Australia animals

AUSTRALIA ANIMALS

The fauna of Australia consists of a large variety of animals; some 46% of birds, 69% of mammals, 94% of amphibians, and 93% of reptiles that inhabit the continent are endemic to it. This high level of endemism can be attributed to the continent's long geographic isolation, tectonic stability, and the effects of a unique pattern of climate change on the soil and flora over geological time. A unique feature of Australia's fauna is the relative scarcity of native placental mammals. Consequently, the marsupials – a group of mammals that raise their young in a pouch, including the macropods, possums and dasyuromorphs – occupy many of the ecological niches placental animals occupy elsewhere in the world. Australia is home to two of the five known extant species of monotremes and has numerous venomous species, which include the platypus, spiders, scorpions, octopus, jellyfish, molluscs, stonefish, and stingrays. Uniquely, Australia has more venomous than non-venomous species of snakes.

The settlement of Australia by Indigenous Australians between 48,000 and 70,000 years ago^[3][4] and by Europeans from 1788, has significantly affected the fauna. Hunting, the introduction of non-native species, and land-management practices involving the modification or destruction of habitats have led to numerous extinctions.^[2]: 8–9 Based on the list of Australian animals extinct in the Holocene, about 33 mammals (27 from the mainland, including the thylacine), 24 birds (three from the mainland), one reptile, and three frog species or subspecies are strongly believed to have become extinct in Australia during the Holocene epoch. These figures exclude dubious taxa like the Roper River scrub robin (Drymodes superciliaris colcloughi) and possibly extinct taxa like the Christmas Island shrew (Crocidura trichura). Unsustainable land use still threatens the survival of many species.^[2]: 8–9 To target threats to the survival of its fauna, Australia has passed wide-ranging federal and state legislation and established numerous protected areas.^[2]: v
Origins and history[edit]
Main article: Natural history of Australia
Evidence suggests that Australia was a part of the supercontinent Gondwana
Both geologic and climatic events helped to make Australia's fauna unique.^[5] Australia was once part of the southern supercontinent Gondwana,^[6] which also included South America, Africa, India and Antarctica. Gondwana began to break up 140 million years ago (MYA); 50 MYA Australia separated from Antarctica and was relatively isolated until the collision of the Indo-Australian Plate with Asia in the Miocene era 5.3 MYA. The establishment and evolution of the present-day fauna was apparently shaped by the unique climate and the geology of the continent. As Australia drifted, it was, to some extent, isolated from the effects of global climate change. The unique fauna that originated in Gondwana, such as the marsupials, survived and adapted in Australia.^[7]
After the Miocene, fauna of Asian origin were able to establish themselves in Australia. The Wallace Line — the hypothetical line separating the zoogeographical regions of Asia and Australasia — marks the tectonic boundary between the Eurasian and Indo-Australian plates. This continental boundary prevented the formation of land bridges and resulted in a distinct zoological distribution, with limited overlap, of most Asian and Australian fauna, with the exception of birds. Following the emergence of the circumpolar current in the mid-Oligocene era (some 15 MYA), the Australian climate became increasingly arid, giving rise to a diverse group of arid-specialised organisms, just as the wet tropical and seasonally wet areas gave rise to their own uniquely adapted species.^{[citation needed]}
Mammals[edit]
Main article: Mammals of Australia
Becoming extinct in 1936, the Tasmanian tiger was the largest carnivorous marsupial to have survived into modern times.^[8]
Australia has a rich mammalian fossil history, as well as a variety of extant mammalian species, dominated by the marsupials, currently however there is limited taxonomic research into Australia's mammals.^[9][10] The fossil record shows that monotremes have been present in Australia since the Early Cretaceous 145–99 MYA,^[11] and that marsupials and placental mammals date from the Eocene 56–34 MYA,^[12] when modern mammals first appeared in the fossil record. Although terrestrial marsupials and placental mammals did coexist in Australia in the Eocene, only the marsupials have survived to the present. Non-volant placental mammals made their reappearance in Australia in the Miocene, when Australia moved closer to Indonesia, and rodents started to appear reliably in the Late Miocene fossil record. The marsupials evolved to fill specific ecological niches, and in many cases they are physically similar to the placental mammals in Eurasia and North America that occupy similar niches, a phenomenon known as convergent evolution.^[13] For example, the top predator in Australia, the Tasmanian wolf,^[8] bore a striking resemblance to canids.^[14] Gliding possums and flying squirrels have similar adaptations enabling their arboreal lifestyle;^[15] and the numbat and anteaters are both digging insectivores.^[16] For the most part, mammals are not a highly visible part of the faunal landscape, as most species are nocturnal and many arboreal.