Rats are a well-understood and widely used laboratory species that should be provided with environmentally enriched caging in line with modern animal welfare guidelines. This paper reviews which sources of enrichment are effective and should be prioritised, and how methods for providing
enrichment might be selected using rats' preferences as a guide. Rats demonstrate high demand for social contact and prefer larger cages, and cages with shelters, nesting material and foraging devices. Rats also discriminate between different methods of providing a given type of enrichment.
It is clear that rats should be provided with enrichments such as social contact and shelter, and, in fact, that these should probably be considered basic husbandry requirements rather than optional improvements. It is still difficult, however, for animal caretakers to access proven, standardised
methods for providing appropriately enriched caging, and the level of enrichment routinely provided to most rats in the laboratory appears to be low. Further research is required to assess the impact of enrichment upon research variables and to develop commercially viable enrichment products
for rats in the laboratory.