Zoogeographical Realms – The Australian Region

Extent

This region consists of Australia, Tasmania, New Guinea, and some smaller islands of the Indonesian archipelago. Many zoogeographers prefer that New Zealand and the Pacific Islands are not included in this region.

They treat New Zealand as an ancient island and Pacific Islands as oceanic islands.

Australian subregion

This region covers Australia and Tasmania. This is situated towards the southwest of the Pacific Ocean. Australian region is separated by the mainland due to the huge oceanic barrier so shows tropical and temperate climatic conditions.

Australian region is known as “Home of Marsupials”. This is because it has 34 genera of marsupials.

Austro-Malayan subregion

This region mainly consists of Malayan Archipelago, New Guinea, Solomon Islands. This is marked by the presence of marsupials, river turtles, crowned pigeons, etc.

Polynesian subregion:

The region consists of Polynesian islands where the diversity of fauna is indigent.

New Zealand subregion

Some zoogeography workers include this in the Australian region. This includes New Zealand. It is well marked by the presence of living fossils – sphenodon, flightless birds – kiwi, and there are no snakes.

Physical attributes and Climatic conditions

This region is partly tropical and partly temperate. Australian region has the unique property that it has no land connection with any other region. The tropical parts include Australia and New Guinea. The temperature in this region is high in summers and is covered by prolific, dense, and thick tropical rainforests.

The temperate climate includes the region Southern Australia. It has forests of eucalyptus and mixed hardwoods. The interior Australian continent has hot, arid plains and deserts.

Zoological Characteristics

The Australian region is marked by the presence of a great variety of primitive life forms and the absence of higher placental mammals. The primitive life forms include monotremes (egg-laying mammals), marsupials, cassowaries, emus, tooth-billed pigeons, scale-footed lizards, lungfish, freshwater mussels, etc.

Australian region is often called the “VeritableMuseum of Archaic Animals”. This is because of its physical isolation, no connection with any other region provided sanctuary and prevented the higher placental mammals from reaching this distinct region.

This region has about 134 families of terrestrial vertebrates. Out of which 30 are unique and exclusive to this region. These 30 indigenous families comprised eight mammals, 17 birds, 3 reptiles, and 2 amphibians’ families.

Mammals

There are 9 families of mammals. Eight families are of monotremes and marsupials. The only one is the placental which is the murid mouse family. Some animals which were introduced by man here are rabbits, bats, cats, dogs, etc.

The most common and conspicuous mammals are kangaroos, wallabies, wombats, phalangers. These marsupials show parallel radiation, occupying all types of niches as placental mammals. So here are all types i.e., herbivorous, carnivorous, arboreal, etc.

Aves:

The bird fauna is unique and rich. This region has 58 families of birds. The 44 families are widely distributed. There are ten indigenous families of birds which include flightless birds such as emus and cassowaries, lyrebirds, tooth billed pigeons, birds of paradise, etc.

Here exist great diversity of parrots and pigeons. Australian parrots have three endemic subfamilies which are cockatoos, pygmy parrots and lories. It shares flowerpeckers, wood-swallows, frogmouths with the Oriental region. However, there are no pheasants, finches, woodpeckers which are abundant in other regions.

Reptiles:

There are only two endemic families of reptiles in the Australian region. These are Crettochelydidae (flying river turtles) and Pygopodidae (scale-footed lizard). There are 250 species of small lizards.

Crocodiles are in tropical parts of this region. One remarkable large lizard is “Komodo Dragon” a varanid.

Amphibians:

This region has no tailed amphibians. Few frogs are found here but no toads are present. 100 species of tree frogs are present. Tree frogs secrete special compounds from their skin glands which act as a mosquito repellent.

Fish:

There is no diversity of freshwater fauna. Lungfishes; Neoceratodus out of three genera is present in rivers of Queensland.

Affinities to other regions

There is no connection between the Australian region with other zoogeographical regions. So, the fauna is mostly primitive and unique here. This region lacks freshwater fauna and some amphibians. Some organisms like frogs, marsupials, etc. resemble the fauna of the Neotropical region.

The terrestrial reptiles and birds show great resemblance with the Oriental region. This region resembles very little with the Ethiopian region.

MCQs