Dingoes were twice the size of female thylacines and could have caused their extinction on mainland Australia through direct attacks, a new Sydney [study](http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034877?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+plosone%2FEvolutionaryBiology+(PLoS+ONE+Alerts%3A+Evolutionary+Biology) suggests.
A comparison of museum specimens has found that thylacines on mainland Australia were smaller than those that persisted into modern times in Tasmania, and significantly smaller than dingoes, which arrived with human seafarers between 3500 and 5000 years ago but did not spread to Tasmania. The last known Tasmanian thylacine died in 1936.
Measurements of the head size and thickness of limb bones of the semi-fossilised remains of thylacines and dingoes from caves in Western Australia have revealed that, on average, dingoes were larger than thylacines.
“In particular, dingoes were almost twice as large as female thylacines, which were not much bigger than a fox,” said ecologist Dr Mike Letnic, an ARC Future Fellow in the UNSW School of Biological, Earth and Environmental Sciences, who led the study with colleagues at the University of Sydney. The findings are published in the journal PLoS One.
There has long been debate as to what caused the extinction of the thylacine from mainland Australia. Because Tasmanian thylacines were much larger than dingoes, direct confrontation between the two species was discarded as a reason.
Another hypothesis is that competition for prey between the two species may have been the cause. But Dr Letnic said competition was “not a strong driver of extinction”.
Other authors have suggested that people caused the extinction of the thylacine through direct hunting or suppression of prey.
“We were aware of old reports that mainland thylacines were smaller than Tasmanian ones,” said Dr Letnic. “Modern ecological studies show that larger predators frequently kill smaller predators, so we decided to test the hunch that dingoes were actually larger than thylacines and caused their extinction by killing them in direct confrontations.
"We also measured the brain size of both species and found that dingoes also had much bigger brains than thylacines, so they may have outwitted them, too.”
Dingoes appear to have had a dramatic impact on the ecology of Australia when they first arrived, and likely also caused the extinction of the Tasmanian devil from mainland Australia, the researchers said.
“However, recent studies suggest that dingoes now play an integral role in maintaining healthy balanced ecosystems by limiting the populations of herbivores and smaller predators, a role that was once filled by the thylacine,” Dr Letnic said.