Growing up, he had a keen interest in all the reptiles he could find on his father's 116 acres (0.47 km2) ranch.
Fish and Wildlife Service (USFWS) as a field biologist in the department of pest control, studying rodents such as squirrels, gophers, and kangaroo rats.
He served from 1941 to 1945 in the Medical Corps as an army pharmacist, stationed initially in the United Kingdom, then France, and finally in Germany.
In 1948, Fitch accepted a position as Superintendent of the University of Kansas Natural History Reservation and instructor of zoology, where he could again pursue his studies of snakes and lizards.
From 1965 on, he did extensive field work in Costa Rica, Mexico, Ecuador, and the Dominican Republic.