Florida State University Biologist Scott Steppan has spent the last decade playing an exhaustive game of cat and mouse–Steppan and his colleagues being the cat, and the mouse being, well, mice. He and his colleagues have classified seven new field mouse species in a small area on the island of Luzon in the Philippines. The findings reveal new insights into the great amount of biodiversity on this planet, and have implications for the future discovery of new species of mammals.