The effects of cage enrichment on agonistic behaviour and dominance in male laboratory rats (Rattus norvegicus).

This experiment was carried out to investigate the effects of enriching laboratory cages on agonistic interaction and dominance of rats. In a series of three replicates, 48 rats were housed in groups of four in either 'standard' or 'enriched' cages for 6 weeks. Successful aggressive and defensive behaviour that ended up in a clear winner and loser were sampled in the first hour of the dark phase of the light/dark cycle every other week. Rats in the 'complex' cages showed lower levels of both successful aggressive and successful defensive bouts compared to rats in the 'standard' cages. Enriching cages of laboratory rat did not change the social order of the animals in the cage. Thus, enhancing the complexity of cages of laboratory rats by the particular cage modification regimen implemented in this experiment could be considered enrichment and could therefore result in an improvement of welfare in these animals.