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Scientists have digitally crash-tested the predator performance of two Australian icons - the feral dingo dog and the extinct Tasmanian "tiger".

The team built sophisticated computer models of the animals' skulls to compare their feeding behaviour.

The study showed that although the tiger was the bigger, more efficient biter, the dingo was better equipped to deal with prey that struggles.

The results are reported in a Royal Society journal.

The researchers say they may help explain why the tiger disappeared.

It has long been suggested that the feral dog Canis lupus dingo out-competed the tiger (Thylacinus cynocephalus) for food, and was a major factor in pushing the marsupial carnivore off mainland Australia.

The new analysis, which simulates the bite forces and stress patterns applying to dingo and thylacine skulls in the act of killing, confirms there would have been substantial overlap in their choice of prey.

Computer comparison

"What this study suggests is that the thylacine had a much more restricted range of prey," explained Dr Stephen Wroe from the University of New South Wales (UNSW), Sydney.

"The dingo, on the other hand, is adept at taking anything from invertebrates through to kangaroos. The dingo can also be a social hunter and it's most unlikely that the thylacine was; and we know that the more specialised an animal is, the more vulnerable it is."


DINGO WILD DOG
Dingo (SPL)
Descended from a domestic dog brought in from Indonesia
The social dingo is a pack hunter but will also scavenge
Females only breed once a year, having four or five pups
The team used a technique known as finite element analysis, which is also employed by engineers to predict distortion and "failure" in load-bearing materials, such as the metal in the body and wings of an aeroplane.

The researchers took CT (X-ray) scans of the animals' skulls and then built high-resolution digital models of each, incorporating realistic representations of details such as the change in bone material across skeletal structures.

They then loaded the models with forces and analysed the visual read-out. The "hotter" the colours appeared on the screen, the greater the mechanical stresses and strains experienced by the skull, jaw, teeth and cranial muscles.

"We are able to simulate various predatory behaviours - biting, pulling and tearing - to see the patterns of stress and strain. With two skulls that are performing the same behaviour, you can then tell which performs best under particular circumstances," said Dr Wroe.

Reduced size

The approach gave insights into the feeding behaviours of the two animals. For the dingo, its eating habits are well known; but for the extinct thylacine, the observational data is sparse.

The study demonstrates, the team says, that despite being armed with a more powerful and efficient bite and having larger energy needs than the dingo, the thylacine would have been restricted to eating relatively small prey. On the other hand, the dingo's stronger head and neck anatomy allows it to subdue large prey as well, they add.


TASMANIAN 'TIGER'
Tiger, AP
The thylacine was a large marsupial carnivore
It ranged widely from Papua New Guinea to Tasmania
Many scientists doubt cloning technology can bring it back
"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," explained Dr Wroe.

"In terms of getting the balance between the energy expended in catching prey versus the amount of energy you get from those food items, the thylacine was sailing close to the wind."

He added: "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."

Complex factors

The dingo was introduced by humans to mainland Australia little more than 4,500 years ago and spread rapidly across the continent - only failing to reach Tasmania because rising sea levels had inundated the Bass Strait some 6,000 years earlier.

This march across Australia is matched by the retreat of the tiger to its last island refuge.

It was there that European settlers then persecuted the animal, believing it to be a wolf-like creature that killed sheep. The last tiger died in a zoo in 1936.

Scientists stress that the tiger's removal from the mainland was not solely down to the dingo. Climate change, and a shift in Aboriginals' land-use and hunting practices would also have been factors.

Dr Wroe conducted the thylacine-dingo study with Karen Moreno (UNSW) and University of Newcastle colleagues, Colin McHenry and Philip Clausen.

Their paper is published in Proceedings B of the Royal Society.