Australia once had giant kangaroos — here's what experts think happened to them

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24-04-2025

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More than 300,000 years ago, giant kangaroos roamed the Australian outback, but didn't travel far from home, which experts say may have led to them disappearing entirely.
The general rule is that the larger a mammal herbivore is, the further it travels for food. It's a trend seen with most modern kangaroo species.
However, new peer-reviewed research published in PLOS One has found that, unlike modern kangaroos, the extinct marsupial megafauna Protemnodon was less mobile and had smaller home ranges than its size would have suggested.
The continent was once home to a suite of giant creatures ranging from 2-metre-tall birds to 2-tonne lizards. ABC TV explores the drivers behind their demise.
The study was a collaboration between the University of Wollongong, the University of Adelaide, Queensland Museum and Monash University.
Lead researcher Chris Laurikainen Gaete, from the University of Wollongong, said the study measured the isotopes in the teeth of fossil giant kangaroos to estimate their foraging ranges over 300,000 years ago.
The expectations were that these giant kangaroos standing at about two metres tall, would be mobile, but the results were that they moved very little and remained in the same geological substrate where their fossils were found.
"This idea of home range is pretty important, because well, your dispersal capacity will kind of dictate your vulnerability to extinction should something change in your environment," Mr Laurikainen Gaete told the ABC.
"We know that at this point in time, they lived in a rainforest habitat, so potentially they had an abundance of resources right around the cave.
"But as the habitat changed, potentially these small home ranges [were] predisposed to extinction, meaning they couldn't walk in a more arid habitat for large distances to get their food."
An illustration of a giant kangaroo from hundreds of thousands of years ago.
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Supplied: Capricorn Caves, Atuchin, Lawrence, Hocknull
)
Change in climate led to giant kangaroos' extinction, research says
Researchers examined the fossil records of the site where some giant kangaroos lived in Mount Etna in Queensland.
For hundreds of thousands of years, the area was a stable rainforest environment, akin to those in New Guinea and other wet tropics in Australia.
Mt. Etna in Queensland was once home to giant kangaroos until a change in climate saw rainforest disappear and be replaced by a more arid climate.
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Supplied: Scott Hocknull
)
According to Mr Laurikainen Gaete, in this habitat, these giant kangaroos could live with a very small home range.
"So this behavioural trait evolved over hundreds of thousands of years, but then around 280,000 years ago, the climate changed, and it became more arid," he said.
"So this rainforest disappeared and was replaced by a kind of more dry-adapted species, which means resources become more patchy.
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And a big kangaroo, who can't move these now larger distances between resources, and therefore that's why we assume they go extinct.
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What is megafauna?
Megafauna were large land animals that roamed the Earth during the Pleistocene, existing millions of years after dinosaurs became extinct.
They were an integral part of the ecosystem and evolved to include some very large animals.
Australian megafauna ranged from huge herbivorous marsupials, such as Diprotodon, to carnivorous reptiles such as Megalania.
We need more research on our megafauna
Lead researcher Mr Laurikainen Gaete believes the most significant finding for this study was that the template used to better understand the specific giant kangaroo species could be replicated.
"The Australian ecosystem used to be dominated by megafauna, marsupials, but at different points in time, virtually all these species died out. And there's no clear answer as to why," he said.
"The key thing from that is the techniques that we have employed here show that we can reconstruct these individual or local population responses to environmental change.
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If we apply this to more fossil sites across Australia, we can have a more inclusive and nuanced interpretation of the unique factors driving local extinction events, rather than that kind of unknown that we have now.
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An image of a giant kangaroo tooth used in the research.
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Supplied: Chris Laurikainen Gaete
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Some experts such as Isaac Kerr from Flinders University, agree.
Mr Kerr, whose
"In Australia, we are only starting to scratch the surface. And by the kind of thing, I mean the proxies for individual life history and palaeoecology in our fossil fauna," he said.
"In America, they've known what we're just finding out for decades. And it's the kind of thing that is very useful in terms of recreating our past environment."
Photo shows
A skeleton of a giant extinct kangaroo placed over a white background. The bones are brown and arranged horizontally.
Researchers from Flinders University have described three new species of extinct kangaroo, helping to solve a nearly 150-year-long scientific mystery.
Mr Kerr explained his work focuses on skeletal comparative morphology, which means looking through the shape of bones to figure out how an extinct animal moved, comparing them to modern animals.
It means he can contrast the similarities and differences to make a "very general hypotheses" about how that extinct animal moved and lived in their environment.
He said the methodology used in the research goes further.
"They have the ability to look at this actual species or actual individual animal's life history. So this is where this animal specifically went and where it fed," he said.
"Which is powerful … [it] needs to be done more because it gives us this completely separate but parallel set of data for how these animals lived.
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It's essential to painting a more complete picture of megafauna.
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