Faster breeding: The Tasmanian devil is afflicted with a consistently fatal infectious facial cancer. The species has responded to this increased adult mortality with a sixteen-fold increase in the rate of early sexual maturity.

Credit: Menna Jones

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SYDNEY: Australia's iconic Tasmanian devils have started having sex at a younger age since the advent of the deadly face cancer, which threatens to wipe out the species.

This is the first known case of an infectious disease leading to an increase in early reproduction in a mammal.

Data collected before and after the cancer-causing disease appeared showed a 16-fold increase in early mating behaviour, says a study published today in the U.S. journal the Proceedings of the National Academy of Sciences.

Disfiguring and fatal

Scientists fear the disease, which causes disfiguring and eventually fatal face tumours, could lead to the marsupial carnivore's extinction within 20 to 25 years.

"We have found that devils are compensating for the disease by breeding early – there is a 16-fold increase in the number breeding at the age of one year," said zoologist Menna Jones of the University of Tasmania in Hobart.

Statistics from five sites showed a majority of female devils are breeding at the age of one, instead of the usual two years.

"The devils are under intense selection for early breeding because the disease is 100 per cent fatal," said Jones. "Any devil that's successful in breeding more than once is putting out more of its genes into the pool of survivors."

Intense selection pressure

The researchers say this is unlikely to prevent the decline of the species, although it may slow progress of the disease.

The Tasmanian devil is restricted to the island state of Tasmania after competition from the dingo led to its extinction on mainland Australia. It is the world's largest marsupial carnivore after the extinction last century of its distant cousin, the thylacine or Tasmanian tiger.

The facial tumours are spread through biting. Since the disease was first observed in 1996, there has been a 64 per cent decline in sightings of the devil across Tasmania.

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.