Chimps Throw Stones at Trees in Mysterious New Behavior

In behavior never before seen, chimpanzees in West Africa have been filmed picking up stones and throwing them at trees, all the while making “hooting” vocalizations.

The resulting accumulation of stones either next to or in the hollows of the trees has created a new puzzle for chimp researchers:


Chimp stone throwing compilation from laura kehoe on Vimeo.

 Scientists from the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) made the discovery with the help of camera traps, placed after field teams noticed piles of stones next to trees at some of their dozens of research sites.

The behavior was exhibited primarily by adult male chimps, but the scientists said some females and juveniles were also seen throwing the stones.

Data on these observations have just been published in the journal Scientific Reports.

“This study reports a new chimpanzee behavior not known,” said Christophe Boesch, a study co-author from the MPI-EVA, in a press release. “As the stone accumulation behavior does not seem to be linked to either the abundance of stones or the availability of suitable trees in an area, it is likely that it has some cultural elements.”

Chimps are known to use tools when foraging for food, such as using sticks to poke around for termites or to extract honey or ants. They’ll also use stone or wooden “hammers” to smash nuts open.

But the researchers say the stone-throwing activity doesn’t seem to have anything to do with foraging.

“This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees,” the authors of the study wrote.

Read more at Discovery News