Which animal group is used least often in laboratory research?

• A. Cats and dogs
• B. Mice and rats
• C. Primates
• D. Fish

Answer: (A)

The frequency with which different animals are used in research reflects practical, ethical, and regulatory considerations. Mice and rats are the dominant models because they are inexpensive to breed, have short lifespans, and there is an enormous amount of genetic and biomedical data available for them. Fish are also common, valued for rapid development, ease of keeping large numbers, and useful traits for genetics and developmental studies. Primates are used in more specialized areas due to higher ethical concerns, greater welfare needs, longer lifespans, and higher costs, so their use is limited. Cats and dogs, however, require substantial welfare considerations, stricter regulations, and greater care resources, and public and regulatory pressures further restrict their use, making them the least frequently used group in typical laboratory settings.