Animals of Australia, New Guinea & the Pacific in U.S. zoos

A continent that drifted alone

Australia and New Guinea both belong to Sahul, the Australian plate that was once part of Gondwana. Australia separated from Antarctica about 50 million years ago and stayed relatively isolated until its plate collided with Asia. The Wallace Line, a tectonic boundary across which no land bridges formed, kept most Asian and Australian land animals apart, birds excepted.

That isolation produced extraordinary endemism. Some 46 percent of Australia's birds, 69 percent of its mammals, 94 percent of its amphibians and 93 percent of its reptiles live nowhere else. Native placental mammals are scarce, so marsupials took over many of their roles. The koala, a eucalyptus-eating marsupial whose closest relatives are wombats, is one example. The red kangaroo is the largest living marsupial. Two of the five living monotremes, the egg-laying mammals, are Australian: the platypus and the short-beaked echidna.

New Guinea's mountain rainforests

New Guinea is the world's largest and highest tropical island. It covers less than 0.5 percent of Earth's land yet holds about 8 percent of known vertebrate species. Land bridges joined it to Australia during Pleistocene ice ages, the last severed about 10,000 years ago, and some Asian species arrived across the Indonesian islands. The result is a mix of Australian and Asian wildlife found nowhere else.

Tree-kangaroos are mostly endemic to New Guinea. Matschie's tree-kangaroo lives only in mountain rainforest on the Huon Peninsula and nearby Umboi island, at 1,000 to 3,000 m (3,300 to 9,800 ft). The Victoria crowned pigeon, the largest living pigeon, forages for fallen fruit in lowland swamp forest. The southern cassowary, a flightless rainforest bird up to 1.8 m (5.9 ft) tall, lives in New Guinea, Indonesia and northeastern Australia.

Pacific islands

Farther out in the Pacific, remote islands have animals of their own. The Guam kingfisher, found only on Guam, was last seen in the wild in 1986 after the invasive brown tree snake reached the island, and it is now Extinct in the Wild. The Laysan duck once lived across the whole Hawaiian chain but nearly died out in 1912, and the crested gecko is native to rainforest in New Caledonia.

Birds and reptiles

Australian parrots make up about a sixth of the world's parrot species, including many cockatoos. The laughing kookaburra is the largest kingfisher, known for a call like human laughter, and the owl-like tawny frogmouth is actually closer to nightjars than to owls. Australia is the only continent where venomous snakes outnumber non-venomous ones, and it has more than 700 lizard species, among them the blue-tongued skink.

Extinctions and invaders

Hunting, introduced species and habitat change since human settlement have caused numerous extinctions, including about 33 mammals in the Holocene. Since the 1960s invasive species have been the leading cause of native animal extinctions. Red foxes prey on native animals, and cane toads poison the predators that eat them.

Many survivors remain at risk. The koala is Vulnerable, with habitat clearing, cars, dogs, disease and bushfires all taking a toll. In New Guinea, logging and the conversion of forest to farmland are the main threats to most bird species. Matschie's tree-kangaroo is Endangered, and its captive population is coordinated through a Species Survival Plan.