September 5, 2012
Saving The Tasmanian Devil From Disease – More Or Less
April Flowers for redOrbit.com - Your Universe Online
Tasmanian devils are carnivorous marsupials found on the Australian island state of Tasmania. The size of a small dog, the Tasmanian devil is known for its muscular build, black fur, pungent odor, extremely loud and disturbing screech, keen sense of smell and ferocity when feeding. That ferocity is causing the problem, and maybe the extinction of the animal.
Devil Facial Tumor Disease (DFTD), a fatal infectious cancer spread by biting, is wiping out the species. A new study suggests that evolving to become less aggressive could be the key to saving the species from extinction, because the less often a devil gets bitten, the more likely it is to become infected with the cancer.
According to Dr. Rodrigo Hamede of the University of Tasmania, lead author of the study published in the British Ecological Society's Journal of Animal Ecology, "Our results — that devils with fewer bites are more likely to develop DFTD — were very surprising and counter-intuitive. In most infectious diseases, there are so-called super-spreaders, a few individuals responsible for most of the transmission. But we found the more aggressive devils, rather than being super-spreaders, are super-receivers."
Dr. Hamede and his colleagues set up dozens of devil traps at two sites for 10-day periods every three months between 2006 and 2010 to find out whether biting frequency predicted acquiring DFTD. They recorded the pattern of injuries in the devils, and identified any tumors. One of the sites — West Pencil Pine — was selected because the devils there seemed less badly hit by the disease.
The team made three discoveries during this study period: the level of bites was similar at both sites; devils with fewer bites were significantly more likely to develop DFTD; and most tumors occurred in devils' mouths.
"This means that more aggressive devils do not get bitten as often, but they bite the tumors of the less aggressive devils and become infected," explains Dr Hamede.
There is no current treatment for, or vaccine against, DFTD. That makes the implications of these findings and next stage of the research extremely important for saving the species from extinction.
"Our next step is fascinating. First, we need to explore the genetic differences that might be lessening the impact of DFTD in the West Pencil Pine devil population. Second, we need more detailed data on devil behavior to define 'shy' or 'bold' types. We could then use this information to develop a management strategy to reduce the spread of the disease by boosting natural selection of less aggressive, and therefore more resilient, devils."
Understanding how infectious diseases spread is key to controlling them, but studying disease transmission in wild animals is often very difficult. And in DFTD, which is spread by biting, ecologists need a better understanding of devil behavior. Devils are solitary yet social animals. They do not live in groups but meet each other often, either during mating, establishing social hierarchies or when feeding around carcasses - all occasions when they bite each other.