15 December 2004
Routine Tool Use By Wild Monkeys Observed
by Kate Melville
University of Georgia psychologist Dorothy Fragaszy and co-researchers, have just published the first direct scientific report of tool use among a population of wild capuchin monkeys. There have been reports of single instances of this behavior but never of a whole population using tools routinely over a long period of time. Using heavy stones transported to an "anvil" site in northeastern Brazil, the cat-sized monkeys routinely crack palm nuts, which grow in clusters close to the ground. This is the first scientific report to confirm a behavior previously studied only in wild populations of chimpanzees.
The study, appearing in the American Journal of Primatology adds important new information to the increasing body of knowledge that human beings are not the only primates who use tools. At one time, the use of tools was considered an important difference between humans and other primates, but scientists some time ago discovered that chimpanzees in the wild use tools in several ways.
"One of the most significant things about this research is that we see the behavior in an entire population and not in isolated individuals," said Fragaszy. "Also, it is the first time this behavior has been observed in wild capuchins. What we found is that these capuchins are extremely skilled weightlifters. The video we took of them cracking stones shows just how remarkable their ability to lift these stones has become."
The researchers observed the monkeys using two forms of action to crack nuts. In one, the monkey sat or stood bipedally, held the stone in both hands and raised and lowered the stone with arm and shoulder movements. A more strenuous method involves a monkey rising quickly to a nearly vertical position by standing explosively and raising the stone to shoulder height before crashing it down on the nut. This is the first time such behavior has been reported in a wild population.