The Bureau of Animal Population (B.A.P.) was established in 1932, and subsequently led, by biologist Charles Elton (1900-1991), as part of the Zoology Department of Oxford University. The Bureau concentrated on initiating important and new research into animal ecology of the United Kingdom, particularly in surveys regarding voles, rabbits, mice and rats, as well as some vegetation and parasites. The Bureau not only carried out important ecology studies locally in Wytham Woods and the Botanic Gardens, but functioned as a training ground for field workers and researchers who would go on to carry out studies internationally, such as in Alaska, Canada and Australia, records of which are in the archive. The B.A.P. was closed by the university in 1967.

Elton is heralded as establishing the principles of modern animal ecology. Prior to opening the Bureau he was also a consultant to the Hudson's Bay Company, regarding furbearing animals and these records feature in the archive of the Bureau. In 1936 he was appointed reader in animal ecology in Oxford, and published numerous papers, the data of which is in the archive (along with data collected and analysed by his colleagues at the Bureau). Charles Elton retired in 1967.