to us Juneau whale-observers. You’d hear one or two reports in a summer, and if you were lucky enough to see it yourself, it warranted breathless boasting to your naturalist friends. In the past five years, though, it feels like we’re seeing this cooperative technique more and more frequently. It’s still incredibly thrilling, but it seems like the thrills come more often.
Now this isn’t necessarily all due to an actual increase in frequency of the behavior. Part of it could be an artifact of more whale-watching boats being out on the water, providing more observations. Some of it could just be the result of our rapidly-increasing population of whales. Still–what if it really is becoming more widespread among the whales? The behavior is obviously very highly coordinated–it appears that each whale in the group has a fixed role or position, reflected in the consistent arrangement when they emerge at the surface (see the photo above). Questions arise: How and why do groups form and dissolve? How do new whales join? How do novice whales learn what’s expected of them?
I got to thinking about group bubble net feeding when I read an article about a different humpback feeding technique, in New England. The behavior, known as lob-tail feeding, involves tail slaps at the surface followed by bubble-feeding. It arose shortly after a drop in herring populations in the late 1970s.
In a recently-published paper in the journal Science, Allen, Weinrich, Hoppitt, and Rendell analyzed 27 years of observations of this “foraging innovation.” According to the study, lob-tail feeding rose in frequency and diffused through the population during subsequent years when sand lance populations were high. The analysis provides strong support for a model of cultural transmission–that is, the evidence suggests the whales are learning the technique from each other, not independently inventing it.
The study invites comparison and speculation… Are we seeing a similar increase in the Southeast Alaskan technique? And what about diffusion not just to other whales, but to other regions? As of this year, cooperative bubble net feeding is not known outside of southern Alaska. Will it eventually be transmitted to other humpback populations? It’s fun to be at the epicenter of such as mystery!
For a lot more on humpback social foraging research in Southeast Alaska, check out the Alaska Whale Foundation’s website.