Herbert William Oakley was keenly interested in natural history from an early age and developed a sound knowledge of the fauna of his country. Around 1870 he was appointed as assistant to the geologist Professor William Boyd Dawkins at the museum of Owens College (which later became the University of Manchester), where he gained knowledge of palaeontology. In 1877 he joined the Cape Mounted Rifles as a gunner, with a view to learning more of the South African fauna. In this position he studied the fauna of the Transkei and collected the birds of the territory. In 1879 he was offered an appointment to the staff of the South African Museum, Cape Town, but his discharge took some time owing to the Anglo-Zulu War. He eventually took up his duties in June 1879 as first assistant to the curator, Roland Trimen*. Three months later his appointment was made permanent, at a salary of £10 per month. From 1 September 1880 to 9 December 1881 he served as acting curator of the museum in Trimen's absence. He had a wide general knowledge and was a competent worker who collected many specimens for the museum, particularly birds. After his death Trimen acknowledged him as one of the contributors of butterflies from the Western Districts to the museum, in the preface to his book South African butterflies... (1887-1889).
Oakley became a member of the South African Philosophical Society in March 1881 and participated actively in its proceedings by exhibiting specimens and presenting papers on birds and snakes. He read his first paper on 26 November 1879, "On the habits of the birds of the Transkei", which was published in the society's Transactions (Vol. 2, pp. 46-51). This was followed in July 1880 by "On the skeleton of the African Darter or snake bird, Plotus levaillantii" [now Anhinga rufa] (Vol. 2, pp. 85-89), and in May 1882 by a paper on the anatomy and habits of South African snakes (Vol. 3, pp. 6-14). He exhibited birds in November 1881 and January 1882, the skulls of snakes in February 1882, and specimens of Peripatus in August 1882 and May 1883. On the latter occasion he read a note on these peculiar arthropods. In 1881 he presented some specimens of a species of tortoise to the Albany Museum, Grahamstown. He was elected a member of the council of the South African Philosophical Society in July 1884, a few months before his death.
In October 1881 Oakley was sent to Fraserburg in the Karoo to investigate finds of fossil reptiles. He collected some specimens for the museum - the first of their kind in its collections - though they seem to have represented only a single species. The specimens were exhibited at a meeting of the South African Philosophical Society in October 1881. These finds made him the first officially employed fossil collector in southern Africa. He was succeeded as museum assistant by L.A. Peringuey*.
Oakley was a modest and retiring person, and a skillful and enthusiastic zoological collector and observer.