For the first time, chimpanzees have been seen making and using spear-like weapons to hunt other animals.

Hunting with tools was previously seen as a uniquely human trait.

Scientists from Ohio State University in the US have observed female and very young chimpanzees in Senegal jabbing African limas in tree hollows.

Researcher Jill Pruetz says the chimps had sharpened the sticks by gnawing them.

"I think it was a response by immatures and females to competition within the group," she said.

"They can't out-compete adult males in terms of resources, so I think this is just an innovative way of solving a problem in terms of food availability."