Primate Rescue Center

Monkeys Show How to Perfectly Crack a Nut

Erika Fleury April 30, 2015

Wild bearded capuchin monkeys could be the second best nut crackers in the animal kingdom, suggests new research on the small primates.

We’re in the number one spot, given all of our gadgets and machinery that can crack nuts, but the monkeys appear to be a close second, since they have their own tools and techniques for getting at the nutritious, tasty snack. (Chimpanzees could tie for second or be a close third, since they too are clever at this.)

Louie is a capuchin rescued by the PRC.

A study in the journal Current Biology describes how the monkeys place uncracked nuts on an anvil, which is usually a piece of hardwood with a depression in it. Using a large rock, the monkeys then smash down on the nut. Next, they examine the nut, to see where the most vulnerable crack is, and then strategically hit that spot, which usually reveals the nutmeat.

This video shows how one capuchin monkey handled the task. (Click to view)

“Wild bearded capuchin monkeys dynamically modulate their strikes based on the outcome of the preceding strike while using stone hammers to crack nuts,” co-author Madhur Mangalam of the University of Georgia at Athens said in a press release. “Until now, this level of dexterity was not suspected of any monkey.”

It’s long been known that the monkeys were good nut crackers that used tools, but the process seemed to be trial and error.

Mangalam, lead author Dorothy Fragaszy and their team took a closer look by videotaping 14 capuchin monkeys cracking nuts. Analysis of the height and velocity of each and every strike found that the smashing was not random at all.

“It was a ‘eureka’ moment when we realized that the monkeys modulated the strikes systematically according to the condition of the nut following the preceding strike,” Mangalam said.

We take this skill for granted, but it’s a big deal when studying animals because the multi-step nut-cracking technique requires sophisticated brain processing. The monkeys must match their actions to the physical state of the nut.

“Our finding opens our eyes to the fact that non-human primates modulate their actions with a tool to accommodate the rapidly changing requirements of the task, which is a cognitive accomplishment,” Mangalam explained.

The researchers are next planning to examine whether or not other species can make adjustments in tool use on the fly.

- Discovery

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