"It's not uncommon to have chimps use tools. But to use them in the context of hunting [is unheard of]," said Jill Pruetz, professor of anthropology at Iowa State University.

Pruetz said the practice is commonest among adolescent females who must compete against physically superior males.

"It's a way of accessing protein or meat that is a creative solution to this problem," she said.

The new observations are 'stunning,' according to Craig Stanford, a primatologist and professor of anthropology at the University of Southern California. "Really fashioning a weapon to get food - I'd say that's a first for any non-human animal."

Adrienne Zihlman, an anthropologist at the University of California in Santa Cruz, believes that these new findings support other evidence that female chimps are more likely to use tools than males, are more proficient users of tools, and are crucial to passing that knowledge to others.

"Females are the teachers," Zihlman said, noting that young chimps in Senegal were repeatedly seen observing their mothers making spears and hunting with them.

"They are efficient and innovative, they are problem solvers, they are curious. They are pregnant or lactating or carrying a kid for most of their life. And they're supposed to be running around in the trees chasing prey?"