Social Behaviour of Testosterone-Injected Male Ducklings in the Presence of Oestrogen-Treated Females

Young domestic ducklings of the Rouen breed were injected with testosterone propionate during their first month of life and their social behaviours (sexual, aggressive and social displays) were observed during encounters with male and female ducklings. Some of the females were injected with oestradiol monobenzoate. All the male sexual behaviours were stimulated by the testosterone injections while only slight modifications of the aggressive behaviour were observed. The sexual receptivity of the oestradiol-injected females was strongly increased as compared with that of control oil-injected birds. Simultaneously oestradiol injections decreased the male-directed aggressivity of the treated females. This allowed a complete expression of the males' sexual behaviour including mounting and copulation. As in previous studies, no social display was observed in testosterone-injected birds. This fact is briefly discussed and possible hormonal basis for these behaviours are suggested.