“Hercules” Monkeys Lift Stones to Crack Nuts

This holiday season I’m featuring a nutcracker of another sort—the bearded capuchin of Brazil.

Native to open woodlands called the Cerrado, these monkeys are nicknamed Hercules with a tail, and for good reason—they can lift a stone heavier than themselves to break open tough palm nuts. (Watch a video of the nutcracking monkeys.)

A monkey with a missing foot can still crack just as well. Photograph courtesy Dorothy Fragaszy

National Geographic grantee Dorothy Fragaszy has been studying these charismatic little critters in the field, and last week she stopped by headquarters to update us on her research. She passed out some of the palm nuts, which seemed as hard as rocks and nearly impossible to crack.

But bearded capuchins do by taking what’s called a hammer stone, hoisting it over their heads with both hands, and then slamming it down on a nut with brute force.

The monkeys resemble human weightlifters when they raise the stone. Photograph courtesy B. Wright

Most of the capuchins in the Cerrado do this behavior, all year long and virtually every day. And the more Fragazny has videotaped and observed the monkeys, the more she’s realized there’s a well-honed science to the housecat-size capuchins’ cracking.

(See video of chimpanzees using tools to hunt mammals.)

For instance, the animals carefully select their hammer stones—made of quartzite and relatively rare in the region—by their weights. They also choose anvils—a broad stone or log where the nut is cracked—that already have pits, in which the animals place the palm nut.

The monkeys are curious about humans, too. Photograph courtesy M. Haslam

And finally, the monkeys orient the nut in a particular way in the pit that increases their chances of getting at the yummy stuff inside—including, sometimes, beetle larvae. (The clever guys can also determine which nuts have the tasty larvae.)

Not only is nutcracking deliberate, it’s also a tradition, Fragazy believes, since it’s “acquired laboriously in a supportive social context.”

For instance, even before they can pick up a stone, youngsters try to crack nuts—”really an act of optimism,” she said. Young monkeys’ persistent interest in cracking suggests the activity of others motivates exploration and practice.

A young bearded capuchin—and possibly future nutcracker. Photograph courtesy Marino Junior Fonseca Oliveira

She showed us a video of a young monkey missing the nut again and again but admirably not giving up—perhaps a wise takeaway for all of us!

Christine Dell'Amore, environment writer/editor for National Geographic News, has reported from six continents, including Antarctica. She has also written for Smithsonian magazine and the Washington Post. Christine holds a masters degree in journalism with a specialty in environmental reporting from the University of Colorado at Boulder. Her book, South Pole, was published in 2012.
  • Mohammad Yusuf Advani

    Tool use i.e. anvil and hammer stone as evidenced in capuchins who found new ways to use tools that other species could not. Capuchins main diet is nuts,beside nuts, eats fruit,insects,larvae,eggs,young birds etc. In some research articles it is noted that cracking the nut by capuchins is ecological and behavioural,nut cracking by capuchins appears to have strong parallels to nut-cracking by wild chimpazees. The presence of abundant anvil sites, limited alternative food resources, abundance of palm nuts via cracking them with stones. A wise takeaway by capuchins.

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  • Rob

    Nature amazes me.

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