The Capricorn and Bunker Cays form part of a distinct geomorphic province at the southern end of the Great Barrier Reef.

The sea level was much lower during the last ice age (at the end of the Pleistocene period) and the coastal plain on which today's reefs and cays developed was completely exposed.

[6] The southern cays and reefs were first chartered between 1819 and 1821 by Lieutenant Phillip Parker King RN initially in the Mermaid and later in the Bathurst.

The main charting exercise for all the islands and reefs was carried out in 1843 under the command of Captain Francis Blackwood in HMS Fly, which was accompanied by the Bramble.

[7] In the 1963–1969, the eastern portion of the reef surrounding Tryon Island was used for coral collecting on a lease by Joyce Burnett & Sirian Hamilton Harlow.

[8] At the end of 1969, Graeme Laver, Professor of Biochemistry and Molecular Biology at the Australian National University in Canberra, organised a trip to Tryon Island and discovered that seabirds on the Great Barrier Reef are riddled with influenza viruses.

[9] Crystals of this neuraminidase were later prepared for X-ray diffraction analysis to elucidate the enzyme's three-dimensional structure,[9] yielding information useful to many pharmaceuticals, such as Gilead Sciences, Hoffmann La Roche, BioCryst Pharmaceuticals, GlaxoWellcome, Eli Lilly and Company, Abbott Labs., ZymeTx Corporation and Pfizer Ltd. in the design and synthesis of novel neuraminidase inhibitors which these companies hoped to market as anti-influenza drugs.

[9][10] In particular, Gilead Sciences in the United States developed a carbocyclic, orally bioavailable neuraminidase inhibitor currently marketed under the name Tamiflu.

A successful ant-baiting program has also significantly reduced Tryon Island's introduced ant population, with no visible effects on native species.