"Fifteen years ago, Ekwoge Abwe was trekking through Ebo Forest in Cameroon when he heard something cracking in the distance. He scanned the forest, searching for the source of the sound.
“One of my local assistants said, ‘Those are chimpanzees cracking nuts,’” Abwe, a biologist, postdoctoral fellow at San Diego Zoo Global and manager of the Ebo Forest Research Project, told Mongabay. “I said, ‘How do you know that?’”
They traveled toward the noise. Then Abwe gazed up at the trees to see several Nigeria-Cameroon chimpanzees (Pan troglodytes ellioti), including a mother with an infant, using quartz stones to crack open nuts from an African walnut tree (Coula edulis)."