The zoo first opened in 1923, its founder and owner being Herbert Whitley. His breeding of pedigree livestock was of national importance and so too was his botanical collection. If Kew gardens had been destroyed in World War 1, Primley could have been called upon to supply many replacement specimens. He considered the commercial aspects of his operation of little consequence and therefore the sixpenny charge for children and the one shilling for adults which he charged users of his private road, was more to control the number of visitors rather than to be an entrance fee to his Zoo. However, in March 1924 he was summoned by Customs & Excise for not levying 'entertainment tax' - something he steadfastly refused to pay. He was brought before the local Bench and fined £1 with 10 guineas (£10.50) costs. He had a similar brush with the Authorities in August 1937 when he was again charged with failing to collect entertainment tax. This time he was fined £25 with 10 guineas costs. Earlier, in June 1927, it was offered as an educational facility and the 1s.2d admission for adults included the tax; children, however, continued to be charged only 6d.
The collection was expanded greatly in the late 1920s and, sometime about 1930, he bought a conure (a small parrot-like bird) from a dealer. It was subsequently named "Whitley's Conure" and was thought to be a natural hybrid. The first Guide to the Zoo appeared in 1930 and still continues after many subsequent editions. Towards the end of the year the zoo became Devon's Zoo & Circus after a specially-chartered train brought animal evacuees from Chessington Zoo. R. S. S. Goddard, who had created Chessington, had bred a lioness; she, together with her four cubs, were an immediate attraction; so too was "Beauty", the tigress who had starred in the Thirties film "Elephant Boy".
Herbert Whitley died in 1955 and the Herbert Whitley Trust was set up soon afterwards. Recently there have been attempts to build a super-market on vacant Zoo land and later, a house development so that as a quid pro quo, the Trust would have funds to maintain and improve the Zoo itself.