Chimpanzees in West Africa have been observed using sharpened branches as "spears" to hunt other primates.
A report in the journal Current Biology documents 22 instances of chimps in Senegal creating tools to stab their bush baby prey. Bush babies are tiny and much more primitive primates related to the lemurs found in Madagascar.
In one case, researchers saw a chimpanzee stab a bush baby which was hiding in a hollow tree, extract it, and then eat it. Iowa State University assistant professor Jill Pruetz told the BBC: "There were hints that this behavior might occur, but it was one time at a different site."
The standard manufacturing technique for the weapons was to break off a living branch and trim the leaves off. Some would then strip the bark and sharpen up the point with their teeth.
The behaviour was particularly prevalent among adult females and adolescent chimps. Preutz said: "It's classic in primates that when there is a new innovation, particularly in terms of tool use, the younger generations pick it up very quickly. The last ones to pick up are adults, mainly the males. It's a niche that males seem to ignore."
The authors interpret that older males miss out on the opportunity for cultural transmission of ideas available to groups of mothers and their offspring.
The news further explodes the myth of chimpanzees as docile vegetarians. UK TV audiences were shocked in 1980s by a David Attenborough documentary which showed chimps hunting down a monkey and then tearing it apart with their bare hands. Hit play for a glimpse of the bloodthirsty truth about our closest relatives. ®