In Australia there are twenty species of monitor lizards, or goannas, as they are known here. They live in almost all the ecosystems of the continent, demonstrating their ability to adapt to all types of environment.
The lizards are, in a way, the final revenge of those enormous dinosaurs which, in remote times, over one hundred million years ago, ruled over these lands, now changed beyond all recognition.
The blue-tongue lizard is much less powerful than its relatives the monitor lizards, but evolution has ensured it is equipped to defend itself in this world of hunters and prey.
The Australian reptiles, like all the other classes of land animals, found their space within the generous and changing island in the southern hemisphere. But, fifty thousand years ago, a new creature arrived from the north. It was different from any of those already living here, and had one devastating peculiarity – instead of adapting to the environment, it forced the surroundings to change and to adapt to it.
The arrival of man brought violent changes.
Never before had Australia changed so rapidly, and at such speed that it did not give time for species to adapt. Along with man, other invaders also arrived. At first, with the aborigines, they came slowly, and in small numbers, giving rise to new species which displaced the native ones. This is the case of the dingo, and the marsupial wolf. But, with the arrival of the white colonists, the influx of aggressive invaders posed a serious threat to the wildlife of Australia. Rats, rabbits, cats and foxes, asses and dromedaries, buffaloes and wild pigs laid bare entire regions.
These new invasions have demonstrated the fragility of an ecosystem which for so long remained isolated. And the not too distant future may well bring yet another threat.
Australia continues on its slow drift northwards, at a speed of six centimetres a year.
At present, a narrow strait is all that separates the fauna of the two continents. But what will happen when the animals of Asia and Oceanía come into direct contact? There may well be enormous upheavals in the uncertain future of this continent. It is easy to image that the evolution of its landscapes and animals will undergo far-reaching changes. But, probably, when new, specialised creatures adapt to the unique conditions of these forests or deserts, causing many of the evolutionary prototypes that now dominate Australia to die out, in the farthest depths of the jungle, with their pacific and archaic way of life, there will continue to be echidnas and duckbill platypuses. And, as in Gondwana in the distant past, there will continue to be mammals who lay eggs.