Emerging disease and population decline of an island endemic, the Tasmanian devil Sarcophilus harrisii

Abstract

We present evidence that Devil Facial Tumour Disease (DFTD) is an emerging disease that is now widespread and constitutes a serious threat to the Tasmanian devil Sarcophilus harrisii. This species, the world's largest extant marsupial carnivore, is endemic to Tasmania. DFTD is a cancerous disease found exclusively in wild devil populations, and appears to be consistently fatal to afflicted individuals. We draw on data from a wide range of sources and locations across Tasmania, acquired through trapping, spotlighting and public observation, to assess the impact and distribution of this disease. The dramatic tumours characteristic of DFTD were first reported in 1996. There were no reports of these signs in any of more than 2020 individuals trapped previously. Since 1996, DFTD has been histologically confirmed in individuals from 41 separate sites, covering 32 930 km2 (51%) of mainland Tasmania. From the few sites for which timing of DFTD emergence can be estimated, there is evidence for geographical spread of the disease. Of 147 devils with DFTD-like signs, at least 140 were sexually mature. Proportion of animals displaying signs at any one site reached up to 83% (15/18) of trapped adults. Spotlighting surveys and trapping indicated a significant local association between population decline and date of first report of DFTD. In the region where the disease was first reported, mean spotlighting sightings declined by 80% from 1993-1995 to 2001-2003. On the basis of the threat posed by DFTD, the devil has been listed as a threatened species in Tasmania, and nominated for listing at national level.