Mainland Tasmanian devil
It is currently believed that Tasmanian devils formerly existed on the mainland, but died out for an unknown reason shortly before European colonization, leaving only the Tasmanian population. Despite this, Tasmanian devils have been theorized to still live in small populations on the mainland of southeastern Australia.
Some of the earlier references to Tasmanian devils on the mainland was In the 1890s, when multiple different sources recorded the presence of Tasmanian Devils in South Australia, Victoria and New South Wales. An example is, that in 1896, a nature column in The Adelaide Observer claimed a "colony of Tasmanian bears" lived near Lake Albert, South Australia.
In 1912, a live Tasmanian devil was captured at Toobarac, Victoria. The animal’s skin and skeleton were preserved in the National Museum of Victoria. Another Tasmanian devil was also caught alive in Dereel, Victoria in 1971 by an 8 year old boy who found it stuck in a rabbit trap.
In 1991, a Tasmanian devil inadvertently ran over by a car near Bendigo, Victoria. Around the same area, tracks from seemingly more specimens were found. The specimen was preserved by the Mammalogy Department of the Museum of Melbourne. In 1997, a pregnant female Tasmanian devil was found underneath a car in a parking lot at Balga, Western Australia, and taken to the Perth Zoo.
The conservation groups Aussie Ark, Global Wildlife Conservation, and WildArk started a breeding program to release Tasmanian devils back to the mainland where they (possibly) went extinct. In September of 2020, they released their first 11 Tasmanian devils into a wildlife sanctuary and are planning on releasing more.