Introduction and dominance manipulations involving old rhesus males

Seniority Versus Age as Causes of Dominance in Social Groups

Seniority systems are fundamental organizing mechanisms of most social groups, but seniority is often confounded with chronological age. An analysis of male dominance orders in troops of Japanese and rhesus macaques showed that seniority within the macaque troops was clearly more predictive of dominance than was mere chronological age. Some quasiexperimental datafrom a sample of humans also revealed that seniority was more important than chronological age in determining employee layoff rankings. The Japanese macaque data camefrom Norikoshi and Koyama 's study of two wild butprovisionedtroops ofmonkeys, each containing 26adult males. The multiple regression of dominance rank on seniority and age produced standardized multiple regression coefficients of .65 and .35 for one troop, whereas thefiguresfor the other troop were .82 and .41, respectively. A secondary analysis of Hill's rhesus macaque data showed that seniority had a standardized multiple regression coefficient of .66, but the coerficientforage was only .16, supporting the Japanese macaque data. Finally, new data from a sample of humans showed a similar pattern When subjects were asked to establish a layoff ranking of hypothetical employees described by seniority and age, their rankings were determined primarily by seniority: The coefficients were. 75 and.10, respectively.

Functional alterations in the social organization of bonnet macaques (Macaca radiata) induced by ovariectomy: an experimental analysis

A group of seven ovariectomized female and three intact male Macaca radiata was compared to a matched control group of intact females and males during a breeding season. A second, replicate, experiment was conducted after the males had been switched between groups to partially control for seasonal effects and differences in the age of males. In the first experiment, 161 hr of quantitative data were collected and in the second, 93 hr. Differences in the social organization of the experimental and control groups were anticipated by five a priori evolutionary predictions focused on aspects of intersexual and intrasexual selection: (1) less affiliative and sexual behavior between males and ovariectomized females; (2) less intrasexual competition between them; (3) more intrasexual affiliation among males and ovariectomized females; (4) more intersexual competition between them and (5) more homogeneous patterns of use of resources. Sixty of 90 applications of these predictions to behavioral measures were confirmed. These admittedly exploratory a priori predictions thus significantly increased the ability to anticipate social consequences of female castration. Contrary to Predictions 2 and 4, ovariectomized females engaged in more intrasexual agonistic behavior and less frequently showed aggression toward males.