Final answer:
Nonhuman primates defend territory to ensure access to high nutritional food resources and to maintain their complex social organization, often employing display behaviors like chest pounding in gorillas to communicate territorial dominance without the need for combat.
Step-by-step explanation:
Defense of territory in nonhuman primates seems tied to protection of high nutritional value food resources and maintenance of social organization. Territorial behavior among primates is not only about protecting the immediate resources such as nesting sites and food but also about the complex social structures that govern their interactions. Having control over a territory allows primates to access better resources, which in turn supports higher survival rates and reproductive success. This territorial defense often involves display behavior rather than direct fighting, as it is less energetically demanding and poses a lower risk of injury.
Examples of such behaviors include gorillas who demonstrate their strength and control over an area by pounding their chests and thumping the ground, signaling to others to keep away. Robins, while not primates, exhibit similar behavior by showing their red breast as a warning. This form of defense allows for the clearer distribution of populations within an area, enhancing the maintenance of social structures that are crucial for cooperative relationships and resource acquisition among primates.