Wild bearded capuchin monkeys are sophisticated nut-crackers

Wild bearded capuchin monkeys show a high level of dexterity when it comes to cracking nuts, scientists, including one of Indian-origin, have found.
Wild bearded capuchin monkeys are known to use stone "hammers" to crack nuts. Researchers have now found that the monkeys are quite careful about the amount of force delivered to those nuts.
They adjust the force applied with each strike based on the condition of the nutshell, making it less likely that they will end up smashing the kernel inside.
"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 of the University of Georgia at Athens.

"Until now, this level of dexterity was not suspected of any monkey," he said.
Mangalam and colleagues videotaped 14 capuchin monkeys cracking nuts. They carefully analysed the tapes to determine the height and velocity of each and every strike. It typically takes several strikes with a stone to reach the nut inside.

They had expected the monkeys to maintain the force of their strikes within a certain range, or possibly to increase it until the nuts cracked.
"It was a 'eureka' moment when we realised that the monkeys modulated the strikes systematically according to the condition of the nut following the preceding strike," Mangalam said.

"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 said.
The findings were published in the Cell Press journal Current Biology.