Orr wrote 260 scientific and popular articles mostly on mammalogy and ornithology. He also wrote three books on fungi, and he co-authored (with his wife, Margaret Cunningham Orr) a book on western North American wildflowers. He authored a textbook on vertebrate biology that was first released in 1961, with the final fifth edition released in 1981. His publications include: • Orr, R.T. 1940. The rabbits of California.
Occasional Papers of the California Academy of Sciences 19:1–227, 10 pls., 30 figs. • —— 1945. A study of captive Galapagos finches of the genus
Geospiza.
Condor 47:177–201. • —— 1954. Natural history of the pallid bat,
Antrozous pallidus (Le Conte).
Proceedings of the California Academy of Sciences 28:165–246. • —— 1965.
The Animal Kingdom Macmillan, New York. 380pp. • —— 1972.
Marine Mammals of California University of California Press, Berkeley. 64pp. • —— and M.C. Orr. 1974.
Wildflowers of Western America. Knopf, New York. 270pp. • —— and D.B. Orr. 1980.
Mushrooms of Western North America University of California Press, Berkeley. 293pp. ==References==