Tasmanian devils puzzle science with picky eating habits

Scavengers are known for their lack of discernment – these animals will eat whatever they can find, whenever they can find it.

At least, that’s what ecology has been telling us. But it turns out there’s one Australian animal that’s breaking all the rules when it comes to scavenging: the Tasmanian devil.

“It’s a scavenger’s job to be a generalist and take whatever it can find,” says Tracey Rogers, a professor at UNSW and senior author of a new study out today in Ecology and Evolution. “But we’ve found that most Tasmanian devils are actually picky and selective eaters – they’ve broken the laws of scavenging.”

It turns out that individual devils have their own tastes and preferences – much like us – and can be decidedly picky eaters, unlike other scavenger species like wolverines and hyenas. And while it might not sound like the most earth-shattering discovery, it actually upends much of what we know about scavenger ecology.

The study analysed the eating habits of 71 devils captured across seven different sites in Tasmania by analysing a small whisker sample from each devil. That’s because whiskers, just like other hairs, carry the chemical imprints of a creature’s diet over time, as stable isotopes.

The team found that only around one in every 10 devils had a generalist diet, meaning they were consuming whatever food was available and convenient. Most devils were only dining on favoured foods, whether possums, wallabies or rosellas. And, just like us humans, the favourite dish varied from devil to devil.

“We were surprised the devils didn’t want to all eat the same thing,” says Anna Lewis, lead author of the study and a PhD candidate at UNSW Science. “Most of them just decided, ‘No, this is my favourite food’.”

Lewis says the findings are radical for our understanding of scavenger behaviour, and prompt more questions, like why the devils might have developed such discerning palates.

“This definitely seems to be a devil-specific habit,” says Lewis. “There are no other scavengers in the world that we know of who do this.”

Rulers of the roost

The scientists’ working theory is that the devils can afford to be picky because they’re alone in Tasmania, kings of the carnivore castle.

“Basically, it’s because they can,” says Rogers. “If you’re a scavenger in Africa, then you’re competing with all these other predators for food. But in Tasmania, there aren’t other predators around or competition for carcasses. Their main competition is just with each other.”

This does raise the question, then, did this behaviour develop after Tasmania’s dominant predator, the thylacine (or Tasmanian tiger), went extinct almost a century ago?

Misunderstood devils have powerful conservation value

Lewis, who completed the work as part of her PhD and captured and handled most of the devils herself, says the mammals, which have at best a mixed reputation, are a hidden ecological gem.

“Devils are actually really easy to work with, which I was surprised about when I first became a volunteer in training,” she says.

“Wild devils tend to be afraid of humans, so most of them just sit in your lap.”

Lewis’ favourite devil, Arcturus (named after one of the brightest stars in the sky), likes to stick to a diet of pademelon and wallabies. But every now and then, Arcturus branches out to dabble in a bit of snake.

“Tasmanian devils are these really cool scavengers that are doing something completely different to every other scavenger in the world,” says Lewis. “We’re lucky to have them here in Australia.”

And while Tasmanian devils are ecologically unique, they’re a species under acute threat. Their numbers have plummeted since the 1990s, after a highly contagious and ravaging cancer called Devil Facial Tumour Disease (DFTD) began ripping through the population.

The disease is ruthless: if a devil brings it into the colony, around 77% of its members will likely die within five years.

To mitigate the threat of DFTD, many conservationists are trying to minimise the spread by keeping some populations in captivity until it’s safe to release them into the wild. In the meantime, the dietary study may help them care for captive devils.

“From a conservation perspective, the findings could help us work out if we’re feeding devils the appropriate thing in captivity,” says Lewis.

“At the moment, there’s a long list of foods that devils can eat, but it’s not specific in how often they eat all those foods or whether most only focus on a few different food types.”

In future, the team would like to figure out what drives the devils’ picky eating habits. Are they making conscious choices based on taste? Do they go for foods other devils in their area aren’t interested in, to minimise competition? Or do they simply choose the foods that are most abundant in their area?