ioral dynamics of social groups. Because social groups are often headed by older individuals, such as in primate societies, it follows that understanding dominance relations is basic to understanding the role of the elderly in nature.

Allee (1931) addressed the issue of stable hierarchies and argued that dominance hierarchies created cooperative groups that were better able to compete with other groups. One of the classic studies on chickens, from which the concept of ''pecking order" was derived, was by Guhl and Allee (1945), who found that chickens with stable hierarchies had individuals that consumed more food and laid more eggs than chickens without hierarchies. Dugatkin (1995) provides further support to this study by demonstrating that subordinate chickens do not challenge superiors but often prefer to wait their turn. Dugatkin shows that this complacency occurs not because subordinates fear damage and retribution but that group selection has "chosen" genotypes that will not contest authority. Closely related to dominance is leadership, which is initiative and control of an activity, usually by one individual. Whereas dominance alone suggests suppression of group activity, even though it may stabilize the social interactions, an individual who is also a leader can contribute to group survival by synchronizing and stimulating group activity (Greenberg, 1947).

Wilson (1975) lists several "special properties" of dominance order that have important bearing on understanding the role of the elderly in social species. First, "the peace of strong leadership" refers to how dominant animals of some primate societies, including those of gorillas, chimpanzees, macaques, spider monkeys, and squirrel monkeys, use their power to terminate fighting among subordinates. Species organized by despotisms also live in peace due to the universally acknowledged power of the tyrant (e.g., the queen bumblebee). Second, "social inertia" refers to the intrinsic stability of a dominance hierarchy. An animal that attempts to change its position in a fixed dominance hierarchy is less likely to succeed than if it made the exertion during the formative, fluid stages of the hierarchy (Guhl, 1968). Third, societies structured as "nested hierarchies" are partitioned into units and exhibit dominance both within and between components. For example, in some primate societies, hierarchies exist both within and between family lines.

Territoriality

A territory is an area occupied either directly by overt defense or indirectly through advertisement (Wilson, 1975). This area usually contains a scarce resource (e.g., steady food supply, shelter, space for sexual display, a site for laying eggs or bearing offspring, etc.). The adaptive advantage of territorial behavior is that successful defense of a territory increases the chances of an individual to secure its necessary share of environmental resources, to mate, and to increase survival of offspring (Kluijver and Tinbergen, 1953). Individuals resident in an area have more to gain from retaining the territory than do intruders from taking



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