Territoriality

Some animals will defend their territory by fighting with those who try to invade it. Fighting, however, is not often the best option, since it uses up a large amount of energy, and can result in injury or even death. Most animals rely on various threats, either through vocalizations, smells, or visual displays. The songs of birds, the drumming of woodpeckers, and the loud calls of monkeys are all warnings that carry for long distances, advertising to potential intruders that someone else's territory is being approached. Many animals rely on smells to mark their territories, spraying urine, leaving droppings or rubbing scent glands around the territories' borders. Approaching animals will be warned off the territory without ever encountering the territory's defender.

On occasion, these warnings may be ignored, and an intruder may stray into a neighboring territory, or two animals may meet near the border of their adjacent territories. When two individuals of a territorial species meet, they will generally threaten each other with visual displays. These displays often will often exaggerate an ani mal's size by the fluffing up of feathers or fur, or will show off the animals weapons. The animals may go through all the motions of fighting without ever actually touching each other, a behavior known as ritual fighting. The displays are generally performed best near the center of an animal's territory, where it is more likely to attack an intruder, and become more fragmented closer to the edges, where retreating becomes more of an option. This spectrum of performances results in territorial boundaries, where displays of neighbors are about equal in intensity, or where the tendency to attack and the tendency to retreat are balanced.

Actual fighting usually only happens in overcrowded conditions, when resources are scarce. Serious injury can result, and old or sick animals may die, leading to a more balanced population size. Under most natural conditions, territoriality is an effective way of maintaining a healthy population. The study of social behaviors such as territoriality in animals may help us also to understand human society, and to learn how individual behavior affects human populations.