MARY LOUISE KELLY, HOST:
Humpback whales sometimes use this very intricate, very cool strategy to catch fish. It is called bubble-net feeding. As NPR's Nate Rott reports, a new study suggests the whales are teaching each other how to do it.
NATE ROTT, BYLINE: OK. Let's start with the obvious question.
EADIN O'MAHONY: Bubble-net feeding is this very interesting feeding behavior that happens in humpback whales.
ROTT: Eadin O'Mahony is a behavioral ecologist at the University of St. Andrews and lead author of the new study.
O'MAHONY: It's very complex. It's very social in particular parts of the world.
ROTT: And, yes, it is objectively cool. Just imagine...
O'MAHONY: A group of whales diving down into the depths of the ocean.
ROTT: Below a shoal of tiny krill or fish. Then one whale starts swimming in a circle, slowly puffing air from its blowhole, making rings of rising bubbles.
O'MAHONY: And the bubbles act as a literal net for multiple reasons.
ROTT: They disorient the fish, making them feel trapped by an ever-tightening wall of air, and at the same time, O'Mahony says...
O'MAHONY: Maybe the same whale that's blowing the net, or maybe another whale in the group - we're not sure - makes these feeding calls.
(SOUNDBITE OF WHALE CALLING)
O'MAHONY: And the calls happen at a frequency that vibrates the swim bladders of the herring, which causes them to clump together tighter.
ROTT: All the easier to eat. Other research has shown that bubble nets can help humpbacks catch seven times more food in a single lunging gulp.
O'MAHONY: Yeah, it's pretty incredible.
ROTT: The question O'Mahony and her collaborators wanted to answer is how they know how to do it. Is this behavior something humpback whales just, like, intrinsically know how to do?
O'MAHONY: Or is there some ability for them to socially learn from each other?
ROTT: What biologists call animal culture, a nonhuman species' ability to share behaviors or knowledge with each other. So to answer that question, they focused in on a defining characteristic of every humpback whale, their tail fin.
O'MAHONY: It's like a fingerprint of a human. It's completely unique to that individual.
ROTT: Using observational data and photographs that had been collected over 20 years, O'Mahony and her colleagues identified more than 500 individual whales living within the Kitimat fjord system in Northern British Columbia, a population that was decimated in the 20th century by whaling. And in piecing together their lives over those two decades...
O'MAHONY: You begin to see who's hanging out with whom, who's socially connected with whom, and who's able to bubble-net feed and who's not able to bubble-net feed.
ROTT: They essentially measured the bond between different whales by how much time they spent together.
O'MAHONY: And what's been quite interesting that we found with this study is that the spread of the behavior seems to follow the social bonds between whales.
ROTT: For example, from 2014 to 2016, a marine heat wave in the North Pacific depleted the available prey for humpbacks and many other species. The new study, published in the journal Proceedings of the Royal Society B, found during that time, whales that had never been seen bubble-net feeding started to, responding to an environmental pressure, the findings suggest, by learning from buddies that knew how.
PHILIPPA BRAKES: This study, I think, is great because it sort of shows adaptation in real time.
ROTT: Philippa Brakes is a marine biologist at Massey University in New Zealand who specializes in animal culture. She wasn't involved in the new study. But she says it demonstrates something important for humans to consider when they're trying to protect a species like humpbacks, that a species' culture, not just their population size, matter too.
BRAKES: We are not alone in needing a really rich social environment in order to survive.
ROTT: Especially in a world grappling with so much change. Nate Rott, NPR News.
(SOUNDBITE OF SUMMER WALKER SONG, "FMT") Transcript provided by NPR, Copyright NPR.
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