Mapping the disease
Devil Facial Tumour Disease (DFTD) is a transmissible cancer which is passed from devil to devil through close contact. The live tumour cells aren’t rejected by the animal’s immune system because the devil’s immune system doesn’t recognise these cells as foreign.
DFTD has been confirmed in devil populations across much of the state of Tasmania, with declines in populations shown through both trapping surveys and annual spotlight counts. In the north-east region, where a devil with unknown tumours on its face was photographed in 1996, there has been a 95 per cent decline in average sightings of devils on the spotlight transects.
The majority of diseased populations studied have shown a standard response to DFTD, which includes a loss of population abundance, loss of older age classes and females breeding earlier than the usual two years of age exhibited in a healthy population. In addition there has been a collapse in synchronised breeding events. The change in population size and demographic profiles has also led to impacts on the ecosystem.
In response, the monitoring team is assessing the diet of the devil as DFTD spreads. This knowledge has been gained through repeated trapping of populations over time following the arrival of DFTD into a devil population. To determine where new cases of DFTD have recently appeared, annual disease front monitoring surveys were conducted from 2009–2013. These surveys involved teams of biologists setting traps close to where the disease was last confirmed, and then moving in a westerly direction until disease was no longer found. These surveys were very successful, but highly resource intensive, and in the areas where disease had very recently appeared it was difficult to catch those single individuals.
In 2012–2013 the Save the Tasmanian Devil Program also monitored the 'disease front' using remote sensing cameras. The aim was to enable the Program to keep track of the disease spread throughout the year, rather than at just one point in time in a year. The biggest issue experienced in monitoring for new cases of disease using cameras was lack of clarity in images collected – meaning biologists were often unable to distinguish between a tumour or a wound or old scar tissue. The only way to make a diagnosis of DFTD is to capture the animal and sample the tumour for analysis – after all, not all tumours are from DFTD.
The Program’s Roadkill Project has become the best source of information on new cases of DFTD on the disease front. Although the project began in 2009, greater emphasis now on getting the public and other agencies involved has seen more members of the public participating by sending in information. Often, this includes information on whether the animal has DFTD, which has lead to the discovery of several new locations of the disease.
The Program now incorporates a combination of Roadkill Project information, data from a trapping trip in the far north-west of the state, and information from other researchers into the DFTD distribution map.