The fauna of Norfolk Island has many characteristics typical of island faunas. Since Norfolk has never been joined to any major landmass the species living there have had to survive both a transoceanic journey and the hazards of colonisation in a new environment. As a result some faunal groups are under-represented on the Island. Whilst only a small number of native species are present, many are endemic forms.
In the absence of exotic predatory fauna such as rats, cats and cockroaches Phillip Island still provides an important breeding ground for seabirds and a vital refuge for some of the indigenous and endemic fauna.
The island boasts a bird list of one 116 species. Of these 66 are vagrants or non-breeding migrants. A number of the seabirds which nest on Phillip Island are subject to agreements which Australia has entered into with the Governments of Japan and the People's Republic of China. Many species of birds widespread in the southwest pacific have established themselves in Norfolk Island since European settlement. Some are probably self introductions while others were bought to the island from other places and deliberately released.
The Lord Howe Island skink Oligosoma lichenigera and the Lord Howe Island gecko Christinus guentheri are endemic to the Norfolk and Lord Howe Island groups. Due to predation by feral animals neither exist on Norfolk Island but both can be found on Phillip Island. More information about these two interesting reptiles can be found in the 2005 survey of the terrestrial reptiles.
A number of endemic invertebrates occur including one species of Collembola, 30 moths, 11 booklice, 65 beetles and one particularly impressive centipede which grows up to 150 mm long and 17 mm wide. The centipede Cormocephalus coynei was recorded on Phillip Island by King in 1792, but it was not described until recently. It is restricted to Phillip and Nepean Islands.
The only native freshwater fish recorded are two eels, the longfinned eel, Anguilla reinhardtii and the shortfinned eel, Anguilla australis. An introduced freshwater fish Poecilia reticulata has established in some streams on the island.
Two species of bats are the only native land mammals recorded from Norfolk Island. They are the Norfolk Island free-tail bat, Tadarida norfolkensis, and Gould's wattled bat, Chalinolobus gouldii. Only the latter has been seen in recent years.
Amongst the more prominent introduced mammals are rats and mice. The Polynesian Rat [Rattus exulans] arrived with Polynesian sailors. The rat was used as a source of food on their great voyages and released on islands en route. It is blamed for the removal on Norfolk Island of two native species of reptile and a large endemic centipede prior to European Settlement.
The Ship Rat [Rattus rattus] also known as black, bush, roof or house rat apparently appeared on Norfolk during the 1940's. This rat poses a threat to Norfolk's endemic land birds as it preys on eggs and nestlings. It also eats seed from the rarer trees and reduces their regeneration prospects. The House Mouse [Mus musculus] probably also made its appearance in the early days of European Settlement.
Control measures for the rats are being introduced in the National Park to protect nesting birds and help the propagation of rare trees whose seed is eaten by the rats. It is important that Phillip and Nepean Islands are kept rat-free as they can provide refuges for birds and other fauna threatened by rats.
Feral cats, Felis catus, are common around the island and seriously affect populations of both land and sea birds. Their devastating effects can be seen in most of the seabird nesting colonies on the Island.
Domestic cattle have severely affected the integrity of the native forest by eating seedlings and trampling vegetation. They have also been a vector in the transport of seeds of introduced plants. Since their exclusion from the Mt Pitt area (by fencing) there has been a marked improvement in the condition of native forest areas.