FACT SHEETS

Have you ever seen an Australian animal as big as a car? Or a bird with a beak the size of a horse’s head? A lion that could climb trees? Or giant snakes and lizards as long as three table tennis tables? It is almost unbelievable, but animals this weird and wonderful really did exist in Australia, and they are collectively known as the ‘megafauna’.

Illustrations: Rocco Fazzari

OUR CURIOUS CAST OF CHARACTERS

So where did they go?

The reason why we don’t see these large critters still roaming the outback today is still debated, but likely due to the combination of hunting and habitat modification by humans. There was possibly a role for climate change, with a decrease in natural resources as it became drier and more fire prone. It was these external pressures that caused the extinction of these creatures some 40,000 years ago. This seems like a long time, but it is far more recent than when the dinosaurs ruled the Earth. In fact, ancient humans had actually seen and lived alongside these extremely large animals throughout past Australian landscapes.

How do we know that they were here?

We know about these prehistoric animals because we find their remains, such as bones, teeth, footprints and dung, preserved in the ground as fossils. They have been found at sites across Australia (eg Naracoorte Caves, South Australia; Alcoota, Northern Territory) and at different depths, telling us where they were, when they were here, and—if we find enough of them—we can reconstruct their appearance, what they ate, and even how they behaved. Indeed, for some of the extinct megafauna, scientists have found over 2,500 fossils. Unfortunately for other Australian animals, like the giant long-beaked echidna (Zaglossus hacketti), we have found only scant evidence.

Why were they here and nowhere else?

To answer this, we have to look deep back in time. Australia was once part of the great southern supercontinent of Gondwana. This enormous land mass started to break up about 140 million years ago (during the age of the dinosaurs), and in doing so, caused the Australian continent to become increasingly isolated as it drifted northwards from Antarctica, cutting off the movement or exchange of species and allowing evolution to occur in isolation.

By the time of the ice ages (the period known as the Pleistocene, covering the last million years or so), Australia was located almost in its present position, and underwent extreme swings in climate, from long periods of cool, arid conditions during times of maximum extent of the northern ice sheets, through to shorter warmer and wetter periods.

At the height of the last ice age about 20,000 years ago, seas were 120 metres below current levels and the islands of Papua New Guinea and Tasmania were connected to mainland Australia. This larger continent was known as ‘Sahul’ and was almost 50 percent larger than today.

The sharing of plant and animal species (including megafauna, until their extinction) occurred across this greater landmass, ending about 14,000 years ago, when glacial conditions began to subside and sea levels rose, blocking the land bridge to the north (Papua New Guinea), and the south (Tasmania). These periods of isolation, first from the supercontinent, then from Sahul, has meant that Australia has evolved a unique and diverse fauna, found nowhere else in the world.

Unfortunately, Australia has an extensive history of extinctions—not only the megafauna, but also more recent examples like the Tasmanian tiger (Thylacinus cynocephalus) and pig-footed bandicoot (Chaeropus ecaudatus). Finding out why extinctions such as these occur is really important for researchers like me, because we are actively trying to stop more such losses occurring in the future.

Dr Jessie Buettel is a researcher at the University of Tasmania and the ARC Centre of Excellence for Australian Biodiversity and Heritage (CABAH). She loves books and learning, and has a deep curiosity about global change, conservation and the relationship bween human and natural landscapes. You can follow her on Twitter @jbuettel.

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