Tasmanian devils, native to the island of Tasmania, face a significant threat from Devil Facial Tumour Disease (DFTD). This rare, contagious cancer poses a severe challenge to the species’ survival, raising global concern among conservationists and researchers.
The Nature of a Transmissible Cancer
Unlike most cancers, DFTD is a clonally transmissible cancer, spreading through the direct transfer of living cancer cells between individuals. Transmission primarily occurs during social interactions, especially through biting during fights over food, territory, or mates. When an infected devil bites another, cancer cells are transferred, often evading the recipient’s immune system.
Two distinct forms, DFT1 and DFT2, arose independently in different devil populations. DFT1 was observed in the 1990s in northeastern Tasmania and has spread widely, affecting most of the devil population. DFT2, a more recent strain, emerged around 2011 and was detected in 2014, remaining confined to southeastern Tasmania’s Channel Peninsula. Both strains are believed to originate from Schwann cells, a type of nerve cell, and spread through biting.
Physical Manifestations and Progression
The disease manifests as visible soft tissue lumps, typically around the devil’s mouth and face. These tumors grow rapidly, often becoming large, ulcerating masses. As they expand, tumors invade and destroy jaw bone, causing severe disfigurement.
These growing tumors severely impair the devil’s ability to feed. Affected animals struggle to open their mouths or chew, leading to starvation. Tumors can also metastasize to regional lymph nodes and other organs like the lungs, spleen, and heart in about 65% of cases. Death typically occurs within six months of lesion appearance due to starvation, organ failure, or secondary infections.
Population-Level Impact
DFTD has had a severe impact on the wild Tasmanian devil population since its emergence. Since its identification in the mid-1990s, the species has experienced significant population declines, with some local populations plummeting by over 90%. Across Tasmania, the overall population has declined by over 80%.
By 2020, DFTD had spread across over 90% of the devil’s range. The wild population peaked at 53,000 in 1996, but was reduced to about 17,000 by 2020. This reduction led to the Tasmanian devil’s reclassification as endangered in 2009.
Conservation and Research Efforts
In response to DFTD’s severe threat, the Save the Tasmanian Devil Program (STDP) was established in 2003, initiating comprehensive conservation strategies. A primary focus is establishing “insurance populations” of healthy, disease-free devils. These populations are maintained in isolated areas, including captive breeding facilities and fenced peninsulas, to preserve genetic diversity.
The insurance population has grown to over 600 animals, safeguarding against extinction and providing a source for reintroduction into the wild. Alongside these efforts, extensive research is underway to understand the disease and develop long-term solutions. Researchers are actively pursuing vaccine development, considered a promising management solution.
Scientists are studying how DFTD cells evade the devil’s immune system, possibly by down-regulating immune recognition molecules. Despite challenges, natural resistance and tumor regression are observed in some wild devil populations, suggesting rapid evolution within the species. Models predict the population decline may begin to level off within the next decade, offering hope for the Tasmanian devil’s future.