TESTOSTERONE AND AGGRESSION IN MALE RED JUNGLE FOWL

We investigated the relationship between aggression, plasma testostero ne level (T), and change in T in captive male red jungle fowl (Gallus gallus). T measured on day 1 of our experiment was positively correlat ed with T on day 8, suggesting that T remains constant in males when t he social environment is stable. During aggressive encounters that esc alated to include physical combat, males that attacked first (won) had increased T relative to their opponent. Males did not differ in T mea sured 1 week before the aggressive encounter. Our data suggest that an increase in T during aggression is associated with winning in escalat ed fights. (C) 1995 Academic Press, Inc.