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Tassie Devil Decline Allows Feral Cats to Flourish

The decline of the Tasmanian devil has serious repercussions for the State’s ecosystem, according to research published in Proceedings of the Royal Society B (https://goo.gl/KSRuXz).

As a top carnivore on the island, the Tasmanian devil plays a very important role in structuring ecosystems, particularly through scavenging. “The severe disease-induced decline of the devil presents a unique opportunity to study how scavenging by devils structures a carnivore community,” said lead author Calum Cunningham, a PhD candidate at The University of Tasmania.

With devil numbers in decline due to the scourge of devil facial tumour disease (DFTD), invasive feral cats are rising in numbers and influence. Not only are feral cats harmful to native wildlife, carrion that would have been gobbled up by the devils is also beginning to accumulate.

Cunningham’s group placed pademelon carcasses in both DFTD-free areas and in areas where DFTD has reduced the devil population. They found that devils consumed significantly fewer carcasses in areas with DFTD, and this increased the food supply for smaller scavengers such as feral cats, forest ravens and spotted-tailed quolls.

Although these smaller carnivores increased their feeding on carcasses, they were much less effective at removing carcasses than devils. As a result, carcasses persisted in the environment 2.6 times longer in areas with DFTD, potentially harbouring diseases affecting wildlife and livestock.

“We expected common scavengers such as ravens to scavenge more in areas with fewer devils, but we didn’t know what to expect with feral cats because they are thought to prefer feeding on prey they kill themselves,” Cunningham said. “This is the first demonstration that the abundance of a larger predator can limit scavenging by cats, highlighting one mechanism by which devils could control cats.

“We still need to understand whether the increase in scavenging by smaller carnivores has led to increases in their abundance, especially for the feral cat, and then what the flow-on effects are on their prey,” Cunningham said.