Bili ape, also Bondo mystery ape, is the name given to large chimpanzees that inhabit Bili Forest in the Democratic Republic of the Congo.
"The apes nest on the ground like gorillas, but they have a diet and features characteristic of chimpanzees", according to a National Geographic report. While preliminary genetic testing with non-nuclear DNA indicates a close relationship with the eastern chimpanzee (Pan troglodytes schweinfurthii) subspecies of the common chimpanzee,a range of behaviors that are more closely related to those of gorillas have greatly intrigued primatologists from around the globe. Though their taxonomic classification has been clarified, the need for further information about these chimpanzees persists.
In local parlance, the great apes of the Bili Forest fall into two distinct groups. There are the "tree beaters", which disperse high into the trees to stay safe, and easily succumb to the poison arrows used by local hunters. Then there are the "lion killers", which seldom climb trees, are bigger and darker, and are unaffected by the poison arrows.
When Karl Ammann, a Swiss photographer and anti-bushmeat campaigner, first visited the region in 1996, he was looking for gorillas, but instead discovered a skull that had dimensions like that of a chimpanzee, but with a prominent crest like that of a gorilla. Ammann purchased a photograph, taken by a motion-detecting camera, from poachers that captured an image of what looked like immense chimpanzees. Ammann also measured a fecal dropping three times as big as chimp dung and footprints as large as or larger than a gorilla's.
In 2000, Ammann returned to the area described by the bushmeat hunter with a group of ape researchers. Although they did not find a live Bili ape, they did find several well-worn ground nests, characteristic of gorillas rather than chimpanzees, in swampy river beds.