Behavioral Characteristics
In some ways, the apes behave more like gorillas than chimpanzees. For example, they build ground nests as gorillas do, using interwoven branches and/or saplings, bent down into a central bowl. However, they frequently nest in the trees as well. Often ground nests will be found beneath or in proximity to tree nests. Their diet is decidedly chimpanzee-like, consisting mainly of fruits (fruiting trees such as strangler figs are visited often).
The Bili apes pant-hoot and tree-drum like other chimpanzees, and do not howl at the moon.
Behavior toward humans has baffled and intrigued scientists. There is little to no aggression, yet no fear, either. "Gorilla males will always charge when they encounter a hunter, but there were no stories like that" about the Bili apes, according to Ammann. Instead, they would come face-to-face with their human cousins, stare intently in half-recognition, then slide away quietly. Hicks's group later confirmed and somewhat expanded those observations, saying that when they encountered a large group of Bili apes in the deep forests (far from the roads and villages), they not only approached the humans, but also would actually surround them with intent curiosity. Hicks clarifies the issue as follows: the apes within 20 km or so of the roads flee humans almost without exception. The adult males show the greatest fear. Further from the roads, however, the chimpanzees become progressively "naive".
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