Think about the article. Why are many middens located at the edge of a group's territory?

They send a friendly invitation to potential mates that live in the territory.
They send a message to other large social groups that food can be found nearby.
They send a stern warning to other animals to stay away from the territory.
They send a message that predators in other large social groups cannot detect.

The most plausible reason why many middens are located at the edge of a group's territory is that they send a stern warning to other animals to stay away from the territory. Middens are essentially piles of waste and debris, including food remains and other discarded items, which can emit strong odors that act as territorial markers. By placing these middens at the edge of their territory, the group is signaling to other animals, particularly individuals or groups of the same species, that the area is already claimed and should be avoided. This territorial message helps to establish and maintain boundaries, reduce conflicts, and protect the resources within a group's territory.