Dr. Norris is a mammalogist and a systematist. His research focuses on determining the evolutionary relationships of rodents and other small mammals and involves questions ranging from deep history to recent patterns in populations. He has worked on projects involving integrating genetic data with fossil information, using genetics to uncover how past climate influenced evolution, and developing and applying molecular evolution techniques. In addition to work in North America, his fieldwork with small mammals has taken him to West Africa and he has worked on species from Central Asia.