http://www.the-scientist.com/blog/display/55495/

Plotting chimps?
Posted by Tia Ghose
[entry posted at 9th march 2009 05:00 pm gmt]
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Chimpanzees may have the ability to plan further into the future than previously thought, according to an article in the online version of Current Biology.
Chimpanzee
Image: barnoid/flickr

The study by Matthias Osvath, a primatologist at Lund University in Sweden, was based on the case report of Santino, a 21-year-old chimpanzee living in on a small island surrounded by a water moat at the Furuvik Zoo in Sweden. For several years, Santino would calmly collect and hoard stones and chunks of concrete in various locations on his island. He would sometimes fashion crude missiles out of the concrete chunks. Later on, Santino would hurl the stones at unsuspecting zoo visitors during "agitated dominance displays," according to the paper. Osvath argued that because Santino was relaxed while gathering the stones, it is unlikely that his current state of mind influenced his desire to gather weapons. Rather, the paper suggests, he was planning for his future outbursts.

"What is new in the present report is the observation that the chimpanzees manufactured the stones before throwing them. This and the initial caching of the stones would suggest a higher level of premeditation than previously reported," Valérie Dufour, an animal cognition researcher at the University of St. Andrews in Scotland, said in an email.

Past work showed that orangutans and bonobos could store hooks, which they later used to grab out-of-reach juice bottles, noted Dufour. Other studies in great apes and birds have also shown some level of planning for the future, she said.

Melissa Emery Thompson, an anthropologist at the University of New Mexico in Albuquerque, added that the results weren't that surprising. "In many forms of tool use in the wild, chimpanzees select and modify items to be useful for a task and sometimes need to use two or more tools in sequence to accomplish their goal," Thompson said in an email. However, wild chimpanzees don't typically target stones to hunt prey or show aggression.

In addition, it's not clear that the report represents true planning, as the researcher didn't track the chimp's stone hoarding from the very first, but only after zookeepers noticed the problem, noted Dufour. That means Santino could have used associative learning to gradually develop the weapon-stashing behavior. "For example, in early days, the chimpanzee might just have grabbed the nearest stone to throw it, and then learned progressively to pile stones on that side of the island or to cache them," Dufour said.

Still, the study's quasi-naturalistic setting offers a nice middle ground between highly controlled lab experiments and field studies in the wild, said Sally Boysen, a primatologist at The Ohio State University in Columbus. Often, researchers observe social or cognitive behavior in the wild, but in experiments, "you lose it by controlling all the variables under tight parameters," she said.