MOUNT CATTLEY, Tasmania: It could be the end of an icon.

Over the past decade, a form of cancer has killed almost three out of four Tasmanian devils, the world's largest marsupial carnivore and inspiration for the cartoon character Taz.

Animals with the disease develop tumors on their heads and in their mouths, making it difficult for them to eat. Most animals die within months of the lesions appearing, often from starvation.

The condition, Devil Facial Tumor Disease, was first noticed by a photographer in 1996. Since then, the estimated population of the animals, which are found in the wild only in the Australian island state of Tasmania, has dropped from 200,000 to between 50,000 and 60,000, according to researchers say.

Two-thirds of the remaining Tasmanian devils are thought to be affected, and scientists wonder whether they will be able to find a cure in time to save the rest.

"The process is now in the works to have it listed as an endangered species," said Hamish McCallum, chief scientist of the Devil Facial Tumor Program, which is financed by the government.

McCallum's researchers say they suspect that the disease is spread when cancer cells are passed between animals, usually by biting.

"The best hypothesis is that it is transmitted as part of biting, and most of the biting happens at the time of mating," he said.

But beyond this, little is known about the cancer. No other species has shown signs of it.

"It might have been pure chance or bad luck, or a devil might have come across a powerful carcinogen or mutagen in a dump, but no one knows," McCallum said.

And there is no test to detect the disease in pre-tumorous animals.

Tasmanian devils have a reputation for bad temper. But Rodrigo Hamede, a specialist on the cancer who traps and monitors the animals, says it is not deserved.

They are reputed to have gotten their name from their black color and the diabolical noise they make.

In Hamede's hands, the devils are placid. To check their mouths for tumors, he gently blows on their snouts, triggering their threat response, which is to open their mouths and bare their fangs.

As he tenderly handled a female devil with a huge tumor covering most of her head, he said, "I'd hoped I wouldn't see her again."

Hamede caught her three months earlier as part his monitoring effort, and she had been badly diseased then. He said he had hoped that nature would have put her out of her suffering by now.

He releases the animals back into the wild with a microchip, regardless of how ill they are.

"If the devils are ever going to develop immunity — and to my mind that is the best bet — by removing creatures you are making it less likely," Hamede said.

The trapping program has taught McCallum's team how quickly the disease can work.

"The chance of any animal caught as an adult surviving to the next year is close to zero," he said.

Those running the Devil Facial Tumor Program say they are hoping that unaffected populations will remain in remote and isolated pockets of the island, but they are taking no chances. They are running a pilot program on an isolated peninsula where all the diseased devils they capture are killed.

There is some evidence that this approach is working to protect the overall population because, over time, the average age of the animals they capture has become older, suggesting that more animals are avoiding the cancer and surviving longer. But the program is expensive, and McCallum said his team was not yet sure about its effectiveness in stopping the disease.

They are also considering establishing a new colony of wild animals on an island off the Tasmanian coast but say the potential for destabilizing that island's ecology by introducing a large predator needs further study.

As an interim emergency measure, they have sent 47 disease-free devils to wildlife parks on the Australian mainland, creating what they call an insurance population to guarantee that the species does not die out completely.

McCallum calls it an imperfect solution.

"If all you end up with is a bunch of captive populations, you've failed," he said.

More animals are going to be sent out of Tasmania, but as the disease spreads it is harder to find healthy animals.

Because there is no way to identify animals carrying the disease before the tumors appear, devils intended for transfer have to be taken from areas that researchers are certain are outside the cancer zone.