If you’ve ever gone camping, you might be told to beware the dreaded drop bear. There won’t be a chase. You’ll just be walking along, minding your own business, when a dark shape plummets onto you from above, pinning you down before your realize that you’re being eaten alive by an overgrown koala.
This is all nonsense, of course. There are no carnivorous koalas with a taste for human flesh hanging around the eucalyptus trees of Australia. Yet, despite the fact that the drop bear is a modern hoax, that the mythical animal’s description closely matches a very real animal that prowled Australia during the last Ice Age. Paleontologists and fossil fans know this beast as Thylacoleo carnifex, the “marsupial lion.”
Despite the mammal’s name, Thylacoleo doesn’t hold much leonine resemblance. The carnivore’s skull is a modified version of a koala’s or wombat’s, just with cleaver-like shearing teeth at the cheek instead of grinders. That fits given that Thylacoleo belonged to the group of marsupial mammals called the diprotodonts, which includes kangaroos, wombats, koalas, and possums today. Thylacoleo was closer to being a carnivorous koala than a pouched cat.
The kinship of Thylacoleo is only half of the drop bear equation, though. The other has to do with its hunting habits. Back in 2010, paleontologist Roderick Wells and colleagues found that the paws of this marsupial predator would have been just as useful for climbing trees as grappling with the large prey of its era. Now Samuel Arman and Gavin Prideaux have forwarded even more evidence that Thylacoleo was a skilled climber: thousands of scratch marks in the lair of Australia’s real drop bear.
Southwestern Australia’s Tight Entrance Cave yielded the essential clues. In addition to a bonebed cradling the bones of both living and extinct marsupial species, the main chamber of the cavern is marked here and there by V-shaped scratch marks. Only one animal in the cave matches the size and anatomy required to make the largest scratches: Thylacoleo. And while Arman and Prideaux concede that some of the smaller scratches could have been made by other animals trying to find their way out of the cave, from possums to Tasmanian tigers, their preferred interpretation is that most of the smaller scratches were left by Thylacoleo joeys who were reared in the safety of the cave.
The nature of the bones in Tight Entrance Cave bolsters this vision of Thylacoleo hunkering down in the dark. Relatively few of the bones in the cave show bite marks. This means that the cave was not the habitat of bone-eaters, like Tasmanian devils, and might indicate that Thylacoleo was much like a cat in primarily dining on flesh and viscera, leaving bones mostly intact.
At different times, off and on between 140,000 and 51,000 years ago, Thylacoleo apparently used the cave as a refuge. And from where the claws marks are situated among the inclines and boulders, it seems that these predators had qualms about taking difficult routes through the dark. “Many claw marks within TEC are located on steep surfaces, despite more gradual inclines being available on other sides of the central rock pile and boulder,” Arman and Prideaux write, and the entrance to the cave itself appears to have been a steep deadfall for other creatures. This suggests that Thylacoleo was a skilled and confident climber, clambering in and out of a cave that trapped other species. And if Thylacoleo could haul itself around rocky caves, it could almost certainly scale trees.
Humans undoubtedly saw Thylacoleo. The mammal was still very much alive when people arrived on Australia around 50,000 years ago, and there may even be Pleistocene art of the mammal. The mythical drop bear, however, didn’t appear as a tall tale until the 20th century, so there’s no link between what people actually saw and stories used to make tourists shudder at the sound of a creaking branch in the night. Its convergence, but it’s a wonderful sort of convergence.
So much of prehistoric life was so strange that we could have never imagined those species if we hadn’t come across their remains. The drop bear is a rare case when our species, in jest, stumbled upon something real and just as scary as our imaginations can muster.