Bones and all: see how the diets of Tasmanian devils can wear down their sharp teeth to blunt nubbins

Zoos Victoria, Author provided

Tahlia Pollock, Monash University; Alistair Evans, Monash University; David Hocking, Monash University, and Marissa Parrott, The University of MelbourneTasmanian devils are expert scavengers, with strong jaws and robust teeth that give them the notorious ability to eat almost all of a carcass — bones and all.
Scientists have even found echidna spikes in their poo.

But regularly crunching through bone comes at a cost: extreme tooth wear. In our new study, we analysed the skulls of nearly 300 devils, and show how regularly crunching through bones wears a devil’s teeth down from sharp-edged weapons to blunt nubbins.

Tasmanian devils are endangered and their wild population is continuing to decline. A key part of conserving this marsupial is by maintaining healthy and happy devils in captivity.

Understanding how their food affects their teeth can help us see if captive devils have the same types of tooth wear as their wild counterparts, and look for signs of any unusual or harmful wear.

Is there anything a devil won’t eat?

Tasmanian devils are the largest marsupial carnivore alive today. As scavengers, they occupy a unique niche in the Australian ecosystem by disposing of dead animal carcasses.

Captive Tasmanian devils are given a variety of foods to replicate what they’d find in the wild. This photo was taken during a carcass feed at Healesville Sanctuary.
Zoos Victoria, Author provided

Devils are highly opportunistic and can eat many different types of prey. While their favourites are the carcasses of native mammals such as wombats and wallabies, they’ll also eat reptiles, amphibians, birds, fish, and even insects.

We know this because we find hair, feathers, scales, small bones, claws and more in their poo.

Almost nothing is off limits to devils — they’ll even have a go at a stranded whale given the chance. Although devils prefer to scavenge, they’re also accomplished hunters.

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Tassie devil facial tumour is a transmissible cancer

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But due to a transmissible cancer, devil facial tumour disease, wild numbers of these remarkable marsupials have plummeted by around 80%.

Right now, 45 Australian zoos and wildlife sanctuaries, plus an island and a fenced peninsula, are collaborating to maintain a healthy population of disease-free devils. It’s important for these institutions to provide captive animals with the right kinds of food for their health and to help make their future release back to disease-free wild locations successful.

Devils naturally wear their teeth down from sharp points and edges to blunt, almost flat surfaces by regularly eating bones.
Tahlia Pollock, Author provided

This is especially crucial for carnivores, who rely on tough foods to help them develop strong jaws.

Like hyaenas, but stronger

The types of food an animal eats will wear their teeth down differently. For example, big cats such as lions prefer to eat the softer parts of a carcass, like flesh or organs, and leave the bones behind.

Spotted hyaenas, however, will happily eat the bones. As a result, hyaenas have incredibly high tooth wear compared with lions.

This might not hinder the hyaena or devil as much as you might think. Both have very strong jaws that can compensate for the loss of sharp teeth. In fact, devils have the strongest bite force per body weight of any living mammal.

In the interactive below, you can check out 3D models of devil skulls to get a better idea of how much their teeth wear down.

Toothwear in Tasmanian Devils by Evans EvoMorph Lab on Sketchfab

Comparing wild and captive diets

By comparing the tooth wear of wild and captive devils, we can see if captive animals are encountering enough hard foods in their diets.

In the Save the Tasmanian Devil Program — an initiative of the federal and Tasmanian governments — captive devils are given a variety of small and large foods at different times, replicating what they’d find in the wild.

We found no signs of different or harmful tooth wear in captive devils, and they showed much the same patterns and types of wear as wild devils.

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However, we noticed captive devils wore their teeth more slowly than those in the wild. This may be due to eating higher quality food, such as carcasses that were fresh, whole, and yet to be scavenged.

This means captive institutions are doing a good job of providing devils with the right types of food for their teeth and encouraging wild behaviours.

Part of the health check for wild devils involves looking at their teeth. This particular devil has nice sharp tips and edges on their canines and molars.
Marissa Parrott/Zoos Victoria, Author provided

Collecting data about Tassie devils after they’ve been released confirms this. In 2012 and 2013, devils were released onto Maria Island in Tasmania after being born and raised for around a year in captivity.

Encouragingly, these devils kept the behaviours required to scavenge and hunt prey, and had diets similar to wild devils.

How you can help save Tasmanian devils

Our research is one small, but promising, piece in the overall puzzle. While captive research and breeding programs help conserve the Tasmanian devil, there are ways you can help, too.

Because they like to scavenge the carcasses of dead animals, road kill is especially tempting for devils. But being so close to the road is dangerous and road mortality is the second-biggest killer of wild devils.

So take care on the roads to help wildlife, especially if driving at night. And if you’re in Tasmania and see a devil that’s been hit on the road, log it in the Roadkill TAS app.

This will help identify road kill hotspots and protect this impressive, but endangered, species.

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Tahlia Pollock, PhD candidate, Monash University; Alistair Evans, Associate Professor, Monash University; David Hocking, Curator of Vertebrate Zoology and Palaeontology at the Tasmanian Museum and Art Gallery (TMAG) | Adjunct Research Associate at Monash University, Monash University, and Marissa Parrott, Reproductive Biologist, Wildlife Conservation & Science, Zoos Victoria, and Honorary Research Associate, BioSciences, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Tasmanian devils look set to conquer their own pandemic

Alecia Carter, Author provided

Hamish McCallum, Griffith University and Austin H. Patton, University of California, Berkeley

In the midst of a human pandemic, we have some good news about a wildlife one: our new research, published today in Science, shows Tasmanian devils are likely to survive despite the infectious cancer that has ravaged their populations.

Tasmanian devils have been devastated by a bizarre transmissible cancer. Devil facial tumour disease, or DFTD for short, was first detected in 1996 in northeast Tasmania. Transmitted via biting, DFTD has spread over almost the entire state, reaching the west coast in the past two or three years. It has led to a decline of at least 80% in the total devil population.

The infectious tumours are spread by biting.
CREDIT, Author provided

Ten years ago, we thought there was a real chance DFTD would drive the Tasmanian devil to extinction. Our concern arose not just because the cancer was almost inevitably lethal, but also because the transmission rate did not appear to slow down, even as devils became very rare.

Our new research has some good news: by pioneering application of genomic analysis typically used for viruses, we have discovered the curve has flattened and the rate of increase of infections has slowed. This means while the disease is probably not going away, neither are Tasmanian devils.

Genomics is a relatively new field of science that uses the vast amounts of data available from modern genetic sequencing techniques to answer some of the most difficult and important questions in biology.

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The genomic approach we used is called phylodynamics. It uses sophisticated mathematical analysis of small changes in DNA to reconstruct the evolution and spread of the tumour through devil populations. This is the same method used to track the COVID-19 pandemic, and it was first developed to study the influenza virus. Viruses have small genomes and evolve rapidly. This is the first time the method has been used for a pathogen with a much more complex and slowly evolving genome.

Screening more than 11,000 genes, we found the R number (the average number of secondary cases for each primary case, now familiar from COVID-19) has fallen from about 3.5 at the peak of the epidemic to about one now. This suggests some sort of steady state has been reached, and the disease and devils are now coexisting.

Reproduction number RE of DFTD from 1990 to the present.
CREDIT, Author provided

This discovery backs up a paper we published last year, in which we reached a similar conclusion using mathematical models based on marking and recapturing Tasmanian devils at a single study site, without taking genetics into account.

Our new study is based on samples collected across Tasmania since the early 2000s. Given the very different nature of the two methods, the agreement between the results lends us increased confidence in our conclusions.

This paper, in addition to several we have published recently, shows there have been rapid evolutionary changes in Tasmanian devils and in the tumours themselves since the emergence of this transmissible cancer. Already, frequencies of gene variants known to be associated with immune function in humans have increased in Tasmanian devil populations, suggesting the devils are evolving and adapting to the threat.

We also now know a relatively small number of genes has a large influence on whether devils become infected, and whether they survive if they do.

Finally, and perhaps most encouragingly of all, we have now seen tumours shrink and disappear — something that was unheard of when the disease first emerged. What’s more, we also know this has a strong genetic basis, again suggesting the devils are genetically adapting to their foe.

Together, all of these discoveries show wild Tasmanian devils can evolve very rapidly — over just five generations or so — in response to this disease. This has profoundly encouraging implications for their likely future survival.

Tasmanian devils now have much better genetic defences against the disease.
Rodrigo Hamede, Author provided

There is still much more to learn about the evolution of the devils and their tumours. But meanwhile, our results provide a warning that a strategy of reintroducing captive-reared animals to supplement diseased wild devil populations is likely to be counterproductive.

When devils from populations that have never been exposed to the disease interbreed with wild animals in diseased populations, the evolution we have seen in wild populations is likely to slow down or even reverse, endangering those populations.

What’s more, the slowing rate of disease transmission may be partly a consequence of reduced devil population densities, resulting in fewer bites. Artificially boosting population densities might accelerate disease transmission, the opposite of the intended effect.

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Sexual aggression key to spread of deadly tumours in Tasmanian devils

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With the growing body of evidence showing extinction of devils is quite unlikely even over the next 100 years, we have time for careful consideration of management strategies. Specifically, models can be developed to assess the evolutionary and epidemiological consequences of reintroductions or translocations.

One possibility would be to captively breed devils that have the right genes to boost their chance of surviving the disease. More broadly, our research underlines the vital importance of taking evolutionary considerations into account when managing endangered species. We now have the genomic tools to do so.

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Many thanks to Andrew Storfer at Washington State University, Menna Jones and Rodrigo Hamede at the University of Tasmania, and Paul Hohenlohe at the University of Idaho for their contributions to this article and the research it describes.

Hamish McCallum, Professor, Griffith School of Environment and Science, Griffith University and Austin H. Patton, Postdoctoral Associate, University of California, Berkeley

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Meet Moss, the detection dog helping Tassie devils find love

Zoos Victoria, Author provided

La Toya Jamieson, La Trobe University and Marissa Parrott, University of Melbourne

Moss bounds happily through the bush showing the usual exuberance of a young labrador. Despite this looking like play, he is on a serious mission to help fight the extinction of some of our most critically endangered species.

Moss is a detection dog in training. Unlike other detection dogs, who might sniff out drugs or explosives, he’ll be finding some of Victoria’s smallest, best camouflaged and most elusive animals.

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These dogs use their exceptional olfactory senses to locate everything from koalas high in the trees, desert tortoises burrowed deep under soil and even whales — often more effectively than any human team could aspire to.

What makes Moss unique, however, is he’ll not only find endangered species in the wild, but will also be part of a larger team helping endangered species breed in captivity. These dogs will be the first in the world to do this, starting with a ground-breaking trial with Tasmanian devils.

Moss will eventually help find the tiny, cryptic Baw Baw Frog in the wild.

Why Moss needed a job

Wildlife detection dogs are a very rare type of dog — they are highly motivated, engaged and energetic, but also incredibly reliable and safe around the smallest of creatures.

And Moss is the first dog to join Zoos Victoria’s Detection Dog squad, a permanent group of highly trained dogs that will live at Healesville Sanctuary.

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Moss was adopted at 14 months old, after he somewhat “failed” at being a family pet. He is a hurricane of energy with an intelligent and playful mind. He’s thriving with a job to keep him occupied and new challenges for his busy brain.

One sign he was perfect for this program was his indifference to the free range chickens at his foster home. For obvious reasons, a dog who likes chasing chickens wouldn’t be a good candidate for protecting some of Australia’s rarest feathered treasures.

Moss will also help monitor incredibly well camouflaged plains-wanderers, which are nearly impossible to spot in the day.

Currently Moss is learning crucial foundational skills, and getting plenty of exposure to different environments. Equally important, he is developing a deep bond and trust with his handlers.

The detection dog-handler bond is crucial not only for his happiness, but also for working success and longevity. Research from 2018 found a strong bond between a handler and their dog dramatically improved the dog’s detection results and reduced signs of stress.

The Tasmanian devil’s advocate

Healesville Sanctuary breeds endangered Tasmanian Devils every year as part of an insurance program to support conservation and research. This program is crucial to help protect the devil following an estimated 80% decline in the wild due to a horrific transmissible cancer, Devil Facial Tumour Disease.

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We developed tools to study cancer in Tasmanian devils. They could help fight disease in humans

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But managing a predator that’s shy, nocturnal and prefers to be left alone can be tricky.

Wildlife, including Tasmanian devils, need a hands-off approach where possible, so they can maintain natural behaviours and thrive in their environment.

Tasmanian devils prefer to be left alone.
Healesville Sanctuary, Author provided

In the wild, devils leave scats (faeces) at communal latrine sites and use scent for communication. Male devils can tell a female is ready to mate by smelling her scat. And we think dogs could be trained to detect this, too.

We aim to train dogs to detect an odour profile in the collected scat of female devils coming into their receptive (oestrus) periods, so we can introduce females and suitable males to breed at the optimal time. The odour profile will be further verified via laboratory analyses of hormones in the scats.

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The project will also explore whether dogs can detect pregnancy and lactation in the devils.

Currently, the best way to determine if a female has young is to look in her pouch, but our preference is to remain at a distance during this important time while females settle into being new mums.

Moss with his trainer, Latoya. Moss is a ball of energy and thrives in the challenging environment of conservation detection.
Healesville Sanctuary, Author provided

If the dogs are able to smell a scat sample (while never coming into contact with the devil) and identify that a female is lactating with small joeys in her pouch, we can support her – for example, by increasing her food – while keeping a comfortable distance.

A new partnership in conservation

The results from this devil breeding research could offer innovative new options for endangered species breeding programs around the world.

Wildlife detection in the field means we can more accurately monitor some of our most critically endangered species, and quickly assess the impact of catastrophic events such as bushfires.

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Detection dogs are the perfect intermediary between people and wildlife — they can sniff out what we can’t and communicate with us as a team.

And over the next few years, the Detection Dog Squad will expand to five full-time canines. They will all be selected based on their personalities rather than specific breeds, so will likely come in all shapes and sizes.

Dogs may yet go from being man’s best friend to the devil’s best friend and beyond, all starting with a happy labrador named Moss.

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This article is co-authored by Naomi Hodgens, Wildlife Detection Dog Officer at Zoos Victoria, and Dr Kim Miller, Life Sciences Manager, Conservation and Research, at Healesville Sanctuary, Zoos Victoria.

La Toya Jamieson, Wildlife Detection Dog Specialist, La Trobe University and Marissa Parrott, Reproductive Biologist, Wildlife Conservation & Science, Zoos Victoria, and Honorary Research Associate, BioSciences, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Tasmanian devils reared in captivity show they can thrive in the wild

Tracey Rogers, UNSW Australia

One of the concerns of any conservation breeding program is how well a species raised in captivity will survive when released into the wild.

Evolutionary changes that are beneficial for an individual while in captivity may reduce its fitness when translocated to the wild.

For some species, like many fish, rapid evolutionary changes can occur within the first generation in captivity. And carnivores raised in captivity have a low chance of surviving the first year following their release.

A review of 45 carnivore translocations, which included 17 different species, including the European lynx, European otter and the swift fox, found that if the animals had been raised in captivity they had on average a 30% chance of survival after release.

Save the devil program

All this was a concern then for efforts to help save the Tasmanian devil.

The devil plays an important functional role within the Tasmanian ecosystem and is the last of the large marsupial carnivores.

But the Tasmanian devil is listed as endangered and their population has declined by 80% over the past ten years. This is due largely to the infectious fatal cancer, the devil facial tumour disease (DFTD).

As part of a conservation effort, a disease-free devil population has been established in captivity.

But given the low rate of survival of released captive-raised carnivores in other conservation programs it was important to identify whether their release could play a viable role in the conservation of the Tasmanian devil.

Captive breeding programs are extremely expensive and resource allocation was very tight. So more than 35 institutions helped to set up the captive devil insurance population.

Different types of enclosure setting were used, some intensive zoo style while others had larger pens to allow for a more free range style. The different enclosure types offered different opportunities for the devils to retain their natural behaviours.

We tested the effect of the various captive-rearing methods on the survival and body mass of captive raised Tasmanian devils that were released on Maria Island, off Tasmania’s east coast.

Our study, published this month in CSIRO Wildlife Research, showed that Tasmanian devils raised in captivity before being translocated into the wild had a high survival success (96%). Most of the devils are still alive two years after their release.

The devils gained weight, are hunting and breeding. This is irrespective of the type of captive-rearing method as both zoo style and free range reared animals are thriving.

Release of the devils.
Wildlife Management Branch, Department of Primary Industries, Parks, Water and Environment

Natural born killers

One cause of translocation failure in other programs has been that the released animals starve. The captive-raised animals had not learnt foraging and hunting skills. Some carnivorous mammals can lose this natural foraging behaviour in captivity.

But the captive-raised Tasmanian devils adjusted to the wild better than other carnivorous species. This was not only because they were released in the relative safety of an island, but it suggests that the devils’ foraging behaviour does not need to be learnt.

Devils have bone crushing jaws.
Wildlife Management Branch, Department of Primary Industries, Parks, Water and Environment.

Devils have a massive head with bone crushing jaws, large tough molars and strong shoulders and neck. They have a very broad approach to what they will eat.

Their diet includes all major critters such as mammals, birds, reptiles, amphibians and invertebrates. Devils have been seen catching gum moths out of the air, slurping tadpoles out of ponds and digging yabbies out of their burrows.

They also live from the intertidal zone to the sub alpine zone. They climb trees like a possum and are good swimmers.

There was less carrion available on Maria Island than on the mainland. Also the captive-raised devils would not have learnt hunting skills while in captivity so we presumed that they would not eat large prey.

Captive devils feeding upon a carcass.

Initially, after the first release, the devils fed on brushtail possums. But relatively soon after we found the devils started to feed on large prey, such as the common wombat and eastern grey kangaroo. These species are much larger than you would predict for a mammal of the devils’ size to prey on.

What’s planned for the devils?

So what does the success of this wild release say for the future conservation of the Tasmanian devil?

The devil facial tumour disease has been detected across the majority of the devil’s range. The wild devil population has been decimated as the disease moved across Tasmania.

It is time to boost the genetic diversity of the wild population. We need to provide the potential for immunity to develop in the species. That’s why it is exciting to have found that the captive-raised devils adjusted so well in the wild.

The next step will be to supplement the wild Tasmanian mainland population by releasing further captive-raised devils, along with those born wild on Maria Island.

But the devils released on the Tasmanian mainland will face other dangers. Alongside the disease they will have to contend with dogs, rodent poison and car collisions.

Clearly there’s some work still to be done, but the Maria Island and captive devils will continue to be an important part of the fight against the deadly facial tumour.

Tracey Rogers, Associate Professor Evolution & Ecology, UNSW Australia

This article was originally published on The Conversation. Read the original article.

Tasmanian devils are evolving rapidly to fight their deadly cancer

Menna Elizabeth Jones, University of Tasmania; Andrew Storfer, Washington State University; Hamish McCallum, Griffith University; Paul Hohenlohe, University of Idaho, and Rodrigo Hamede, University of Tasmania

For the past 20 years, an infectious cancer has been killing wild Tasmanian devils, creating a massive challenge for conservationists. But new research, published today in Nature Communications, suggests that devils are evolving rapidly in response to their highly lethal transmissible cancer and that they could ultimately save themselves.

Cancer is usually a disease that arises and dies with its host. In vertebrates, only two known types – Canine Transmissible Venereal Cancer in dogs and Devil Facial Tumour Disease (DFTD) – have taken the extraordinary evolutionary step of becoming transmissible. These cancers can grow not just within their host but can spread to other individuals. Because the cancer cells are all descendants of one mutant cell, the cancer is effectively immortal.

To grow in the new host, the tumour cell must evade detection and rejection by the immune system. Both the devil and dog transmissible cancers have sophisticated mechanisms for hiding from the host’s immune system. Our research suggests that the devil is nevertheless evolving resistance to the disease.

Ecological disaster

The Tasmanian devil is too important to lose – and this would seem careless following the extinction of the thylacine, the world’s largest marsupial predator, in the 1930s. Since the thylacine’s extinction, devils have stepped up to the role of top marsupial predator, keeping numbers of destructive feral cats at bay in Tasmania. With the decline of the devils, invasive species have become more active.

Since it was first detected in northeastern Tasmania in the mid-1990s, DFTD has spread slowly southward and westward. It will reach all parts of Tasmania within a few years; only the far northwest coast and parts of the southwest are still disease-free.

Devil Facial Tumour Disease has spread across the island over two decades.
Menna Jones

Devil populations have declined by at least 80%, and by more than 90% in some areas within six years of local disease outbreak.

DFTD kills most devils at sexual maturity. Before the disease arrived, most devils produced three litters over their lifetime. Most now raise only one.

The cascading effects of the loss of Tasmania’s top predator on the rest of the ecosystem could lead to loss of further species. Already, feral cats have increased activity and small mammals on which cats prey have declined.

Cats may also be preventing recovery of the eastern quoll. Brushtail possums behave as if devils were already extinct, grazing freely on pasture in the open.

Evolution in action

Our research has been a truly international effort. We used data collected by Menna Jones at the University of Tasmania since 1999. This archive of tissue samples now represents one of the best resources globally for studying evolution of an emerging infectious disease in wildlife.

Andrew Storfer at Washington State University and Paul Hohenlohe at the University of Idaho compared the frequency of genes in devils in regions before DFTD arrived to devils 8-16 years after DFTD arrived.

We identified significant changes in two small regions in the DNA samples of devils from regions with DFTD. Five of seven genes in the two regions were related to cancer or immune function in other mammals, suggesting that Tasmanian devils are indeed evolving resistance to DFTD. Evolution is often thought of as a slow process, but these changes have occurred in as few as 4–8 generations of devils since disease outbreak.

Devils are surviving at our long-term sites, despite models that predicted extinction. Previously, studies have shown that devils with lower rates of DFTD showed specific changes in their immune response. Our genetic results might explain why.

New infectious diseases put strong pressure on their hosts to evolve, leading to rapid changes in resistance or tolerance. Rapid evolution requires pre-existing genetic variation. Our results are surprising because Tasmanian devils have low levels of genetic diversity.

Evolution doesn’t just act on the devils; it also also acts on the disease. The disease evolves to not kill the host before it can spread to another host, but also to overcome the host’s defences. Over the long term, pathogen (the cause of the disease) and host usually evolve to live together as rabbits and Myxoma virus have evolved together.

Our results suggest that devils in the wild may save themselves through evolution. However, it is essential for managers to develop strategies that help the devils do so. For example, releasing fully susceptible devils that have had no exposure to the disease into populations where resistance is developing is likely to be counterproductive.

DFTD presents a unique opportunity to study the early stages of the evolution of a new disease and transmissible cancer with its animal host. Ultimately, through future research, we may understand how cancers can become transmissible and how their hosts respond.

Menna Elizabeth Jones, Associate professor, University of Tasmania; Andrew Storfer, Professor & Associate Director, School of Biological Sciences, Washington State University; Hamish McCallum, Professor, Griffith School of Environment and Acting Dean of Research, Griffith Sciences, Griffith University; Paul Hohenlohe, , University of Idaho, and Rodrigo Hamede, Post Doctoral Research Fellow, Conservation Biology and Wildlife Management, University of Tasmania

This article was originally published on The Conversation. Read the original article.

Tasmanian Devils Fighting Back