Tracking the Tasmanian Tiger

Today we're going to head into the green forests of Tasmania, searching for surviving relicts of a once-great population of predators: the thylacine, or Tasmanian Tiger. The island of Tasmania was once rich with these wolf-like marsupials who were kings of the food pyramid, running about in packs, looking like strong, skinny dogs with a striking splash of misplaced zebra stripes along their back and haunches. But despite their earlier prevalence, the last confirmed specimen died in the Hobart Zoo in July of 1936. It has since become declared officially extinct in the world. Sightings, however, have continued unabated. Is it possible that the thylacine has survived?

Of course the obvious comparison that everyone points to is the coelacanth, the prehistoric fish believed to have gone extinct 65 million years ago, but that is represented today by two living species, both critically endangered. It's what we call a Lazarus taxon; we think it's gone, but then we discover it still survives. There are a whole host of Lazarus taxa living today, including animals on the same approximate timescale as the thylacine. Dozens of birds are thought to have gone extinct up to several hundred years ago but are now known to survive, including various petrels and woodpeckers. The Caspian horse, the Arakan forest turtle, the terror skink, and Gray's monitor lizard are other large animals that made reappearances. The idea of thylacines being rediscovered in the wild is not, at all, remotely implausible.

There is famous black and white video, widely available online, showing the last surviving thylacine walking back and forth in its cage, eating meat, and doing other doggy things, taken at the Hobart Zoo about three years before the animal died. Despite looking like a tiger-striped dog, it is a pouched marsupial, like a kangaroo. It was declared extinct in 1982. Why 1982, if the last one died in 1936? There actually is an authority for this; it's the International Union for Conservation of Nature located in Switzerland. They maintain the IUCN Red List of Threatened Species, which gives the conservation status of every species. A declaration of extinction means the following: "Species not definitely located in the wild during the past 50 years". Although the Hobart Zoo specimen died in 1936, the last wild thylacine had been confirmed in 1932.

Sightings still happen every year, but nobody ever seems to get good enough photography or video to raise any eyebrows. Interestingly, the sightings are not confined to Tasmania, also being reported on mainland Australia. And, it turns out, there may be a good reason for this.

The modern thylacine appeared some four million years ago, the largest of some seven species known over the past 30 million years. Thylacines were not limited to Tasmania. They were also native to mainland Australia and New Guinea. Thylacines went extinct in Australia about 2,000 years ago, and probably earlier in New Guinea. The cause is believed to have been a combination of hunting by aboriginals and competition from dingoes — wild dogs native to Southeast Asia, but that were introduced to New Guinea and Australia by humans. The dingo spread quickly throughout Australia beginning around 6,000 years ago but possibly several thousand years earlier. The arrival of aboriginals and dingoes left no room for another apex predator, and the thylacines disappeared.

However, dingoes never made it to Tasmania, and the thylacines flourished. The greatest impact on them came when Europeans arrived and began raising sheep in 1824. Thylacines were widely hunted by sheep farmers, and the government even put a bounty on them. It's also hypothesized that a marsupial disease, perhaps similar to the facial cancer that's now decimating the Tasmanian Devil population, may have cut the species' numbers even more. Their count dwindled to where they could no longer maintain a viable population, and the survivors simply died out by the 1930s.

It turns out that thylacines, for being as large as wolves, had more fragile jaws. Therefore the best current theory is that they preyed on smaller animals, and were probably not going for the sheep so much as the settlers thought. If true, this means they were under even greater pressure, because the dogs the settlers brought would have played the same role in the wild as the dingoes played in Australia and New Guinea: competing with the thylacines for smaller game.

Thylacines and wolves are related, but only about as far as is possible for two different mammals. They're both Theria, which includes mammals that give live birth without an egg. Canids are eutherians, or placental mammals; while marsupials are metatherians, the pouched mammals. The two lines diverged at least 160 million years ago, a number which increased by 35 million years as recently as 2011 with the discovery of Juramaia sinensis, a late Jurassic rat-like creature, and the earliest placental mammal known so far. Interestingly, the timeline suggested by its discovery better matched predictions made by comparing DNA from modern Theria than the previous oldest-known eutherian, a 125-million year old Eomaia scansoria discovered in 2002.

So, suffice it to say that wolves and thylacines are very far apart and went in completely different directions. And then, because both played similar roles as top-level predators with similar environmental pressures on their respective continents, wolves and thylacines went through convergent evolution that produced animals whose gross anatomy is nearly identical. A comparison of their skulls is particularly remarkable; the differences are small enough that most non-experts can't even tell them apart.

What this means is that there's a good chance that many of the sightings since the presumed extinction may well have been of dogs. The stripes were pretty prominent, but when you see any animal at any kind of a distance, it's hard to resolve markings like that. So any sighting of a presumed thylacine has to be of pretty darn good quality to be unequivocally differentiated from a dog.

Over the decades, many targeted searches have been launched in northern Tasmania, ground zero for most sightings. These have included professional photographers with cameras at the ready and a whole lot of automatically triggered game cameras. No groups have ever come back with any evidence that they might still exist, although some who identify more with cryptozoology rather than proper zoology have claimed to have heard vocalizations that they believe are from thylacines, or to have collected eyewitness stories. There are no compelling photographs, and certainly no specimens.

The lack of evidence has not been due to a lack of trying. Various rewards have been offered over the years, including one for over a million dollars offered by the Australian magazine The Bulletin (defunct since 2008) in 2005 to anyone who could capture a live, uninjured specimen. The reward sent more armies of enthusiasts into the forests of northern Tasmania, but again, nobody had any luck.

Hopeful searchers have two additional clues to help them discern thylacines from dogs, beyond the obvious striping. One is that the thylacine could open its jaw really, really wide, up to 120 degrees, in fact; a characteristic that's not obvious unless the animal is yawning. The other is that its tail, like that of a kangaroo, was very rigid, not at all like that of a dog. It is believed that thylacines could stand tripod-like on their tail and hind legs, though there's scant evidence of them having actually done this.

These two characteristics, but without the stripes, have often been described by cryptozoologists who have visited New Guinea searching for stories of the thylacine. There is a legendary animal called a dobsegna which is mentioned in nearly every cryptozoology article from the region, which at first glance, sounds compelling. If the native people have a name for the creature, then it seems like it must be real. However, this turns out to be not very reliable. As we discussed in the episode on the orang pendek, the huge number of tribes and cultures and languages in New Guinea and Indonesia means that there is a local tradition or legendary being to match just about anything and everything you could come up with. Sumatra's ebu gogo doesn't make the orang pendek real; the Athabascan sasquatch doesn't make Bigfoot real; and the New Guinean dobsegna doesn't mean the thylacines still survive.

Regardless, The Bulletin's reward went unclaimed, despite uncounted trompings into the forest by zoologists, cryptozoologists, reward hunters, and Tasmanian Tiger enthusiasts alike. Tasmania is only about the size of the state of Maine, and although it's considerably less developed, even its remotest locales are simply not all that remote. With every other known species being commonly encountered and captured on game cameras, it seems less and less credible that a viable population — which would have to number at least around 100 individuals in close proximity — would remain hidden and have no observable effect on the ecology and the populations of available prey. This observation, consistent with no thylacines being extant, has held solid now for three quarters of a century. The smart money says the thylacines are indeed as extinct as they appear to be. But will they remain that way?

We do have plenty of genetic material from thylacines. Quite a lot of museums have specimens preserved in alcohol, and a lot of thylacines have been taxidermied, and viable tissue can be extracted from these pelts. Grandiose plans to revive the species were announced in 1999 and again in 2005 by Professor Mike Archer from the University of New South Wales, but the announcements seem to have been as far as the plan ever got. Reconstructing a species from DNA is a much harder project than most people realize. Having bits of DNA, even of high quality, is still a very far cry from having complete sets of chromosomes, which have to be manually constructed by molecular biologists; and even if you had that, it would still be a far cry from implanting those chromosomes into enough donor eggs before you'd have one that survives to grow into an embryo.

In 1863, the English naturalist John Gould wrote of the thylacine, while on an expedition to Tasmania:

When the comparatively small island of Tasmania becomes more densely populated, and its primitive forests are intersected with roads from the eastern to the western coast, the numbers of this singular animal will speedily diminish, extermination will have its full sway, and it will then, like the Wolf in England and Scotland, be recorded as an animal of the past.

Gould saw the end coming 73 years before it did, so he probably wouldn't be surprised to learn that the rewards went uncollected and the cryptozoology pages remain full of only hopeful speculation. Perhaps one day we might bring the thylacine back, but for now we can only remember the crazy striped dog-like skinny kangaroo with the hyperextending jaw.

By Brian Dunning
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