For a specific collective of cetaceans, collaborative efforts are instrumental to their collective success.
Many decades following commercial hunting practices that brought them to the brink of extinction, a sophisticated foraging technique known as bubble-net feeding is proving instrumental in the resurgence of a segment of humpback whales (Megaptera novaeangliae) in Canadian waters. Research findings, derived from observational datasets spanning two decades, indicate that a select cadre of individuals is instrumental in transmitting this knowledge through their social networks, as reported on January 21 in the journal Proceedings of the Royal Society B.
Within the Kitimat Fjord System, situated in northern British Columbia, the population of humpback whales has experienced a growth rate of six to eight percent annually, with the current number now surpassing 500 individuals. In this locale, aggregations of up to sixteen humpbacks can frequently be observed employing a synchronized bubble-netting strategy. Certain members of the pod undertake circular swimming patterns while expelling air through their blowholes, while others emit vocalizations. Beneath the water’s surface, entire schools of herring become ensnared within the generated bubble rings, thus facilitating the whales’ ability to surge upwards and capture their prey.
“It evokes a profound sense of awe in me. It stands as one of the most extraordinary phenomena I have ever had the privilege to witness,” remarks Éadin O’Mahony, an ecologist specializing in marine mammals at the University of St. Andrews in Scotland.
The practice of bubble-net feeding had been extensively documented in Alaska by the time scientific investigations commenced in the Kitimat Fjords in 2005. This endeavor was undertaken in partnership with the Gitga’at First Nation, whose members consistently monitor the whale population through Indigenous-led ecological stewardship initiatives.
Co-author Nicole Robinson, a member of the Gitga’at First Nation with over a decade of experience observing this behavior, notes that the whales arrive at the Kitimat Fjords to engage in bubble-net feeding, congregating in “familiar ensembles” typically from April or May each year. During their dives, each whale adheres to a prescribed sequence within the group’s formation.
The frequency of bubble-netting occurrences has shown a consistent upward trajectory, with a notable surge observed during a period of intense heat that affected the North Pacific from 2014 to 2016. As the availability of fish and krill diminished, this tactic emerged as strategically advantageous. According to O’Mahony, it enabled the whales to access a greater variety of prey than would have been possible through solitary lunging efforts.
However, the mechanisms by which these whales acquire this technique remained a subject of inquiry. “The critical question is whether this represents individual invention and repeated innovation, or if they are socially connected and actively teaching one another,” O’Mahony posits.
Utilizing a dataset comprising nearly 7,500 photographic records, the research team constructed a comprehensive depiction of the whales’ social interactions. This visualization was subsequently superimposed with the chronological order in which each individual initiated bubble-netting. A sophisticated statistical analysis was then employed to ascertain the trajectory of this behavior’s dissemination across the different social cohorts.
The findings strongly suggest that certain pivotal individuals within the social structure served as instructors, imparting the bubble-netting technique to others. While it is plausible that Canadian whales acquired this skill from their Alaskan counterparts in Hawaii, a location where both populations engage in breeding, there is currently a paucity of observational data to substantiate this hypothesis, O’Mahony adds.
Nevertheless, the results provide compelling evidence of social learning, according to Vanessa Pirotta, a marine mammalogist at Macquarie University in Sydney, who was not involved in the present study. She opines that foraging expertise may be propagating in a similar fashion within the Australian whale populations under her observation.
“Cetaceans may find it imperative to adopt more versatile foraging methodologies as they are compelled to adapt to a transforming ecological landscape,” Pirotta observes.
Foraging strategies akin to bubble-netting significantly enhance a whale’s adaptability. The demise of a single whale capable of teaching this intricate method could diminish the entire population’s resilience. Consequently, areas such as the Kitimat Fjord System, where whales learn vital feeding techniques from one another, warrant prioritized conservation measures, according to O’Mahony.
The Gitga’at people have maintained the ecological equilibrium of this important marine environment for millennia, even when undertaking marine mammal hunts for sustenance, Robinson states. The fundamental principle of their Indigenous wisdom lies in discerning shifts in food availability to ensure sustainable harvesting. Ultimately, this practice is rooted in a core tenet. “In my language, we refer to it as łoomsk: respect,” Robinson conveys. “This encompasses reverence for our lands, our waters, our elders, and our progeny.”