The effect of numeric, spatial and resource crowding on behaviour of albino rats

Abstract

Investigated the effects of crowding on 128 rats. In Exp 1, crowding was conceived only in terms of numbers. Ss were assigned to the following conditions: (1) 2 Ss of like sex per cage, (2) 4 Ss of like sex per cage, and (3) 8 Ss of like sex per cage (the severe crowding condition). In Exp 2, crowding was conceived not only in terms of numbers, but in terms of space and food availability as well. Crowding influenced growth rate negatively in all conditions. Crowded animals showed less activity than animals reared under normal conditions. Open-field stress reactivity and caffeine sensitivity were unaffected by crowding. Ss in the food-restricted condition showed the highest metabolic rate. In Exp 1, Ss in Condition 3 were more aggressive than Ss in Conditions 1 and 2. In Exp 2, limited space and limited food contributed to aggressive behavior. Reduction of growth-rate and aggression were more pronounced in male Ss than in female Ss.