Deep in the Congolese jungle is a band of apes that, according to local legend, kill lions, catch fish and even howl at the moon. Local hunters speak of massive creatures that seem to be some sort of hybrid between a chimp and a gorilla.
The most detailed and recent data comes from Cleve Hicks, at the University of Amsterdam, who has spent 18 months in the field watching the Bili apes - named after a local town - since 2004. His team's most striking find came after one of his trackers heard chimps calling for several days from the same spot.
When he investigated he came across a chimp feasting on the carcass of a leopard. Mr Hicks cannot be sure the animal was killed by the chimp, but the find lends credence to the apes' lion-eating reputation.
From the rare eyewitness sightings, bone discoveries and a video recording, the animals have large, black faces, are up to two metres tall and weigh between 85 and 102kg.