Repetitive backflipping behaviour in captive roof rats (Rattus rattus) andthe effects of cage enrichment

Repetitive 'stereotyped 'behaviours are often performed by both wild and do mestic rodents in small laboratory cages. In this study, a behaviour resemb ling a backwards somersault or backflip is described and quantified in capt ive roof rats (ship or black rats, Rattus rattus). Videotapes of captive-br ed rat pups showed that repetitive backflipping developed rapidly after wea ning. In all subjects, the behaviour was highly cyclical, with more than 90 per cent occurring during the dark phase of the light:dark cycle. Individu al variability in the performance of backflipping was considerable but perf ormance levels for each individual were consistent from day to day and at 3 0 and 60 days of age. Highly significant differences were found between lit ters (families), indicating important maternal and/or genetic effects on pe rformance 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 developm ent and expression of backflipping in young roof rats may be triggered by w eaning and maintained by a heightened state of arousal in a relatively impo verished environment with limited opportunities for perceptual and locomoto r stimulation.