Ontogeny

Younger individuals are more submissive than older monkeys (13, 9). This follows a general pattern in monkeys -- rank is strongly correlated with age. Submissive behaviors are seen throughout the lifespan of monkeys. They are performed more frequently in younger animals. In macaques, even the youngest individuals will respond to threat by crawling to the dominant individual and laying before it (2). Adult males, and even older adolescent males are dominant to females of all ages (3), although females have a status hierarchy among themselves.

Maternal Effects

In old world monkeys, particularly in species where there is a firm status hierarchy, infant and juvenile individuals inherit their rank in the social hierarchy from their mothers. In confrontations with their peers, high-ranking infants can depend on their mothers to intervene (13). Infants will seek out high-ranking playmates and will treat their higher-ranking peers with care, allowing infant rank to continue into juvenile and adult stages of life (13). Juveniles are submissive to adults that rank above their mothers, but may be aggressive to adults that rank lower than their mothers (13). Maternal rank has been shown to correlate with mass in juvenile and adolescent males (9).

Rank acquisition in infancy is similar in males and females. In females, the acquisition of rank may be permanent, or at least very long lasting (13). In some species, this is also true of the males. Generally, the social hierarchy among females will be organized with the highest ranking female at the top, followed by her daughters in order of age. Next will be the matriarch of the second highest family followed by her daughters, etc. (13, 15). Therefore, maternal effects are very important among females as female rank is very stable. Male rank is generally much less stable and depends on more factors.

Change of Rank in Adolescence

Primates are characterized as having a long period of adolescence between the juvenile and adult stages of life (9). Male mandrills have a particularly long adolescent period because they are so much larger than females (up to three times heavier). For that reason, they have a long and easily discernable adolescence. Researchers often choose to work with mandrills when studying male adolescence, which involves more change in rank than female adolescence. Male adolescence is generally defined as the time between the onset of puberty (when the testes drop) and the point when an individual is fully reproductively and socially mature (3).

juvenile drillThroughout adolescence, male mandrills and other monkeys show a decline in the amount of submission shown. Young adolescent mandrills perform more submissive acts than any other sort of social interaction and submit to nearly member of the troupe including females and juveniles (3). However, as they grow older, adolescents perform fewer and fewer submissive acts. Older adolescents submit only to fully adult males. They remain completely submissive to adult males (3).

Adolescent males that are more submissive generally have less testosterone and show less secondary sexual traits than their more dominant peers. More subordinate males develop more slowly and, in mandrills, tend to live on the periphery of the group (9). It appears that in monkeys, lower testosterone levels are the effect rather than the cause of high subordinance. Stress caused by subordinance may suppress testicular function, reducing testosterone and prolonging adolescence (9).

Juvenile drill (similar to mandrill); image from Bioko Biodiversity Protection Program

Rank in Adulthood

Females generally retain their rank throughout their life. If a matriarch dies, her oldest daughter inherits her rank (15). Male rank is more tenuous, however. Maternal effects may still be important in establishing rank. However, they are probably obscured by other factors, including chance (9). Dominant males may be displaced from their position by challenges from other males. Displaced dominant males often drop far more than one place in the hierarchy and will suddenly find themselves submitting to individuals they dominated only a short time before (15).