While a number of researchers pursue reported sightings of Tasmanian tigers in Australia in hopes to prove that the thylacine is not extinct, others are starting with the idea that the creature is gone and are trying to figure out if the accepted reasons for its demise are valid or if something else killed off the creatures – something that may spell doom for other unique Australian animals today.
Most accounts of the final days on Earth of the Tasmanian tiger point to the one that died in 1936 in a Hobart Zoo as the last of the thylacines wiped out primarily by Tasmanian hunters, with lesser numbers meeting their end in competition for food with wild dogs or felled by diseases. On the other hand, the last of the species on the Australian mainland was believed to have died off about 3,000 years ago. Fossil remains show that this time period coincides with the introduction of dingoes to Australia and that led researchers to believe these wild dogs wiped out the smaller Tasmanian tigers. A less-accepted theory is that Aborigines hunted the Australian thylacine to extinction but there’s little evidence to support it.
A study published this week in the Journal of Biogeography presents a new theory based on old DNA. Researchers from the University of Adelaide's Australian Centre for Ancient DNA (ACAD) led by Associate Professor Jeremy Austin, co-author of the study, began by comparing the ancient DNA of Australian and Tasmanian thylacines and found that the lines spilt about 10,000 years ago, most likely due to water levels rising to cut Tasmania from the mainland.
Fossils show that the Australian thylacines survived in southern Australia until 3,000 years ago. The DNA tests showed that the extinction was swift and dramatic – traits not indicative of killing by a foreign species or Aboriginal hunters. Interestingly, Austin found evidence of a population implosion and a loss of genetic diversity at exactly the same time on Tasmania. What could have caused these events and why did the Tasmanian thylacines survive it?
If you had your money on either ‘El Nino’ or ‘climate change’, you’re today’s big winner. Evidence shows that an El Nino climate event occurred over a few years at about the same time. In warm, wet climates like Tasmania and southern Australia, El Nino caused droughts and this was a particularly severe one that seems to have dried out the food supply of the Australian thylacines. Those in Tasmania, while hit hard, managed to survive because the island has a higher annual rainfall that gave enough relief from the drought to save its tigers.
So, El Nino-induced climate change 3,000 years ago killed off Australia’s thylacines. Or did it? Other species around at the same time managed to survive, as did the thylacine’s Tasmanian cousins. Could small packs of them have lived through more droughts, human invasions, diseases, development and other non-native species?
Dr. Austin thinks not. For those still hoping, only time and motion-triggered cameras will tell.