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Why do chimpanzee communities patrol territorial boundaries?

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A common chimpanzee (Pan troglodytes) sits on a rock holding a long blade of grass in its mouth, with dense green foliage in the background. — chimpanzee The West African, or masked, chimpanzee (*Pan troglodytes verus*) is a critically endangered subspecies of chimpanzee.

Chimpanzee communities patrol their territorial boundaries primarily because relations between different groups are inherently hostile. These patrols are a form of territorial behaviour, an adaptive strategy used to protect a group's home range from incursions by others of the same species.12

By engaging in these patrols, adult males defend their territory against intruders, who may be attacked if they enter the group's range. This behaviour is driven by between-group competition, as communities seek to maintain access to resources and protect their members. In extreme cases, these hostile interactions can lead to the invasion of neighbouring territories, resulting in fatalities, infanticide, and cannibalism. Ultimately, such defensive actions help the community manage competition and secure the area necessary for their survival.12