The Cultural Cetacean
New studies support the contentious idea that, like humans, whales and dolphins can learn and pass on local customs
EAVESDROPPING on killer whales isn’t easy. In the field, biologist Harald Yurk of the University of British Columbia faces the same challenges as does a hard-boiled private eye tailing a suspect in a detective novel. The difference is that Yurk tracks his subjects from a boat rather than a Buick, wearing rubberized rain gear instead of a trench coat. "It’s usually raining," he says, "and I often sit and wait for hours before I hear whales on the hydrophone."
It’s all worth it to get the goods on these talkative whales. Along the Alaskan and British Columbian coasts, pods of resident orcas call in patterns so distinctive that Yurk and his colleagues can tell instantly by sound which group of whales they are hearing. Orca dialects are as different from each other as Oxbridge English and Texas drawl.
Yurk is among a growing number of researchers who believe such findings are evidence that whales and dolphins are cultural creatures, even if they don’t attend opera like people do. Wild cetaceans seem to teach each other everything from new songs to creative hunting and defense strategies. These traditions are passed from generation to generation, and new customs can be invented and spread quickly through a population. In human societies, such practices are considered culture.
Photo: © BRANDON D. COLE
SLAP ATTACK: In the Gulf of Maine, a humpback whale slaps the water with its tail while feeding, a behavior, called lobtailing, unique to this group of whales that may stun fish and krill below the surface.
According to biologists Luke Rendell and Hal Whitehead of Dalhousie University in Nova Scotia, "Culture is information or behavior—shared by a population—which is acquired through social learning." But when the scientists argued in a recent issue of the journal Behavioral and Brain Sciences that there is strong evidence for culture among cetaceans, they set off an intense debate. Though social learning has so far been observed among chimps, orangutans and even some birds and fish, many people within the research community and general public cling to the idea that culture is a solely human—or at least primate—trait.
Among primates, the great apes appear to be the most cultural. After many years of field studies, scientists have documented more than 39 different cultural traits in wild chimpanzees, from clasping hands with a grooming partner to dancing in the rain. Drop a trained observer almost anywhere in Africa, and she’ll be able to tell where a given chimpanzee comes from by its behavior. An individual that uses a stone hammer to open cola nuts, wields a short stick to collect edible ants and knocks his knuckles to attract the attention of a potential mate would hail from the Ivory Coast’s Tai Forest, for example.
Earlier this year, an international team of researchers published similar evidence for culture among orangutans. In the journal Science, they describe 24 socially learned behaviors that vary among different groups of the animals. Examples include using sticks as tools to harvest insects or to gather nutritious seeds and building sun shades over sleeping nests. "This finding emphasizes that human culture didn’t just arise de novo, but reaches far back in evolutionary time," says biologist and coauthor Carel van Schaik of Duke University.
Photo: © FLIP NICKLIN (MINDEN PICTURES)
MATERNAL INFLUENCE: Sperm whales, such as these five socializing off the Azores, live in groups that are organized around matriarchs. Group members communicate using unique clicking patterns, or codas, that biologists believe the animals learn from their mothers.
Some scientists say that, although the animals’ behaviors are less complex, even birds can belong to the culture club. Song sparrows, marsh wrens, Darwin’s finches and many other birds pass distinctive song patterns from father to son by learning. Most birds are taught a single song pattern when young, then repeat it throughout life. But a few species, including red-winged blackbirds, canaries and starlings, learn to produce new sounds by imitation over time. Biologists Peter and Rosemary Grant of Princeton University, who have documented transmission of song patterns over generations of Galápagos finches, see such behavior as an example of bird culture.
Among cetaceans, the killer whales Yurk works with provide one of the best-studied examples of culture. These animals live in close social groups consisting of a mother and one or more generations of her offspring. Families of closely related mothers associate in larger groups, called pods, that share the same dialect of 7 to 17 distinctive calls. Within a pod, genetic studies show that each individual may have a different father, yet all members speak the same dialect. If killer whale lingo were encoded in an offspring’s DNA, some paternal influence would show up. Since this doesn’t happen, Yurk and his colleagues say dialects must be learned from other pod members.
DNA evidence collected by Lance Barrett-Lennard of the Vancouver Aquarium Marine Science Center shows that the orcas do not mate with members of their own or any closely related pod. "Acoustic patterns have a huge influence on how and with whom they mate," says Yurk. He and his colleagues believe the need to avoid inbreeding may have driven the evolution of orca dialects as a means of identifying who is or is not an eligible mate.
Sperm whales, which are sometimes hunted by orcas, also live in groups organized around matriarchs. After studying the animals for more than 15 years in the South Pacific and Caribbean, Rendell and Whitehead conclude that they possess cultural traits similar to those of their predators. Sperm whales communicate using distinctive patterns of clicks, called codas, that differ from one group to the next. Like orca dialects, the whales’ coda types match up with their mothers’. "The simplest way to explain that," says Rendell, "is if they learn their codas from their mothers. So we infer that coda repertoires are culturally transmitted."
In a study spanning the South Pacific, Whitehead found that some sperm whale families protect themselves during killer whale attacks by forming a "wagon wheel," with their heads in the center and their tails out. Like the use of coda dialects, this defensive tactic appears to be a learned behavior, a tradition passed on among families. As evidence, he notes that offspring of some matriarchs have tails that are obviously scarred by orca attacks while those belonging to other groups do not.
Some evidence for cetacean culture is as old as Darwin’s theory of natural selection. Since 1847, a group of bottlenose dolphins off the coast of Brazil has been voluntarily cooperating with human fishermen—driving fish into the men’s nets, then signaling with a special rolling dive when it is time to pull in the catch. The dolphins in turn feed off the fish that the nets miss or merely stun. According to biologist and pioneering dolphin trainer Karen Pryor, who studied the interspecies collaboration, only young dolphins that have seen their mothers working with fishermen take up the custom, which has persisted through several generations of both dolphins and people.
Bottlenose dolphins in Shark Bay, Australia, have come up with other inventive ways of finding dinner, strategies they pass on to their young. One group regularly visits a popular beach where the animals get fish handouts from enthusiastic tourists. Members of another small contingent wear sponges over their snouts, which behavioral ecologist Rachel Smolker of the University of Vermont theorizes may help protect them from scrapes while foraging on the ocean floor. All dolphins that sport sponges are female, and the few youngsters who take up the practice are daughters of sponge-carrying moms, which appear to teach the trick to their offspring.
Humpback whales also seem quick to learn new ways of doing things from each other, whether it’s capturing food or attracting a mate. In the 1980s, for example, a humpback in the Gulf of Maine began slapping the surface of the water with its tail before feeding. Biologists think the behavior may stun swarms of fish or krill below, making it easier to gulp up a meal. The practice, called lobtail feeding, quickly spread throughout the local population. Mason Weinrich, chief scientist at The Whale Center of New England, found that young whales are more likely to learn the new technique than are older adults.
Photo: © HIROYA MINAKUCHI (SEASPICS.COM)
FEED ME: In Australia’s Shark Bay, bottlenose dolphins regularly visit a popular beach where tourists supply the cetaceans with fish. Off the coast of Brazil, this species has been cooperating with fishermen for more than a century, driving fish into their nets and gobbling up the ones that humans miss.
But old whales can learn new tricks. Off the eastern coast of Australia, biologist Michael Noad of the University of Sydney discovered a radical change in the song of an entire population of humpbacks. In 1995, a few whales strayed east from a separate population on the country’s west coast, and the easterners quickly copied the western vocal style. Within two years, the original east coast song had vanished. The changes were cultural, says Noad, because the animals learned a different song from their new neighbors. "The complete replacement of a complex song over a period of less than two years is revolutionary rather than evolutionary," he adds, "and suggests that novelty drives changes in humpback whale song."
According to Stan Kuczaj, a developmental psychologist at the University of Southern Mississippi, the new humpback song from Australia is the most convincing evidence yet of socially learned behavior in cetaceans. Kuczaj himself studies the ways in which captive bottlenose dolphins learn, and he’s found that they are quick to copy behaviors that are new and different. Calves are much more likely to imitate other youngsters than their mothers. "In terms of passing information along," says Kuczaj, "mothers probably provide the stability in what might be called dolphin culture. I think peers provide the innovation, they motivate one another to try new things. When one of them tries something and it turns out to be pretty cool, all of a sudden a lot of them are doing it in a very short period of time."
But for Kuczaj and some other scientists, the traditions of wild cetaceans will not qualify as culture until more is known about how youngsters learn them. Do parents deliberately teach their young certain ways of foraging or communicating, or do calves pick these things up by observation? The distinction, says Kuczaj, is an important one. "I don’t think just any form of learning implies culture," he says. Yurk disagrees, pointing out that if this requirement were applied to humans, many behaviors that we think of as cultural would be disqualified—habits like body piercing or listening to heavy metal that parents discourage rather than teach, for example.
Part of the argument, explains Rendell, stems from a clash between different academic disciplines. "Anthropologists and psychologists have long considered culture to be unique to humans and therefore uniquely their preserve," he says. "Of course when biologists come along and say we think these animals do this too, there’s a bit of a fuss."
Take psychologists Marc Hauser of Harvard University and David Premack of the University of Pennsylvania, who scoff at the idea that whales have culture. "All socially acquired behaviors in cetaceans appear to be of the trivial variety," they write in a response to Rendell and Whitehead’s article. Whale traditions are no more meaningful than differences in which side of the road people drive on in different countries, say Premack and Hauser. In their eyes, no other animal exhibits signs of human culture, which "functions to clarify what people value, what they take seriously in their daily lives, what they will fight for." Because people cannot know what other creatures value, that definition—often used in anthropology texts—is "a cop out," responds Rendell. "It shifts the question from what is culture to what is human."
To biologists like Rendell and Yurk, the argument is more than a war over wording. "Culture should be accepted as an indicator with important conservation implications," says Yurk. As an example, he points out that the three pods comprising the resident killer whale population off southern Vancouver Island is dwindling and now includes only four males of breeding age. Three of those males are from the same pod and will not be chosen as mates by females within the same pod. Language and behavioral barriers also stop southern females from mating with whales off the northern coast. Twenty years ago, biologists might have assumed there were plenty of killer whales off Vancouver Island. Now, because they understand something of the whales’ culture, they recognize that some unique groups may be dying out.
It may be tempting to see culture as the one trait that separates humans from other animals, says Yurk, but that attitude is now changing. "It’s better," he adds, "to accept ourselves as closely linked to the natural world."
Like the resident orcas of the eastern Pacific, California writer Sharon Levy was raised in a matriarchal culture.
Impact of Whaling Written in DNA
While an eerie whale song passed from elder pod members to calves offers evidence that cetaceans are cultural creatures, new research indicates that the number of whales crooning tunes today is a smaller representation of the historic population than any previous estimates have ever indicated.
According to a genetic study recently published in the journal Science, scientists may have greatly underestimated the number of whales swimming the world’s oceans before the advent of commercial whaling. Such findings could have major implications for nations hoping to resume whale hunting when the populations rebound.
Stephen R. Palumbi, a biology professor at Stanford, and Joe Roman, a graduate student at Harvard, investigated hundreds of DNA samples from North Atlantic humpback, fin and minke whales—three species decimated by commercial whaling. They found that the DNA had much more genetic variation than would be consistent with previously accepted historic population estimates taken from whaling records.
For instance, whaling logs put the historic humpback population in the North Atlantic at around 20,000 animals. Palumbi and Roman’s genetic analyses show the population could have been more than ten times greater, containing as many as 240,000 whales. Worldwide, the humpback population may have been as high as 1.5 million—more than 10 times the historic estimate of 100,000 published by the London-based International Whaling Commission (IWC). Genetic samples from fin whales and minke whales show similar results.
The researchers’ findings could represent a major setback for countries that advocate lifting the 17-year moratorium on commercial whaling established by the IWC. According to the commission’s policies, commercial whale hunting can resume when populations reach slightly more than half of their historic numbers. Under those rules, the harvest of humpback whales might resume this decade if long-held estimates remain unchanged.
The discrepancy between the whaling records and genetic study findings presents a real “conundrum,” says Palumbi. The message written in the DNA suggests that current humpback, minke and fin whale populations are not even close to being ready for harvest by IWC standards.