Snack-size: A model of the mechanical stresses placed on a thylacine skull engaged in a 'lateral shake' of prey. Blues areas represent the least- and red the most-stressed parts of the skull.

Credit: Wroe et al./Proceedings of the Royal Society B

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SYDNEY: A new anatomical analysis of the thylacine's bite, and the mechanical stresses involved in killing large prey, hint that competition with dingoes may have been the major factor that pushed it to extinction in mainland Australia.

Existing studies suggest that the thylacine, or Tasmanian tiger, hunted relatively large prey and didn't directly compete with the dingo. The dingo can take large animals such as kangaroo and sheep, but most often takes smaller prey such as lizards and rodents. Experts had linked a mix of factors – including climate change, the dingo and altered land management practices of Australian aborigines – to the thylacine's extinction on the mainland 2,000 to 3,000 years ago.

Now, a new study published today in the Proceedings of the Royal Society B journal suggests the dingo – which first arrived in Australia with people from Asia around 3,500 years ago – may have had a more direct role in the marsupial carnivore's (Thylacinus cynocephalus) decline.

Engineering method

Researchers led by palaeontologist Stephen Wroe from University of New South Wales in Sydney, used a computerised engineering technique called 'finite element analysis' to compare the skulls and bite force of the dingo and the marsupial carnivore.

The method is more typically used to predict distortion and failure in load-bearing structures, such as the body and wings of an aeroplane. The three-dimensional simulations illustrated mechanical stresses and strains on the skulls, jaws, teeth and cranial muscles of both animals across a range of biting, tearing and shaking motions that simulated a kill.

The results of the study backed up the idea that 'convergent evolution' has driven two predators with very different origins to have a similar body form and mode of life, but also highlighted some interesting differences, said the researchers.

"The thylacine has a greater bite force than the dingo but its skull becomes more stressed than the dingo under conditions that simulate the influence of struggling prey," said Wroe. He argues that despite being larger than the dingo, and having greater energy requirements, the marsupial took relatively small prey.

"If the thylacine had been better able to hunt large prey, such as adult kangaroos and emus, as well as smaller species, then it would have faced less competition from the smaller dingo," said Wroe.

Enormous gape

The dingo might also have enjoyed a competitive advantage as a pack hunter, rather than the thylacine's lone predator strategy.

"I wasn't expecting that the dingo would have such a straightforward knockout effect on the thylacine," added co-author Colin McHenry of the University of Newcastle in New South Wales. "They were bigger animals and had an enormous bite [or gape] relative to the dingo, we didn't expect them to be competing for the same prey."

"It's important to understand what thylacine were eating to interpret that dingoes were responsible for their extinction," commented Jeremy Austin who is studying thylacine remains at the Australian Centre for Ancient DNA at the University of Adelaide.

The study is most "interesting from the point of view of the new technology being used," he said, adding that the analysis would benefit from a comparison of the eating habits and anatomy of a larger number of carnivores.

Despite its extinction on the mainland, the thylacine clung on in dingo-free Tasmania until 1936, when the last one died in Hobart Zoo. Here the extinction is largely attributed to hunting pressure following European colonisation.