January 31st, 2013 by James Ayre
The Tasmanian Tiger, also known as the thylacine, was killed off entirely by humans, disease did mot factor in, new research from the University of Adelaide has found. The primary cause of the iconic animal’s extinction was the paid bounties that the Tasmanian government put on their heads.
Previously, some people have argued that bounty killing alone couldn’t have killed them off, and that disease must have contributed. They were very common throughout most of Tasmania before European settlement in 1803. Between only the years of 1886 and 1909, the government encouraged people to hunt them, paying bounties for their carcasses. The bounty was eventually lifted, but by 1933 they were essentially extinct.
For the new research, a new population modeling approach has clearly shown that the thylacine could have very easily gone extinct solely from human hunting and other human activities such as deforestation. The research directly contradicts “the widespread belief that disease must have been a factor in the thylacine’s extinction.”
“Many people, however, believe that bounty hunting alone could not have driven the thylacine extinct and therefore claim that an unknown disease epidemic must have been responsible,” says the project leader, Research Associate Dr Thomas Prowse, School of Earth and Environmental Sciences and the Environment Institute.
“We tested this claim by developing a ‘metamodel’ — a network of linked species models — that evaluated whether the combined impacts of Europeans could have exterminated the thylacine, without any disease.”
“The mathematical models used by conservation biologists to simulate the fate of threatened species under different management strategies (called population viability analysis or PVA) traditionally neglect important interactions between species. The researchers designed a new approach to PVA that included species interactions.”
“The new model simulated the direct effects of bounty hunting and habitat loss and, importantly, also considered the indirect effects of a reduction in the thylacine’s prey (kangaroos and wallabies) due to human harvesting and competition from millions of introduced sheep,” Dr Prowse says.
“We found we could simulate the thylacine extinction, including the observed rapid population crash after 1905, without the need to invoke a mystery disease.”
“We showed that the negative impacts of European settlement were powerful enough that, even without any disease epidemic, the species couldn’t escape extinction.”
The new research was just published online in the Journal of Animal Ecology.
Source: University of Adelaide
Image Credits: University of Adelaide, reproduced with permission from the Tasmanian Museum and Art Gallery
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