Sexual and aggressive behaviour of adult male marmosets ( Callithrix jacchus) castrated neonatally, prepubertally, or in adulthood

Abstract

During early postnatal development, males of some primate species exhibit higher levels of plasma testosterone than females. The possible significance of this for behavioural development was examined in male marmosets castrated neonatally (NC), prepubertally (PC), or in adulthood (AC) and reared in their natal groups. Age-matched intact (AI) adult males served as controls. All males were removed from their natal groups as adults for pair testing with unfamiliar conspecific males and females. NC males did not mount, but were frequently aggressive during tests with females. NC males also elicited aggression from females but rarely from intact males. PC and AC males attempted copulation during the majority of tests with females; less aggression occurred but more so in tests with PC males than between females and AC males. Aggression between PC or AC males and intact males was much more frequent than when NC males met intacts in paired encounters. Results show that secretion of testicular hormones during infancy in male marmosets has important effects upon the development of sexual and aggressive behaviour. Castration in infancy has measurably different effects upon behavioural development than castration performed later in life (prepubertally or in adulthood).