If This Monkey Had a Hammer

Because of their love for palm nuts, capuchin monkeys purportedly employ rocks as hammers to crack the hard shells open.  Recent observations have confirmed that, indeed, these pensive-looking primates are members of the exclusive club of tool-users.

Humans were once thought to distinguish themselves from other primates by their proclivity with tools.  But several years ago field biologists witnessed wild chimpanzees sticking twigs into termite holes to pull out a meal.  The chimps would even remove leaves from a twig to improve their "fishing pole."

Dorothy Fragaszy from the University of Georgia and her colleagues have now observed wild capuchin monkeys in northeastern Brazil raising heavy stones over their heads and then slamming them onto palm nuts placed on the ground. 

The cat-sized monkeys apparently carry the relatively large rocks - some which may be half their weight - to what are called "anvil" sites.  These areas of sandstone slabs show signs of repeated smashing.  Fragaszy's team placed cameras around one such site.

"What we found is that these capuchins are extremely skilled weightlifters," said Fragaszy. "The video we took of them cracking stones shows just how remarkable their ability to lift these stones has become."

Although stories of rock-wielding monkeys were common among locals, this is the first scientific observation of the behavior in the wild. The study was published online in the American Journal of Primatology.

-- Michael Schirber

Credit: University of Georgia