Worldwide, an estimated 192.1 million animals are used every year for scientific purposes. In the United States, some of these animals are protected by the federal Animal Welfare Act (AWA), which means their use must meet certain (minimal) welfare standards and that their numbers are tracked, including where they are used, how many are used, and what they are used for. Animals including dogs, cats, and primates, for example, are covered by the AWA.
However, the overwhelming majority of animals used in science — somewhere between 95 and 99% — are not protected. Of these unprotected animals, nearly all are mice or rats. Because these animals are not regulated, we do not have solid data for their numbers. By extrapolation, however, experts have estimated that around 111.5 million rats and mice are used annually in medical research in the United States. In terms of animals used in research that are covered by the AWA, the most recent data available (2019) shows that Massachusetts leads the country at nearly 85,000 animals.
