Lack of effects of castration on scent marking, displays, and aggression in a South American primate (Saguinus fuscicollis).

The social interactions of 12 adult, permanently cohabiting male-female pairs with strange conspecifics were studied before and after the male of each pair was either castrated or underwent control surgery. Prior to surgery, the pairs directed a relatively high amount of injurious aggression and displays toward the stranger. Aggression, display behavior, and scent marking tended to be more frequent in females. Moreover, female strangers received more aggression than male strangers, particularly by female subjects. Castration of the males did not result in a decrease in aggression, display behavior, and scent marking. On the contrary, the agression scores of all subjects tended to be higher after surgery, an increase which was probably caused by extraexperimental variables.