ENVIRONMENTAL ENRICHMENT AND AGGRESSIVE-BEHAVIOR - INFLUENCE ON BODY-WEIGHT AND BODY-FAT IN MALE INBRED HLG MICE

The influence of environmentally stimulated aggressive behaviour on bo dy weight development and body composition was studied in 90 male HLG/ Zte inbred mice between day 61 and 125 of life. Male mice were kept in groups of three in Macrolon cages type III (800 cm(2)) as controls (C -groups) or in two different enriched cages (6500 cm(2)) structured ei ther by a closed passage-way of 7.8 m (P-groups) or by 13 parallel-arr anged open corridors (O-group) between fodder rack and water bottle. T he number of inflicted bites as an indicator of aggressive behaviour w as about 45 times higher in the P-groups than in the C- and O-groups. In P-groups the bites were predominantly found on tails (60%), while i n the other two groups 90% occurred on the back. A negative correlatio n was found between the number of body wounds and the body weight in I -groups. Their body weight development was already significantly delay ed after two weeks of differential caging compared with controls. Simi larly weighing C- and O-groups showed significant differences in the b ody composition, i.e. standard laboratory caged C-groups were fatter. The body fat content of I-groups amounted to only about half that of t he controls, which was exclusively responsible for their lower body we ight. We assume that only in the I-cages the environment induced the e stablishment of a strong territorial dominance maintained by a single male, because it was easily possible to occupy the only existing way b etween fodder rack and water bottle. By contrast, a single male in the O-groups was not able to control the numerous ways to the fodder rack . The Macrolon cages were possibly too small and unstructured to estab lish territorial behaviour.