Acute changes in plasma steroids and agonistic behavior in male Japanese quail.

A systematic analysis of the acute (minutes to hours) fluctuations of plasma steroids [androstenedione (A), 5 alpha-dihydrotestosterone (DHT), testosterone (T), corticosterone (B)] was investigated in relation to the fighting behavior displayed by experienced male Japanese quail (Coturnix coturnix) in short-term (2 min) dyadic encounters. Plasma levels of hormones measured in competitors either 1 hr before, during, or 3 min to 6 hr following a fight related poorly to either the attacking or nonattacking behavior displayed by opponents. However, transient fluctuations measured by the percentage change from prefight levels of plasma DHT, T, and B were identified in individuals following the onset of the fight. Winners demonstrated significantly greater percentage changes than did the losers at 3, 32, and 362 min for DHT and T and at 7 min for B. These differences in hormonal responses to the fight are attributed to the more aggressive behavior displayed by the victorious opponents (winners) over their defeated competitors (losers). Significance of these rapid changes is discussed in relation to the physiology and behavior of aggressive interactions.