The Hierarchy of Dominance in a Group of Macaques

Abstract

(1) The linear dominance hierarchy of a group of six caged macaques was studied over a twenty month period. The monkeys, two males and four ovariectomized females, were two to three years old when they were placed together. The rate at which the different monkeys acquired peanuts from an apparatus as well as their aggressive and grooming behavior were scored. (2) When the monkeys were tested in groups of two, three, four, and five, the relative positions of individual monkeys changed. From these shifts in order and from aggressive patterns, it was seen that the position of a monkey in a group was dependent on more than his size and boldness. It was also a function of his relations to other monkeys in the group and of their relations to one another. (3) Both in the full colony and in most of the smaller groups, the most dominant animal set the over-all pattern of the hierarchy, first, by establishing an alliance with a subordinate monkey (by supporting his aggression) and thus raising his status and, second, by forcibly depressing the power of one or more other monkeys, which lowered their positions relative to other animals in the group. Monkeys below the most dominant were not successful in maintaining alliances with other subordinates, but they showed preferences in whom they attacked, and thus contributed to the total balance of forces within the group. The tendency to form alliances appeared in the absence of any specifically sexual basis for it. (4) The ovariectomized female was able to maintain her dominance over the males, one of whom came to weigh 45 per cent more than she did. (5) Grooming behavior was not related in any simple way to dominance positions. Choice of grooming partners cut across hierarchical lines, with the most dominant monkey being groomed most. However, grooming seemed at times to create or reinforce an alliance relationship.