When two or more animals use limited amounts of resources, such as food, mates, or shelter, competition may occur. Individuals may gain access to the same resources when the resources can be shared, or some individuals may retreat and find other resources to avoid direct conflict. However, when one or more individuals take forceful action to monopolize resources (or claim a larger share than other individuals), aggression may occur. Individuals also use aggression to increase their social status which may influence their reproductive success (Clutton-brock 1988). Investigating patterns of aggression, such as frequency, severity, and context, is a useful tool to understand the social system of a species, social relationships among individuals, and the environment in which the individuals live.