Post-fight levels of plasma lactate and corticosterone in male copperheads, Agkistrodon contortrix (Serpentes, Viperidae): differences between winners and losers

During the mating seasons (late summer and spring), male copperheads (Agkis trodon contortrix; Serpentes, Viperidae) engage in aggressive physical inte ractions for priority of access to females. These fights generally involve two individuals and are characterized by prominent vertical displays, a hig h degree of physical contact, and the absence of biting. Ritualized aggress ion does not occur in females. Although intrasexual aggression in conspecif ics has obvious energetic costs (e.g., lactate accumulation) that can affec t subsequent behavior, few studies have addressed these costs in reptiles, and no studies have examined snakes. Moreover, recent studies suggest psych oneuroendocrine (catecholamines, glucocorticoids) regulation of metabolism during and following aggressive episodes. There were three main questions a ddressed in this study. Do winners and losers of staged, pair-wise encounte rs show differences in post-fight (60-min) levels of plasma lactate and cor ticosterone (CORT)? Are levels of plasma lactate correlated with levels of plasma CORT? Is fight duration correlated with levels of plasma lactate and CORT? Two different control groups (cage and arena) were used. Body length , body mass, duration of fighting, and season of testing were not correlate d with levels of plasma lactate and CORT. At 60-min post-fight, losers had significantly higher levels of mean plasma lactate and CORT when compared t o levels in winners and controls, and there were no significant differences between winners and controls. From our results, we suggest the following c onclusions. First, elevated levels of CORT in losers, but not winners, resu lt from psychoneuroendocrine factors rather than simple exercise. Second, e levated levels of CORT in losers retard metabolic recovery resulting in hig her lactate levels in losers, whereas winners return to pre-fight levels wi thin 60-min post-fight. Last, the CORT response has a net negative effect o n metabolic recovery and may be implicated in the protracted suppression of aggressive behavior in losers. (C) 2000 Elsevier Science Inc. All rights r eserved.