Lessons from the Looming Extinction of the Tasmanian Devil

Abstract

Extinction in the wild is now regarded as likely for the Tasmanian Devil Sarcophilus harrissi. In 1996, a disease, Devil Facial Tumour Disease (DFTD), was seen in a Devil in the wild. By mid-2008, the population had declined by about 70%, and the disease was spreading rapidly from east to west across Tasmania. DFTD is an infectious cancer, passed from one Devil to another principally, or entirely, by biting. The bite implants the cancer cells; the low genetic diversity in the Tasmanian Devil population from previous population bottlenecks or selective sweeps means that those cancer cells are not recognized by the immune system and the cancer grows in the infected Devil. Estimates of the time to extinction in the wild range from about 20 to 35 years. If, however, there are resistant genotypes within the Devil population then extinction in the wild may be averted, with numbers augmented through captive breeding programmes and active management to spread these genotypes in the wild.