Nut-Cracking Monkeys Use Tools with Skill: Study

Bearded capuchin monkeys use tools with skill to crack open nuts, finds a new study.

A team of researchers led by Dorothy Fragaszy from the University of Georgia has found that Brazil's bearded capuchin monkeys employ tool-using strategies similar to humans, to place the nuts in a stable position before smashing them open for snacks.

The research team videotaped adult monkeys cracking palm nuts on an anvil that they used frequently. Before giving the nuts to the monkeys, researchers marked the flat sides of the nuts with a line and the other side of the nut with color-coded pens, in order to figure out how the monkeys placed the nuts, reports LiveScience.

They noticed that the monkeys positioned the nuts flat side down more frequently to achieve a stable position. The monkeys knocked the nuts against the surface a few times to place them in the most stable position, before cracking them open.

"Knocking likely provides the monkeys with information about the fit between the nut and the pit, perhaps from the sound and/or perhaps from the vibrations of the nut after it strikes the anvil surface," the researchers said.

Next, the researchers carried out a similar experiment with blindfolded people, because they suspected that the monkeys could place the nuts by feel. They wanted to find out if humans could do the same, the LiveScience report said.

Researchers gave nuts to seven male and female participants and asked them to place nuts into the pit of an anvil just like the monkeys. Volunteers too placed the nuts in the most stable position. But, unlike monkeys, they did not knock the nuts against the surface. Instead, they rolled the nuts in their hands to feel the shape of the nuts and placed them flat-side down on the anvil.

The findings of the study are published in the journal PLOS ONE.