Differential effect of handling on adult aggression in male mice bidirectionally selected for attack latency

Individual variation in intermale aggression is to a significant degree bas ed upon genetic variation, but environmental factors can also exert their i nfluence on the level of aggression. Moreover, genotype-environment interac tions are a well-known phenomenon. In the present experiment, I tested whet her cage size or handling during development had an influence on adult atta ck latency scores. To be able to study a genotype-environment interaction, mice from two bidirectionally on attack latency selected lines were used. T he size of the cage in which the mice grew up had no long-term effect on ag gression, neither in the high- nor in the low-aggressive line. Handling, ho wever, significantly increased the adult aggression of males from the low-a ggressive line. Despite the differential effect of handling on genetically high- and low-aggressive mice, handling was not able to undo the marked dif ferences in attack latencies between mice from both lines. (C) 1999 Wiley-L iss, Inc.