They are the only known scavengers in the world that follow a picky diet.
If there is one thing scavengers do, it is to earn: feed whatever is available, whenever it is available.
Scavengers all over the world share this trait, from wolves across the Northern Hemisphere to spotted hyenas in sub-Saharan Africa.
But a new study led by the University of New South Wales in Sydney finds Australia’s Tasmanian devils are breaking that mould.
In fact, individual devils have their own tastes and preferences – in other words, they are picky eaters.
“It is the job of the scavenger to be a generalist and to take whatever they can find,” says Tracy Rogers, a professor of science at the University of New South Wales.
“But we’ve found that most Tasmanian devils are actually eclectic, picky eaters — they’ve broken the garbage laws.”
The study, published today in Ecology and Evolution, analyzed the eating habits of 71 captive demons across seven different locations across Tasmania. The researchers tracked these eating habits by analyzing a small, longitudinal sample of each devil — each roe contains chemical fingerprints, called stable isotopes, from the food they’ve eaten in the past.
Surprisingly, only about one in 10 fiends has a general diet – that is, a broad diet consisting of any available and suitable food. The vast majority chose to dine mostly on their favorite foods, whether it was wallabies, possums, or rosellas.
And like humans, these favorite meals varied from demon to demon.
“We were surprised that the demons didn’t want to eat the same thing,” says Ms Anna Lewis, lead author of the study and a doctoral candidate at the University of New South Wales for Science.
Most of them just decided, ‘No, this is my favorite food.’
Ms Lewis, also a researcher at The Carnivore Conservancy, says the findings change what we know about scavengers — and lead us to wonder why Australia’s demons break the rules.
“This seems to be a devil’s habit,” says Mrs. Lewis.
“There are no other scavengers in the world who know who does this.”
base crash under
The researchers’ current theory is that the selective eating of devils has something to do with their being alone in Tasmania.
“Basically, that’s because they can,” Professor Rogers says.
“If you are a scavenger in Africa, then you are competing with all these other predators for food,” she says.
But in Tasmania, there are no other predators or competition for carcasses. Their main competition is only with each other.”
The team found that although rotting devils come in all shapes and sizes, the heaviest devils tend to be the most satisfying to eat.
This could mean that the devil’s size is a driving factor in his choice of food, or alternatively, that specializing in certain types of food can help the devil gain weight.
Our demons have a misunderstanding
Ms. Lewis, who completed this work as part of her PhD, captured and dealt with most of the Tasmanian devils involved in the study. She and her team set traps for a week at a time, checking them daily. They generally hunt about 10 devils a day before taking their samples and returning them to the wild.
Ms. Lewis says these mammals often get a bad reputation – but there’s more to it than meets the eye.
“Demons are really easy to deal with, and I was surprised by that when I first became a training volunteer,” she says.
“Wild demons tend to be afraid of humans, so most of them sit on your lap.”
Her favorite demon, Arcturus (named after one of the brightest stars in the sky), loves to stick to a diet of pademelon and wallabies. Every now and then though he does branch out, occasionally indulges in a little rattlesnake.
“Tasmanian Devils are these really cool scavengers who do something completely different than every other scavenger in the world,” says Ms. Lewis.
“We are fortunate to have them here in Australia.”
Helping Conservation Efforts
Tasmanian devils are ecologically unique, but their numbers have declined since the 1990s when a highly contagious cancer — called devil’s face tumor disease, or DFTD — began spreading through its population.
This disease has a high mortality rate: If a demon introduced DFTD into its colony, it would likely wipe out about 77 percent of the population within five years.
Many conservation groups have tried to reduce the spread by keeping some groups in captivity until it is safer to release them.
This nutritional study may help these groups decide how best to care for the mammals in the meantime.
“From a conservation perspective, the findings can help us see if we’re feeding demons the right thing in captivity,” says Ms. Lewis.
“Right now, there’s a long list of foods demons can eat, but it’s not specific in how often they eat all of those foods or whether most of them focus only on a few different types of food.”
Next, the team plans to take a closer look at why demons make certain choices in their diet—for example, do they choose food consciously, choose foods that other demons don’t care about, or simply choose the foods they are most interested in. Abundance?
“Our next step will be to consider why daemons tend to be so inclined towards certain foods, such as pademelons and possums, and whether humans have a role to play in this specialty,” says Professor Rogers.
In the meantime, this study paves the way for future global research on specialization in scavengers’ diets.
“It’s hard to believe a scavenger can be such a specialist,” says Ms. Lewis.
“It makes you wonder if other scavengers, like hyenas or wolves, would behave like demons if they didn’t have other species to compete with.”
Reference: “Influences of nonspecific competition and body mass on diet specialization in mammalian scavengers” by Anna C. Lewis, Channing Hughes, and Tracy L. Rogers, Jan. 11, 2022, Ecology and Evolution.
Funding: Winnifred Scott Foundation, The Carnivore Conservancy