Whales may have learned from Alaskan humpback whales how to make bubble nets to encircle fish.
For a population of whales, teamwork makes the dream come true.
Decades after commercial whaling nearly drove them to extinction, a feeding behavior known as bubble netting is helping a group of humpback whales (Megaptera novaeangliae) in Canada recover. Observational data collected over 20 years suggests a few key people transmit their knowledge via social networksthe researchers report on January 21 in Proceedings of the Royal Society B.
In the Kitimat Fjords system of northern British Columbia, humpback whale numbers are increasing at a rate of 6 to 8 percent per year; the population now exceeds 500 individuals. Here, groups of up to sixteen humpback whales can now be spotted in teams making bubble nets. Some of them swim in circles blowing air through their blowholes, others vocalize. Beneath the water’s surface, entire schools of herring are trapped in rings of bubbles, making it easy for whales to swoop in to catch them.
“It gives me chills. It’s one of the most incredible things I’ve ever seen,” says Éadin O’Mahony, a marine mammal ecologist at the University of St. Andrews in Scotland.
Bubble nets were already well documented in Alaska by the time scientists began tracking them in the Kitimat Fjords in 2005, in collaboration with the Gitga’at First Nation, which continually monitors the population through Indigenous-led environmental management programs.
Co-author Nicole Robinson, a member of the Gitga’at First Nation who has monitored the bubble nets for more than a decade, says whales come to the Kitimat Fjords to feed on the bubble nets in “regular groups” starting in April or May each year. Each time they dive, each whale follows a specific order within the group.
Sightings of bubble nets increased steadily and peaked when a heat wave hit the North Pacific between 2014 and 2016. As fish and krill became scarce, the tactic turned out to be strategic – thanks to it, O’Mahony says, whales have access to more types of prey than they would have by lunging alone.
But it’s not clear how the whales learned this technique. “Are they individual inventions or innovations over and over again, or are they socially related to each other and teaching each other? O’Mahony said.
Using nearly 7,500 photographs, the researchers created a map of the whales’ social interactions. Then they overlaid it with the order in which each individual began creating a bubble net. Statistical analysis allowed them to predict how behavior evolved across social groups.
The results suggest that some key people in the group taught others how to create bubbles. Canadian whales likely learned from Alaskan whales in Hawaii, where both populations breed, but there is no observational data yet to support this hypothesis, O’Mahony says.
Still, the results show strong evidence of social learning, says Vanessa Pirotta, a whale scientist at Macquarie University in Sydney who was not involved in the study. She believes feeding know-how spreads similarly among the Australian whale populations she studies.
“Whales may need to be more adaptable in their feeding methods because they need to adapt to a changing environment,” says Pirotta.
Feeding strategies such as bubble nets help whales adapt. If a boat hits and kills a whale capable of teaching bubble net fishing, then the entire population becomes less resilient. That’s why places like the Kitimat Fjord system, where whales learn to prey on others, need to be targeted for conservation, O’Mahony says.
The Gitga’at people have maintained the balance of the ecosystem that whales are a part of for thousands of years, even as they hunted marine mammals for food, Robinson says. The core of their indigenous knowledge is recognizing changes in food sources in order to harvest them sustainably. Ultimately, it comes down to one value. “In my language we call it loomsk: respect,” Robinson says. “Respect for our lands, respect for our waters, respect for our elders, respect for our children. »
