Cat Island is a granite

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

 island, with an area of 39 ha

Hectare

The hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...

, in south-eastern Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. It is part of Tasmania

Tasmania

Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...

’s Babel Island Group, lying in eastern Bass Strait

Bass Strait

Bass Strait is a sea strait separating Tasmania from the south of the Australian mainland, specifically the state of Victoria.-Extent:The International Hydrographic Organization defines the limits of the Bass Strait as follows:...

 off the east coast of Flinders Island

Flinders Island

Flinders Island may refer to:In Australia:* Flinders Island , in the Furneaux Group, is the largest and best known* Flinders Island * Flinders Island , in the Investigator Group* Flinders Island...

 in the Furneaux Group, and is part of the Babel Island Group Important Bird Area

Important Bird Area

An Important Bird Area is an area recognized as being globally important habitat for the conservation of bird populations. Currently there are about 10,000 IBAs worldwide. The program was developed and sites are identified by BirdLife International...

.

Fauna

Seabird

Seabird

Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...

s and wader

Wader

Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...

s recorded as breeding on the island include Little Penguin

Little Penguin

The Little Penguin is the smallest species of penguin. The penguin, which usually grows to an average of in height and in length , is found on the coastlines of southern Australia and New Zealand, with possible records from Chile.Apart from Little Penguins, they have several common names...

, Short-tailed Shearwater

Short-tailed Shearwater

The Short-tailed Shearwater or Slender-billed Shearwater , also called Yolla or Moonbird, and commonly known as the muttonbird in Australia, is the most abundant seabird species in Australian waters, and is one of the few Australian native birds in which the chicks are commercially harvested...

, Silver Gull

Silver Gull

The Silver Gull also known simply as "seagull" in Australia, is the most common gull seen in Australia. It has been found throughout the continent, but particularly coastal areas. The South African Hartlaub's Gull and the New Zealand Red-billed Gull The Silver Gull (Chroicocephalus...

, Pacific Gull

Pacific Gull

The Pacific Gull is a very large gull, native to the coasts of Australia. It is moderately common between Carnarvon in the west, and Sydney in the east, although it has become scarce in some parts of the south-east, as a result of competition from the Kelp Gull, which has "self-introduced" since...

, Crested Tern, Sooty Oystercatcher

Sooty Oystercatcher

The Sooty Oystercatcher, Haematopus fuliginosus, is a species of oystercatcher. It is a wading bird native to Australia and commonly found on its coastline. It prefers rocky coastlines, but will occasionally live in estuaries....

, Pied Oystercatcher

Pied Oystercatcher

The Pied Oystercatcher, Haematopus longirostris, is a species of oystercatcher. It is a wading bird native to Australia and commonly found on its coastline. The similar South Island Pied Oystercatcher The Pied Oystercatcher, Haematopus longirostris, is a species of oystercatcher. It is a wading...

 and Australasian Gannet. Resident reptile

Reptile

Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s include White's Skink

White's Skink

White's Skink is a species of skink in the Scincidae family. It is found in south-eastern Australia, including Tasmania and many Bass Strait islands. It is slow-growing, to a maximum length of about 90 mm, and may take four years to reach maturity. It gives birth to live young. It is...

 and Tiger Snake. The Rakali has also been recorded on the island.

Gannet colony

The historically important breeding colony of Australasian Gannets, with an estimated 5000-10,000 birds at the beginning of the 20th century, declined to extinction by the mid 1980s as a result of, at first, human intrusion, followed by fires, disturbance and, finally, predation by White-bellied Sea-Eagles.