Repetitive Backflipping Behaviour in Captive Roof Rats(Rattus Rattus)and the Effects of Cage Enrichment

Abstract

AbstractRepetitive ‘stereotyped’ behaviours are often performed by both wild and domestic rodents in small laboratory cages. In this study, a behaviour resembling a backwards somersault or backflip is described and quantified in captive roof rats (ship or black rats,Rattus rattus). Videotapes of captive-bred rat pups showed that repetitive backflipping developed rapidly after weaning. In all subjects, the behaviour was highly cyclical, with more than 90 per cent occurring during the dark phase of the light:dark cycle. Individual variability in the performance of backflipping was considerable but performance levels for each individual were consistent from day to day and at 30 and 60 days of age. Highly significant differences were found between litters (families), indicating important maternal and/or genetic effects on performance levels. Cage enrichment in the form of a wooden nest box resulted in dramatically lower rates of performance. Increased cage height resulted in delayed development of backflipping, as well as changes in the form of the behaviour. Results are consistent with the hypothesis that the development and expression of backflipping in young roof rats may be triggered by weaning and maintained by a heightened state of arousal in a relatively impoverished environment with limited opportunities for perceptual and locomotor stimulation.