[en] Aggression/drug effects ; Animals ; Ducks ; Humans ; Male ; Sexual Behavior, Animal/drug effects ; Social Behavior/drug effects ; Testosterone/pharmacology
[en] One-month old testosterone-injected ducklings were observed in groups of three males and their social behaviour compared to that of oil-injected control birds. Most elements of adult sexual behaviour and one pattern of aggressive behaviour (chest fight) occurred more frequently in the experimental animals. It was shown that the same hormonal treatment induces different behavioural responses in different animals. Unlike previous studies, no social displays were observed in the testosterone-injected ducklings. Possible explanations of this fact are discussed.