Eastern grey kangaroo. Picture: Jamie Kidston/ANU
ASK anyone what first springs to mind when they think of Australia and they’ll most likely say a kangaroo; the marsupial is ingrained in our national identity. But have you ever wondered why kangaroos never ventured beyond our shores?
A major study led by biologists at The Australian National University (ANU) and ETH Zurich in Switzerland provides a new explanation for why you won’t find kangaroos, koalas and other Aussie marsupials in Indonesia, but you will find many groups of animals that originated in Asia, such as goannas, rodents and kookaburras in Australia.
Biologists have long described this asymmetrical distribution of Australian and Asian species by using an imaginary line that separates Australia, New Guinea and parts of Indonesia from continental Southeast Asia. This invisible boundary is known as Wallace’s Line.
In a new paper published in Science, the researchers say that changing plate tectonics and a dramatic shift in Earth’s climate tens of millions of years ago are the reasons for the uneven distribution of Australian and Asian creatures on both sides of the invisible boundary — finally providing an explanation for the enigma of Wallace’s Line, which has long baffled scientists.
The ANU researchers found species that originated in Asia could tolerate a wide variation in climactic conditions and were more successful at adapting to and settling in Australia, which explains why there is more Asian fauna found in Australia compared to the other way around.
“If you travel to Borneo, you won’t see any marsupial mammals, but if you go to the neighboring island of Sulawesi, you will. Australia, on the other hand, lacks mammals typical of Asia, such as bears, tigers or rhinos,” Dr Alex Skeels, from ANU, said.
According to Dr Skeels, this uneven distribution of animal species on both sides of Wallace’s Line is partly due to changes in ancient plate tectonics — dating back 45 million years — that ultimately led to a “continental collision” that altered the geographic composition of Earth.
“About 35 million years ago, Australia was located much further south and was connected to Antarctica,” he said.
“At some point in Earth’s timeline, Australia broke away from Antarctica and over millions of years drifted north, causing it to crash into Asia. That collision gave birth to the volcanic islands that we now know as Indonesia.”
The islands of Indonesia served as “stepping stones” for animals and plants that originated in Asia to reach New Guinea and northern Australia, and vice versa.
“Our research shows far more groups of Asian fauna crossed over and established themselves in Australia than in the opposite direction,” Dr Skeels said.
But as ANU researchers explain, a shift in plate tectonics is just one piece of the puzzle in explaining the migration of Asian species to Australia. When Australia broke away from Antarctica, there was a climactic shift that led to a trend of global cooling and drying of the continents, which led to mass extinction events around the world.
“When Australia drifted away from Antarctica, it opened up this area of deep ocean surrounding Antarctica which is now where the Antarctic Circumpolar Current is. This dramatically changed Earth’s climate as a whole; it made the climate much cooler,” Dr Skeels said.
“Despite this global cooling, the climate on the Indonesian islands, which organisms used as a gateway to hop to Australia, remained relatively warm, wet and tropical. So Asian fauna were already well-adapted and comfortable with these conditions, so that helped them settle in Australia.
“This was not the case for the Australian species. They had evolved in a cooler and increasingly drier climate over time and were therefore less successful in gaining a foothold on the tropical islands compared to the creatures migrating from Asia.”
The researchers analysed a dataset of about 20,000 birds, mammals, reptiles and amphibians to determine which species hopped between Indonesia and Australia, and which ones were able to successfully adapt to their new home.
“Our findings could also inform predictions for animal migration in the future and help us predict which species may be better versed at adapting to new environments, as changes to Earth’s climate continue to impact global biodiversity patterns,” Dr Skeels said.
Source: Australian National University.
I am just wondering when reading the headline to the story that reads WHY YOU WONT SEE KANGAROOS OUTSIDE OF AUSTRALIA,
As I have personally seen a KANGAROO inside a very well known American celebrity’s private place , together with many other exotic animals from around the world 🌎..
And want let you know that from the minute I witnessed that , I knew that it was absolutely disappointing to see these poor animals completely outside of their natural habitat to think that in some very peculiar way this kind of behaviour is being overlooked…
Thankyou for your story.
Whoever says there are no kangaroos in Australia obviously hasn’t been here! I’ve never seen our type of kangaroo in Scotland or Ireland, going to England in January so I will check it out. My guess is if they exist in America that they’ve been taken there.
You’ve never been to PNG then have you… Kangaroos everywhere (out side of Australia).
Generalisations prove false yet again:
“ Dingiso Tree Kangaroo is found in the Tembagapura and Kwiyawagi areas of West Papua”. Definitely not Australia, so much for the headline.
I believe there has been a typo. It should say “climatic”, not “climactic”.
Thanks for the pick-up Ronan. You are absolutely correct. Now amended, and added to our editorial style manual for future reference. Editor
I live in the Isle of Man and we have had wild wallabies since the 1960s.
https://www.mwt.im/wallabies-and-isle-man#:~:text=Red%2DNecked%20Wallabies%20(Notamacropus%20rufogriseus,Isle%20of%20Man's%20cooler%20climate.
Hello, First I want to say that Stephen is correct, we do know our past timeline very well and very accurately. So Charlie, please educate yourself a bit, knowledge is power my good man. Secondly i want to say to Cecilia that there is no reason to be upset about the man in Texas selling wallabies for $5k.. As I mentioned above to Charlie, knowledge is power. It’s important, especially when it comes to the field of animals, and maybe even more so the field of animal information, to understand that around 95% of animal related information that the general public is exposed to is false/fake. The reason its false is because for the last 30+ years the lions share of published animal information has came from those involved in the animal welfare movement. Which are the people who have the least amount of real world experience or knowledge about animals. The people and organizations involved in this movement have acquired great wealth and power by doing nothing except spreading false and misleading animal information. So here is a fact. In America there are thousands of people who raise and sell kangaroos & wallabies. All species of them. Even white ones. Kangaroos live well in every state and in every climate. Except Arizona where they are highly sensitive to Valley fever which is a sickness caused by a type of spore that exists only in Arizona. Next I want to say that the Texaas man as well as tens of thousands of other exotic animal owners in America are true conservationists. When animals have a monetary value, then they flourish. When species become restricted/protected, that makes it more difficult or in many cases impossible to aquire, own, buy,sell, import export said species. So population of that now protected species starts making its way to extinction. If they would eradicate all restrictive rules that pertain to that species then industry would step in and supply and demand would cause the species to have a monetary value and the numbers would increase. Just the same way that chickens and cows and dogs are in such great numbers. Take rhinos for example.. in China they pay huge money for rhino horns, its worth more ny weight then gold., but they have to buy the horn illegaly from illegal sources that do often poach a rhino to aquire the horn… But if they lifted the ban on rhino horn and aloud for world wide trade in rhino horn, then people would be building rhino ranches all over the world and they would be giving them the best care, the best environment, the best enrichment the modern world has to offer and they would be producing rhinos like its going out of style. And they would end rhino poaching permanently, And no rhino would ever again be killed just for his horn. Because ranchers would not harm an animal that’s growing something on its face that’s more valuable then gold. They would create easy and harmless methods of harvesting portions of the horn in cycles just like harvesting the wool from sheep. And in ten years time there would be 100x more rhinos on tbe planet then there is today and the sane thing would happen if they allowed the free trade of elephant tusks, or pangolin scales and every other species that can provide soothing that’s in high demand. Also if they eradicated all restrictions on all species and allowed fir free trade it would make a huge dent in world wide poverty because a great deal of poverty is do to the locals not being able to exploit the natural resources in there region. Many of the poorest people on the planet live in areas that are chalked full of restricted animals. There would be no question that opening up free trade for all species would not only save endangered species but it would have a massive positive impact on the human species as well.
Well, all l can say to Charlie’s comments 26/07/2923 is as a consumer of all things
anthropological, it’s his ignorance on that science and it’s a shame he had to “open his mouth, to prove his stupidity in lieu of keeping it shut and only be thought a fool”
Cheers 4Now
Stephen D.
During my last trip to the USA I visited my family in
Houston Texa, they live there,
This was around Christmas so we got involved in many activities, one of them we went to was a type of park with lots of Christmas things to do. As we were walking around we came to an enclosure with different baby animals, among them was a young wallaby. To say the least I was shocked to see the beautiful marsupial there, so I asked the man in charge why he had the wallaby , it was no reply, however, he said he breeds them and sells them for US $ 5,000 each.
I can’t begin to tell how upset I felt.
Although there are no known kangaroos roaming around the world except England, there is a man selling them inTexas.
Regards
Cecilia
What a load of garbage! How anybody knows what happened 45 million years ago is beyond me. How they even think the earth is that old is doubtful. Nobody ever born knows exactly what happened before man arrived. It’s all hearsay. It’s theories only.
Very interesting article, a change for our day to day involvement.
There are tree kangaroo’s in south America. A remnant of when South America, Antartica and Australia were all joined.
Mister kangaroo only live in Australia if you say are America thay should not be there.