University of Oklahoma biologists carried out active field expeditions from 1924 – 1936. These expeditions typically were joint ventures between the Biological Survey and the then Museum of Zoology. Animal specimens were deposited in the museum and plants in the Bebb Herbarium (see Bebb Herbarium background). The results of many of these expeditions were published by the Biological Survey itself (see early publications of the Oklahoma Biological Survey). During the severe economic depression of the 1930s and World War II, the field expeditions and publications were discontinued. The last issue of the Biological Survey publication series appeared in 1933.