Chimps making spears, attacking small prey

Published February 24, 2007

Chimpanzees living in the West African savannah have been observed fashioning deadly spears from sticks and using the hand-crafted tools to hunt small mammals - the first routine production of deadly weapons ever observed in animals other than humans.

The multistep spearmaking practice, documented by researchers in Senegal who spent years gaining the chimpanzees' trust, adds credence to the idea that human ancestors fashioned similar tools millions of years ago.

The landmark observation also supports the long-debated proposition that females - the main makers and users of spears among the Senegalese chimps - tend to be the innovators and creative problem solvers in primate culture.

Using their hands and teeth, the chimpanzees were repeatedly seen tearing the side branches off long straight sticks, peeling back the bark and sharpening one end, the researchers report in the online issue of the journal Current Biology. Then, grasping the weapon in a "power grip," they jabbed into tree-branch hollows where bush babies - small monkey-like mammals - sleep during the day.

After stabbing their prey repeatedly, they removed the injured or dead animal and ate it.

"It was really alarming how forceful it was," said lead researcher Jill Pruetz of Iowa State University, adding that it reminded her of the murderous shower scene in the Alfred Hitchcock movie Psycho. "It was kind of scary."

Scientists have documented tool use among chimpanzees for several decades, but the tools were simple and used to extract food rather than kill it.

Pruetz and coworker Paco Bertolani of the University of Cambridge made the observations near Kedougou in southeastern Senegal. Unlike other chimpanzee sites under study, which are forested, this site is mostly open savannah. That environment is very much like the one in which early humans evolved.