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A complex interplay of the history of the continent
with its present geology and climate determines where Australian
animals live. The rainforests along the east coast and the
animals that have lived there have evolved from the ancient
forests of Gondwana, isolated over millions of years from
the influences of other landmasses. Australia is the flattest,
driest (after Antarctica) continent in the world, with some
of the oldest and least fertile soils. These conditions determine
plant growth - and it is on plants that animals ultimately
depend for food. Their survival also depends on how they meet
the climatic and seasonal challenges of their habitats. The
habitats of Australia's animals extend from Antarctica to
the tropics, encompassing oceans, seashores, swamps and rivers,
coastal heathlands, mountain forests, alpine meadows, woodlands,
shrublands, and the dry grasslands of the interior.
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The Big Picture
South of the Tropic of Capricorn, in the temperate forests
and woodlands of eastern Australia, rain falls year-round;
summers are warm or hot and winters are mild to cool, and
may be really cold in the high country. North of the Tropic,
temperature and annual rainfall increase, but in the woodlands
of Cape York and the Top End summers are very wet and there
is a long dry season in winter. The temperate forests of southern
Western Australia have cool, rainy winters and warm or hot,
dry summers. The arid interior includes most of the spinifex
or hummock grasslands, shrublands and tussock grasslands;
rainfall is sparse and sporadic, falling mainly in winter
in the south and in summer in the north.
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The Small Picture
Within these large environments there are many smaller
habitats. In the desert around Alice Springs are waterholes
where black-fronted dotterels pick among the pebbles for food,
dragonflies dart above the shoreline vegetation, and in the
evening cave bats flutter above the water and rock-wallabies
emerge from the boulder-piles to graze and drink. In the semi-arid
zone, springs sustain unique species of snails and freshwater
fishes; a small fish with a big name - Scaturignichthys vermeilipinnis
- has been found only in five shallow springs on a property
in Queensland. Many animals in the interior became apparent
only after rain. The shield-shrimp's eggs are scattered by
the wind; when it rains they hatch in puddles and develop
rapidly to mate and lay more eggs to produce the next generation.
When watercourses dry up, desert burrowing frogs and freshwater
crabs enter a state of suspended animation underground, and
it may be years until fresh rains awaken them to feed, breed
and renew the cycle.
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Oceans
Australia's oceans have a great diversity of animal life.
In northern waters, coral species display an enormous variety
of colours and shapes, and their complex structures provide
homes for worms, molluscs, crustaceans, sea stars and fishes.
Reptiles and mammals also use this habitat: sea snakes and
sea turtles navigate the reefs, saltwater crocodiles patrol
inshore waters and estuaries, and the dugong grazes in the
shallow seagrass beds. Fewer species live in temperate waters
than in tropical ones, but the cooler seas are richer in plankton
and support enormous numbers of individual fishes. The abundant
plankton feeds the great baleen whales, while the vast shaols
of small fishes such as pilchards provide food for seals and
sea birds.
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Seashores
The pools, ledges, boulders and seaweeds of rocky shores
form complex structures rather like coral reefs, and harbour
sea snails, sea stars and sea urchins, worms, sea anemones,
sponges, crustaceans and fishes. On open sandy beaches, the
spaces between the grains of sand are home to a variety of
creatures, many of then so little known that they have no
common names.
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Mangroves
Mangrove swamps are valuable animal habitats. Many invertebrates,
fishes, reptiles and birds, such as the mangrove kingfisher,
live exclusively in mangroves, and their sheltered, shallow
waters act as nurseries for the juveniles of many fish species
and for crustaceans such as prawns: up to 25 mangrove species
grow along the coasts of Queensland and the Northern Territory,
along with just as many prawn species.
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Rainforests
Rainforests probably house the largest numbers of species
of land animals, particularly in the tropics. In the northern
rainforests, cassowaries pick over the forest floor for fruits;
another fruit-eater, the wompoo pigeon, rarely alights on
the ground. These forests are also home to many marsupials;
some possum species, including the striped possum and the
green ringtail possum, are found nowhere else. Tree-kangaroos
clamber along the branches and the smallest of the macropods,
the musky rat-kangaroo, forages on the forest floor or climbs
with its unique grasping big toe.
The rainforests on the Queensland-New South Wales border
support pouched frogs, which raise their young in pouches
on the sides of the males. Some insects are most diverse in
rainforest areas: the forests around Cairns and the Queensland-New
South Wales border house up to 140 butterfly species. New
rainforest species, such as skinks, are still occasionally
discovered. Possibly ten times the number of invertebrate
species currently described await discovery in the ferns and
mosses that cloak the trees in the canopy and in the leaf
litter below.
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Tall Forests
Mammals of the tall forests include rare and endangered
species, such as Leadbeaters possum in the Central Highlands
of Victoria, the long-footed potoroo, found in east Gippsland
and a tiny area of south-eastern New South Wales, and the
numbat of Western Australia. More widespread inhabitants of
tall forests are koalas, common wombats and ringtail possums.
Damp gullies in the forests of south-eastern Australia are
the preferred habitat of the superb lyrebird. By day, the
canopy may echo with the sound of gang-gangs cracking open
seeds and fruits, while by night arboreal mammals and roosting
birds fall prey to powerful owls.
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Mountains
The Snowy Mountains are Australia's only truly alpine
area, where animals must survive in snow cover for several
months of the year. Many invertebrate species of the High
Country are found nowhere else on the continent. Among the
vertebrates, the best known are the black-and-yellow corroboree
frog, found in marshlands above the tree-line and along creeks
in the lower forests, and the dainty mountain pygmy-possum
- the only marsupial that hibernates. It was known only from
fossils until a live animal was found at Mount Hotham in 1966.
It is now also known from near Mount Kosciuszko.
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Low Woodlands
Low woodlands are home to a great variety of Australian
animals. Some, like grey and red kangaroos, ringtail and brushtail
possums and spotted grass frogs, have ranges that extend from
these areas into both the tall forests and the drier shrublands
and grasslands of the interior. For others, such as quolls,
yellow-footed marsupial mice, yellow robins and superb blue
wrens, low woodland is their major home.
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Shrublands
This open habitat, sometimes known as scrub, supports
a surprising number of parrots, including the scarlet-breasted
and mallee ringneck parrots, as well as birds that spend most
of their time on the ground, such as the mallee fowl and the
plains wanderer. Shrublands are a generally harsher environment
than forests and woodlands, and the many varieties of insects
that thrive in these conditions are an important part of the
diet of the lizards, such as geckoes, that feed in and among
the shrubs.
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Tussock Grasses
Native rodents, such as Forrests mouse and the long-haired
rat, search for food among the clumps of tussocky grass, while
overhead letter-winged kites scan the ground for unwary rodents
or hare-wallabies.
Forblands
Two small but spectacular plant communities along the
Queensland-South Australian border and in the Ashburton Range
of Western Australia have been named the forblands. When the
rains come they burst into flower, and animals from surrounding
shrublands and tussock grasslands move into the forblands
to graze and feed on seeds.
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Spinifex or Hummock Grasslands
Spinifexbirds, grasswrens and spinifex pigeons peck and
flit among the clumps of spinifex, while the calls of chiming
wedge-bills sometimes fill the air. Desert rodents like the
hopping mice and the spinifex mouse, marsupials like the bilby
and reptiles such as the thorny devil make their home among
the clumps. Many of these animals have evolved burrowing or
nocturnal lifestyles to avoid heat and water loss. In this
arid and semi-arid zone there are more ant species than anywhere
else in Australia. Reptiles here have also diversified remarkably:
there may be up to 120 species in just one area of this country
- equal to the numbers found throughout the entire tropical
east coast. These include the perentie, which can grow to
2.5 metres and emerges from rock crevices to feed on insects,
small mammals, birds, and other reptiles.
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