Did dingoes kill thylacines?
3 May 2012
There has long been debate as to what caused the extinction of the thylacine from mainland Australia. Was it dingoes, humans or hunger? Findings recently published in PLoS One by School of Biological Sciences researcher, Dr Mathew Crowther, and colleagues at the University of Sydney and UNSW, point the finger of blame back at dingoes.
Tasmanian thylacines (now also extinct) were much larger than dingoes, so direct confrontation between the two species was initially discarded as the reason for the thylacine decline. But 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.
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,' says ecologist Dr Mike Letnic, co-author on the paper.
Killing of the smaller, female thylacines would have depressed the reproductive output of thylacine populations. Therefore direct attacks by the introduced dingoes may have led to the extinction on the Australian mainland of the thylacine.
Another hypothesis is that competition between the two species may have been the cause: however, competition is not thought to be a strong driver of extinction. More recently, it has been suggested that humans caused the extinction of the thylacine through direct hunting or suppression of prey. The authors of this paper suggest that there may be contributions from all these factors, but their study shows the evidence for dingo driven death.
'We were aware of old reports that mainland thylacines were smaller than Tasmanian ones,' says Letnic, former researcher in the School of Biological Sciences, Sydney University. '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.'
Dingoes appear to have had a dramatic impact on the ecology of Australia when they first arrived between 3,500-5,000 years ago, probably introduced by human seafarers, and likely also caused the extinction of the Tasmanian devil from mainland Australia (devils are still found in Tasmania, which does not have dingoes).
'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,' says Dr Letnic.