Location

            Even though the Australian “Outback” doesn’t officially exist within governmental frameworks or boundaries, the area generally refers to the remote areas of Australia’s interior.  Traditionally, “the bush” (slightly rural stretch of land) ends at the “black stump,” and anywhere beyond that is the Outback.  Also referred to as the “never-never,” the Outback is roughly 2.5 million square miles.  There are primarily three sections of the outback: the north (top end), middle (red center), and south (southern outback).

Abiotic Factors

            Australia is the driest habitable continent on Earth, and the arid Outback has a very unique climate.  Maximum temperatures average 36-39°C in summer and 18-24°C in winter.  Remember summer and winters are in opposite months than the U.S.A.  During the cooler months of July and August, night temperatures can drop well below freezing causing frosts up to fifty percent of the mornings.  Rainfall varies in different regions of the Australian Outback.  In the tropical north of Australia, an average of 40 cm of rain falls annually, but in the colder southern and eastern Australia, only about 15 cm falls.  Western Australia’s average rainfall is 20 cm.  The driest part of Australia is the center where rainfall can drop below 12 cm per year.  Average rainfall is difficult to calculate in Australia because the rainfall is so unpredictable.  Besides the northern part of Australia, there are no seasons.  Rain can fall any day of the year or not at all for many years.  Average evaporation rates in the Outback are greater than 340 cm.

            All of the soil in the Outback is poor, eroded, and impossible to support livestock or crops.  However, the rangelands in the Lake Eyre Basin contain a few fertile plots of land to raise cattle and sheep.  The Outback is extremely rich in iron, magnesium, aluminum, and uranium ores along with major deposits of gold, nickel, lead, and zinc.  Basically, hot, dry weather; small, random amounts of rain; and poor soil define the non-living setting of the Australian Outback.

Indicator Species

            The red kangaroo (Macropus rufus) is native to the Australian Outback.  They have powerful hind legs, large feet, muscular tails, and small heads all ideal for leaping, their mode of locomotion.  These large herbivores chew on grass, roots, and cud.  They are crepuscular which means they are mainly active during the cool evenings and morning in the Outback.  While a kangaroo jumps, it’s breathing rhythm adjusts so that little energy is required to travel at a moderately high speed long distances to find fresh pastures of food.  Being marsupials, kangaroos protect their young, called joeys, from the heat and predators in a pouch until they are fully developed and ready to hop on their own.  Kangaroo mothers also have the ability to freeze the embryo’s development until the previous joey leaves the pouch.  The kangaroo’s adaptations to life in the Outback are useful and interesting.

            Another good indicator species of the Australian Outback is the Eucalyptus, meaning well-covered, species of trees.  In fact, no other continent is so characterized by a single genus of tree.  These trees can survive dry spells, poor soil, and even fire.  Thick bark covering the Eucalyptus tree protects its core from damage, and fire actually helps the tree species thrive.  Heat causes chemical changes in Eucalyptus trees, sprouting new buds.  Also, the fire’s hot winds help circulate Eucalyptus seeds.

Food Web

See poster.

Symbiosis

Commensalism

            The spinifex hopping mouse (Notomys alexis) lives in tunnels underground concealed by large clumps of spinifex grass.  The grass helps hide the mice’s homes from predators, but is not affected at all.

Mutualism

            Mistletoe birds are small animals that feed on the flowers and fruit of the Australian mistletoe plant.  The berries are eaten by the bird and pass through the digestive system very quickly.  Sticky remains of the seeds left in the bird’s droppings land on branches and sprout new mistletoe plants.  The seeds grow well in their natural fertilizer and are once again eaten by the mistletoe birds.

            Eucalyptus trees are abundant in the Outback.  They provide food and shelter for numerous animals.  Eighty percent of all the Eucalyptus trees in the Outback are hollowed out by termites.  The termites turn the wood into a pulp they use for food and to build nurseries in their homes.  Kookaburras, cockatoos, sugar gliders, and other animals live in the Eucalyptus hollows.  In return, the trees obtain nutrients from their residents’ droppings and leftover food.

Parasitism

            Many types of Australian terrestrial orchids like the Thelymitra ixioides form fungi around its roots and takes nutrients the fungi extracted from the soil.  These orchids lack chlorophyll and need the fungi around its roots to survive beyond the germination stage.

Present Condition and Man’s Effect

            Less than ten percent of the Australian population lives in the vast Outback; however, tourism is one of the Outback’s main economic activities.  Organized travel to the Outback is popular and doesn’t have a large negative impact on the ecosystem.

            Rangers Frank Manthey and Peter McRae started the Save the Bilbies Fund in 1999.  Bilbies are an endangered species of bandicoot.  This program funds the fenced-off bilby haven in Currawinya National Park, Queensland.  Some main goals of this research are to find out why bilby populations are declining, reintroduce bilbies to the wild, and encourage people to stop practicing activities that might hurt the bilbies’ chance of survival.

            The largest wildlife culling on the planet occurs in Australia.  The current number of kangaroos allowed to be shot by commercial hunters annually is seven million.  This practice is a controversial topic throughout the country and the world.  Farmers say that a controlled killing is the best way to stop them from eating crops, destroying fences, and depleting the Outback’s water resources.  The estimated population of kangaroos in the Outback is over 13 million, and some scientists believe that culling the animals is the only way to protect their species from breeding themselves out of existence.  Others state that the estimated population could be over inflated.  Also, inexperienced hunters cause kangaroos massive amounts of pain as they slowly die.  The Royal Society for the Prevention of Cruelty to Animals (RSPCA) in Australia is most concerned about having control over the kangaroo hunters.  Every year companies make millions selling kangaroo meat and leather.  Hunters killing the fittest males give females less breeding options, and the joeys of dead mothers are usually decapitated or left to starve.

References

Biggs, Alton, et al.  Biology:  The Dynamics of Life.  New York.  Glencoe.  2002.  p. 36-55.

Bryson, Bill.  “Australian Outback.”  National Geographic.  October 1999.

Mercer, Phil.  “Kangaroo cull targets millions.”  BBC News.  February 21, 2002.  <http://news.bbc.co.uk/1/hi/world/asia-pacific/1834061.stm>

“Outback Animals.”  PBS Online.  <http://www.pbs.org/wnet/nature/kakadu/html/intro.html>

Patterson, A.B.  “Climate.”  Diamantina Touring.  <http://www.diamantina-tour.com.au/outback_info/climate.htm>

Tarski, Christine.  “A Bit of Red – Mistletoe Birds.”  About.  September 25, 2006.  <http://birding.about.com/library/weekly/aa122000a.htm>