‘No bigger than a kelpie’: US PhD student resizes thinking on Tasmanian Tiger

With a background in carnivorous mammals, PhD student Douglass Rovinsky found no animal more intriguing than the Tasmanian tiger.

He moved to Australia from the United States to work on his thesis at Monash University, asserting that “the coolest carnivorous mammal that I could think of down here [in Australia] was the Tassie tiger”.

“It also just happened to be one where there’s just not a lot known about it because it was exterminated and kind of considered vermin, which means that when it was alive, there weren’t any real studies on it.”

But it wasn’t until he saw a thylacine skeleton up close for the first time that the inspiration for his research project struck.

“The acknowledged norm or the estimate of how big they were is about 30 kilos,” Mr Rovinsky said.

3D computer models of a thylacine, from the skeleton to fully rendered stage.
Douglass Rovinsky used computer modelling as part of his research.(Supplied: Monash University)

“[But when] I saw my first Tassie tiger and picked up the skeleton of the skull, and was like, ‘that’s not a 30 kilo animal, this is a lot smaller’.”

“That’s been kind of rolling over in my head for a couple of years and I finally figured out a way to quantitatively test that,” he said.

Illustration showing thylacine illustrations, with human and domestic dog for purposes of scale.
An illustration showing thylacine sizes, with a human and domestic dog for purposes of scale.(Supplied: Monash University)

Mr Rovinsky’s research instead found the size of the thylacine was, “on average, about 17 kilos”.

“The females were about 14 kilos, and the males were about 20 kilos,” he said.

Standing at about 60 centimetres tall, the animal would have been similar in stature to another well-known Australian animal, he said.

“It’s about as big as a big coyote … but an even better example is an Australian kelpie.”

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The last-known thylacine died in a Hobart zoo in 1936.

Resizing an icon

To estimate the size of the extinct animal, Mr Rovinsky scanned thylacine specimens at museums in Victoria and Tasmania.

He was loaned a 3D scanner and visited Museums Victoria and the Tasmanian Museum and Art Gallery in Hobart to scan the surface of the skeletons and taxidermised animals.

“After we did that, we were able to digitally weigh the taxidermy specimens pretty much as is because you just get the volume of that surface scan and then you can calculate the mass from the volume.”

Building that foundation then allowed Mr Rovinsky to grow his dataset to 93 thylacines in total.

“I was able to go ‘if the skull is this big, I know that the animal should weigh about this much because I weighed it in the computer’,” he said.

“Then I can say ‘let’s build an equation based on that and weigh all of these other thylacines that I don’t have a whole skeleton for’, and that let me weigh almost 100 thylacines.”

Tassie Tiger
No audio recording of the Tasmanian tiger exists today.(Doctor Mike Letnic explains new research which suggests the Tasmanian Tiger may have been wiped out by dingoes.)

A change in understanding

Mr Rovinsky believes his research could mean “quite a bit” in terms of our understanding of the thylacine — in particular, what they would have preyed on.

“Small ones [animals], almost always eat very small things, and the interesting thing about this study is that it puts the thylacine down below that point,” he said.

“It was on average below 21 kilos, so it probably ate things that were smaller than half that size … so that’s kind of a radical rethinking of its place in the ecosystem.”

Mr Rovinsky said he thinks the thylacine would be “eating things like pademelons or bettongs, or maybe young or small wallabies”.

He said the thylacine’s skull also suggests its diet was largely comprised of smaller animals.

“It seems that the thylacine had a pretty delicately built skull, which is another point of evidence pointing to [a diet of] smaller animals.”

Mr Rovinsky said despite his findings suggesting the thylacine could well be considered in a new light, he does not think there is any reason for Tasmanian tiger research to be put back to stage one.