Wild, Bearded Monkey Changes the Force of Its Hammer Strikes When Cracking Nuts

When it comes to cracking nuts, monkeys have it down. Scientists have found that wild bearded capuchin monkeys use tools in order to crack open nuts for food.

The monkeys are actually known to use stone "hammers" to crack the nuts. In this latest study, the researchers examined the behavior more closely and found that the monkeys are careful about the amount of force they deliver in order to avoid smashing the kernel inside.

The researchers have studied nut-cracking in these monkeys since 2005. They were especially curious how the monkeys managed to crack such hard nuts and wondered if they would change their approach with softer nuts. They videotaped 14 capuchin monkeys cracking nuts and then analyzed the tapes to determine the height and velocity of each strike.

In the end, the scientists found that the monkeys modulated their strikes. While the scientists expected them to maintain the force of their strikes, it seems that isn't the case.

"Wild bearded capuchin monkeys dynamically modulate their strikes based on the outcome of the preceding strike while using stone hammers to crack nuts," said Madhur Mangalam, one of the researchers, in a news release. "Until now, this level of dexterity was not suspected of any monkey."

The findings show that these monkeys have a sophisticated ability to match their action 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," said Mangalam.

Currently, the scientists hope to see if other species make adjustments in tool use on the fly like these monkeys.

The findings are published in the journal Current Biology.

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