Tuesday, March 27, 2007

Monkeys Learn Stone Skills from Each Other

stoned monkeyMonkeys can learn skills from each other in the same way that humans do, according to a new study of capuchin monkeys in Brazil. While not conclusive, this research into the way monkeys use stones adds to a mounting body of evidence that suggests other species have something approaching human culture.

Dr. Antonio Moura, a Brazilian researcher from the University of Cambridge Department of Biological Anthropology, has discovered signs that a group of capuchin monkeys in northeastern Brazil bang stones together as a signaling device to ward off potential predators.

"One of the most interesting things is that they make a noise to scare off predators," Dr. Moura said. "They would seem to be communicating the danger to one another at the same time."

A strong case has already been made for great apes, such as gorillas and chimpanzees, having a capacity for social learning, but until now there has been no evidence of such culture among the New World primates of Central or South America, including capuchins.

Banging objects is an innate behavior in capuchin monkeys, but in all wild groups observed before this research the behavior had only happened in a foraging context. Banging stones is "an entirely new variant," Dr. Moura said.

This research in the Serra da Capivara National Park, in the Piaui state of northeast Brazil. There Dr. Moura observed episodes of stone-banging among a group of 10 monkeys.

At first, the act was apparently an aggressive one directed at Dr. Moura as a potential predator, and as the group became used to his presence in the area the stone-banging decreased.

In many cases, adults and juvenile monkeys were seen banging the stones together without paying the researcher any attention at all. Dr. Moura says this suggests that the younger monkeys were learning the skill from their more experienced elders.

Captive monkeys released into the area also appeared to learn to bang stones from the others.

Dr. Moura describes this act of stone-banging as "a remarkable and novel" behavior which has yet to be observed in any other non-human primate species.

Biological anthropologists are divided over whether other species have the capacity to acquire skills by social learning, or whether the different skill sets exhibited by different groups of the same species are a result of environmental influences.

In this case, Dr. Moura could find no environmental cause for the capuchins acquiring this skill, so he suggests that they had learned it by observing and imitating one another.

"We already know that these monkey populations use stones as tools to dig holes or to forage and questions remain about why this happens in this area," Dr. Moura said. "Because it is quite dry and barren, it is possible they learn these skills from one another because they have to develop them quickly."

Story here.


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