"Hot Tub Monkeys" Offer Eye on Nonhuman "Culture"

February 6, 2004

When Japanese macaques (Macaca fuscata) began receiving food handouts more than 50 years ago— freeing them from the daily grind of foraging for food—they invented "cultural activities" to fill their newly acquired leisure time, researchers say.

Stone-play, hot-tubbing in volcanic springs, and potato and wheat washings have all become mainstay behaviors within various troops of macaques around Japan that are still given daily food provisions at research stations. Half a century later many of these behaviors persist and are the subject of studies exploring nonhuman primate culture.

In 1979, during a 14-month stay at the Arashiyama macaque study site, Michael Huffman, a primatologist at the Primate Research Institute (PRI) at Kyoto University, noticed one female monkey playing with stones. "I had never seen, or heard about, anything like it. It was like a child playing with building blocks."

When Huffman returned to the site a few years later in 1983 he was astounded by what he saw. "Half the group was playing with stones, banging them on nearby roofs and making a total racquet," said Huffman. "I couldn't understand why a behavior that seemed to have no adaptive significance—it didn't provide an edge for survival or reproduction—could spread through a group and be maintained in a society for so long."

New Monkey Traditions

Japanese macaque studies began in 1948 when scientists visiting the southern Japanese island of Koshima, encountered a troop of wild monkeys. To facilitate observation they lured the creatures out of the forest with rations of sweet potatoes and wheat.

With these daily handouts, and more free time, the macaques began to invent new behaviors.

The great innovator within the Koshima troop was a one-and-a-half year old infant female named Imo. In 1953, Imo was the first to begin washing the sweet potatoes. She passed the behavior to her mother and it slowly began to spread. A decade later, potato washing had become a fixed behavior in the troop. Most newborns picked up the skill quickly. By 1962, about three quarters of Koshima monkeys over two years old washed their food.

Imo's second feat of genius was to develop a method for sorting wheat from sand. Imo discovered that rather than eat the wheat handouts grain by grain, a mixture of wheat and sand could be dropped in water allowing the wheat to float and the sand to sink. Within several years many of the younger monkeys practiced this behavior.

When behaviors or innovations are adopted by other members of the group, passing from parent to offspring, infant to parent, or adult-to-adult, a "culture" or tradition is born, said Satoshi Hirata, a primatologist and a colleague of Huffmans at PRI.

"Culture and innovation are often ways of adapting to environmental changes, or a response to a change in lifestyle," said Huffman, who studies both chimpanzee and macaque behavior.

Hot Tub Monkeys

Continued on Next Page >>


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