Nut-cracking monkeys use shapes to strategize their use of tools

Feb 27, 2013
A bearded capuchin monkey cracks open a stably-placed palm nut with a stone for a hammer. Credit: Barth Wright

Bearded capuchin monkeys deliberately place palm nuts in a stable position on a surface before trying to crack them open, revealing their capacity to use tactile information to improve tool use. The results are published February 27 in the open access journal PLOS ONE by Dorothy Fragaszy and colleagues from the University of Georgia.

The researchers analyzed the ' tool-use skills by videotaping adult monkeys cracking palm nuts on a surface they used frequently for the purpose. They found that monkeys positioned the nuts flat side down more frequently than expected by random chance. When placing the nuts, the monkeys knocked the nuts on the surface a few times before releasing them, after which the nuts very rarely moved.

The researchers suggest that the monkeys may have learned to optimize this tool-use strategy by repeatedly knocking the nut to achieve the stable position prior to cracking it. They conclude that the monkeys' strategic placement of the nut reveals that the monkeys pay attention to the fit between the nut and the surface each time they place the nut, and adjust their actions accordingly.

This video is not supported by your browser at this time.
This video shows two episodes in which a bearded capuchin monkey places and strikes a nut with the Stop meridian marked with a black line or a black-hatched line, and the Roll meridian marked with a red or green line. Credit: PLoS ONE 8(2): e56182. doi:10.1371/journal.pone.0056182

In a parallel experiment, the scientists asked blindfolded people to perform the same action, positioning palm nuts on an anvil as if to crack them with a stone or hammer. Like the monkeys, the human participants also followed to place the nut flat-side down on the anvil.

Explore further: Orchid named after UC Riverside researcher

More information: Fragaszy DM, Liu Q, Wright BW, Allen A, Brown CW, et al. (2013) Wild Bearded Capuchin Monkeys (Sapajus libidinosus) Strategically Place Nuts in a Stable Position during Nut-Cracking. PLoS ONE 8(2): e56182. doi:10.1371/journal.pone.0056182

Related Stories

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

3 hours ago

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

21 hours ago

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

23 hours ago

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

23 hours ago

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

Telekinetic
3.3 / 5 (3) Feb 27, 2013
More absurd patronizing on the part of human researchers. These monkeys could probably crack a safe.
dan42day
3 / 5 (2) Feb 27, 2013
Bet I could teach one to shoot a mean game of 8-ball.
Astricus
1 / 5 (2) Feb 27, 2013
The Nuts who did this research should be cracked! Bizarre!!!

More news stories

Researchers develop new model of cellular movement

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.