The discovery of a genetically different population of Tasmanian devils has raised hopes for the survival of the iconic Australian mammal threatened by a deadly cancer.
In today's edition of the journal Proceedings of the Royal Society B, researchers from the universities of Tasmania and Sydney reveal devils in the northwest of Tasmania may be potentially resistant to the devil facial tumour disease.
Tasmanian devils, the world's largest remaining marsupial carnivore, face extinction within the next 25 to 35 years due to the emergence of the contagious cancer, the devil facial tumour disease (DFTD).
University of Sydney Associate Professor Kathy Belov says DFTD has affected more than 70% of the state's total devil population, including the entire eastern half of Tasmania where it is invariably fatal, and has wiped out more than 90% of the population.
But, Belov says this study study confirms Tasmanian devils in the geographically isolated northwest of the state are genetically different.
The Faculty of Veterinary Science researcher says the difference is in the major histocompatibility complex (MHC) genes, which in humans help stop rejection of organs in organ transplantation.
"The more different you are at the MHC gene level the more likely an organ is going to be rejected," says Belov.
She says this is critical in the spread of the DFTD because it is transmitted like a skin graft or transplant - most likely passed on by biting - "rather than developing in each individual animal".
The study is based on DNA samples collected from about 400 animals in the wild.
Belov says the work evolved out of a 2007 paper that stated that devils were immunogical clones.
"People responded to this by sending samples, including bits of road kill, to us," says Belov.
The breakthrough occurred when samples arrived from animals that were sent from the northwest of the state "and we detected this difference".
Belov and colleague Dr Menna Jones, of the University of Tasmania, believe the difference in the MHC gene of the northwest population of devils means their immune systems "should be able to see the cancer and start a response to fight it".
She says this theory is supported by the arrival of the DFTD at West Pencil Pine in Tasmania's northwest.
Belov says anecdotal evidence from field studies shows in the three years the disease has been present in the West Pencil Pine region only 26 devils have caught the deadly disease and all have the eastern MHC genotype.
"We are watching this area closely and are more and more confident there is something to this [idea of disease resistance]," says Belov.
"These animals may not remain resistant to the disease forever, but it gives us a bit more time and a bit more hope."
Belov says researchers are now discussing how this finding can be used to ensure the species' survival.
"There is the possibility of breeding up a lot of resistant devils in captivity and releasing them into the areas where the disease is common," she says.
But the long-term aim of the breeding program, she says, should still be to maintain as much genetic diversity as possible for future generations.
"A loss of genetic diversity in the species … would increase the vulnerability of the insurance population to new infectious diseases," she says.