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Planet Earth

Thylacines: Getting Inside the Head of an Extinct Predator

Dead Things iconDead ThingsBy Gemma TarlachJanuary 19, 2017 12:00 AM
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Benjamin, the last living thylacine (as far as we know), photographed in 1933 at Tasmania's Hobart Zoo, three years before his death. Credit: Photographer unknown, Wikimedia Commons. While I have mixed feelings about de-extinction, particularly for animals that have been out of the picture for thousands of years (I'm looking at you, woolly mammoth), I'd argue the species with the strongest case for giving it a shot would be Thylacinus cynocephalus, better known as the Tasmanian Tiger or thylacine. This fascinating marsupial, once found in much of Australia (particularly the island of Tasmania, as its name suggests), went extinct in the 20th century — though reports of alleged sightings continue to accumulate. Whether any of those sightings are legit, or the thylacine earns a second chance through de-extinction, new research is giving us a novel look into the workings of the thylacine brain and how it might have lived in the wild. Why are thylacines so cool? So many reasons. So very many...hang on. I get a little emotional about thylacines. Ahem. [Takes a sip of water, dabs at eyes with tissue.] Despite looking like a dog wearing a low-quality tiger costume for Halloween, thylacines aren't related to either cats or dogs. They're the last members of a carnivore family that goes back more than 20 million years. Both females and males had a pouch, though it was less developed in males. Thylacines were able to open their jaws nearly 90 degrees, a trait shared with their nearest living relative (admittedly not that close on the family tree), the Tasmanian devil.

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Neville, a member of Sarcophilus harrisii, showing off the impressive range of motion seen in the jaws of both Tasmanian devils and thylacines. Image taken at Trowunna Wildlife Park, Mole Creek, Tasmania, 2011. Credit: G. Tarlach.

To The Memory of Thylacines

Thylacines once roamed much of Australia and even as far north as New Guinea. But dingos, in competition with them, muscled them into ever-smaller territory (and also, on occasion, probably found them to be delicious). By the time Europeans were poking around Australasia, the mercurial marsupials were restricted to Tasmania. Before you gruffly mutter that thylacines had their chance and Nature voted them off the island, so to speak, consider that habitat destruction due to farming, coupled with a ruthlessly successful bounty program begun in 1830 and in place for nearly a century, led to the thylacines' extinction from their last stand, on Tasmania.

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In May 1930, the last Tasmanian Tiger shot in the wild was done in by Wilfred Batty of Mawbanna, Tasmania, reportedly after finding it in his hen house. Credit: Wikimedia Commons. By the time humans started thinking hey, maybe we should be learning about these interesting and unique animals, the last Tassie tigers, living in captivity in a handful of zoos, were shuffling off this mortal coil. So incredibly, even though the species went extinct less than a century ago, no one ever studied thylacines in the wild. All we have are a handful of anecdotal observations by hunters, trappers and farmers. Not the most unbiased bunch to provide information about a predator's lifestyle.

A New Hope

Now, however, a new era in thylacine research arrives with the first reconstruction of its cortical maps. Published today in PLOS One (which is open access, folks, so enjoy), researchers got their hands on two of the four known thylacine brains preserved for posterity, as well as two Tasmanian devil brains, and used MRI-based diffusion tensor imaging (DTI) to map out their neural connections. Yeah, that sounds like some fancy (and also expensive) research, but what did it tell us? Well, for starters, it showed us that DTI is even possible on a century-old specimen (it's typically used in brains less than 10 years old) and that identifiable pathways, or tracts, are still present after sitting in a jar on a museum shelf for that long. But today's study also revealed that the thylacine cortex had a larger caudate zone than that of the Tassie devils, which means the tigers likely devoted more brain power to action planning and decision making than their smaller distant kin.

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A pair of thylacines action planning and decision making before our species offed them all (nice going, humans). Credit: Smithsonian Institutional Archives, 1904. The difference in cortex between the species makes sense: devils are scavengers, while thylacines were hunters. Today's findings also augment previous studies that looked at other specialized aspects of the thylacine anatomy, including tooth shape and elbow joint, which point to it being more of an ambush predator than one of pursuit. The new research brings us closer to understanding what the thylacine might have been like in the wild — and what it might be like again, should the de-extinctionists have their way. Of course, there is a sizable camp of thylacine enthusiasts who believe that the animals never really went the way of the passenger pigeon and dodo, and instead live on in areas of mainland Australia, action planning and decision making blissfully unmolested by humans.

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