Why culling won't save the Tasmanian devils from the devil facial tumour disease.
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The Tasmanian devil is a unique animal. It claimed the title of the world's largest surviving marsupial carnivore after the extinction of the Tasmanian tiger, and its dramatic and noisy displays of bluff and bluster have made it famous.
The devil's survival is currently being threatened by an equally unique disease. Devil facial tumour disease, or DFTD, is one of only two or three infectious cancers in the world.
Among these, it is particularly unique in that it looks likely to cause the extinction of the Tasmanian devil without human intervention. The devil could become extinct on the Tasmanian mainland in as little as 25 years - a terrifying prospect when it is considered that the disease was first confirmed in 1997, only 14 years ago.
The disease is spread when devils bite one another, transferring tumour cells directly to an uninfected devil's flesh, which can then multiply and grow. These facial tumours can grow to the point where a devil is unable to even eat, causing it to starve. The disease, once contracted, is unfortunately invariably fatal.
It was thought that removing infected animals from affected populations via selective culling may, given enough effort, eradicate or at least slow the disease in certain areas. This concept was trialled in the isolated Forestier Peninsula, near Port Arthur, between 2004 and 2010.
Unfortunately, despite some promising signs, the trial failed to slow the progress of the epidemic and was ended. We used mathematical modelling to test whether increasing effort or trying a different trapping regime would positively change the outcome, and found that the amount of effort required would be far more than is currently possible. Selective culling therefore cannot be considered as a feasible option until new technologies or techniques are available to change the state of play.
However, selective culling is by no means the only tool at the disposal of those fighting to save the Tasmanian devil - a number of different strategies are either being planned or implemented. In some devil populations, the disease seems to be progressing much more slowly. As a result, work is currently underway to examine the possibility that some devils are resistant to DFTD, or alternatively that some strains of the disease have evolved to become less pathogenic.
Other researchers are attempting to develop a vaccine based on knowledge about the workings of the disease. A captive breeding program has already provided 490 disease-free devils. And plans are underway to fence off a farm in the as-yet undiseased north-west of the state to protect devils there from the spread of the disease and to send devils to Maria Island to establish a healthy free-ranging population there.
There is no single magic bullet that can guarantee the devil will continue to survive in the wild. It is a combination of strategies, combined with opportunities arising as a result of continuing research, which will give the Tasmanian devil its best chance at life.
Nicholas Beeton is a mathematical modeller from the School of Zoology at the University of Tasmania, where he working on modelling the effects of the devil facial tumour disease.
