This region includes Australia, New Zealand, New Guinea, Sulawesi, and some islands in the southwest Pacific. The Australian fauna is the least diverse in terms of the number of orders and species present, but certainly the most distinctive of all the major regions. Excluding Cetacea, only eight orders of mammals are native to Australia, but five of these, Monotremata and four orders of marsupials, are endemic. The other three indigenous orders are Chiroptera, Rodentia, and Carnivora. The latter is represented only by seals, though one terrestrial species, the dingo (Canis familiaris dingo), was brought to Australia by early human inhabitants several thousand years ago. Further introductions have been made by European settlers. There are 17 endemic families, and 60% of the genera and nearly 90% of the species are also endemic.
This distinctive fauna is the result of long isolation after the region broke away from Gondwana around 55 million years ago. When this event took place, only the monotremes
and marsupials were present. The Monotremata are an ancient evolutionary line composed of three species, the duckbilled platypus (Ornithorhynchidae) and two species of echidna or spiny anteater (Tachyglossidae). Marsupials appear to have reached Australia by a filter route from South America via Antarctica. When Australia and Antarctica separated, these original marsupials were isolated. During the 40 million years that followed they radiated to fill most of the niches occupied elsewhere by placental mammals. Larger species of kangaroos and wallabies occupy the large herbivore niche filled by ungulates in most of the rest of the world.
Rodents arrived in two separate migrations. It appears that rodents reached New Guinea from Southeast Asia and moved on into Australia by using islands as stepping stones. Upon reaching Australia, they radiated into many species. There are currently around 13 genera of rats and mice. Some bats are also thought to have reached the continent at a very early stage, with others entering the region later from the north. There are two endemic genera.
There are four orders of marsupials. Dasyuromorphia contains 17 diverse genera including the Tasmanian wolf (Thy-lacinus cynocephalus), Tasmanian devil, and the numbat or banded anteater. Order Peramelemorphia consists of small species, the bandicoots and bilbies. Order Notoryctemorphia has two species of burrowing marsupial "moles." The Diprodontia contains ten families and about 113 species including the familiar kangaroos, wallabies, and koala, as well as cuscuses and possums. The Australian region contains very few carnivores compared with other regions, only six species in Australia and five in New Guinea.
In more recent times, European settlers introduced several species that have succeeded in colonizing all or large parts of the continent. These include the house mouse (Mus muscu-lus), rabbit (Oryctolagus cuniculus), red fox (Vulpes vulpes), and feral cat (Felis catus). Several domestic herbivores have also established feral populations. Rabbits have degraded vegetation over vast areas and introduced foxes are blamed for the destruction of much of the native fauna. House mice and feral cats are distributed across most of Australia, and the rabbit and fox over about 60%.
The island of Tasmania has many common forms and has acted as a refuge for others. The recently extinct thylacine or Tasmanian wolf (Thylacinus cynocephalus) was present here in historic times and is unconfirmed from the mainland. It is still thought by some to be possibly present. The Tasmanian devil (Sarcophilus harrisii) survives only on the island but was formerly found across Australia. Both may have suffered from competition with the dingo.
Australia and New Guinea have been isolated for most of the last 45 million years by the 100-mi (160-km) wide Torres Strait, and they have been only intermittently connected to each other. New Guinea has many marsupial species including endemic genera and one endemic monotreme species, the long-beaked echidna (Zaglossus bruijni). There are also a number of highly endemic mice and bats. The murid fauna has evolved in isolation from that of Australia. The fauna of the islands at the western end of the region, lying between
the two continental shelves, is a mix of Australian and Oriental forms. The largest island, Sulawesi, contains a number of endemic species. These include the babirusa (Babyrousa babyrussa)—an aberrant type of wild pig, two species of anoa— the smallest of the wild cattle, and four species of macaques.
New Zealand's mammal fauna is a special case. The islands broke away from Gondwana and drifted across what is now the Pacific about 80 million years ago. Only 11 mammal species are indigenous—four bats and seven pinnipeds (seals and sea lions). However, many more have been introduced and its mammal fauna consists of 65 species. The first introductions, of rats and dogs, were made by Polynesian settlers who reached the islands around 1,000-1,200 years ago. European colonists arriving from 1769 onwards brought in many more, mostly for food or game. These include 23 marsupials and 14 ungulates (deer, chamois, and Himalayan tahr). Out of 54 known introductions, 20 came from Europe, especially Great Britain, 14 from Australia, six from Asia (three surviving), and 10 from North or South America (three are estab-
lished locally). Introduced species far outnumber native mammals and there are now more large species than small mammals, the opposite of the usual situation.
The smaller Pacific Islands have generally impoverished mammal faunas reflecting the difficulties in colonizing them. The bats are the best represented order, which is unsurprising in view of their ability to fly to small oceanic islands. Sixteen species of endemic bats occur on the Solomon Islands and two more are extinct. There are five endemic species of bats on the Melanesian Islands. One endemic species on Guam (Pteropus tokudae) is extinct, but a new species of bat was discovered on Guadalcanal in 1990. Rodents are the next most frequent group and there are some endemic mice. Ancestors of some of these presumably reached the islands by chance, floating on logs or rafts of vegetation.
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