Evaluating Sex Differences in Aggressiveness in Cattle, Bison and Rhesus Monkeys

AbstractThe assumption has often been made that aggressiveness is predominantly a masculine characteristic (e.g. COLLIAS, 1944; MOYER, 1974; SCOTT, 1975; BOUISSOU, 1983a, b). Many investigators simply accept the idea that males are more aggressive than females. Based on generally applicable operational terms, the validity of the "notion of universal male aggressiveness" (JOHNSON, 1972) has been tested in three different mammalian species. The study was done under nonexperimental conditions by scoring partner-directed aggressions (potentially injurious actions) among members of three undisturbed, heterogeneous groups of Bos taurus, Bison bison and Macaca mulatta. The expression of aggression was regulated by the number of subordinate partners (animals who, without being the target of aggression, consistently withdrew), with high-ranking individuals having more opportunities to display aggressions than low-ranking individuals. Hence, it was self-evident that, whenever the two sexes differed in dominance status (number of subordinates), they also differed in terms of aggression rate (total number of aggressions shown per unit time). The average number of aggressions directed by dominant animals against individual subordinate partners (aggression index: REINHARDT & REINHARDT, 1975) did not exhibit a significant sex difference in any of the three species studied (Bos taurus: xf= 1.8 vs xm = 1.8; Bison bison: xf= 6.9 vs xm = 6.6 ; Macaca mulatta: xf= 4.1 vs xm = 2.9). This was not only true in general but was also consistently confirmed when comparing the sexes within different age classes (adults and juveniles). From this it was inferred that the two sexes were equally aggressive in the general day-to-day situation of dominance reinforcement in all three species. The data thus did not support the general belief that mammalian males are more aggressive than females.