Fuller is best known in academic circles for his long-term studies on population fluctuations of small mammals, especially in the boreal forest (see Boreal Zone). After 12 years with the Canadian Wildlife Service (1947–59), during which he studied larger mammals and surveyed several northern areas, he joined the University of Alberta’s zoology department in 1959 and stayed there until his retirement in 1984. During his wildlife-service career, he was the first biologist to see the last remaining natural nesting grounds of the whooping crane.
Fuller applied ecological principles to conservation problems. He chaired a subcommittee of the International Biological Program and the National Research Council of Canada’s Associate Committee on Ecological Reserves. He served on the board of the International Union for the Conservation of Nature and Natural Resources, as well as Canada’s Review Panel on Northern Diseased Bison. The author of more than 50 scientific articles, Fuller also co-wrote five books.