What's Special about Tasmanian Carnivores?
Overall, Australia accounts for more than half of the world’s mammal extinctions in the last two centuries. Almost all the extinctions have occurred on the Australian mainland, where two invasive predator species — the fox and the feral cat — have caused major ecological damage since their introduction by European settlers in the 19th century. The extinct mainland species were all small to medium-sized mammals, a size range particularly susceptible to predation by foxes and cats.
Despite multiple attempts, foxes were never successfully introduced in Tasmania, and feral cats have never reached the density seen on the mainland. As a result, Tasmania has largely been spared the scourge of mammal extinctions. (The notable exception is the thylacine, or Tasmanian "tiger" — a large, doglike marsupial carnivore that was driven to extinction in the early 20th century as a result of relentless persecution by European settlers.)
Many ecologists believe that the carnivore “guild” formed by the Tasmanian devil, spotted-tailed quoll and eastern quoll prevented foxes from becoming established and kept feral cat numbers in check in Tasmania. Collectively, the three native carnivores consume prey of the same size and weight range as the fox and cat, so they pose direct competition to the invaders. And devils and spotted-tailed quolls would likely prey on young foxes and cats.
Today, the Tasmanian native carnivore guild is at risk of collapse. Tasmanian devil and eastern quoll populations have declined sharply, potentially creating an opportunity for feral cat numbers to increase. A new fox incursion was first detected in the late 1990s, and the fox stands a better chance of becoming successfully established than would have been the case when devils were plentiful. If feral cats increase in number and foxes gain a permanent foothold, Tasmania could see the same type of extinction cascade that has occurred on the mainland. Conserving Tasmania's native carnivores is the best way to maintain the state's unique animal biodiversity.
Thylacine: Photo in public domain.
Spotted-tailed quoll: Photo © C. Hughes 2006.
Tasmanian devil joeys: Photo © J.-F. DuCroz 2013.