Which statement best describes the majority of research animals?

• A. Mice & rats
• B. Dogs & cats
• C. Non-human primates
• D. Zebrafish

Answer: (A)

The majority of research animals are mice and rats. They’re favored because they’re small and quick to breed, which keeps maintenance costs low and allows researchers to obtain large sample sizes for robust statistics. Their biology is well understood, and there’s a vast array of established tools and resources—many inbred and genetically modified strains, standardized husbandry practices, and broad historical data—that make them highly versatile for a wide range of studies. While dogs and cats, non-human primates, and zebrafish are important in certain fields or specialized experiments, their numbers are much smaller due to higher care costs, ethical and regulatory considerations, and practical constraints.