Orangutan Report: Orangutans Have a Big Idea

 

by Rebecca Widiss for Science AAAS

Even when they are very young, orangutans may start to form ideas about their world—specifically, how and when to use certain tools. That’s the    conclusion of a new study, which indicates that ape cultural traditions may not be that different from our own.

Like humans, orangutans have behavioral traditions that vary by region. Orangutans in one area use tools, for example, whereas others don’t. Take the    island of Sumatra, in western Indonesia. By the age of 6 or 7, orangutans from swampy regions west of Sumatra’s Alas River use sticks to probe logs for  honey. Yet researchers have never observed this “honey-dipping” among orangutans in coastal areas east of the water.

How do such differences arise? Many experts say that social learning is key—that the apes figure out how to honey-dip by watching others. But even the    most careful field researcher can have difficulty proving this, says Yale University anthropologist David Watts. Wild apes are always responding to their  environment, he says. And it may be influencing their behavior far more than social learning.

An unfortunate series of events has finally allowed scientists to test social learning’s importance. Deforestation has caused a large number of orangutan    orphans, many of whom come from both sides of the Alas River, to wind up at the Batu Mbelin shelter in northern Sumatra. At first they’re quarantined, and  then they move to large social groups.

Psychologist Thibaud Gruber of the University of Zurich’s Anthropological Institute & Museum in Switzerland and his colleagues began studying Batu    Mbelin’s quarantined apes because political unrest made it unwise for the researchers to work in the field. The team gave the orangutans two stick-based    challenges: raking food into their cage and dipping for honey. Apes from both sides of the river picked up the raking behavior relatively quickly. This  suggests that all of the animals could understand sticks as tools, Gruber says. But while nine of 13 west-side apes “knew” to honey-dip, only two of 10    east-side apes did, Gruber’s team reports this month in Current Biology. What’s more, the savvy west-side apes were just 4 years old on average—too young to have begun honey-dipping when they were in the wild. Gruber says this indicates that  specific ways of using tools come from observing others.

The young orangutans who “knew” to honey-dip likely formed the idea of honey dipping in their heads before they were physically able to do it, Gruber says.    And when it came to applying this idea years later, they had little trouble. Gruber calls such mental representations of stick use “cultural ideas.” If  they really exist, he says, then behavior differences among apes are closer to human cultural differences, which also often stem from ideas.


Primatologist Dorothy Fragaszy of the University of Georgia in Athens says orangutans might have ideas of the sort that Gruber describes, but that’s not    the most plausible explanation. Fragaszy cautions that Gruber cites only one study that discusses orangutans developing stick skills in the wild—and she  says that work isn’t conclusive about when orangutans begin experimenting. “I would say [the orphans] were somewhere along the normal process of learning    about [tool use], which involves watching and trying,” when they left the wild. “They had enough practice,” she adds, “that they [could] do it later, in  this simpler situation.”

For Watts, it’s the site that Gruber chose that stands out. He credits Gruber with making a “good logical case” for social learning by running experiments    “partway between” lab work and fieldwork. He and Fragaszy both say that Gruber’s study spotlights a valuable, if regrettable, new type of place to conduct research.

Gruber fears it may one day be the only place to do such research in northern Sumatra. Fires are burning in the forests where the tool-using apes    live, he says. “The loss of their habitat,” he adds, “probably also means loss of their culture.”

This article originally appeared on and is courtesy of the Science AAAS website.  The photo is courtessy of  iStockphoto/Thinkstock.

Comments

  1. Great article. Thanks for sharing Terrifying that they are so endangered.

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