Lean and mean rats: Some effects of acute changes in the food supply upon territorial aggression

Abstract

In experiment 1, individually housed rats subjected to short-term food restriction displayed more territorial aggression toward conspecific intruders than controls maintained on a free-feeding diet. In experiment 2, small groups of three adult male rats had access to either a standard laboratory diet or the standard diet plus sucrose. Groups with the sucrose supplement were significantly less aggressive toward intruders than controls. Sucrose availability did not produce appreciable gains in body weight but it did reliably decrease within-colony weight variation. The results suggest the existence of an effective dietary mechanism that enables a social species such as Rattus norvegicus to tolerate each other in dense feeding aggregations when food is abundant. Conversely, when food is limited, social intolerance increases and serves to limit the development of large feeding groups.