Science & Technology, UK (Commonwealth Union) – A new study reveals that chimpanzees, our closest evolutionary relatives, employ a seemingly human-like warfare tactic – using high ground for reconnaissance before venturing into rival territory. This observation, made during a three-year study of neighboring chimpanzee groups in Côte d’Ivoire’s West African forests, suggests a level of strategic thinking previously unseen in animals other than humans.
Researchers observed chimpanzees climbing hills at more than double the rate when approaching shared borders compared to when traveling within their own territory. Upon reaching these elevated vantage points, the chimpanzees would remain quiet, refraining from noisy activities like eating or foraging, allowing them to better detect sounds of rival groups.
The study’s lead author, Dr. Sylvain Lemoine of the University of Cambridge’s Department of Archaeology, suggests that chimpanzees use hilltop reconnaissance to assess the risks of entering rival territory. By gauging the distance of potential adversaries, they can make informed decisions about whether to proceed or retreat, minimizing the likelihood of costly confrontations.
While other mammals, such as meerkats, utilize high ground for predator surveillance or mate communication, this study marks the first evidence of an animal other than humans strategically using elevation to assess intergroup conflict risks.
This discovery challenges the notion that tactical warfare is solely a human domain, highlighting the cognitive abilities and strategic thinking of primates closely linked to us. It also underscores the evolutionary roots of human behavior and the complex social dynamics that shape intergroup interactions.
“Tactical warfare is considered a driver of human evolution,” added Dr Sylvain Lemoine, who is a biological anthropologist from the University of Cambridge, Department of Archaeology, as well as a lead author of the study appearing in the journal PLOS Biology.
“This chimpanzee behaviour requires complex cognitive abilities that help to defend or expand their territories, and would be favoured by natural selection.”
The research was conducted at the Taï Chimpanzee Project, where Lemoine conducted his PhD. Currently, the project is overseen by Dr. Roman Wittig from CNRS in France, who is the senior author of the study.
Within this project, teams of researchers devoted 8-12 hours each day to monitoring four habituated chimpanzee groups accustomed to human presence. This unique endeavor allows for simultaneous data collection from multiple wild chimpanzee communities, a rarity in the field of research.
To aid in their investigations, the project’s researchers employed GPS trackers. These trackers enabled the study’s authors to generate maps of two adjacent chimpanzee territories, complete with elevation data. These maps were cross-referenced with historical French colonial maps to validate the topographical information.
Each chimpanzee group consisted of approximately 30-40 adult individuals at any given time. The study utilized over 21,000 hours of tracking data from a total of 58 animals observed between 2013 and 2016.
Chimpanzees establish and safeguard their territory through regular patrols along the periphery, akin to a “border patrol,” as described by Lemoine. These patrols are often carried out by subgroups, maintaining proximity and minimizing noise. As an observer, one can sense when a patrol begins, as the chimpanzees move and pause simultaneously, resembling a coordinated hunt.
Lemoine explains that these inselbergs served more as “listen-out points” than lookout points. Chimpanzees would drum on tree trunks and emit vocalizations known as pant-hoots, which were filled with excitement. These vocalizations were used for communication among group members and to assert territorial claims. Their resonating sounds could be heard from over a kilometer away, even within the dense forest.
In reflecting on this behavior, Lemoine suggests that the utilization of the landscape for territorial control has deep evolutionary roots. The study of chimpanzees employing war-like strategies may provide insights into the ancient practices of territorial defense that likely existed in prehistoric hunter-gatherer populations.
