Rats are both widely used research animals and popular companion pets, with welfare needs that are better understood than most rodents and frequently underprovided.
Rat welfare science is well-developed compared to most rodents: their social nature, cognitive complexity, and emotional responsiveness have been studied extensively. Solo housing — still common in research and sometimes in pet keeping — causes demonstrable psychological harm, with isolated rats showing depression-like behaviour, altered stress responses, and impaired cognitive performance. Both as research subjects and as companions, rats flourish in socially complex, enriched environments and suffer in isolation.