The effect of captivity on fighting by Rattus villosissimus (Rodentia : Muridae)

Abstract

Fifteen-min encounters were staged between adult male R. villosissimus in a neutral cage. Rats (F0) which had been trapped in the wild from a dispersed and declining population were quicker to start fighting and spent more time in the offensive sideways posture and fighting each other than did rats (F1) which had been born and raised in captivity. This result may support Chitty's hypothesis on the natural selection of self-regulatory behaviour. The differences between F0 and F1 encounters were not so great when the F0 rats were retested after a further 4 months in captivity. Possible explanations are discussed.