University of Arkansas, Fayetteville


Male chimpanzees are known to be aggressively territorial in the wild. It is expected that the limited enclosures of captivity would make them even more aggressive. The Kansas City Zoo was chosen as an ideal venue to explore this assumption because it boasts the largest outdoor enclosure of its kind, and the apes alternate between this and much smaller indoor housing. Quantitative data on crowd size, time of day, temperature, and frequency/intensity/duration of aggressive behaviors were recorded for the alpha male in both enclosures during 300 hours of observation. These data were used to test the following hypotheses: as measured by frequency/intensity/duration, aggression will increase 1) inside relative to outside, 2) with number of visitors, 3) with temperature, and 4) during the middle of the day. Statistical tests and graphical analysis showed that the frequency and duration of aggressive events did, in fact, increase inside, while the intensity decreased. The number of visitors, temperature, and time of day showed little relationship to aggressive interaction, although a few patterns were seen. These conclusions not only aid in the understanding of captive chimpanzee aggression, but also can be used to improve conditions for chimpanzees in zoological parks throughout the United States.