In an area that is rich in terms of ecological flora communities, the Southwest National Park is also a wilderness area that is uniquely rich in biodiversity in terms of the variety of fauna species that either have all of their Tasmanian population or a majority of their population inhabiting the park. Within this national park alone there are, as noted by Driessen and Mallick 2003, three species of terrestrial mammals, 10 terrestrial bird species, seven reptile species, three frog species, four freshwater fish and or marine fish that are endemic to this 600-thousand-hectare national park. However, more pertinently the park is an important habitat to several species, including the
orange-bellied parrot (
Neophema Chrysogaster) and freshwater fish
Pedder galaxias (
Galaxias pedderensis), that are listed as critically endangered and extinct in the wild respectively under both Australian Commonwealth and Tasmanian legislation.
Birds Of the threatened, endangered and the eight species that are simply endemic to the park, such as the
fairy tern,
wedge-tail eagle,
green rosella and
dusky robin respectively, the species that adds to the park's cultural and conservation uniqueness is the
Neophema Chrysogaster, or more simply the Orange-bellied Parrot. As noted under the Commonwealth's National Recovery Plan 2016 listed as Critically Endangered under Commonwealth
Environment Protection and Biodiversity Conservation Act 1999, Endangered under New South Wales
Threatened Species Conservation Act 1995, South Australia's
National Parks and Wildlife Act 1972, Tasmania's
Threatened Species Protection Act 1995 and Threatened under Victoria's
Flora and Fauna Guarantee Act 1988. At an international level the species has also been listed as Critically Endangered under
International Union for Conservation of Nature and Natural Resources Red List (IUCN). What makes the area unique is that this National Park, or more specifically within 10 kilometres of Melaleuca Lagoon, remains the only known significant breeding ground of this parrot. This occurs primarily between November and March with the birds migrating back to the coast of South-East Australia over winter following a route along the west coast of Tasmania and
King Island. This breeding ground remains significant as there are currently only 50 Orange-bellied Parrots remaining in the wild with another 320 in captivity. the breeding success, in particular, the egg fertility and genetic diversity, as noted in the National Recovery Plan, is lower in the captive population than the wild population. As such it has been seen as critically imperative to ensure that the remaining numbers in the wild and quality habitat is retained, particularly in regards to the breeding program. Fortunately, through regular monitoring, supplementary feeding, artificial nest boxes and protection of their nesting and foraging habitat in the park, this appears to be occurring despite the existing potential threats posed by fire, climate change and damage to habitat.
Mammals With the number of mammal species that inhabit the park, the only one that appears threatened is the
New Zealand fur seal, which as noted by the Melaleuca-Port Davey Plan, only regularly visits the offshore
Maatsuyker Island during the breeding season.
Fish Another unique aspect to this park is the freshwater community, particularly the fish. As noted by Tasmania Parks and Wildlife, the aquatic system in the park has had no introduced fish species recorded, which gives it high conservation value as there are few systems in Australia where this has occurred. Although fish are relatively well studied within the park, that is, 37 percent of species have been discovered once, the numbers and research undertaken suggests that there is potentially a relatively large number of undescribed or undiscovered fish species that are endemic to the park. With such potential for discovery of new species, that alone would indicate that it remains a significant area for increased biodiversity amongst the marine life and warrants conservation. However, of those fish species discovered such as the
cusk-eel (
Microbrotula sp.) and
maugean skate (
Zearaja maugeana) which are endemic to the park, which were part of conservation management program undertaken in the 1980s to protect the species. Alongside the now extinct
Thylacine in Tasmania, this case is indicative of ensuring that conservation measures are taken to protect species that are endemic to a particular area and have high conservation value, such as the Southwest National Park.
Reptiles and amphibians Alongside a number of bird and mammal species, there are several reptile and frog species that are uniquely endemic to the park alone. These include three reptiles, the
Tasmanian tree skink,
ocellated skink and
she-oak skink, and amongst the frogs, the
Tasmanian tree frog,
Tasmanian froglet and recently discovered
moss froglet. == Environmental problems and threats ==