Rats are the most commonly used rodent in biomedical research, with significant advances in welfare science improving their housing, handling, and enrichment over the past two decades.
Rats have been extensively studied for their social complexity, emotional lives, and capacity for empathy. Research shows that rats help each other escape from stressful situations and show apparent concern for distressed conspecifics. This cognitive and emotional complexity means that laboratory housing conditions have profound welfare implications - isolated, unenriched rats experience genuine psychological suffering. The good news is that welfare improvements for rats are well-researched and implementable with relatively modest investment.