The Wallace Line Australia and the islands of New Guinea Sulawesi Halmahera and Flores are separated from the islands of Borneo Bali Java Sumatra and the mainland of Southeast Asia by an invisible line the Wallace Line This is named for the British naturalist Alfred Russel Wallace who recognized that the mix of animals one side of it were very different from those on the other side This is especially true for mammals and birds For example the native mammals of Australia and New Guinea are marsupials those to the northwest of the line are not During ice ages when ice sheets expanded at high latitudes the sea level fell and the islands to the northwest of the Wallace Line became joined in one landmass as did those to the southeast Even then however a trench of deep ocean still separated the two areas of land as it had for more than 50 million years That separation had allowed species to evolve separately and differently on either side Above the tree line in the Great Dividing Range of Victoria and New South Wales is high-altitude alpine grassland Here conditions are mild for much of the year but there is snow cover in winter The Critically Endangered marsupial Mountain Pygmy-possum lives near Mount Bogong and Mount Higginbotham Semiarid grassland and desert stretch across Australia’s vast interior Much of the natural grassland has been turned over to arable farming or the grazing of animals Some native animals have suffered as a result of these changes for example the plains wanderer a ground-living bird now classified as Endangered Areas of suitable habitat low plants with plentiful bare patches are just a small fraction of what they once were In good years plains wanderer numbers may reach 7,000 but in years of harsh drought they may fall to only 2,000 Another Endangered bird of this environment is the night parrot whose nocturnal lifestyle makes it very difficult to estimate its population The Australian interior or Outback can experience scorching daytime temperatures and long periods without rain although when it falls the rain may be torrential Despite these challenging conditions this environment supports large numbers of animals Many remain in underground burrows during the day only becoming active at night This is the domain of many reptile species including bearded dragons perenties and thorny devils which have grooves in their body scales to channel dew to their mouth 6 The Great Barrier Reef lies off the northeast coast of Australia and is the largest coral reef on Earth stretching 1,600 miles 2,575 km The reef’s biodiversity is extraordinary including more than 1,500 species of fish 17 species of sea snake 30 different kinds of dolphin and whale and a healthy population of dugongs It is protected by law but as with all reefs is likely to suffer as global ocean temperatures rise as a result of climate change New Zealand The two main islands of New Zealand North Island and South Island have big areas of temperate forest and high-altitude meadows on mountains such as the Kaikoura Ranges New Zealand’s only native mammals are three species of bat but one of the biggest threats to the country’s fauna has come from introduced mammals rats cats and dogs especially since many native birds are flightless This threat explains why so many native animals now live only on rocky offshore islands These natives include the tuatara a reptile in a family of its own and the Critically Endangered kakapo a nocturnal flightless parrot that is adept at climbing trees Several hundred miles southeast of New Zealand the small Chatham Islands are home to many seabirds including Chatham Islands taiko and Chatham petrel which breed nowhere else A termite nest in Kakadu National Park Australia Several endangered mammals birds and reptiles live in this preserve
HABITATS THREATS AND CONSERVATION 7
EX EW CR EN VU NT LC O Dugong Dugong dugon The vegetarian dugong has been hunted to the brink of extinction throughout most of its range The future of the species may now rest almost exclusively with the fate of one population living off the coast of Australia Sightings of dugongs and their kind are often said to have given rise to stories of mermaids The large blubbery animals with their huge bristle studded lips and tough gray hide may be far removed from the traditional image of the fabled sea maidens but dugongs are nevertheless graceful gentle and curious animals In areas where they are not persecuted they readily approach divers and small boats apparently attracted by unusual sounds Dugongs have excellent hearing and good eyesight Dugongs also face a number of natural hazards In the past when the animals were common the population could withstand losses from predation by sharks killer whales and estuarine crocodiles It could even recover from local catastrophes such as flooded rivers that dumped thousands of tons of silt over their sea grass pastures causing mass starvation Today with so many dugong populations at the very limit of viability such pressures could mean extinction for the remaining groups The dugong’s alternative name of sea cow is The plight of the African and Asian populations fitting since the animal’s behavior reflects that of the land cow Like its land-dwelling namesake it lives mostly in herds and it feeds on underwater pastures of sea grass It has intelligence similar to a cow or deer and its flesh is reputed to taste much like veal The dugong is the only living species in its family Its closest relative Steller’s sea cow was hunted to extinction over a period of just 27 years during the 18th century Hunting and Natural Hazards At one time dugongs were common around the edges of the Indian and southwestern Pacific Oceans However dugongs make good eating and have other uses They have been hunted for meat their oil and their thick hides which produce good leather Dugongs are mammals so they have to breathe air Consequently when they come up from a dive to breathe at the surface they are easy to catch and kill in nets The dugong has now been brought to the brink of extinction across its range 8 is cause for extreme concern In 1998 it was reported that the last remaining viable population of East African dugongs had probably declined to just 21 individuals barely a sustainable number Around the coasts of Madagascar India Sri Lanka and Southeast Asia the situation is equally critical The dugong is protected by law throughout its range but in many areas the law is difficult to enforce Illegal killing undoubtedly still occurs sometimes by accident sometimes deliberately in order to obtain food hides and body parts for use in traditional medicines and treatments substances derived from the dugong are used as aphrodisiacs Last Stronghold Dugongs once lived around the Australian coast in great herds numbering many thousands of individuals Although such herds are almost certainly a thing of the past groups of several hundred dugongs are still reported off the coast of western Australia However it is the seas between Australia’s northern coast and
DUGONG DATA PANEL Dugong sea cow Dugong dugon Family Dugongidae World population Probably fewer than 150,000 Distribution Indian and southwestern Pacific Oceans Habitat Shallow seas of tropical coasts Size Length head to tail 8 9 ft 2 4 2 7 m occasionally up to 13 ft 4 m Weight 300 800 lb 230 360 kg occasionally up to 2,000 lb 900 kg Form Large superficially seal-like mammal with gray almost hairless hide jointed front flippers and broad flat tail Small eyes and large upper lip with tough bristly pads Diet Mostly sea grasses occasionally green and brown seaweed Breeding Single young rarely twins born every 3 7 years at any time of year after gestation of 13 14 months Young first graze at 3 months fully weaned at 18 months mature at 9 10 years Life span up to 73 years Related endangered species Steller’s sea cow Hydrodamalis gigas EX No close living relatives but 3 species of manatee listed as Vulnerable Amazon manatee Trichechus inunguis Florida manatee T manatus and African manatee T senegalensis Status IUCN VU 9 the island of New Guinea that represent the closest thing the dugong has to a stronghold Here a limited amount of hunting by native Australians and Torres Strait Islanders is still permitted About 1,200 dugongs are killed in the region each year mostly by nets or harpoons Such hunting is strictly monitored because there are fears that even limited kills might be too much It remains to be seen if hunting will result in the same fate for the dugong as it did for Steller’s sea cow extinction The dugong uses its tail for swimming and its flippers for steering and walking along the seabed while it feeds The tail has a distinctive concave trailing edge which helps distinguish the dugong from the similar manatees
