Paleo Safaris: Ice Age Australia

Queensland, Australia, 50,000 years ago

The last Ice Age is usually associated with cold, frozen landscapes with Mammoths, Sabre Toothed Cats, Woolly Rhinos and Ground Sloths dominating the landscape. However in some places on earth these conditions and animals weren’t present at all. For an example of this look no further than Australia. Instead of colder temperatures, the Ice Age caused Australia to become drier in glacial periods and wetter in interglacials. During interglacial periods conditions were mild enough to allow for more extensive temperate forests and dry grassland to grow and encircle the vast central desert. Just like today, Australia was home to a host of weird and unusual animal species exclusive to the continent. For example there were (and still are) not many placental mammals; the large phylum that encompasses the majority of all mammal families elsewhere in the world, from cats, to whales, to cows and to humans. Instead a completely different type of mammal is dominant here. They are the marsupials. Their main distinguishing trait is their young being born very early in development and then spending the rest of the development cycle maturing in an external skin pouch instead of internally in a placental linked womb. If we journey back 50,000 years we find that Australia’s signature marsupials can still be spotted; Kangaroos leap across the arid land, Koalas snooze in the afternoon sun and Wombats lumber along the forest undergrowth. However among these animals also live a large cast of unfamiliar Australian fauna.

It’s late April, and on the arid plains of Queensland, Central Australia one marsupial munches on the dry grass in the dead of night. It’s bigger than any Australian animal alive today, about the same size as a Rhino but is a close relative of the Wombat. This is Diprotodon; at 3 metres long, 1.8 metres tall and roughly 2.8 tonnes it is the largest marsupial that has ever lived. Diprotodon usually live in big herds that seasonally migrate across the Australian outback, but this young male has become separated from the rest of the herd. He picks up the sound of a disturbance in the bush and notices something moving quickly through it. He looks up towards the sound and readies himself for an attack! The animal emerges! But to the Diprotodons relief it’s not what it was fearing. Instead it is a female Thylacine, on the hunt for prey that is more her size. Thylacines are only a metre long and weigh 17 kilos (smaller than a medium-sized dog) and as such usually stay out the way of the larger animals. Once he realises that the Thylacine is no threat the big Diprotodon goes back to munching on the surrounding grass. In fact the female Thylacine that is more relieved that there was no escalation in this encounter. Getting trampled by the rhino sized marsupial would have been fatal not only to her, but to her unborn baby.

File:Diprotodon optatum.jpg
Diprotodon. The largest Marsupial to ever exist!
Image Credit: Nobu Tamura, http://2.bp.blogspot.com/-5Ckt4LUHKz8/T9dwmTycaMI/AAAAAAAABt8/70-K8CMYL5k/s1600/Diprotodon_BW2.jpg

By late May when we next see her, the female Thylacine has now officially become a mother! Within the safety of her pouch pokes out the head of her joey. Sadly he is the only survivor of an original litter of four. Two of his siblings were stillborn and the other couldn’t reach the pouch and perished in the harsh Australian environment. He is not yet strong enough to leave it yet and is still totally dependent on milk he gets from mammary glands within the pouch. While she’s carrying around this new arrival, the female Thylacine will be keen to take any free meal she can find. She is in luck as the distinctive smell of carrion wafts through the wind. Using her keen sense of smell she tracks the scent towards its source; a Diprotodon that has succumbed to old age and the battering heat of the Australian sun. However she is not the only predator drawn to the carcass. To her left emerges a crocodile! But there is no river or lake for miles around. How can this be?! This is no ordinary crocodile! This is a Quinkana. A 6 metre long crocodilian who, unlike its water loving relatives, is almost entirely terrestrial with legs that are located more underneath its body to allow it to chase down prey. Quinkana is another animal that dwarfs the Thylacine. However she is more nimble, and if she’s careful she can sneak up to the carcass and steal a mouthful or two before the Quinkana notices. She starts to stealthily venture towards the other side of the carcass as the Quinkana tears into it. But then she hears a sharp hiss from the thicket! She flees the scene as another giant reptile enters stage right! Megalania. A 7 metre long monitor lizard, roughly twice the size of a Komodo Dragon! It too has smelt the carcass and unlike the Thylacine it has the size and power to potentially muscle the Quinkana off the carcass. The Megalania grabs the hind leg of the carcass and attempts to drag it away. But the Quinkana isn’t going to let go easily and proceeds to grab onto the carcasses’ neck. A massive tug of war ensues between the two reptiles, one that could potentially escalate further! Understandably the Thylacine isn’t willing to stick around to find out the result and with the two giant predators all over the carcass there is no chance of her stealing anything now. Frustrated, she is forced to move on.

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Quinkana. One of the many large predators our Thylacine family has to avoid!
Image Credit: Mr Fink, https://commons.wikimedia.org/wiki/File:Quinkana_fortirostrum.JPG

It is now late November and the baby Thylacine has finally left the safety of the pouch and is taking his first independent steps into a wider world. The Australian summer is now in full swing. Conditions are much hotter and drier, and all animals are feeling the strain. One such animal is Genyornis. Genyornis is a flightless bird that is part of the ratite family; the same family that contains the Ostrich of Africa and another Australian bird called the Emu. However Genyornis is a giant, and at 2 metres tall it is about 6 times bigger than a regular Emu. Genyornis is a vegetarian, feeding on leaves and seeds, and it is this that draws it close to a nearby tree. The tree also provides much needed shade and allows the Genyornis some respite from the hot sun. But it is not as safe as it thinks it is. The Genyornis looks round, alerted by a sound coming from the nearby bush. But before the bird can even react a powerful marsupial slams into it and bites very hard into the Genyornis’ neck. It’s all over in just a few seconds. This predator is the largest Mammalian carnivore in Australia; a Thylacoleo. The Thylacoleo looks around, checking that no other large predator has caught wind of the fresh kill, then drags the big carcass up into the safety of the tree to consume at her leisure. Unbeknownst to her the female Thylacine and her joey have been awoken by the disturbance. Thylacines are nocturnal, meaning they operate mostly between Dusk and Dawn, and so the pair were taking the opportunity to have a daily siesta! The mother knows better than to linger around a full grown Thylacoleo and ushers her joey away to find a quieter place to nap. At first glance Thylacoleo looks similar to the big cats that occupy the rest of the world. However like Diprotodon this “Marsupial Lion” is actually another relative of the wombat. Thylacoleo is an incredible animal, perhaps the most unique mammalian carnivore to ever live. The bite that instantly ended the Genyornis’ life is the strongest pound for pound bite of any mammal ever! It’s even stronger than an African Lion despite Thylacoleo being nearly half its size! Like big cats Thylacoleo possesses large retractable claws and these, along with its dentition of large stabbing incisors and sharp shearing carnassials (i.e. molars) make this marsupial quite the formidable hunter. The Thylacine family definitely made the right choice in avoiding it!

File:Leon marsupial, Thylacoleo carnifex 3d restoration.jpg - Wikimedia  Commons
Thylacoleo. The most unique Mammalian carnivore to ever exist.
Image Credit: Jose Manuel Canete, https://commons.wikimedia.org/wiki/File:Leon_marsupial,_Thylacoleo_carnifex_3d_restoration.jpg

Fast forward to early February and the end of the Australian summer is approaching. With each passing day the baby Thylacine grows stronger and more independent. He also isn’t the only youngster around anymore. Not far from the Thylacine family a group of Procoptodon (or “Short Faced Kangaroos) lie in the shade of the nearby trees. These giant members of the Kangaroo family grow up to 2 metres tall and weigh 230 kilograms. Despite this size, they are still capable of hopping and reaching great speeds as other kangaroo species are*. They’re also just as dangerous, a fact that two males are demonstrating by sparring together. The kicks from their strong legs can crack bones and result in serious internal bleeding. But in this session both males walk away scot free. The Procoptodon joeys are also sparring, copying the behaviour of the males. But for these youngsters this is more playfighting than real sparring! Life for our Thylacine family finally seems peaceful. But there’s a dangerous smell in the air. The smell of smoke. A fire has started in the east, and to the sides of the flames are the cause. Humans. Their flaming torches have lit the surrounding dry grass with the aim of driving the Procoptodon out into the open. However the fire has also engulfed all the other animals in the area and all around the flickering red and orange flames the Thylacine mother and child hear the terrified cries of animals engulfed by smoke and flames. The fire spreads panic and chaos all over the place and out of the nowhere the mother Thylacine is smacked into by another big animal. Both animals are dazed by the blow and the mother Thylacine looks up at the Thylacoleo, who has managed to shake off the blow and stagger to her feet. This is a nightmarish for the Thylacine and yet all she can think of is the safety of her joey somewhere in the fire. But the Thylacoleo could care less about the Thylacine right now and runs on past her. In shear panic the Thylacoleo had only accidently ran into the Thylacine while trying to escape! The mother Thylacine desperately calls out for her joey. One coughing bark; nothing. Another two barks; still nothing! The fear is absolutely overwhelming now and to her it truly feels like the end of her world. But then she hears a bark, one she recognises! It’s her joey, still alive! The pair run for their lives but no matter which way they turn the fire blocks their path. Running out of places to go there seems to be no escape as the fire surrounds them and starts to burn brighter and hotter….

File:Procoptodon BW.jpg - Wikimedia Commons
Procoptodon: The giant kangaroo targeted by the fire wielding humans!
Image Credit: Nobu Tamura, http://1.bp.blogspot.com/-caAabAGbDtI/T9UY-vMc6oI/AAAAAAAABoI/ARER5hK_3Dw/s1600/Procoptodon_BW2.jpg

Later that evening the fire finally dies down. The humans have long since moved on with their prizes. But in their wake lie the consequences of their actions. From black widow spiders, to wallabies, to Diprotodons and Procoptodons all manner of life has burnt to a crisp. Not even the mighty Megalania and Quinkana, those two reptiles vying for top predator supremacy, could escape the flames. As fierce as they were, they were ultimately no match for a species who could wield a superweapon like fire. Luckily our Thylacine family managed to survive the fire by seeking refuge in a large and deep burrow. Walking through the burned vegetation and past the bodies, the mother recognises a familiar face. It is the female Thylacoleo. Once a great threat to our Thylacine, the Thylacoleo lies motionless with smoke floating from her burnt skin like a blown out candle. The Thylacine regards her from as close as she has ever managed before. But this time there’s no response, and after a while the Thylacine and her child, as always, are forced to move on to survive. This tragedy is a sign of things to come for the great megafauna of Australia. Even 50,000 years ago species like the Thylacoleo are in decline and within 30,000 years nearly all of the spectacular animals we have encountered on this journey will have disappeared. While the humans’ efficient hunting strategies are a threat the herbivores of Australia are unprepared for, and one the carnivores can’t hope to match, they are not the main reason why the megafauna disappear. By comparing the extinction dates of the Australian megafauna with the arrival of humans it was found that they were actually able to co-exist together for nearly 20,000 years, a piece of information that doesn’t correlate with overhunting. Instead there is another danger, one more devastating than even the humans; the changing climate. Over time Australia becomes even drier and more arid. This results in habitat loss and without their habitat this Ice Age ecosystem will not be able to survive. As for the plucky Thylacines, they will manage to cling on for a while longer. However even they will eventually be unable to adapt to the new human world. After going extinct on mainland Australia 2,000 years ago they were reduced to a small population living exclusively on the island of Tasmania, leading to their more commonly known name of “The Tasmanian Tiger”. However the arrival of Europeans in Tasmania would put them under even greater pressure than before. Their habitat was destroyed to make way for farms, imported disease would strike them down and Europeans would kill them in the mistaken belief that they hunted their sheep and cattle. The last Thylacine, a male that’s often incorrectly thought to have been called Benjamin, passed away on the 7th of September 1936 in Beaumaris Zoo in Hobart Australia. Tragically it is thought that he was a victim of neglect, locked out of his shelter and left out in the bitter cold of the Australian night. It was a truly sad end to a species that was a remnant of a lost world.

pungulv – Store norske leksikon
The Thylacines. The plucky heroes of this safari!
Image Credit: John Gould, https://snl.no/pungulv

*EDIT: This sentence is inaccurate and a mistake on my part! Procoptodon and its relatives, the Sthenurinae Kangaroos, are NOT thought to have hopped like modern Kangaroos do. Instead the currently accepted theory is that they walked on two legs (a bit like humans do). This idea was put forward by a study published in 2014 by Janis, Buttrill & Figueirido and backed up by a 2019 paper by Janis et. al. Links to both papers can be found below in the References/Further Reading section.

References/Further Reading

An article on the National Museum Australia’s website about the extinction of the Thylacine in 1936

National Museum Australia, “Extinction of the Thylacine”, National Museum Australia, www.nma.gov.au, https://www.nma.gov.au/defining-moments/resources/extinction-of-thylacine#:~:text=On%207%20September%201936%20only,the%20time%20of%20European%20settlement.

Rovinsky et. al. 2020. A paper that provides a new size estimate for the Thylacine

Rovinsky Douglass S., Evans Alistair R., Martin Damir G. and Adams Justin W. 2020Did the thylacine violate the costs of carnivory? Body mass and sexual dimorphism of an iconic Australian marsupialProc. R. Soc. B.28720201537, http://doi.org/10.1098/rspb.2020.1537

An interesting web page from the Thylacine Museum section on the Natural Worlds website on Thylacine Reproduction and Development

Natural Worlds, “Biology: Reproduction and Development”, www.naturalworlds.org, http://www.naturalworlds.org/thylacine/biology/reproduction/reproduction_2.htm?fbclid=IwAR13a8Y9GJTCG6vT2vR-GNc8Xv96M7t5aYSE8WsQKjCTaojxQFIZJeju6EM

And another web page from the Thylacine Museum on Thylacine sounds.

Natural Worlds, “Vocalisation”, http://www.naturalworlds.org, http://www.naturalworlds.org/thylacine/biology/behaviour/behaviour_12.htm

• A video by Ben G Thomas (uploaded coincidentally while I was writing this blog article) about the Marsupial Lion, Thylacoleo

An article written by Alice Klein for New Scientist on Thylacoleo

Klein, Alice, “Australia’s ‘marsupial lion’ was a meat-ripping, tree-climbing terror”, New Scientist, www.newscientist.com, 12th December, 2018, https://www.newscientist.com/article/2187990-australias-marsupial-lion-was-a-meat-ripping-tree-climbing-terror/

An article on National Geographic by Laelaps (Riley Black) on the new size estimate of the giant monitor lizard Megalania.

Black, Riley, “Australia’s Giant, Venomous Lizard Gets Downsized”, National Geographic, March 19, 2014, www.nationalgeographic.com, https://www.nationalgeographic.com/science/phenomena/2014/03/19/australias-giant-venomous-lizard-gets-downsized/

Hocknull et. al. 2020: A study that provided evidence that the extinction of Australias megafauna (specifically in the Eastern Sahul region) was mainly due to a changing climate.

Hocknull, S.A., Lewis, R., Arnold, L.J. et al. Extinction of eastern Sahul megafauna coincides with sustained environmental deterioration. Nat Commun 11, 2250 (2020). https://doi.org/10.1038/s41467-020-15785-w

A 2017 article published on The Conversation, written by Gilbert Price, about Diprotodon and it’s seasonal migrations across Ice Age Australia

Price, Gilbert, “Giant marsupials once migrated across an Australian Ice Age landscape”, 27th September, 2017, www.theconversation.com, https://theconversation.com/giant-marsupials-once-migrated-across-an-australian-ice-age-landscape-84762?fbclid=IwAR0G3JDp8KZo-HTLBPIPGIyu2mMKW6yAZ5RlAipREqCL0VZjckZkZhvvGXM

The Australian Museums factfile on Procoptodon. Last updated in 2018 and written by Anne Musser

Musser, Anne, “Procoptodon goliah”, 4th December, 2018, www.australian.museum.com, https://australian.museum/learn/australia-over-time/extinct-animals/procoptodon-goliah/

Janis, Buttrill & Figueirido 2014 paper on Sthenurine (e.g. Procoptodon) locomation

Janis CM, Buttrill K, Figueirido B (2014) Locomotion in Extinct Giant Kangaroos: Were Sthenurines Hop-Less Monsters? PLoS ONE 9(10): e109888. https://doi.org/10.1371/journal.pone.0109888

Janis et. al. 2019 paper that followed up the 2014 study on Sthenurine locomotion by examining the humerus bones of these extinct giant Kangaroos

Janis, C.M., Napoli, J.G., Billingham, C. et al. Proximal Humerus Morphology Indicates Divergent Patterns of Locomotion in Extinct Giant Kangaroos. J Mammal Evol 27, 627–647 (2020). https://doi.org/10.1007/s10914-019-09494-5

Prehistoric Wildlife’s factfile on Genyornis

Prehistoric Wildlife, “Genyornis”, www.prehistoric-wildlife.com, http://www.prehistoric-wildlife.com/species/g/genyornis.html