salt lakes form after heavy rainfall and at times fill the underlying salt flats. The salt lakes occupy relatively small areas in the desert areas. For example, a major salt lake is Lake Eyre, which spans areas of the Gibson and Tirari deserts and fills up completely and then dries up about once every 25 years. Seventeen headwaters have formed in the deserts as a result of the subsurface Great Artesian Basin, one of the largest freshwater basins in the world. The water coming out of the springs is rich in minerals. The springs partially form the habitat of endemic fish and the spring area is overgrown with rare plants. Numerous springs have dried up due to extensive agricultural use in the last 100 years. Threats to biodiversity include wildfires, feral animals, weeds, and uncontrolled grazing. Wildlife Significantly fewer animals live in the Australian deserts than in the Australian coastal regions. The most common creatures in Australia's arid regions are insects, such as termites and ants, which are of great importance to the ecology. Animals in the desert include feral camels, dingoes, goannas (including the large perentie) and numerous species of lizards and birds. Mammals include bilbies, woma python, mulgara, malleefowl, common brushtail possum, rufous hare-wallaby, burrowing bettong, the black-flanked rock-wallaby, marsupial moles, rufous hare-wallabies, yellow-footed rock wallaby, western grey kangaroos, and red kangaroos. Some of the bird-life found within the desert include the rare Alexandra's parrot, wedge-tailed eagles, Australian bustard, the mulga parrot, the scarlet-chested parrot and the chestnut-breasted whiteface (Aphelocephala pectoralis) found on the eastern edge of the Great Victoria Desert and the malleefowl of Mamungari Conservation Park. About 95 species of mammals lived there at the time of European colonization, of which 17 are extinct, such as the desert bandicoot (Perameles eremiana), the numbat (Myrmecobius fasciatus) and the long-tailed bouncy mouse (Notomys longicaudatus). The main survivors are small rodents, insectivorous bats, marsupials, kangaroos and wallabies. A major threat to vegetation are the free-roaming camels in the desert. Over 200 species of birds live in the desert areas, including emus, ratites, parrots, cockatoos, owls and raptors. The desert includes many types of lizards, including the vulnerable great desert skink (Egernia kintorei), the Central Ranges taipan (discovered in 2007), and a number of small marsupials, including the endangered sandhill dunnart (Sminthopsis psammophila) and the crest-tailed mulgara (Dasycercus cristicauda). One way to survive here is to burrow into the sands,