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WHERE
AUSTRALIAN ANIMALS LIVE
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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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