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Are Tasmanian Devils Fighting Their Way Out of Extinction?

Tasmanian devil
The Tasmanian devil is just a foot tall but has a ferocious reputation. It also likes to swim and usually is active at night. Mark Newman/Getty Images

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The continent of Australia features some of the most fascinating and unique creatures in the world. For all the bouncing kangaroos and cuddly-looking koalas, however, the Tasmanian devil delights not so much in appearance as it does in reputation. Despite the species' tendency for ferocity (what else would you expect from an apex predator?), no one wants to see it wiped off the face of the earth. In fact, much effort has been expended in recent decades to keep that from happening.

A few facts about these animals: Tasmanian devils used to be abundant in Tasmania and Australia, but about 500 years ago, they became extinct on the Australian continent, probably due to dingoes. On Tasmania, the animals were considered a nuisance as they ate farmers' chickens and were nearly wiped out too, until they were protected by law in 1941.

Devils live in relative isolation, feasting on the dead flesh of kangaroos, wallabies, possums and even fellow devils. Although they're the world's largest carnivorous marsupials, adult males measure barely a foot tall (30 centimeters) and weigh up to 26 pounds (12 kilograms). In relation to their small body size, Tasmanian devils' jaws are more powerful than tigers', able to chew through entire bodies, including bone [source: National Geographic].

But it wasn't those champion chops that earned Tasmanian devils their villainous name. The story goes that European settlers who came to Tasmania in the 19th century were terrified by the nocturnal marsupial's piercing screams and thus christened them as devils. Indeed, Tasmanian devils are chatty creatures, with 11 distinct forms of vocalizations used to locate each other, defend themselves and communicate that they're peeved [source: Tasmanian Government].

Tasmanian devils are known for their belligerent nature. When irritated, their ears turn purple, and they release a loud shriek as a warning sign to back off. Their devil-eat-devil lifestyle begins at birth. Female Tasmanian devils produce litters of up to 40 tiny babies. But there are just four nipples inside of the mother's pouch, which means that only the strongest survive. After weaning the babies for a few months, the young devils must set out on their own, or risk being devoured by their mother. From there, they lead mostly solitary lives, except during mating season. And when adults encounter each other, it isn't a heartwarming reunion. Tasmanian devils fight each other readily, inflicting wounds – and sometimes death.

That innate urge to brawl has become an increasing threat to the livelihood of the species in the past two decades. The frequency of Tasmanian devil fighting hasn't risen, but the outcomes have turned far deadlier. Instead of a couple of nicks and scratches, a skirmish between two devils could leave behind a festering cancer known as Devil Facial Tumor Disease (DFTD).

DFTD, a contagious cancer introduced by feral cats, foxes and other pests, has raced across Tasmania at a swift pace, reaching all of the island state, except for the western and northwestern regions [source: University of Cambridge]. The typical lifecycle of DFTD begins with a showdown between two Tasmanian devils. If one of the animals is already infected with DFTD, a bite will deliver the virus into the other devil's healthy flesh. After that, the Tasmanian devil will develop the symptomatic facial tumors. As the tumors metastasize, they may destroy the devil's jaw and cause their teeth to deteriorate. Eventually, the animals lose their ability to eat and starve to death. This process takes place over a period of three months to a year. There is no treatment available for the disease.

There are two strains of DFTD: DFTD1 and DFTD2. DFTD1 is far more common and found throughout the country.

Once upon a time, experts believed that DFTD packed the potential to wipe out the entire Tasmanian population in a couple of decades. (The population had dropped from 140,000 to perhaps 20,000, over the last 25 years [source: National Geographic].) However, the species appears to be adapting, as many devils have developed infection resistance, helping to ease the decline significantly. Still, despite assurances by scientists that DFTD will not cause total extinction, the fact that it has eradicated fully 80 percent of the wild population keeps it a constant area of concern for Tasmanian devil enthusiasts [source: ScienceDaily].

Tasmanian devil with Devil Facial Tumor Disease
A Tasmanian devil is captured exhibiting advanced signs of Devil Facial Tumor Disease Oct. 10, 2005 near Fentonbury, Australia. Adam Pretty/Getty Images

DVTD was first observed in 1996, when wildlife photographer Christo Baars noticed something odd about certain Tasmanian devils he watched through his camera lens. Camped out in Mount William National Park in Tasmania, Baars spotted large, gruesome lumps around the devils' mouths and necks [source: Quammen].

Scientists have found only a handful of cancers that are contagious like DFTD. Viruses can trigger cancer, but rarely does cancer itself act as a virus, jumping among individuals. That makes DFTD not only easy to catch, but also highly fatal due to the genetic isolation among Tasmanian devils. The marsupials live in the wild only in Tasmania, which has resulted in a lack of genetic diversity among the species. In addition, the genetic sequencing of DFTD is so similar to that of a Tasmanian devil that the animal's body doesn't recognize the virus as a threat. Consequently, the animal's immune system doesn't respond to fight off the virus before it develops into full-blown cancer.

So, what's the best way to stop it? Scientists hoped that a devil named Cedric from the west held the key to halting the cancer. Immunologists injected the Tasmanian devil with live tumor cells, and after five months, Cedric's body produced antibodies to fight the virus. Scientists therefore hypothesized that Cedric might have a slightly different genetic coding that triggers a stronger immune response. By cracking that genetic code, scientists could develop a potential method for identifying and quarantining other resistant devils. After reintroduction into the wild, the immune devils would breed and form a stronger population. But Cedric ended up dying in 2010 after developing tumors a year after he appeared to have resisted the disease [source: Nature].

Vaccinations seem like another way to stop Devil Facial Tumor Disease (DFTD) from infecting more Tasmanian devils. Numerous studies had been done to determine whether developed vaccines were successful at eliciting an immune response. Finally, in March 2020, 19 immunized devils were released into Narawntapu National Park and will be monitored to determine immunization success. Most had already shown signs of immune response in the lab [source: University of Tasmania].

Back in 2003, the Tasmanian State Government set up a Save the Tasmanian Devil Program and created an insurance population, made up of 700 animals across 44 institutions (in Australia, New Zealand, Europe and America). The species is reported to do well in captive breeding situations, and as such the effort has been successful. The program also spearheaded a successful campaign urging motorists to slow down at night and created virtual fence devices that warn animals of approaching cars. More than 350 devils are killed each year by motorists.

If Tasmanian devils were allowed to disappear entirely, it would have a deep impact on the island's ecology. The carnivorous marsupials keep the cat and fox population in check. No more devils would mean a spike in the number of those predators, which would spell the demise of more than a dozen other species, including some birds and lizards. And as scavengers, devils also remove sick and dead animals from the landscape.

Fortunately, things appear to be looking up for Tasmanian devils. Only very recently, researchers have begun to note that animals in the wild appear to be fighting off tumors entirely, so a devil that previously had a tumor might not have one only a few months later [source: Gough].

Natural selection also appears to be playing a role in the leveling out of this endemic disease, as the Tasmanian devils who are capable of fighting off the disease are the ones reproducing, causing a much-needed ripple effect. In fact, in 2019, researchers forecast a 57 percent chance of DFTD fading out within the next 100 years versus a 22 percent chance of the disease coexisting [source: Timmins].

Although surprising, this quick and nimble adaptation of the species to the disease is certainly in keeping with their overall reputation as quick and nimble predators. Still, although the decline appears to be leveling off, the devil population is still nowhere what it was in the 1990s.

Last editorial update on Apr 29, 2020 03:48:47 pm.

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Sources

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  • "Dying Tasmanian devils turn to teen pregnancies." New Scientist. July 19, 2008. (Dec. 17, 2008)http://www.newscientist.com/article/mg19926655.600-dying-tasmanian-devils-turn-to-teen-pregnancies.html
  • Gough, Myles. "Bringing the Tasmanian devil back to mainland Australia would restore ecosystem health." Phys.org. Aug. 11, 2015 (April 20, 2020) https://phys.org/news/2015-08-tasmanian-devil-mainland-australia-ecosystem.html
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  • Timmins, Beth. "Tasmanian devils 'adapting to coexist with cancer.'" BBC News. March 30, 2019 (April 20, 2020) https://www.bbc.com/news/science-environment-47659640
  • Trofimov, Yaroslav. "Tasmanian Devils Get Reprieve in Australia's Old Penal Colony." The Wall Street Journal. May 28, 2008.
  • University of Cambridge. "Tasmanian devil facial tumour disease." 2020 (April 20, 2020) https://www.tcg.vet.cam.ac.uk/about/DFTD
  • Woods,Gregory M and Samantha Fox, Andrew S Flies, Cesar D Tovar, Menna Jones, Rodrigo Hamede, David Pemberton, A Bruce Lyons and Silvana S Bettiol. "Two Decades of the Impact of Tasmanian Devil Facial Tumor Disease." Integrative and Comparative Biology. Dec. 2018 (April 20, 2020) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6927850/

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