Researchers conducted behavioral observations and collected urine samples for cortisol analysis of male chimpanzees of the Tai National Park, Ivory Coast, during periods of intense male-male competition. They showed that all males had higher stress levels during periods of increased male-male competition while aggression rates were actually lower during this time. This may indicate that in times of social instability animals refrain from aggressive actions to avoid escalation of conflicts and to promote group cohesion.