Cancer forces Tasmanian devils to breed earlier

Randolph E. Schmid, Associated Press Yahoo News 15 Jul 08;

The little devils just can't wait. Faced with an epidemic of cancer that cuts their lives short, Tasmanian devils have begun breeding at younger ages, according to researchers at the University of Tasmania in Australia.

"We could be seeing evolution occurring before our eyes. Watch this space!" says zoologist Menna Jones of the university.

Tasmanian devils live on the island of Tasmania, south of Australia. They weigh 20 to 30 pounds and were named devils by early European settlers because the furry black marsupials produce a fierce screech and can be bad-tempered.

Since 1996 a contagious form of cancer called devil facial tumor disease has been infecting these animals and is invariably fatal, causing death between the ages of 2 and 3.

In the past devils would live five to six years, breeding at ages two, three and four, but with the new disease, even females who breed at two may not live long enough to rear their first litter.

Jones, who has been studying the animals' life cycles since before the disease outbreak, noted that there has been a 16-fold increase in breeding at age one. She reports her findings in this week's edition of Proceedings of the National Academy of Sciences.

"What we are suggesting in this paper is that there is likely to be strong selection for rapid evolution" toward early maturity, Jones said in an interview via e-mail.

"It was an exciting discovery," she added.

The disease could cause the devils to become extinct in 25 years or so, she said, but this change to younger breeding may slow population decline and reduce the chance of them disappearing.

"To our knowledge, this is the first known case of infectious disease leading to increased early reproduction in a mammal," Jones and her colleagues report.

Meantime, the search for a vaccine continues.

The research was funded by the Australian Research Council, the Australian National University and the Tasmanian Government Save the Tasmanian Devil Program.

Tasmanian Devils Fight Cancer with Sex
Jeanna Bryner, LiveScience.com Yahoo News 14 Jul 08;

Tasmanian devils have for some years been plagued with a mysterious and lethal cancer. Now, the dog-sized mammals are fighting back: They are breeding at younger ages.

Devils are furry marsupials, mammals that have no true placentas - females usually have pouches to carry and suckle newborns. They reside only on the island of Tasmania, though fossil evidence suggests that long ago Tasmanian devils (Sarcophilus harrisii) were spread across the Australian mainland. Devils are known for their offensive odor, disturbing screeches and viciousness when they eat, mostly carrion.

Hunters considered the devils pests to livestock and took a toll on the population in the mid-1800s. Now the devil facial tumor disease is killing the animals within a year of reaching maturity. The infectious cancer is spread directly through biting. The tumors mainly affect adults at least 2 years old, causing death within months.

Menna Jones of the University of Tasmania and colleagues examined data collected before and after the arrival of the disease from five Tasmanian devil populations on the island.

A much higher proportion of older adults, over the age of 3, were present in the populations before the disease appeared.

After disease emergence, precocial breeding by 1-year-old females increased dramatically at four sites, increasing from between zero and 12.5 percent beforehand to between 13 percent and 83 percent after. The range in percentages reflects the different findings at each of the sites on the island.

Reduced population density and reduced competition for food could be behind any growth spurts that would allow juveniles to reproduce before their time, the researchers suggest.

Symptoms of the disease, including cancerous lesions around the mouth, face and neck, were first reported in 1996 at one spot on Tasmania. By 2007, the disease had spread over more than half of the devils' home range there. Some populations have lost up to 89 percent of their members as a result of the facial tumors.

The newly discovered precocial breeding could help to keep the species from vanishing, the researchers speculate.

The study, reported this week in the journal Proceedings of the National Academy of Sciences, was funded by the Australian Research Council, the Australian National University Faculties Research Grants Scheme, and the Tasmanian Government Save the Tasmanian Devil Program.