Wildlife biologist David Pemberton said the finding appeared to be linked to recent research showing that the animals were also having sex younger since the disease appeared.

The illness, which causes facial tumours, is spread by contact between the animals and generally kills them within three to six months. As a result they are generally living for only two years compared to six in the past, he said.

But researchers had also found that their young were being born throughout the year, which appeared to be a way the species was compensating for its low population density.

Pemberton, who has been studying the creatures for more than two decades, said that in the past, mating was restricted to a three-week period around March and April, the southern autumn.

"Where the population has decreased dramatically there is extended breeding," he said, saying it appears to have extended the period during which the female can reproduce.

"With a low population at least if a 'girl' cycles now it appears that a 'boy' will find her."

The facial tumours are spread through biting. Since the disease was first observed in 1996, there has been a sharp decline in sightings of the devil across Tasmania.

The species is restricted to the island state after competition from the dingo led to its extinction on mainland Australia.

It is Australia's largest marsupial carnivore after the extinction last century of its distant cousin, the thylacine or Tasmanian tiger.

Early European settlers named the feisty marsupial the devil for its spine-chilling screeches, dark appearance and reputed bad temper which, along with its steeltrap jaw, made it appear incredibly fierce.

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