Why Is This Australian Spotted Cat in Trouble?

Bad news for the Tasmanian devil also may mean tough times for another one of Tasmania’s predators, the eastern quoll.

Since 1996, the virally transmitted “devil facial tumor disease” has ravaged the Tasmanian devil population. In the areas of the Australian island (map) where the disease has struck, it has killed more than 95 percent of the famously cantankerous carnivores. (See related video about the cancer ravaging the species.)

An eastern spotted quoll caught in a research trap. Photograph by Jason Edwards, National Geographic

Tasmanian devils are the world’s largest marsupial predator, growing more than 20 inches (51 centimeters) long and weighing more than nine pounds (four kilograms); they resemble angry baby bears.

Their decline appears to have had an impact on Tasmania’s smaller eastern quoll, or eastern native cat, a spotted marsupial predator about half the size of the devils, reports a team led by Tracey Hollings of the University of Tasmania in an upcoming study in the journal Current Biology.

Eastern quoll numbers have “declined rapidly” in island areas where the devils have been afflicted with the facial tumor disease, according to the study.

What’s happening? It appears that Tasmanian devils had effectively shielded the eastern quoll from predation by the feral cats that had been introduced to Australia two centuries earlier.

Feral cat populations are now rapidly growing in areas where Tasmanian devils have been wiped out, and the researchers suspect the cats are preying on the eastern quolls.

tasmanian devil picture
A Tasmanian devil with devil facial tumor disease. Photograph by Dave Watts, Visuals Unlimited/Corbis

Cascading Troubles

The bad news for eastern quolls is an example of a “trophic cascade,” the researchers suggest, in which the top predator, or apex predator, in an ecosystem is eliminated and sometimes surprising consequences result for the other species in the food chain.

Examples range from deer and coyote numbers surging in parts of North America that now lack wolves, to sea urchins wiping out Pacific kelp forests that were denuded of sea otters.

“Until now, Tasmania has been a refuge for mammals that have been driven to extinction on mainland Australia, probably by introduced predators,” concludes the study.

“In ecosystems throughout the world, apex predators play a keystone role, and their preservation and restoration is important for building resilience into natural ecosystems and the conservation of many vulnerable species.”

Wildlife