Drying climate led to marsupial lion’s demise, say scientists

The Thylacoleo carnifex was a fearsome predator that disappeared about 35,000 years ago. Reconstruction by Peter Schouten.

CLIMATE CHANGE has been this way before. Researchers are now suggesting the extinction of Australia’s fiercest predator, the marsupial lion, was due to changing weather patterns and loss of habitat, rather than humans.

Palaeontologists from UNSW Sydney, university of Qld and Vanderbilt university  in Tennessee USA pinpointed the demise of Thylacoleo carnifex by studying its chemistry. The carnivores were widespread in Australia for about two million years, disappearing about 35,000 years ago. Fossils have been found along the Warburton and Cooper creeks near Lake Eyre, and a near-complete skull was discovered on the Darling Downs in the 1800s.

Thylacoleo were closely related to megafauna such as the wombat-like diprotodon optatum, the largest known marsupial. In 2012, palaeontologists went public with news of a big megafauna fossil field at Bundoona station near Eulo, after finding the remains of diprotodons, a giant lizard, freshwater crocodile and forest wallaby.

The researchers said the chemical signature preserved in fossil teeth suggested Thylacoleo carnifex hunted primarily in forests, rather than open habitats. This was supported by features of the skeleton that indicated it was an ambush hunter, relying on catching its prey unaware rather than running them down across open plains.

A model of a bolt-cutter tooth from a Thylacoleo carnifex compared with a molar from a Microleo attenboroughi.

For nearly two million years the marsupial lion, about the size of an African lioness, was one of Australia’s top predators. The study led by Larisa DeSantis of Vanderbilt university posited that, despite being well-adapted for consuming flesh and bone, Thylacoleo was likely the victim of the drying out of Australia, which began about 350,000 years ago.

The carnivores persisted for thousands of years afterwards, as more and more forests disappeared, surviving the influx of humans to the continent about 60,000 years ago. Ultimately, the loss of forest habitats likely led to the extinction of these predators, with the last known record sometime between approximately 35 and 45 thousand years ago.

“These data provide evidence that the marsupial lion was an ambush predator and relied on prey that occupied denser cover,” DeSantis said in a press release. “As the landscape became drier and forests less dense, these apex predators may have become less-effective hunters and succumbed to extinction. The study of these ancient fossils provides us with cautionary lessons for the future. Climate change can impact even the fiercest predators.”

The marsupial lion lived alongside the Thylacine, or Tasmanian tiger, which survived until the 20th century. The preference of the Thylacine for prey from more open habitats likely led to its survival, despite having a much weaker bite than Thylacoleo carniflex.

A Wakaleo schouteni, a leopard-sized ancestor of the marsupial lion, which lived about 18 million years ago, challenges a Thylacine over a kill. Drawing by Peter Schouten

Michael Archer, a vertebrate palaeontologist at the UNSW, said the lion had bolt-cutter teeth that could snip through the leg of giant kangaroos, making it the most-specialised mammalian carnivore in the world. They had proportionately larger brains than African lions and were probably tree climbers, as they had formidable can-opener-like thumb claws. “Humans would’ve encountered these things, which would’ve been interesting, to say the least,” he said.

“What’s increasingly clear now is that it evidently survived the arrival of humans 60,000 years ago, but apparently not the profound impacts of a rapidly drying climate that undermined the survival of a range of megafauna mammals in Australia.”

Artist’s impression of Microleo attenboroughi Riversleigh by Peter Schouten.

Artcher said other flesh-eating marsupials were documented in the 25-million-year fossil record from the Riversleigh site in northwest Qld.  They included pussy-cat-sized marsupial carnivores such as Microleo attenboroughi and leopard-sized species such as Wakaleo schouteni.

Study co-author Gilbert Price, of the university of Qld said, “When you’re big and bitey, you can eat pretty much anything you want. But our findings show that even the top predators are no match for extreme climate.”

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