SYDNEY – Climate change was most likely responsible for the extinction of the Tasmanian tiger from western Australia some 3,000 years ago, according to a study published on Thursday.
The climate change, which started 4,000 years ago, was particularly driven by a greater tendency for more drought-prone seasons due to the “El Niño-Southern Oscillation” phenomenon, linked to changes in ocean and atmospheric heat, according to the research by the University of Adelaide’s Center for Ancient DNA published in the Journal of Biogeography.
Known as a tiger-like species (but not related to tigers) because of its striped lower back, the Tasmanian tiger or thylacine used to inhabit areas of continental Australia and the island of New Guinea.
However, when Europeans arrived in Australia in the 18th century, the population of this animal was concentrated on the island of Tasmania, southern Australia.
As thylacines were blamed for attacking livestock, an intense hunting campaign was launched between 1830-1909 and encouraged by rewards, which subsequently contributed to the extinction of what is considered to be the largest terrestrial predator on the Australian continent in modern times.
Tasmanian tigers, about the size of a large dog, became extinct 81 years ago when the last one died in captivity at the Hobart zoo on Sept. 7, 1936. The animal, called Benjamin, was by mistake locked out of its sheltered sleeping area and died from the cold.
There are people who claim to have seen Tasmanian tigers in the wild in recent years, but no scientific proof of any remaining animals have been provided.
“But the reasons for its disappearance in mainland Australia and its continued survival in Tasmania remain a mystery,” Jeremy Austin, research coordinator and deputy director of the Center for Ancient DNA, said in statement.
The reasons for the extinction have been attributed to climate change, an increase in human activity or the presence of dingoes (Australian wild dogs), he added.
The study traces back the history of thylacine populations over the past 30,000 years through the genetic analysis of bone samples found in museums, generating about 51 mitochondrial DNA sequences.
This provides the first genetic evidence that the thylacine was divided into two populations, the western and eastern populations in the southern part of Australia, before the last Ice Age, 25,000 years ago.
The large and diverse genetic population of the western thylacine became extinct 3,000 years ago.
“The ancient DNA tells us that the mainland extinction was rapid, and not the result of intrinsic factors such as inbreeding or loss of genetic diversity,” said University of Adelaide PhD student and the paper’s lead author, Lauren White.
Austin added that the team also discovered that there was a simultaneous population crash in thylacines in Tasmania around that time, which reduced their number as well as genetic diversity.
This situation resembles what happened with another carnivorous marsupial, the Tasmanian devil, which still survives on the island, although the population of thylacine seemed to expand during the time when first Europeans arrived.
Austin said that Tasmania would have been somehow shielded from mainland Australia’s warmer, drier climate due to its higher rainfall, hence climate change was “the only thing that could have caused, or at least started, an extinction on the mainland and caused a population crash in Tasmania.”