all

　　warnings

　　that

　　carry

　　for

　　long distances, advertising to possible invaders that someone else's territory is being approached.Many animals rely on smells to mark their territories or leaving droppings around the territories.Other animals will be warned off the territory without ever meeting with the territory's defender.

　　Sometimes,

　　these warnings may be

　　ignored,

　　and an invader may move accidentally into a neighboring territory, or two animals may meet near the border of their nearby territories.When the two animals meet, they will generally threaten each other with visual (视觉的) displays.These displays will often exaggerate an animal's size by putting up feathers or fur, or will show off the animal's weapons.The animals may go through all the behavior of fighting without ever actually touching each other.The displays are generally performed best near the center of an animal's territory, where it is more likely to attack an invader and where retreating becomes more of a choice.

　　Actual fighting usually only happens in overcrowded conditions, when resources are not enough.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 also help us to understand human society.

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