Chimpanzees have been observed using elevated areas such as hills to gather information about rival groups and plan safe routes into enemy territory. This behavior is considered an essential military strategy for humans and now researchers have found that it is also used by chimpanzees.
A study conducted by Sylvain Lemoine and his colleagues at the University of Cambridge focused on two neighboring groups of western chimpanzees in Taï National Park, Ivory Coast. The researchers observed the behavior of the chimpanzee communities, each consisting of between 30 and 37 individuals, every day for three years.
The chimpanzees were found to be highly territorial, engaging in regular border patrols in the periphery of their territories. During these patrols, the chimpanzees would often stop and rest on hilltops when they approached rival land. This behavior was believed to be a way for the chimpanzees to take advantage of the favorable acoustic conditions on high ground, allowing them to listen out for potential enemies.
The chimpanzees would rely on the sounds they heard, such as calls and drumming, to judge the level of risk in entering the other group’s territory. The researchers found that the closer the rival group was, the less likely the chimpanzees were to advance into enemy territory. For example, the chimpanzees proceeded into enemy territory 60% of the time when their rivals were 3 kilometers away, but only 40% of the time when their rivals were 50 meters away.
This study highlights that chimpanzees are not willing to take unnecessary risks and instead weigh the costs and benefits of engagement. When the risk of conflict is low, such as when there are fewer rival chimpanzees or they are further away, the patrol groups feel more confident to expand their territory. This expansion provides the group with access to more resources, increasing their chances of survival and reproduction.
This research reveals that chimpanzees employ sophisticated territorial strategies to maximize their chances of success. The findings contribute to our understanding of chimpanzee behavior and their similarities to human military strategies.
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