Last Updated: Tuesday, 4 November, 2003, 00:13 GMT|graham_inglis|space@eurobell.co.uk|11/06/03 at 19:32:50|graham_inglis|xx|0|217.43.51.190|http://news.bbc.co.uk/1/hi/sci/tech/3237791.stm

Last Updated: Tuesday, 4 November, 2003, 00:13 GMT

Dog doubts over Tasmanian tiger
By Jonathan Amos
BBC News Online science staff

[img]http://www.eclipse.co.uk/cfz/bb/thy1.jpg[/img]

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.

[img]http://www.eclipse.co.uk/cfz/bb/thy2.jpg[/img]

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.

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.

"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.

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