Blame Game

Humans can’t duck responsibility for the disappearance of the Tasmanian tiger any longer. While people have argued that a disease helped wipe out this species, a new study suggests that human-related threats were enough to drive the animals to extinction.

These wolf-like mammals once roamed much of Tasmania, Australia. The country “has a particularly woeful record of mammal extinctions, having lost 22 mammal species over the last 200 years,” the study authors note in Journal of Animal Ecology. Bounty hunters killed at least 2,184 Tasmanian tigers in the late 1800s and early 1900s, and the species vanished soon afterward. But some researchers believe that a disease must have helped push the animals over the brink.

In the new study, a team ran a computer model to simulate the effects of humans and disease on virtual Tasmanian tiger populations. The researchers accounted for people’s impact on the animals’ food supply. For example, European settlers introduced sheep to grasslands that housed the Forester kangaroo and Bennett’s wallaby, two of the Tasmanian tiger’s favorite prey species. And people hunted hundreds of thousands of wallabies for food or fur.

Because of competition with sheep, kangaroo and wallaby numbers quickly dropped in the 1800s, the model suggested. Tasmanian tiger populations followed suit. When the team didn’t include disease in the model, the virtual animals still vanished. “[E]ven without a disease epidemic, the species was committed to extinction,” the authors write. Roberta Kwok | 4 February 2013

Source: Prowse, T.A.A. et al. 2013. No need for disease: testing extinction hypotheses for the thylacine using multi-species metamodels. Journal of Animal Ecology doi: 10.1111/1365-2656.12029.

Image © Ljupco Smokovski |