Outer Sister 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...

 and dolerite island, with an area of 545 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 Sisters Island Group

Sisters Island Group, Tasmania

Sisters Island Group is an unofficial name applied to a group of three islands off the north end of Flinders Island in the Furneaux Group off the north-east coast of Tasmania. The Sisters Island group consists of:* Inner Sister Island * Outer Sister Island...

, 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 northern point 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. The island is grazed by sheep and annual muttonbirding

Muttonbirding

Muttonbirding is a seasonal harvesting activity, which may be recreational or commercial, of the chicks of petrels, especially shearwater species, for food, oil and feathers...

 takes place.

Other islands in the Sisters Group are:

• Inner Sister Island
  Inner Sister Island
  Inner Sister Island is an island, with an area of 748 ha, in south-eastern Australia. It is part of Tasmania’s Sisters Island Group, lying in eastern Bass Strait off the northern point of Flinders Island in the Furneaux Group...
  
  
• Shag Reef
  Shag Reef
  Shag Reef is a small granite island, with an area of 1.24 ha, in south-eastern Australia. It is part of Tasmania’s Sisters Island Group, lying in eastern Bass Strait off the northern point of Flinders Island in the Furneaux Group...
  
  

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...

 and 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....

. 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 are the Metallic Skink

Metallic Skink

The Metallic Cool-skink or Metallic Skink is a species of skink in the Scincidae family. It is endemic to Australia, found in southern Victoria, as well as in Tasmania where it is the most widespread and common lizard, occurring on many offshore islands in Bass Strait as well as the mainland. It...

, 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...

, White-lipped Snake

White-lipped Snake

The White-lipped Snake is a small species of elapid snake that is restricted to south-eastern mainland Australia and Tasmania. It is the smallest of 3 species of snake found in Tasmania and is Australia's most cold tolerant snake, even inhabiting areas on Mount Kosciuszko above the snow line...

, Lowland Copperhead

Lowland Copperhead

The lowland copperhead or lowlands copperhead is a venomous snake species in the family Elapidae. It is commonly referred to as the copperhead, but is not closely related to the American copperhead, Agkistrodon contortrix...

 and Tiger Snake. Apart from the sheep, mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s present on the island include the Tasmanian Pademelon

Tasmanian Pademelon

The Tasmanian Pademelon , also known as the Rufous-bellied Pademelon or Red-bellied Pademelon, is the sole endemic species of pademelon found in Tasmania, and formerly throughout south-eastern Australia...

 and the introduced House Mouse

House mouse

The house mouse is a small rodent, a mouse, one of the most numerous species of the genus Mus.As a wild animal the house mouse mainly lives associated with humans, causing damage to crops and stored food....

, as well as feral cat

Feral cat

A feral cat is a descendant of a domesticated cat that has returned to the wild. It is distinguished from a stray cat, which is a pet cat that has been lost or abandoned, while feral cats are born in the wild; the offspring of a stray cat can be considered feral if born in the wild.In many parts of...

s.