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Last Updated: Tuesday, 4 November, 2003, 00:13 GMT
Dog doubts over Tasmanian tiger
By Jonathan Amos
BBC News Online science staff

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 dingo it seems had an accomplice in driving the Tasmanian "tiger" off mainland Australia - human hunters.

There appears little doubt the famous feral dog out-competed the tiger for food and helped push it back to its final island habitat 3,000 years ago.

But researchers say changes in Aboriginal land use, population size and technology taking place at the same time would also have affected numbers.

The species finally became extinct in 1936 when the last tiger died in a zoo.

"On the evidence, juries have always convicted the dingo, but it is a largely circumstantial case," said Dr Stephen Wroe, from the University of Sydney, New South Wales.

"You can make just as good a circumstantial case for human involvement," he told BBC News Online.

Dinner and dogs

Taken at face value, the evidence against the dingo (Canis lupus dingo) is certainly persuasive.

The dog arrived on 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.

It is even possible Aboriginals and dingoes combined to effectively form a single super-predator
Dr Stephen Wroe
This march across Australia is matched by the retreat of the tiger (Thylacinus cynocephalus) to its last island refuge. It has to be more than just coincidence, many believe.

"The dictum historically has been that the dingo competed with the thylacine for resources - for some foods - and may have brought disease," said Dr Wroe, who has reassessed the evidence for the tiger's demise with colleague Chris Johnson, of James Cook University, Queensland.

"Being social animals, dingoes may have been more efficient hunters. But in truth, we actually know very little about thylacine behaviour so it's difficult to say."

Top team

Johnson and Wroe's argument is that the dingo has been prematurely judged. It probably did have a hand in driving out the tiger but human activity on the Australian mainland, they say, has to be factored in, too.

It is a theory that is gaining ground.

"At about the same time as the arrival of the dingo, we see a growth in human population and intensification of land use.

DINGO WILD DOG
Dingo, AP
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
"There were new technologies for a start - new spear technologies - that would have improved hunting efficiency, and there were other technologies that allowed humans to permanently colonise areas of the country they could only do seasonally before.

"All of this would have put pressure on other fauna. But the point is - just as with the dingo - none of this got to Tasmania."

By the time European settlers arrived in the early 18th Century, the tiger had nowhere left to run. Sheep farmers and bounty hunters quickly took out the last animals and the final thylacine, called Benjamin, died in a Hobart zoo.

"Extinctions are always complex. There is usually a combination of factors including climate change and at this stage you just can't say that one or the other was responsible," said Wroe. "It is even possible Aboriginals and dingoes combined to effectively form a single super-predator."

Johnson and Wroe publish their assessment in the journal The Holocene.




SEE ALSO:
Monster marsupial's weight gain
17 Sep 03  |  Science/Nature
First dingo 'was Indonesian pet'
30 Sep 03  |  Asia-Pacific


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