A grainy, yet haunting, image of one of the last thylacines.

Credit: Archives Office of Tasmania

Related articles

• Tasmanian devil epidemic reaches key refuge
• Tasmanian tiger gene fragment resurrected
• Tasmanian devils face extinction
• Facing extinction, devils mating younger
• Threatened devils have more sex

SYDNEY: DNA from 50-year-old droppings are being extracted by Australian zoologists to test the idea that the fabled Tasmanian tiger may have survived beyond its reported extinction in the 1930s.

"The last known wild individual was killed in 1918. If some survived another 40 years with no sightings, than it adds to the chance that others could still be around today," said Jeremy Austin from the Australian Centre for Ancient DNA at the University of Adelaide.

"Glimmer of hope"

The Tasmanian tiger, or thylacine, was widespread in Tasmania when European settlers arrived in 1803; it resembled a large, long dog with stripes, a stiff tail and big head.

It was the world's largest marsupial carnivore until 1936 when the last one died in captivity in a zoo in Hobart, the capital of the southeast Australian island state.

Austin is now extracting ancient DNA from purported thylacine droppings found in Tasmania in the late 1950s and '60s, which have been preserved in a Tasmanian museum.

"The scats were found by Eric Guiler, Australia's last real thylacine expert, who said he thought it more probable they came from the Tasmanian tiger rather than a dog, Tasmanian devil or quoll," Austin said.

It's only recently that techniques have become good enough to reliably extract DNA from scats. Austin is now working in collaboration with zoologist Oliver Berry from the University of Western Australia in Perth, who has experience of extracting ancient DNA from scats collected in Tasmania to find evidence of foxes.

The scientists will compare any DNA they are able to extract with thylacine DNA sequences already collected from museum specimens.

The time is now

"If we find thylacine DNA from the 1950s scats it will be significant," said Austin. "It adds an extra glimmer of hope that thylacine might still be clinging on somewhere today."

He hopes to have some data by the end of 2007.

"Getting DNA from scats has been difficult, but the technology is getting a lot more reliable and Austin is one of the Australian leaders in the study of ancient DNA," commented ecologist Hamish McCallum at the University of Tasmania in Hobart.

"It's highly likely with a nocturnal predator that the last one would die out some substantial time after the last one was spotted by humans anyway… leaving the very remote possibility that some may survive today," said McCallum.

"If it is the case that there are any thylacines out there, then the next five years will be the time that we find them," added McCallum, "as there are some of the most comprehensive fox and Tasmanian devil surveys ever conducted taking place."

Austin's research team is also extracting ancient DNA from bones of both the Tasmanian tiger and individuals of the Tasmanian devil found on mainland Australia. Experts believe the tiger remained on the mainland until about 2000 years ago and the devil persisted there until as recently as 400 to 500 years ago.

Doomed anyway?

Though it's unlikely, the researchers believe that the DNA may reveal these populations were distinct species to the Tasmanian animals. "It's only been 10,000 years since Bass Strait flooded and Tasmania was separated from the mainland. That's not a long period of time in evolutionary terms," said Austin.

Some experts think that the Tasmanian population of the thylacine may have been a separate species because it was significantly larger than its mainland counterpart. "[The size difference isn't] surprising given the climate, because the colder the environment, the larger the animal," said Austin, referring to the fact that species show a tendency to grow larger in cooler climates.

Anecdotal evidence suggests that Tasmanian thylacines may have had a population numbering in the tens of thousands when European colonisers arrived. The big question is – was the thylacine population healthy at this time, or was it already on the path to extinction and Europeans just sped up the process?

"Islands have a higher rate of extinctions than the mainland anyway," says Austin. He plans to take DNA samples from thylacine remains pre- and post-European colonisation to estimate genetic diversity and population size over time and "test if the population was already small and in decline – and potentially doomed anyway – at the time of European arrival."