Naive encounters with chimpanzees in the Goualougo Triangle, Republic of Congo

We describe the behavior of an unhabituated population of chimpanzees in the Goualougo Triangle, Republic of Congo. We encountered chimpanzee parties on 218 occasions during two field seasons ( February 1999 - December 1999, June 2000 - June 2001). Overall contact rate was 0.63 contacts per day in the field (n = 347). During the first 5 min of observation, we recorded individual responses as curious, ignore, hide, or depart. In contrast to other unhabituated chimpanzees, curiosity was the most common response (84%) of individuals in the Goualougo Triangle. However, the responses were deeply integrated in the group's reaction to our arrival and behavior throughout an encounter. Based on the behavior of the majority of individuals in a group, we categorized entire contact events as naive, ignore, nervous, or depart. Naive contacts accounted for 69% of all encounters. Other contacts types occurred much less frequently: nervous (12%), depart (11%), ignore (8%). Naive contacts were characterized by chimpanzees that continued to exhibit curiosity throughout the encounter, the arrival of other individuals at the contact location, and relatively prolonged contact with observers ( average duration: 136 min). It is likely that the high frequency of curious responses and naive contacts are due to the remote location of the Goualougo Triangle and the chimpanzees's lack of experience with humans. Documentation of this naive phenomenon has been successfully used to lobby for the protection of the chimpanzees and their habitat.