In Australia, some dolphins suit up for dinner. Before poking through seafloor mud for a delectable crustacean or cephalopod, the dolphins protect their sensitive snouts with marine sponges. What's more, dolphins teach each other this behavior. It's a kind of cultural learning observed in other highly intelligent animals, such as chimpanzees, who teach one another how to forage for honey using tools made from leaves and twigs, how to fish for termites and ants with sticks, and how to roll over logs to find grubs. In fact, researchers have found that different groups of chimps living in different regions have distinct methods of foraging, communicating, and using tools. Chimps, it turns out, have local customs. These customs are preserved through social learning within a single group and sometimes shared across groups.
We expect such sophistication from animals whose intelligence seems closest to our own, but other supposedly less brainy animals are stepping up to claim a seat at the table of culinary culture. Crows, for example, learn a lot from watching each other eat. Through observation and imitation, some crows in urban Japan have learned how to turn cars into nutcrackers. The birds wait for the pedestrian crossing signal to light up, drop an especially tough nut on the crosswalk, allow the cars to smash it open, and swoop in to claim their treat at an opportune time.
The latest critter to prove its cultural cleverness is the banded mongoose, which belongs to the same family as the more familiar meerkat. Mongooses are experts at cracking open shells, and most of them are particular about their methods: once they choose a strategy, they stick to it and teach it to younger members of their social group. In other words, banded mongooses learn traditions through imitation, according to a study in the June issue of Current Biology. The researchers claim this is the first experimental evidence showing wild mammals pass on traditions.
"Some people argue that even today only humans are capable of social learning," says Corsin Müller, a University of Exeter zoologist and lead author of the new study. "But traditions and imitations are not restricted to large-brained animals like dolphins and chimpanzees. They potentially occur in many other animals."
Müller worked with five groups of wild mongooses at Queen Elizabeth National Park in Uganda. Banded mongooses live in large social groups of between 20 and 70 members, sharing a den at night and foraging together during the day. Mongoose pups form exclusive relationships with adult male mentors, learning—among other things—how to crack open the shells of cherished foods like bird eggs and rhinoceros beetles.
To crack open shelled snacks, mongooses use two main methods: (1) the biting method, in which they hold their snack in place with their paws and fracture the shell with their teeth, and the (2) smashing method, in which they hurl the shell against a rock or tree trunk.
Müller designed a modified plastic Kinder egg containing a mixture of rice and fish, which could be opened by either mongoose method. When he presented adult mongooses with the Kinder egg, most consistently preferred to crack it open with one of the two methods, even maintaining their preferences over several months. In order to test whether the adults would pass on their preferred method to pups, Müller allowed pups to observe their mentors tackle the Kinder eggs for two to four weeks. Then he waited two to four months and presented the same pups—now established as independent juveniles—with their own eggs.
Even though the juveniles had no contact with the Kinder eggs during the interim, and had never opened an egg themselves, they reliably imitated the shell-cracking method preferred by their mentors. Juveniles whose mentors smashed the eggs also smashed the eggs; juveniles whose mentors dug into the shells with their teeth did the same. And the young mongooses preserved their learned preferences into adulthood—even 10 months later.
There's an important distinction between Müller's study and earlier research on culture and tradition in nonhuman animals: Müller is the first to use an experimental design to show that wild mammals teach each other traditions. Whereas earlier studies used captive animals or observed behavior in the wild, Müller introduced an experimental variable—the Kinder egg—into wild populations and systematically compared the influence of this variable on different groups of animals (in this case, Müller grouped the mongoose pups by which shell-cracking method their mentor preferred.)
A particularly surprising finding is that even the adult mongooses who neither smashed nor bit the Kinder eggs, but completely ignored the plastic puzzles, managed to pass on their particular customs. "The pups who saw the adults ignoring the items also ignored the items," Müller says. "If they observed smashing, they copied the smashing. If they observed ignoring, they also coped ignoring." The finding emphasizes that even for the relatively small-brained mongoose, social learning can have a big influence.
Image of banded mongoose courtesy of Wikimedia Commons