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

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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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Read more:
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.

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

Shutterstock

Andrew S. Flies, University of Tasmania; Amanda L. Patchett, University of Tasmania; Bruce Lyons, University of Tasmania, and Greg Woods, University of Tasmania

Emerging infectious diseases, including COVID-19, usually come from non-human animals. However our understanding of most animals’ immune systems is sadly lacking as there’s a shortfall in research tools for species other than humans and mice.

Our research published today in Science Advances details cutting edge immunology tools we developed to understand cancer in Tasmanian devils. Importantly, these tools can be rapidly modified for use on any animal species.

Our work will help future wildlife conservation efforts, as well as preparedness against potential new diseases in humans.

The fall of the devil

Tasmanian devil populations have undergone a steep decline in recent decades, due to a lethal cancer called devil facial tumour disease (DFTD) first detected in 1996.

A decade after it was discovered, genetic analysis revealed DFT cells are transmitted between devils, usually when they bite each other during mating. A second type of transmissible devil facial tumour (DFT2) was detected in 2014, suggesting devils are prone to developing contagious cancers.

A Tasmanian devil with devil facial tumour disease.
Save the Tasmanian Devil Program

In 2016, researchers reported some wild devils had natural immune responses against DFT1 cancers. A year later an experimental vaccine for the original devil facial tumour (DFT1) was tested in devils artificially inoculated with cancer cells.

While the vaccine didn’t protect them, in some cases subsequent treatments were able to induce tumour regression.

But despite the promising results, and other good news from the field, DFT1 continues to suppress devil populations across most of Tasmania. And DFT2 poses an additional threat.

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Deadly disease can ‘hide’ from a Tasmanian devil’s immune system

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Following a blueprint requires tools

In humans, there has been incredible progress in treatments targeting protein that regulate our immune system. These treatments work by stimulating the immune system to kill cancer cells.

Our team’s analyses of devil DNA showed these immune genes are also present in devils, meaning we may be able to develop similar treatments to stimulate the devil immune system.

But studying the DNA blueprint for devils takes us only so far. To build a strong house, you need to understand the blueprint and have the right tools. Proteins are the building blocks of life. So to build effective treatments and vaccines for devils we have to study the proteins in their immune system.

Until recently, there were few research tools available for this. And this problem was all too familiar to researchers studying immunology and disease in species other than humans, mice or rats.

Into the FAST lane

You could build a house with just a saw, hammer and nails – but a better and faster build requires a larger, more versatile toolbox.

In our new research, we’ve added more than a dozen tools to the toolbox for understanding tumours in Tasmanian devils. These are Fluorescent Adaptable Simple Theranostic proteins – or simply, FAST proteins.

The term “theranostic” merges therapeutic and diagnostic. FAST proteins can be used as a therapeutic drug to treat a disease, or as a diagnostic tool to determine its cause and better understand it.

A key feature of FAST proteins is they can be tagged with a fluorescent protein marker, and can be released from the cells that we engineered in the lab to make them.

This way, we can collect and observe how the proteins attach and interact with other proteins without needing to add a tag later in the process.

To understand this, imagine trying to use a tiny key in a tiny lock in the dark. It would be difficult, but much easier if both were tagged with a coloured light. In the context of the immune system, it’s easier to understand what we need to turn on or off if we can see where the proteins are.

By mapping how proteins within the devil’s immune system interact, we can find better ways to stimulate the immune system.

An overview of the FAST protein system. Fluorescent proteins and immune system proteins from different species can be rapidly swapped to make new FAST proteins.
Andrew S. Flies/WildImmunity

The FAST system is also adaptable, meaning new targets can be cut-and-pasted into the system as they’re identified, like changing the bits on a drill. Therefore, it’s useful for studying the immune systems of other animals too, including humans.

Also, the system is simple enough that most people with basic cell culture and molecular biology experience could use it.

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Needle in a haystack

Cancer cells in humans and animals can travel via the bloodstream to spread, or “metastasise”, throughout the body. Identifying single tumour cells in blood can shed light on how cancer invades devils’ organs and kills them.

Using FAST tools, we discovered CD200 – a protein that inhibits anti-cancer responses in humans – is highly expressed in devils. With FAST tools, we were able to mix DFT2 cancer cells into devil blood and pick them out, despite there being about one cancer cell for every 1,000 blood cells.

CD200 is a powerful “off switch” for the immune system, so identifying this off switch allows us it can help us produce a vaccine that disables the switch.

A devil facial tumour 2 (DFT2) cell, with the cell nucleus shown in blue.
Andrew S. Flies/WildImmunity

By rapidly sifting out the best ways to stimulate the devil’s immune system, FAST tools are accelerating our research into developing a preventative vaccine to protect devils from DFT.

Why study animal immune systems?

COVID-19 has once again brought emerging infectious diseases onto the global stage. The ability to rapidly develop immunology tools for new species means we can jump into action when a new virus jumps into humans.

Additionally, species are going extinct at an alarming rate, and wildlife disease is increasingly threatening conservation efforts.

Understanding how the immune systems of other animals fight diseases could provide a blueprint for developing vaccines and therapeutics to help them.

Andrew S. Flies, Senior Research Fellow in Immunology, University of Tasmania; Amanda L. Patchett, , University of Tasmania; Bruce Lyons, , University of Tasmania, and Greg Woods, Professional Research Fellow, University of Tasmania

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

Saving the Tasmanian Devil

Sexual aggression key to spread of deadly tumours in Tasmanian devils

Both male and female Tasmanian devils can become very violent during sexual interactions.
Shutterstock/PARFENOV

David Hamilton, University of Tasmania; Elissa Cameron, University of Tasmania; Menna Elizabeth Jones, University of Tasmania, and Rodrigo Hamede, University of Tasmania

Tasmanian devils have a reputation as a fearsome animal – most of the time this is undeserved. When it comes to the mating season, however, it’s a fair judgement. Between February and April, mating can be incredibly aggressive, with male and female devils prone to biting one another both during and after the act.

That could be deadly for the devils, according to new research published online in the journal Behavioral Ecology.

Unfortunately, biting drives the spread of devil facial tumour disease (DFTD) a transmissible cancer that has been afflicting the species since the mid-1990s.

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DFTD is highly unusual for a cancer because it can transfer between individual devils and grow in its new host.

The fact that devils regularly bite one another around the mouth means tumour cells can easily transfer from an infected devil to an open wound on a healthy devil. This makes the buildup of wounds in devils extremely important to our understanding of this disease.

When devils mate

In our study, we examined the accumulation of bite wounds in a population of wild devils in northwest Tasmania.

We found males were much more likely than females to pick up high numbers of bite wounds. But these wounds appear to be related to the amount of time males spent in mating season interactions with females, as opposed to fights with other males (as we had previously thought).

In the mating season, after male devils have mated with females, they spend an extended period either confining the female in a den, or closely following her to make sure other males are unable to mate with her.

During our study we found this behaviour could go on for up to two weeks in the wild. The process is known as “mate guarding” and is relatively common in the animal kingdom.

We found the longer males spent engaging in mate guarding behaviour, the more bite wounds they received. This would seem to put successful males, who mate with a high number of females, in the firing line when it comes to acquiring DFTD.

But no pattern of sex bias in DFTD prevalence has ever been observed in the wild.

So how does this fit with our study on the increased vulnerability in males?

A Tasmanian devil with the Devil Facial Tumour Disease.
Menna Jones/PLOS ONE, CC BY

Disease transfer

A crucial unknown in the DFTD transmission process involves directionality – which way the deadly disease is passed on by a devil. There are two possibilities:

1. an infected devil bites an uninfected animal, transferring tumour cells (from its teeth or saliva) directly into the wound it causes

2. an uninfected devil bites into tumours on an infected animal, and cells transfer into an open wound inside the biter’s mouth.

The reality is likely to involve a combination of the two.

Our results indicate that most disease transmission occurs during extended mating season interactions, when females appear to be causing high numbers of wounds to their mates.

If DFTD can transfer in either direction during these encounters, then both the males receiving the wounds and the females causing them would be equally at risk of acquiring the disease.

Future of the devil

We have highlighted mating season encounters between the sexes as crucial transmission points for the spread of DFTD. The behaviour of male devils appears to be driving patterns that support transmission of the disease.

This information is important for potential disease management options, as it pinpoints males in good condition – who are likely to be reproductively successful – as targets for management interventions, such as vaccinations.

Most importantly, these results add one more piece to the puzzle of rapid evolution in the Tasmanian devil, in response to the strong evolutionary pressure DFTD is placing on this iconic species. With almost 100% mortality once devils reach breeding age, any advantage an individual devil might have to survive a little longer and reproduce should – over time – spread through the population.

The species has already shown remarkably rapid shifts in their life history and genome, while some are able to mount an immune response and recover from the tumours.

DFTD is spread through biting so we can expect strong evolutionary pressure for devils to become less aggressive towards each other over time.

With these new results, we can now pinpoint for the first time who (healthy, successful males) and when (guarding females after mating) the intense selection pressure on aggressive behaviour in devils will operate.

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Ultimately, devils will solve the DFTD problem themselves by evolving resistance, tolerance and changing their behaviour. One of the best things we can do is let evolution take its course, giving a helping hand along the way via well guided management actions.

David Hamilton, PhD Candidate in Zoology, University of Tasmania; Elissa Cameron, Professor of Wildlife Ecology, University of Tasmania; Menna Elizabeth Jones, Associate Professor in Zoology, University of Tasmania, and Rodrigo Hamede, Post Doctoral Research Fellow, Conservation Biology and Wildlife Management, University of Tasmania

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

Could Tassie devils help control feral cats on the mainland? Fossils say yes

The Tasmanian devil once thrived on mainland Australia.
Shutterstock/mastersky

Michael Westaway, Griffith University and Gilbert Price, The University of Queensland

The Tasmanian devil – despite its name – once roamed the mainland of Australia. Returning the devil to the mainland may not only help its threatened status but could help control invasive predators such as feral cats and foxes.

The idea of returning devils to the mainland has been raised before.

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

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But now we’ve explored the idea from a palaeontological view. We looked at the fossil record of mainland devils, in a paper published online and in print soon in the journal Biological Conservation.

A well preserved devil mandible (lower jaw) recovered from excavations west of Townsville.
Gilbert Price, Author provided

The fossil record helps us better understand how the devils co-existed on mainland Australia with other wildlife. It also helps us see how these iconic animals may possibly interact with small and medium-sized animals if reintroduced to the mainland in the future.

Back in the wild

Ecologists have reintroduced several apex predators to environments where they were once driven to localised extinction. This has helped restore past ecosystems by providing a clearer ecological balance.

One of the best-known examples is the reintroduction of wolves to Yellowstone National Park in the United States, to check the overgrazing and destruction of habitat by elk.

By reintroducing Tasmanian devils into mainland Australia, can we possibly help restore ecological systems that support devils along with small to medium-sized native mammals?

Native and exotic predators

Tasmanian devils and thylacines (Tasmanian tigers) were displaced across the mainland of Australia sometime after the dingo was introduced from southeast Asia at least 3,500 years ago.

But these iconic Australian predators were still able to survive in Tasmania. The island was created 10,000 years ago by rising sea levels, well before the arrival of dingoes on mainland Australia.

Dingoes have now been eradicated across much of mainland Australia, particularly within the seclusion zone of the dingo fence in the southeast of the continent. The 5,400km fence stretches eastwards across South Australia into New South Wales and to southeast Queensland.

Exotic predators such as foxes and cats now thrive across many parts of Australia, and have devastating impacts on small to medium-sized Australian mammals.

But until recently they have not been able to gain a foothold in Tasmania. Many ecologists believe the presence of the devil has prevented these other animals making their destructive mark on the ecology of Tasmania.

Sadly the situation is changing as a result of the deadly devil facial tumour disease, an infectious cancer that has destroyed many populations of Tasmanian devils. Estimates range up to 90% of some population groups now wiped out.

As a result, feral cats are now moving into former devil habitats and hunting native species on Tasmania.

A fossil window to the past

So what does the fossil record tell us about the past life of the Tasmanian devil in mainland Australia?

The Willandra Lakes World Heritage Area, in southeast Australia, provides an extraordinary archaeological and palaeoecological record of Ice Age Australia.

Recovery of fossils and devil coprolites from eroding bettong burrows at the Willandra Lakes World Heritage Area.
Michael Westaway, Author provided

In the past, skeletal remains buried within the landscape were commonly fossilised. Evidence of small animals that dug burrows (such as burrowing bettongs) and the predators that pursued them in their burrows, are exceptionally well preserved.

Our excavations reveal how devils and other small-to-medium sized mammals and reptiles interacted over more than 20,000 years in this area. Even during the peak arid phase, known as the Last Glacial Maximum, it seems that devils and their prey successfully co-existed.

The fossil record (10,000 to 4,000 years ago): This shows the fauna reference condition prior to the arrival of the dingo. (1 Western Quoll, 2 Tasmanian Devil, 3 Thylacine, 4 Bilby, 5 Western Barred Bandicoot, 6 Southern Brown Bandicoot, 7 Burrowing Bettong, 8 Brush Tailed Bettong, 9 Wombat, 10 Nail-Tailed Wallaby, 11 Hare Wallaby, 12 Western and Eastern Grey Kangaroo, 13 Red Kangaroo, 14 Crest Tailed Mulgara, 15 Greater Stick Nest Rat, 16 Hopping Mouse, 17 Fox, 18 Cat, 19 Rabbit)
Toot Toot Design, Author provided

The contemporary record: This shows today’s situation in the Willandra Lakes World Heritage Area. Light grey animals represent those animals that are now locally extinct.
Toot Toot Design, Author provided

The fossil record shows that the range of habitats occupied by devils in the past was far more diverse than today, with populations being found across environments from the central arid core to the northern tropics.

This suggests that devils today should, theoretically, be able to reoccupy a similarly extensive range of habitats.

Former devil range across Australia as revealed by the known fossil record.
Toot Toot Design, Author provided

Better the devil you know

Some ecologists suggest dingoes should be reintroduced into Australian habitats in order to reduce the impact of cats and foxes on native mammals.

One problem is that dingoes also prey on livestock. This is the reason the dingo fence was constructed during the 1880s.

But devils are not active predators of cattle and sheep. So reintroducing a predator that has a much longer evolutionary history with other native mammals in this country would likely receive far less opposition from pastoralists.

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Read more:
Deadly disease can ‘hide’ from a Tasmanian devil’s immune system

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A reintroduction of devils back to the mainland may be a new approach to consider for controlling the relentless, destructive march of exotic predators and restore crucial elements of Australia’s biodiversity.

It still needs to be demonstrated that devils can suppress the activities of cats and foxes on the mainland, as they seem to have done in Tasmania. Experiments with devils in a range of different settings would help to establish this.

A new research approach involving palaeontologists, conservation biologists and policy makers may help us understand how we can restore biodiversity function in Australia.

Michael Westaway, Senior Research Fellow, Australian Research Centre for Human Evolution, Griffith University and Gilbert Price, Lecturer in Palaeontology, The University of Queensland

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

Tassie devils’ decline has left a feast of carrion for feral cats

Healthy Tasmanian devil populations have cornered the market on carrion.
Menna Elizabeth Jones, Author provided

Calum Cunningham, University of Tasmania; Christopher Johnson, University of Tasmania; Menna Elizabeth Jones, University of Tasmania, and Tracey Hollings, University of Melbourne

The decline of Tasmanian devils is having an unusual knock-on effect: animal carcasses would once have been gobbled up in short order by devils are now taking many days longer to disappear.

We made the discovery, published today in the journal Proceedings of the Royal Society B, by placing carcasses in a range of locations and watching what happened. We found that reduced scavenging by devils results in extra food for less efficient scavengers, such as feral cats.

Tasmanian devils have struggled for two decades against a typically fatal transmissible cancer, called devil facial tumour disease. The disease has caused devil populations to plummet by about 80% on average, and by up to 95% in some areas.

DFTD has spread across most of Tasmania over a 20-year period. Dashed lines show the estimated disease front.
Calum Cunningham/Menna Jones

Scavengers are carnivores that feed on dead animals (carrion). Almost all carnivores scavenge to a greater or lesser degree, but the devil is Tasmania’s dominant scavenger. Since the extinction of the Tasmanian tiger, it is also the island’s top predator.

A scavenging experiment

In our study, we put out carcasses of the Tasmanian pademelon (a small wallaby weighing roughly 5kg) in a variety of places, ranging from disease-free areas with large devil populations, to long-diseased areas where devil numbers are very low. We then used motion-sensor cameras to record all scavenger species that fed on the carcasses.

The Carnivores of Tasmania: a Scavenging Experiment.

Unsurprisingly, much less carrion was consumed by devils in areas where devil populations have declined. This has increased the availability of carrion for other species, such as the invasive feral cat, spotted-tailed quoll, and forest raven. All of these species significantly increased their scavenging in places with fewer devils.

Consumption of experimentally placed carcasses.
Proceedings of the Royal Society B

The responses of native scavengers (quolls and ravens) were subtly different to those of feral cats. The amount of feeding by quolls and ravens depended simply on how much of each carcass had already been consumed by devils. Ravens and quolls are smaller and less efficient than devils at consuming carcasses, so they get the chance to feed only when devils have not already monopolised a carcass.

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Read more:
Tasmanian devils reared in captivity show they can thrive in the wild

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In contrast, feral cats tended to scavenge only at sites where devils were at very low abundance. This suggests that healthy devil populations create a “landscape of fear” that causes cats to avoid carcasses altogether in areas where they are likely to encounter a devil. It seems that the life of a feral cat is now less scary in the absence of devils.

Predator prevalence

By looking at 20 years of bird surveys from BirdLife Australia, we also found that the odds of encountering a raven in Tasmania have more than doubled from 1998 to 2017. However, we were unable to directly link this with devil declines. It is likely the raven population is growing in response to a range of factors that includes land-use change and agricultural intensification, as well as reduced competition with devils.

Other studies have shown that cats have also become more abundant in areas where devils have declined. This highlights the potential for devils to act as a natural biological control on cats. Cats are a major threat to small native animals and are implicated in most Australian mammal extinctions.

Carcass concerns

Although smaller scavengers consumed more carrion as devils declined, they were unable to consume them as rapidly as devils. This has resulted in the accumulation of carcasses that would previously have been quickly and completely eaten by devils.

In places with plenty of devils, carcasses were completely eaten within an average of five days, compared with 13 days in places where devil facial tumour disease is rife. That means carcasses last much longer where devils are rare.

DFTD has spread across most of Tasmania over a 20-year period. Dashed lines show the estimated disease front.
Calum Cunningham/Menna Jones

Around 2 million medium-sized animals are killed by vehicles or culled in Tasmania each year, and most are simply left to decompose where they fall. With devils consuming much less carrion, it is likely that carcasses are accumulating across Tasmania. It is unclear how much of a disease risk they pose to wildlife and livestock.

Conserving carnivores

Large carnivores are declining throughout the world, with knock-on effects such as increasing abundance of smaller predators. In recent years, some large carnivores have begun returning to their former ranges, bringing hope that their lost ecological roles may be restored.

Carnivores are declining for many reasons, but an underlying cause is that humans do not necessarily appreciate their pivotal role in the health of entire ecosystems. One way to change this is to recognise the beneficial services they provide.

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Read more:
Tasmanian devils are evolving rapidly to fight their deadly cancer

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Our research highlights one of these benefits. It supports arguments that we should help the devil population recover, not just for their own sake but for other species too, including those threatened by feral cats.

The devil seems to be solving the disease problem itself, rapidly evolving resistance to facial tumours. Any management plan will need to help this process, and not hinder it. Potentially, returning devils to mainland Australia could provide similar benefit to wildlife threatened by feral predators.

Calum Cunningham, PhD candidate, University of Tasmania, University of Tasmania; Christopher Johnson, Professor of Wildlife Conservation and ARC Australian Professorial Fellow, University of Tasmania; Menna Elizabeth Jones, Associate professor, University of Tasmania, and Tracey Hollings, Senior Scientist, Ecological Modelling at Arthur Rylah Institute for Environmental Research, and Honorary Research Fellow, University of Melbourne

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

Tasmanian Devils in Trouble

Survival of the fittest? Perhaps not if you’re a Tasmanian devil

Aggressive behaviour exhibited by socially dominant Tasmanian devils may predispose them to infection with devil facial tumour disease.
Sebastien Compte/University of Tasmania, Author provided

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

Tasmanian devils in their prime are most likely to become infected with deadly facial tumour disease (DFTD), our research shows.

The findings, published today in Ecology Letters, contradict conventional wisdom that infection of relatively weakened individuals is commonplace in the spread and persistence of diseases.

Instead, it’s the devils that enjoy the highest survival and breeding success who eventually succumb to the fatal disease.

DFTD has had a devastating effect on devil populations in Tasmania, with the marsupial carnivore placed on the endangered list in 2009.

So what is it that makes the fitter devils more prone to infection?

The devils in detail

DFTD is unique in that it is one of only a few known cases of transmissible cancer, where the deadly tumours do not originate from the host body.

The disease is transmitted into an individual when devils bite each other.

To track DFTD in a population, over ten years we repeatedly surveyed more than 500 wild devils, visiting the same field site at least four times per year.

This allowed us to study both survival and reproduction of the devils in the context of infection dynamics and tumour growth.

Our results add to our understanding of how DFTD spreads through devil populations, and reveal more details of how disease-induced evolution in devil populations (such as resistance to the disease) may be occurring.

We suggest the way disease is transmitted plays a key role in who gets infected.

It is the dominant devils who are more likely to engage in aggressive behaviour, such as during mating. This puts them at higher risk of biting an infected individual and thus becoming infected themselves.

So it’s the devils who are otherwise very fit (in the evolutionary sense) that the disease takes out. These are the ones that have the highest survival and reproduction rates, before being killed by the cancer.

Impact on devil populations

So what does this say about the future survival of devil populations in Tasmania’s wild?

Too often, a dramatic-looking disease such as DFTD leaves the impression that it must have detrimental effect on the overall population growth.

But this is not necessarily the case if diseased individuals had a chance to reproduce before they got infected.

Possible scenarios of Tasmanian devil survival and reproduction amid the risk of DFTD infection. The horizontal thick lines indicate individual devil survival over time, small devils reproduction and red dots infestation with tumours.
David Sargent/Queensland College of Art/Griffith University

In the graphic (above) we can see that some devils may not reproduce because either (A) of their social status, or (B) if they get an infection early in life and rapid tumour growth results in death.

In contrast, devils who get the disease late in life © may have already reproduced earlier. In (D) devils may still get infected, but if the tumour grows slowly they may still have chance to reproduce before death.

As for healthy and dominant devils who don’t get the disease (E), they may reproduce several times in their life.

Such details can be vital to understand the spread of DFTD and the outcome for Tasmanian devil populations.

It is the complex interplay of devil demography and disease dynamics that ultimately determines whether DFTD is a conservation threat for devils.

Infection decline

Our results also show a recent decline in the likelihood that devils become infected in this population. This could indicate some evolving resistance of devils to the cancer, as was recently shown by researchers from our team.

Alternatively, the decline in infection rate could have resulted from a reduction in the number of socially dominant devils, if these are responsible for most transmissions of the disease.

If adult devils with high fitness are those that become infected, the potential for selection for resistant animals would be limited.

This is because these individuals still contribute more offspring (and their genetic constitution) to future generations than those not infected and with little engagement in reproduction.

Devil conservation

Our findings could have an impact on some of the conservation strategies for devils, such as vaccination or translocation of devils to other areas.

For example, a targeted vaccination of socially dominant individuals would be more efficient than randomly picking individuals for vaccination.

If devil individuals from captive insurance populations were to be released into wild populations, the consequences for disease spread and population viability would be unpredictable without a better understanding of the role of social behaviour in disease transmission.

If introduced individuals distract existing social structure and more frequently engage in biting behaviour, they may favour the spread of DFTD.

If devils develop resistance to DFTD, the introduction of individuals from captive populations may dilute the natural selection process.

Our study suggest that DFTD appears to be selectively spread and does not affect all individuals in a population. Understanding disease transmission pathways is a prerequisite to aid conservation efforts to stop the spread of unwanted diseases.

Konstans Wells, Research Fellow in Ecology, Griffith University; Andrew Storfer, Professor & Associate Director, School of Biological Sciences, Washington State University; Douglas Kerlin, Postdoctoral Reseach Fellow, Environmental Futures Research Institute, Griffith University; Hamish McCallum, Professor, Griffith School of Environment and Acting Dean of Research, Griffith Sciences, Griffith University; Menna Elizabeth Jones, Associate professor, University of Tasmania; 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.