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Study reveals complex orangutan culture

By Marsha Walton

Orangutans using a stick to grab a bite
Orangutans using a stick to grab a bite

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Of about three dozen cultural behaviors observed, 10 involved specialized feeding techniques, including the use of tools. Among the most common:

Kiss-squeak with leaves:
Using leaves on mouth to amplify sound, then drop leaf.
Kiss-squeak with hands: Using fists (like a trumpet) or flat hands on mouth to amplify sound.
Play nests: Building nest for social play, not to rest
Sun cover: Building cover on nest during bright sunshine
Hide under nest: Seek shelter under nest for rain
Scratch stick: Using detached stick to scratch body parts
Autoerotic tool: Using tool for sexual stimulation
Branch as swatter: Using detached leafy branches to ward off bees or wasps that are attacking
Leaf gloves: Using leaf gloves to handle spiny fruits or spiny branch, or as seat cushions in trees with spines.
Tree hole tool use: Using tool to poke into tree holes to obtain bees, wasps, or their products
Seed extraction tool use: Using tool to extract seeds from the protected fruits of the neesia fruit.
Branch scoop: Drinking water from deep tree hole using leafy branch.

Remember how the television show "The Waltons" used to end each evening: Good night, John Boy. Good night, Mary Ellen. Good night, Grandpa. In orangutan culture, there's a little less formal way to say good night: Ppppffffffffttttttttt.

It's the spluttering "raspberry" sound that humans use in jest or sarcasm.

Researchers say this vocalization, plus more than two dozen other signals and skills observed in wild orangutans, provide evidence that these great apes show cultural variations. Their culture, described as geographically distinct behaviors, comes from observing and mimicking their peers. It goes above and beyond what's instinctive, and what they learn from their mothers.

So who do young orangutans look to for role models in gaining this playful and productive know-how?

"Those who have the most skills are the coolest," said Carel van Schaik, professor of biological anthropology at Duke University in Durham, North Carolina. His research is published in this week's Science magazine. Many of the skills involved access to food and water, and comfort.

Van Schaik and colleagues studied six different wild orangutan populations on the islands of Sumatra and Borneo in Southeastern Asia. While the socially transmitted behaviors were often similar, there were geographic variations. That, say researchers, shows that distinct great ape cultures exist, and may have been around for at least 14 million years.

"We used to think culture was something specific just to humans and chimps, going back just six or seven million years," he said. Chimp culture was first documented in the 1980s.

For example, a "kiss squeak" is a common orangutan signal. It is just like it sounds, the same exaggerated kiss sound a human might make to a child or in jest to a loved one. Van Schaik said the kiss squeak is used by orangutans when there is something near them that they don't like, such as a predator or perhaps an intrusive human being.

"What we didn't know was how this signal varied," said Cheryl Knott of Harvard University, co-author of the study.

"For example, at the site of Gunung Palung in Borneo, orangutans almost always grab a handful of leaves and produce the sound by kissing into the leaves. At other sites they may use their fist, a flat hand, or nothing at all to amplify the sound. We had no idea of this fascinating variety," she said.

Sometimes it's even more elaborate, van Schaik said. Some orangutans would pull off a bunch of leaves from a branch, fling their arms in a theatrical gesture, toss the leaves and let them rain down to draw as much attention to themselves as possible.

"That way they made the intruder even more aware that they were annoyed," said van Schaik.

Yet these practices were never observed in Sumatra. The practices common in one group and absent in another are of great interest to researchers.

Ready to play, or mate

Harvard anthropologist Cheryl Knott conducting orangutan research
Harvard anthropologist Cheryl Knott conducting orangutan research

Scientists also discovered that the same gestures sometimes had different meanings in different ape populations. Tearing a leaf along the mid-rib makes a nice shearing sound, van Schaik said. In one group, that action means "I'm ready to mate," while in another it means "I'm ready to play." An important distinction in any species culture!

While some of the behaviors are playful, others are critical to survival.

"Natural selection has favored the ability to have culture, because many of these actions have to do with skills," said van Schaik.

For example, animals that don't use tools may not have access to the best food. Therefore, the "culture of copying" animals with an inventive spark isn't just for copying sake. The animal learns there's often a payoff as well: a long stick can relieve a hard- to- reach itch; a curled leaf can reach water in an out of the way place.

From the day they are born, orangutans will "suck up information from anyone who comes close," said van Schaik. Youngsters spend seven or eight years in close relationships with their mothers, then another four or five associating more with juvenile peers and other orangutans before they are sexually mature adults.

So how do chimp and orangutan cultures differ from humans? Human culture is cumulative; great ape culture is not. Knowledge and behavior are not passed on from one generation to the next.

"I use a phone and a computer every day, taking advantage of what humans before me created," said van Schaik. "I could not have created those tools on my own," he said.

On tap for further research will be tests for just that type of cultural innovation. Van Schaik would like to look at how simple behaviors evolve into the complex traditions that distinguish human beings from ape ancestors.

Orangutan researchers are warning of threats to any further study of these primates in the wild. Logging, mining, hunting, and forest fires threaten the animals. Their populations are dwindling throughout their range in Indonesia and Malaysia.

"This is our last chance," said van Schaik. "You cannot recreate cultures." He said a stepped up collaboration between researchers and habitat conservation efforts can prevent further destruction.

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