Riverland Flora & Fauna Nature Trail
Riverland Flora and Fauna
The animals and plants in this area occupy four distinct zones. The river itself forms one zone where aquatic plants and animals live. Beside the river is the floodplain that has its own unique plant species. Once the land begins to rise, the grouping changes again, and the area most distant from the river features the distinctive Mallee trees. This zonation applies to some extent to the region’s fauna though many live in more than one zone. We have attempted to give you an idea of the dominant groups and added a few interesting and rare ones to tempt you to look further into the Riverland’s ecology.
There are many plants adapted to live in the water. Ribbon Weed (Vallisneria americana), characterised by its strap-like appearance, frequently grows submerged in the shallow water near the banks. It provides habitats and food resources for native fish and other life forms, particularly from the film of algae and bacteria that coat its leaves. The red and green Azolla (Azolla filiculoides) is often seen floating along the river. During spring or in shade the upper parts of the plant are green while in summer and autumn, when exposed to full sunlight, they usually become bright red.
As the name suggests, this zone is the area between the river and the upland rises. The main plant species are the Black Box (Eucalyptus largiflorens) and the River Red Gum (Eucalyptus camaldulensis). River Red Gums are found close to the water’s edge, while the Black Box is able to live further away. Clearly distinguishable lines through Black Box woodlands show how seed is deposited at the wash line during a flood. Old specimens high above the current river level attest to significant floods in the past. An old tree at Overland Corner is known to have been there since around 1770.
The upland rises vary in height and steepness. They are often a sandy environment and ideal habitat for the Native Pine (Callitris preissii). This tree was used heavily by early settlers for its timber which is resistant to white ant and rot, and hence ideal for fence and vineyard posts. The soft yellow timber is still commercially available from the Eastern States.
Main plant species are a variety of Mallee trees (really shrubs from the Eucalyptus family) adapted to harsh low rainfall conditions. Their multi-stemmed habit is an adaptation to wate gathering. The tough Ligno-tuber or ‘Mallee Root’ is able to maintain life even if the tree completely looses its leaves during prolonged drought or fire. There are many types of Mallee tree: their occurrence depends on soil and climatic conditions.
Animals in the River
The river contains several species of larger fish including the Murray Cod (Maccullochella peelii peelii), the largest and most sought after economic species. Before the era of locks and barrages these handsome fish often reached a large size with specimens up to 1.83m weighing 113kg reported. Sadly they are now less frequently seen in the lower reaches of the river. Surprisingly there are manysmall native fish about which little is known. The Australian Smelt (Retropinna semoni) is one such example. Growing to 100mm they are widely found in Australia river waters including the Murray-Darling system. They are bright silver with darker olive lower sides, and have large eyes, a rounded snout and transparent fins. Preferringto live in slow moving on still water, they can be found in schools near the surface. Their food sources include small larvae, crustaceans and insects. Another vulnerable local species is the Southern Bell Frog (Litoria raniformis). Its low growling call means it is also known as the Growling Grass Frog. This attractive creature is voraciously carnivorous, eating almost anything smaller than itself – including other frogs. It has been declared vulnerable as, like many frogs, the population has suffered from habitat reduction and water quality issues.
Animals of the Floodplain
Although many animals travel across the floodplain to reach the river, there are those that make this area their primary habitat. Perhaps one of the most spectacular of these is the Carpet Python (Morelia spilota) which lives in hollows in cliffs and in trees. The loss of floodplain habitat has endangered this species in the Riverland. The Common Brush-tail Possum (Trichosurus vulpecula) frequently shares trees with the python and often provides it with a food source. These gregarious small animals have adapted to living near humans but feral cats and foxes continue to reduce the population.
Animals of the Upland Rises
This zone is home to many birds and animals that can survive a little further from the river. Flocks of Major Mitchell Cockatoos (Cacatua leadbeateri) populate the trees. These noisy birds use their strong beaks to open the nuts of the Native Pine (Callitris preissii) to eat the seeds. Another interesting and rarely seen resident of the rises is Bolam’s Mouse (Pseudomys bolami). This small native rodent burrows in the ground and lives by eating seeds, fruits, blossoms, grasses and insects. Nocturnal in habit, it is believed to breed in spring with a maximum litter size of six. Unlike most native mice in the Riverland it is not a marsupial.
Animals of the Mallee
A wide range of animals use the Mallee environment including the endangered Blackeared Miner (Manorina melanotis) that is the subject of a major conservation program across three states. These quiet, shy birds exist in small colonies in old growth Mallee. Much of this Mallee is contained in the Riverland Biosphere Reserve including Gluepot Station, Danggali WPA (Wilderness Protected Area), Taylorville Station and Calperum Station. Another animal rarely found is the beautiful Ningaui Yvonneae. Pronounced ‘nin-gow-ae’, this small marsupial mouse feeds on insects and, despite its size, has an enormous appetite. It still exists in reasonable numbers in areas with extensive Porcupine Grass (Triodia scariosa) or Spinifex, in which it makes its home. They have been recorded climbing a single leaf of spinifex, wrapping their tails around as they go.