Overview:The first episode provides an overview of Australia's natural history. Tasmania gives a glimpse of Australia's lush forests of the past. A group of Tasmanian devils are filmed squabbling over a wallaby carcass. In eastern Australia, buckling formed the Australian Alps, high enough to attract snowfall. Wombats bulldoze the snow to reach buried grass and platypus hunt shrimp in the mountain streams. In the ancient tropical rainforest of the Top End, cassowaries, striped possums and sugar gliders are filmed. Kangaroos and koalas inhabit the more open eucalpyt woodlands, and kookaburras feed their chicks in the nest hole. As Australia dried out, many rivers became intermittent or turned to creeks. Billabongs attract wildlife such as flocks of corella parrots, a sign of water to early explorers.They are curious, sociable birds, and are shown playing on branches and investigating the nest holes of budgerigars. In north Australia's wet season, the tropical wetlands of Kakadu attract millions of magpie geese and other water birds. When the land begins to dry out again, freshwater crocodiles must move to avoid being trapped in shrinking pools. Aerial photography is used to show features of Australia's deserts, such as parallel dunes and Uluru. A planigale hides from a taipan, the world's deadliest snake, and a sand goanna digs out a scorpion. The Great Barrier Reef was formed 10,000 years ago as sea levels rose. At certain tides after a full moon, its corals engage in the planet's greatest synchronised spawning event.