The person who played the most important role in the development of the White Dorper was G. Colerous who farmed near Grootfontein Agricultural College. He did not act as a co-operator but kept close contact with Grootfontein officials. His Merinos had a low lambing percentage under his veld circumstances and he became interested in mutton sheep. He bought Persians and also two Dorset Horn rams of outstanding quality which were imported from Australia during 1937.
The first crosses between Persian and Dorset Horn were mostly spotted but there were also white lambs. He mated 12 (white) half-cross Dorset x Persian rams with his Merino ewes and produced quarter-cross Dorset lambs (1/4 DH : ¼ BP : ½ Merino). Thus, he became a Dorset x Persian (Dorper) breeder but he concentrated on the white variation. In later experiments, Dorset Horn x Van Rooy cross-breeding was also done and the Dorper was also built up partially by this cross-breeding.
In the early stages, there was quite an argument about the name. Rous wanted to call his breed the Dorsian, while Engela favoured the name Dorper. Eventually, in 1964 the two Societies amalgamated and by explanation of F.N. Bonsma that these sheep actually carried exactly the same genes, the name Dorper was accepted and acknowledged as such by Stud Book. Exactly the same breed standards are applied to both Blackhead Dorper and White Dorper except regarding colour and pigmentation.