Australia: The Land Where Time Began

A biography of the Australian continent 

The Coongie Lakes are about 100 lm northwest of Innamincka. The wetlands are included on the Ramsar convention list as an important habitat for birds and other fauna, with 205 species of bird being recorded in the area of the lakes. The lakes contain water most of the time, the ephemeral wetlands around them have water only after heavy rain or more usually flood from the Cooper Creek. The fauna and flora of the area is dependant on flood water from Cooper Creek for their very survival. Their survival is now threatened by the Queensland government assessing an application for reactivating water licences for a proposed cotton farm to take water from Cooper Creek. Heard of Cubby Station and the Murray?

These are a number of interconnected lakes and a few that aren't connected to the rest of the lakes. Cooper Creek branches about 30 km south of Innaminka, bringing water to the lakes of the complex along the northwest branch, in times of flood. The water first enters Tirrawarra Swamp before moving on to the Coongie Lakes.

Unlikely as it seems, these lakes that are in the middle of a salty desert, are relatively permanent and the middle reaches of the Murray River are 4 times as salty. The water is brought to them by Cooper Creek from the Queensland high country in the wet season, along the northwest branch. The water comes via Tirrawarra Swamp, filling the 3 most southerly of the linked lakes, Lake Coongie, Lake Marroocoolcannie and Lake Marroocutchanie. Brown Creek then takes the water to the northern lakes, Lake Toontoowaranie, from which Ella Creek takes it to Lake Goyder. A high sand dune complex to the north of Lake Goyder prevents the water from flowing further north, the lakes north of Lake Goyder depend for their water on local rain from the northeast, on Sturt's stony Desert, and then only when there is intense local rain, which means they are more ephemeral than the lakes of the Coongie system, resulting in a different aquatic fauna. One difference between them and the Coongie lakes is that they lack fish.

The Coongie lakes are about 2 m deep, so could be expected to dry up if they got no water from Cooper Creek for about 8 months. This is believed to be the reason for the depauperate nature of the fish fauna, that would normally be expected to be much more diverse because the catchment of the Cooper is about 300,000 sq km. There are widely diverse habitats in the system. Of the approximately 26 fish species found in the Lake Eyre Basin, only 13 are found in Cooper Creek.

Fish

Australian inland waters are extremely variable, any fish need to be able to survive a wide range of environmental conditions, with temperatures getting as low as 3^o C on winter nights to 40^o C on summer days, and salinity that can vary from fresh, at 1 PPT, to hypersaline at 350 PPT, sea water is 35 PPT. The levels of dissolved oxygen can range from 0 %, stagnant, to 192 %, supersaturated. The ranges of these characteristics can vary in any one water body over time, or between different water bodies, and from season to season, year to year and even over a single day. Salinity can vary over the range in 2-6 months, and dissolved oxygen can range from 15 % to 80 % daily. All up, the difficulty of being green has nothing on being a fish in central Australia.

Among the families of fish that have proven to be adaptable enough to survive these conditions, eel-tailed catfish, hardyheads and perches (grunters). Of the fish of the arid Australian interior, most come from these families. Some of the most successful and widespread fish are the  bony bream (Nematolosa erebi) Lake Eyre hardyhead (Craterocephalus erysii), spangled grunter (Leiopotherapon unicolor), central Australian catfish (Neosilurus argenteus), rainbow fish (Melanotaenia splendida), central Australian goby (Chlamydoglobius eremius) and western chanda perch (Ambassis castelnaui).

Most inland fish don't appear to have their distribution limited by environmental conditions other than salinity. Bony bream are found in a wide range of habitats, but most of the fish species have a preferred habitat, some preferring the sheltered habitats in swamps and backwaters. The fish of these sheltered habitats move about in complex ways, moving to different layers of the water column, to the sides and migrating diurnally.

Frogs

There is a rich diversity of frog species in the channels and lakes of the Coongie system. Among these are about 8 species of water-holding frogs, tree-frogs and grass-frogs.

Mammals

There are many mammal species found around the lakes region, about 12 species, some of which are 2 planigales, Planigale tenuirostris and  P. gilesi, which is larger. These planigales inhabit places such as the floodplain, channel edges and the edges of channels where there are claypans that develop deep cracks that they can hide in to avoid heat and cold, their flattened heads being adapted to squeeze into the cracks.

Forrest's Mouse (Leggodina forresti) is found on floodplains that have a cover of low chenopods, ephemeral lake beds that are densely vegetated and around the edges of salt lakes.

The long-haired rat, or native plague rat, (Ratus villosissimus), is not common in between wet times, but after good rains it can breed up in plague numbers, reducing to small populations in damp locations after the passing of the wet conditions. It is believed the dense lignum beds near the lakes of the Coongie system are a refuge area between plague years. There was a big wet in 1967 and in 1968 a cyclone brought a lot of rain, then by 1969 the rats reached plague numbers, said to be the worst plague ever seen of the rats. A refuge for the rats is the Barkly Tableland with its cracking claypans. After 2 good wet seasons the claypans became a swamp. They reached places where they had never been seen before, travelling along the rivers of the channel country towards Lake Eyre. Places such as Katherine in the Northern Territory, in the Tanami Desert and the Simpson Desert.

The huge numbers of rats led to good breeding seasons of their predators. Among these were the Letter-winged kite, barn owls and dingos, as well as introduced predators such as cats. The letter-winged kite is normally rare, hunting at night, preys almost exclusively on the plague rat.

Birds

There are about 205 bird species, aquatic and terrestrial, found around the Lakes. There are no other arid regions of Australia that can boast such a high number of species. The water birds get to about 20,000, but can reach as high as 35,000, that occupy the lakes throughout the year. The majority of these are teal and pink-eared ducks. There are also hardhead, maned-duck, Eurasian coot, red-necked avocet, and pelicans that arrive in flocks of up to a thousand, Pacific black duck, Australiasian shoveler (rare), black-winged stilt, hoary-headed grebe, pied cormorants, terns, silver gulls, herons, ibis, spoonbills, etc.

In floodplain habitats the endangered bush thick-knee is found, feeding in grasslands. In the flooded lignum margins are the habitat of the vulnerable freckled duck, of which there are about 1000.

There are 17 raptor species, grey falcon (rare), letter-winged kite, black-breasted buzzard. Sandhill spurge (Phyllanthus) is a characteristic vegetation of the white dunes of the district. It attracts hundreds of bronzewings, that elsewhere have been in decline for 100 years. In the region of the lakes, there are at least 100 species of terrestrial birds, dependant on the fresh water supply and the riparian woodland of river red gum (Eucalyptus camaldulensis) and coolabah (E. microtheca).

Other fauna

There an endemic tortoise species, (Emydura sp.), water-rats (Hydromys chrysogaster), mainly carnivorous, only occasionally eating vegetation.

Riparian woodlands

The riparian woodlands, around the lakes provide nesting sites for the water rats and tortoises. The reptiles found in the denser parts the woodlands along the channels and edges of the lakes include 2 skink species, a legless lizard and a dragon. On the floodplain habitat there are other species of reptile. Not far to the north, the Simpson Desert has a richer diversity of reptiles, and a different suite of reptile species. The Simpson Desert fauna has more skinks, the Cooper region has more snakes.

The woodlands are composed of river red gums and coolabahs that line the streams and water bodies are common across the arid zone. The woodland along the Cooper has a dense crown cover, with at least 4 distinct levels recognised. A number of species are restricted to the various levels of the woodland along the Cooper, some of which are the barking owl, evenly spread along the Cooper, Mallee ring-necked parrot, sacred kingfisher and restless flycatcher. Many other songbirds are associated with this habitat. There are some inland birds that avoid the riparian woodlands, staying in the more arid areas around the, inland thornbill, pink cockatoo, hooded robin, rufous whistler.

The predominant vegetation of the floodplain is shrubland of Lignum (Muehlenbeckia cunninghamii) that is 1-2 m high. This habitat has a number of birds that are commonly found in it, such as the chirruping wedgebill, banded whiteface and a rare bird, the grey grasswren that was discovered in 1967. It is the only grasswren found in swamps. The section of the habitat they live in is the dense lignum and swamp cane that is 1 m or more tall, probably because at this level it is above the floods that spread out over the land. They eat seeds, insects and occasionally water snails. They have a very restricted distribution, being found only at Goyder's Lagoon, the mouth of the Diamantina River and the Bullo River, always in a similar habitat. It is believed those known are relict colonies of a once widespread species. The swampy regions would have been much bigger before the last glacial period.

Sources & Further reading

Penny Van Oosterzee, The Centre - The Natural history of Australia's Desert Regions, Reed Australia, 1993