Until fairly recently, many scientists thought that only humans had culture, but that idea is now being crushed by an avalanche of recent research with animals. Two new studies in monkeys and whales take the work further, showing how new cultural traditions can be formed and how conformity might help a species survive and prosper. The findings may also help researchers distinguish the differences between animal and human cultures.
Researchers differ on exactly how to define culture, but most agree that it involves a collective adoption and transmission of one or more behaviors among a group. Humans' ability to create and transmit new cultural trends has helped our species dominate Earth, in large part because each new generation can benefit from the experiences of the previous one. Researchers have found that similar, albeit much simpler, cultural transmission takes place in animals, including fish, insects, meerkats, birds, monkeys, and apes. Sometimes these cultural traits seem bizarre, such as the recently developed trend among some capuchin monkeys to poke each other's eyeballs with their long, sharp fingernails—a behavior that originated among a small group of individuals and which has spread over time.
In humans, once a new fad arises, everyone starts doing it, and in tomorrow's issue of Science, two back-to-back papers find this to be true among animals, too. Two international teams led by researchers at the University of St. Andrews in the United Kingdom report new evidence for the strength of cultural conformity in two very different species suspected to exhibit cultural behavior: vervet monkeys and humpback whales.
In the first study, a research group led by psychologist Andrew Whiten of St. Andrews tried to induce conformity in four groups of wild monkeys, 109 animals in total, living in a private game reserve in South Africa's KwaZulu-Natal province. The team gave each group two plastic trays filled with corn; the corn was dyed blue in one tray and pink in the other. (These colors were chosen because they are prominent in the genitals of male vervets and so were likely to draw the monkeys' attention.) One set of corn was soaked in bitter aloe leaves and made distasteful to the monkeys. In two groups, the blue corn was made bitter, while the other two groups got bitter pink corn. Over a period of 3 months, the monkeys easily learned to entirely avoid the bitter-tasting food.
Four months later, after 27 baby monkeys had been born and were old enough to eat solid food, the monkeys were again offered pink and blue corn, although this time neither had the bitter taste. During the next 2 months, both adults and infant monkeys strongly preferred the same color as before—even though both trays were now edible. Indeed, 26 of the 27 infants ate only the corn preferred by their mothers, ignoring the other tray. Moreover, during the period of the experiments, 10 male monkeys migrated from a group that had preferred one color of corn to a group that preferred the opposite color. Seven of the 10 immediately took up the color choice of their new, adopted group, suggesting that they were influenced by the norms of that cohort.
The study demonstrates that learning from others and cultural conformity play an important role in the behavior of animals as well as humans, Whiten and his colleagues conclude. Deferring to the experiences of others—rather than relying on only personal experience—can help animals adapt.
In the second study, a different research team led by St. Andrews marine biologist Luke Rendell, the researchers studied a tradition—invented by humpback whales themselves—involving a fishing method called bubble-feeding: The whales blow bubbles around schools of fish, confusing the fish and herding them together, and then charge into the bubbles and gobble up their prey. In 1980, one whale was observed to have invented a new twist on this technique, striking the water surface several times with its tail before blowing the bubbles, a strategy now called lobtail feeding. Researchers don't know what advantage this gives the whales, but lobtail feeding arose at the time of a crash in the population of the whales' preferred prey, herring, and the rise of another fish, the sand lance. The team speculates that striking the water helps herd the sand lance together.
Observers had the impression that lobtail feeding was spreading, but there was no solid evidence. So the team analyzed a 27-year database on whale behavior collected in the Stellwagen Bank National Marine Sanctuary, in the mouth of Massachusetts Bay between Cape Cod and Cape Ann. It entered 73,790 sighting records into the computer, involving 653 whales that had been spotted at least 20 times. Over the years, lobtail feeding had spread to 37% of the population, and up to 87% of the whales that adopted the technique appeared to have done so by being in close association with another whale that was already clued in to the method. (Individuals were counted as "associated" if they came within two body lengths of each other and demonstrated coordination in their behavior.)
Outside researchers say that the two studies serve as a milestone: "Their back-to-back publication marks the moment where we can finally move on to discuss the implications of culture in animals," rather than simply whether culture is present or absent, says Carel van Schaik, a primatologist at the University of Zurich in Switzerland. The vervet monkey findings are a "big surprise," he says, because the animals "gave up existing preferences when they [entered] a group with a different preference." Previously, researchers had assumed that such choices were dictated primarily by a drive to get at the most nutritious food, rather than by social factors. "In retrospect, that monkeys rely on the wisdom of the local crowd makes perfect sense."
The whale study also gets a thumbs up. It's "an amazing compilation of … data," says Susan Perry, an anthropologist at the University of California, Los Angeles. "I find this to be a highly convincing case for a foraging tradition in a cetacean."
Nevertheless, van Schaik, Perry, and other researchers say, there is still a lot of work to be done to figure out how much cultural transmission in animals resembles that in humans. "Both these papers show that animals pay attention to and are influenced by what other animals are doing," says Mark Pagel, an evolutionary biologist at the University of Reading in the United Kingdom. But neither study demonstrates the kind of sophisticated copying typical of humans and which demarcates humans from other animals, Pagel says. Without the ability to truly copy others, Pagel adds, animals cannot develop the increasingly sophisticated behaviors that have ratcheted human culture to such a high level.