Behavioural and endocrine predictors of dominance and tolerance in female common marmosets, Callithrix jacchus

Abstract

As a result of social subordination, female common marmosets undergo suppression of ovulation and inhibition of sexual behaviour. This study examined the possibility that subordination also results in decreased aggressiveness and increased submissiveness towards same-sex strangers. Thirty-two adult females were pre-assigned to eight mixed-sex social groups. The females' behavioural and adrenocortical responses to brief confrontations with each of three female strangers were assessed under two conditions: while subjects were pair-housed with a male and while they were living in established, mixed-sex groups. Only 22% of subjects threatened stimulus females in the heterosexual pairs condition, 47% submitted and 31% showed no agonism. These agonistic behaviour patterns reliably predicted whether a female would become dominant or subordinate in a mixed-sex group. When animals were housed in established social groups, both dominant and subordinate females either showed similar responses to stimulus animals as they did in the earlier condition or became somewhat less responsive. Plasma cortisol levels did not correlate with agonistic behaviour and were not elevated by stranger-encounter testing. Finally, in the first 10 days following group formation, subordinate females that had shown ovulatory cyclicity prior to group formation were significantly more likely to receive persistent aggression from their dominant female groupmate than subordinates that had been anovulatory. These results suggest that attainment of social status between female marmosets is closely related to pre-existing individual differences in agonistic behaviour, whereas tolerance between females depends upon ovarian function.