After herring became scarce in the early 1980s, an innovative humpback whale developed a new hunting strategy that has since been adopted by hundreds of other humpbacks, according to a paper released yesterday in Science. The research indicates that whales are able to learn from others, scientists say.
Researchers first observed a lone whale use the novel hunting technique in 1980. Over the next 27 years, the technique spread to almost 40 percent of the humpback population — evidence suggesting that humpbacks are capable of socially transmitting information and sustaining a culture, according to the team of researchers from the University of St. Andrews in Scotland that headed the study. Debates about whether or not animals have culture have raged for years, and if supported, the new research would offer clues to how social learning evolved throughout the animal kingdom, including in humans.
Humpback whales often use a hunting strategy known as bubble feeding to corral their prey. The whales blow bubbles underneath and around schools of fish, producing “bubble nets” that they then dive through to consume the trapped fish. When herring — the whales’ main food — declined, scientists observed one humpback change its behavior — it smacked the surface of the water with its tail before blowing the bubbles, a method now known as lobtail feeding. The researchers are still stumped about the function of the tail slapping behavior, but they think it must be useful, since the technique spread relatively quickly.
Using data gathered from humpback sightings in the Gulf of Maine, where the animals frequently spend their summers, researchers tracked the gradual transmission of the feeding strategy through humpback social structures. The analytical method they used, called Network Based Diffusion Analysis, measures how much time individual whales associate with one another, taking into account the order in which they meet. Whales that spent more time with other whales who used lobtail feeding learned and adopted the strategy faster than more antisocial individuals.
Though 37 percent of humpbacks used lobtail feeding in 2007, according to the whale-watchers observations, the strategy isn’t employed consistently. Instead, the feeding pattern follows peaks in the population of sand lance, another common humpback prey. Whales that were frequently seen in the Stellwagen Bank sanctuary, where sand lance often congregate, also picked up the lobtail strategy faster — though not as fast as the individuals with well-connected social networks.
The researchers ruled out genetics as an explanation for the hunting strategy’s spread. Having a mother who was “informed” about lobtail hunting did not increase the rate at which an individual learned the strategy, which makes sense, since after weaning humpbacks don’t associate any more with their mothers than they do with other humpbacks.
Scientists have previously attempted to describe cultural transmission in animals, but such efforts are difficult because observing animals in the wild doesn’t allow researchers to eliminate biological or genetic interpretations of behavior. This is especially true of marine mammals, as their watery habitat limits scientists’ ability to observe them consistently. Network Based Diffusion Analysis is particularly useful in studying whales, the researchers noted, since it enables scientists to simultaneously take into account the ecological, social and genetic factors that interact to shape behavior in the real world.
Lobtail feeding has endured through multiple generations and is now considered a “tradition,” along with the whale songs that humpbacks are famous for, the researchers wrote. They concluded that social learning enabled the whales to adapt to changing ecological conditions when their primary food source was disrupted. There is some evidence to suggest that the same mechanism holds true for learning in other animals — perhaps we can learn something about ourselves from how whales learn from each other.