THE ENVIRONMENT, HORMONES, AND AGGRESSIVE-BEHAVIOR - A 5-YEAR-STUDY IN GUINEA-PIGS

This paper summarizes persistent consequences of varying rearing and t esting conditions on intermale aggression, endocrine responses, and bo dy weight (BW) in guinea pigs. Pairs of unfamiliar males were placed i n chronic confrontations for 3-50 days in 2 m2 enclosures. Their behav iour was recorded in more than 1000 h of observation time. About 900 s amples were assayed for plasma glucocorticoid (GC), testosterone (T), and norepinephrine (NE) before and at different times after the beginn ing of the confrontations. The males were reared either in large mixed -sex colonies (CRM) or with a single female (FRM). When FRM males were confronted, high levels of aggressive behaviour occurred and high deg rees of stress were found in losers, especially when the environment w as familiar and a female was present. In contrast, CRM males confronte d in the same situation, but in a nonaggressive way, showed no changes in GC, NE, and BW. These differences between FRM and CRM developed ar ound puberty. A 50-min agonistic experience with an unfamiliar male ar ound this time shifted the subsequent adult behaviour of a FRM to a CR M pattern. These findings suggest a causal relationship between social experiences occurring around puberty, subsequent behaviour as adults, and degree of stress in chronic social encounters.