Humans have restricted the diets of Tasmanian devils

The Tasmanian devil is Australia’s apex terrestrial predator. Since most of these animals are known to be “individual specialists,” feeding on the same food items consistently over time, human impacts on their environment could be influencing whether they have access to their favorite foods, according to a recent study led by the University of New South Wales in Sydney (UNSW Sydney).

“We found Tasmanian devil populations had different levels of variation in their diet depending on their habitat,” said lead author Anna Lewis, a doctoral candidate at UNSW Sydney. “The more that habitat was impacted by humans, the more restrictive the diet became.”

The experts investigated the diets of Tasmanian devil populations across habitats with various levels of disturbance – ranging from undisturbed rainforests to clear pastures – by analyzing stable isotopes from whisker samples. They discovered that devils in human-impacted environments, such as cleared land or regenerated native forests, fed primarily on medium-sized mammals, while in undisturbed areas like rainforests, they ate a broader range of prey and incorporated smaller animals, such as birds, into their diets.

“We found devils in heavily altered areas like cleared land fed on a smaller range of prey compared to populations living in ancient undisturbed regions, who had much more variety in their diet,” Lewis reported. “They may be turning to human-derived sources of food, such as highway roadkill, which are more readily available.”

Interestingly, devils living in regenerated forests also ate a smaller variety of food items, suggesting that, despite appearances, regenerated land lack complex features such as tree hollows in large old trees, which support the diversity of small mammals and birds devils living in rainforests consume.

According to the scientists, devils with limited food opportunities run the risk of interacting more frequently with their conspecifics around carcasses, possibly leading to the proliferation of a highly contagious and lethal cancer, the Devil Facial Tumor Disease (DFTD), which has already reduced local devil populations by 82 percent.

“The highest rate of cancer transmission other than during the mating season occurs when they’re feeding around these large carcasses. So, there could be an increased chance for the disease to spread amongst devils, and the devils themselves are also at risk of being hit while feeding,” Lewis explained.

These findings highlight the urgent need to protect what remains of untouched landscapes for the benefit of both Tasmanian devils and their prey.

“It’s apparent there is much more diversity of species available in these old-growth forests, and the devils are shining a light on how vital these pristine areas are, and the urgent need to preserve what remains from the constant threat of clearing and mining,” concluded senior author Tracy Rogers, an ecologist at UNSW Sydney.

The study is published in the journal Nature Scientific Reports.

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By Andrei Ionescu, Earth.com Staff Writer

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