Flora and fauna
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Waterlilies such as the lotus flower abound in Kakadu National Park.
Grevillea
Kakadu is ecologically and biologically diverse.
Flora[edit]
Main article: Flora of Kakadu National Park
Kakadu's flora is among the richest in northern Australia with more than 1700 plant species recorded, which is a result of the park's geological, landform and habitat diversity. Kakadu is also considered to be one of the most weed-free national parks in the world.
The distinctly different geographical areas of Kakadu have their own specialised flora. The environment referred to as the "Stone Country" features "resurrection grasses" that are able to cope with extreme heat and long dry spells followed by periods of torrential rain. Monsoon forests often develop in the cool moist gorges dissecting the stone country. The southern hills and basins support several endemic plants that are only found in Kakadu such as Eucalyptus koolpinensis near Jarrangbarnmi (Koolpin Gorge). Lowland areas form a large proportion of Kakadu National Park and are mainly covered in eucalypt-dominated open woodland with the ground layer consisting of a large range of grasses including spear grass, sedges and wildflowers. The Kakadu plum, Terminalia ferdinandiana, is commonly found in the area.
The floodplains, which are inundated for several months each year, feature sedges such as spike rush as well patches of freshwater mangroves (itchy tree), pandanus and paper bark trees (Melaleuca). Varieties of water lilies, such as the blue, yellow and white snowflake, are commonly found in these areas. Estuaries and tidal flats are populated with varieties of mangroves (39 of the 47 Northern Territory species of mangrove occur in Kakadu) that are important for stabilising the coastline. Mangroves serve as feeding and breeding grounds for many fish species including the barramundi.
On the tidal flats behind the mangroves, hardy succulents (samphire), grasses and sedges grow. Isolated pockets of monsoon forest grow along the coast and river banks. These forests contain several impressive trees, among them the banyan fig, which can be recognised by its large, spreading aerial roots, and the yellow-flowered kapok bush or cotton tree, Cochlospermum fraseri, whose pods split to release cotton-like material.
Fauna[edit]
There is a remarkable variety and concentration of wildlife, including:
over 280 bird species
roughly 60 mammal species
over 50 freshwater species
over 10,000 insect species
over 1,600 plant species
some 117 species of reptiles
The diverse environments of Kakadu National Park supports a great array of animals, a number of which have adapted to particular habitats. Some animals in the park are rare, endangered, vulnerable or endemic. Responding to the extreme weather conditions experienced in the park, many animals are active only at particular times of the day or night or at particular times of the year.
Black wallaroos at Nourlangie Rock
Agile wallaby in grassland at Kakadu National Park
Short-eared rock-wallaby in Kakadu
Plumed whistling ducks
Black-necked stork, aka "Jabiru"Kakadu National Park
Brolga and magpie geese
Saltwater crocodile
Australian darter
Great-billed heron in Ngurrungurrudjba, Kakadu National Park
Black-necked stork, aka "Jabiru", in Ngurrungurrudjba, Kakadu National Park
Mammals[edit]
Brumbies (feral horses) at Yellow Water Billabong (Ngurrungurrudjba)
About 74 mammal species—marsupials and placental mammals—have been recorded in the park. Most of them inhabit the open forest and woodlands and are nocturnal, making it difficult to see them. Others, such as wallabies and kangaroos (macropods, 8 species), are active in the cooler parts of the day and are easier to see.
Among the larger more common species are dingoes, antilopine kangaroos, black wallaroos, agile wallabies, and short-eared rock wallabies. Smaller common mammals are northern quolls, brush-tailed phascogales, brown bandicoots, black-footed tree-rats, and black flying foxes. Dugongs are found in the coastal waters. However, recent surveys have revealed a disturbing decline of nearly all mammal species throughout Kakadu, including once common and widespread species such as northern tart bats.
Birds[edit]
Kakadu's many habitats support more than 280 species of birds, or about one-third of Australia's bird species. Some birds range over a number of habitats, but many are found in only one environment.
Some 11,246 km2 (4,342 sq mi) of Kakadu's savanna habitats has been identified by BirdLife International as an Important Bird Area (IBA) because it supports populations of the endangered Gouldian finch, the vulnerable red goshawk, the near threatened partridge pigeon and chestnut-backed button-quail, and the restricted-range hooded parrot and rainbow pitta. The Kakadu Savanna IBA also supports varied lorikeets, northern rosellas, silver-crowned friarbirds, white-gaped, yellow-tinted, white-lined, bar-breasted and banded honeyeaters, sandstone shrike-thrushes, white-browed robins, canary white-eyes, and masked and long-tailed finches.
Waterbirds include large populations of magpie geese, wandering whistling ducks, green pygmy geese, comb-crested jacana, black-necked stork, Australian pelicans, little black cormorant, Australian darter, nankeen night herons, pied herons, black bittern, sarus crane and brolga.
Reptiles[edit]
Estuarine crocodile in Yellow Water Billabong
Some 117 species of reptiles have been recorded in Kakadu. Being cold-blooded, these animals rely on heat from an external source such as the sun to regulate their body temperature. This is not to say that reptiles are active only during the day; in fact, few snakes can withstand Kakadu's midday heat and most are active at night. Since the arrival of the cane toad in the park, many populations of reptiles have crashed. Reptiles which were once a common sight such as large goannas, eastern brown snakes, death adders and many others were rare by 2010. The iconic frill-necked lizard has also significantly dropped in numbers.
Two species of crocodile occur in Kakadu: the freshwater crocodile (Crocodylus johnstonii) and the estuarine, or saltwater crocodile (C. porosus). Freshwater crocodiles are easily identified by their narrow snout and a single row of four large boney lumps called "scutes" immediately behind the head. Estuarine crocodiles do not have these scutes and their snout is broader. The maximum size for a freshwater crocodile is 3 metres (9.8 ft), whereas a saltwater can exceed 6 metres (20 ft).
On 22 October 2002, a 24-year-old female German tourist was killed by a saltwater crocodile assault while swimming in Sandy billabong with other foreign backpackers including her sister.
Frogs[edit]
Kakadu's 25 frog species are extremely well adapted to the region's climatic extremes. Many remain dormant during rainless times. With the onset of the wet season, when the billabongs and swamps start to fill with water, the night air is filled with the sounds of frogs such as the northern bullfrog and the marbled frog. As the water builds up, frogs and tadpoles have an abundance of food, such as algae, vegetation, insects, dragonfly nymphs, and other tadpoles. Not all of Kakadu's frogs are found in the wetlands: many live in the lowland forests.
Fish[edit]
Driving near Red Lily Lagoon at Gunbalanya
Fifty-three species of freshwater fish have been recorded in Kakadu's waterways; eight of them have a restricted distribution. In the Magela Creek system alone, 32 species have been found. In comparison, the Murray–Darling river system, the most extensive in Australia, now supports only 27 native fish species. Although introduced fish have been found in most Australian waterways, none have been recorded in the park.
Insects[edit]
Kakadu supports more than 10,000 species of insect. Among the insect groups are grasshoppers, beetles, flies, termites, butterflies and moths, bees, wasps, ants, dragonflies and damselflies, caddisflies, non-biting midges and mayflies. The great variety of insects is a result of the varied habitats and relatively high temperatures throughout the year.
Perhaps the most striking insect-created features in the park are the termite mounds. The mounds in the southern part of the park are particularly large and impressive. Leichhardt's grasshopper, in colours of orange-red, blue and black, is perhaps the most spectacular insect found in Kakadu. It is also found on the Arnhem Land plateau and in Gregory National Park.