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The Tasmanian Devil

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Ivana Latalisa

on 4 December 2015

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Transcript of The Tasmanian Devil

The Tasmanian Devil
Population Dynamics:
Population Characteristics
Density
Distribution
Dispersion
Primary Characteristics
Age Structure
Genetic Diversity
Environment Carrying Capacity
Population Growth
Estimated Population Size
Present
Historical
Fluctuations in Population
Future Population Size
Limiting Factors
Species Interaction
Human Influence
Conservation Biology
The Tasmanian devil population has declined over 80% since 1990 in some parts of Tasmania
The remaining wild population is approximately 10 000-25 000 individuals
In the early to mid 1990s the total devil population was at one of its highest, an estimated 130 000-150 000 individuals
The estimated population in 2007 was 50 000 devils
Tasmanian devil joeys have a relatively low mortality rate
In areas greatly affected by DFTD, the ratio of mature devils to young devils is much lower, as the disease most often affects older individuals
Since DFTD affects females and males equally, the ratio of females to males is equal for the most part
About the Tasmanian Devil
The Tasmanian devil is the largest marsupial carnivore in the world
They are know for their short temper and loud screech
They were first classified as endangered in 2008
A law protecting the Tasmanian devil was put into force in 1941, and the population slowly recovered
A population boom occurred in the 1970s, where the devil population peaked
In 1988,
Trichinella Spiralis,
a parasite, killed around 30% of the devil population
Since then the devil population had been increasing up until the DFTD became spread significantly, leading to a very sharp decrease in population
The Tasmanian devil has been classified as endangered since 2009
Populations have been steadily decreasing yearly despite efforts to preserve and increase the existing population
Recent programs to isolate healthy devils and increase reproduction have helped to slow down their decline
Attempts to develop a vaccine for DFTD are underway, with little success
Based on that, their future population is expected to continue to decrease
If current patterns continue, the Tasmanian devil is expected to become extinct within a few decades
The Tasmanian devil has a relatively low genetic diversity compared to other Australian marsupials or placentals
This is likely due to the founder effect of when the species transitioned into the island of Tasmania
The extreme reductions in population in the past may have also lead to their low genetic diversity today
Devils from the north-east are genetically distinct from the ones in the east due to habitat related barriers
This low genetic diversity makes devils less resistant to diseases and has subsequently made them more vulnerable to the spread of DFTD
Red Foxes
Wedge-Tailed Eagles
Wombats
Possums
The species that the Tasmanian devil interacts with the most are:
Tasmanian Devils
Wallaby
Red Foxes
Red Fox (Competition )
Wallaby (Predation-Prey)
Possum (Predation-Prey)
Wombat (Predation-Prey)
Wedge-Tailed Eagle (Predation-Predator)

Tasmanian devils generally live all over the Tasmanian main land and show a clumped dispersion pattern
They are mostly found in dry woodland environments, but may live on any habitat on the island
The estimated density of Tasmanian devils on the island is ~0.26 individuals/km², assuming an area of 68 401km² and a population of 17 500
Scientific Name:
Sarcophilus harrisii
Devils are nocturnal and are hard to spot by humans, so their exact density is unknown
The only place in the world where Tasmanian devils are found in the wild is in Tasmania, Australia
More specifically, they are found in the mainland of the Tasmanian islands
Tasmanian devils were once abundant in mainland Australia, but became extinct there around 400 years ago
Though their dispersion is relatively even across the island, they are most abundant in the north-west and east of the island
The north-west region is thought to have the highest population density of devils
There have been two significant population declines in the devil's history
In the early 1900s, devils were hunted based on the belief that they would kill livestock, which brought them close to extinction
Since the arrival of the devil facial tumor disease, Tasmanian devil populations have been plummeting at an alarming rate
The Effect of DFTD on Devil Population
Tasmania is relatively isolated from any other ecosystems and is home to an abundant quantity of biotic and abiotic resources
Devils are carnivores but can eat almost anything, including carcases
As long as they are provided with hiding places, soil suitable for burrowing, and hunting areas, the devils can thrive
Tasmania provides them with the perfect environment, devils are extremely well adapted to the island
Therefore, Tasmania has a very high carrying capacity of Tasmanian devils, roughly estimated to be able to hold over 300 000 devils sustainably
Prior to DFTD their estimated density was ~0.7 devils/km², and up to 8 devils/km in highly populated areas
Devil Facial Tumor Disease
Tasmanian devils and red foxes share similar habitat and diet preferences and must therefore compete for shelter and food
Red foxes are an invasive species introduced to Tasmania by European colonists
The foxes have been known to prey on young devils, but due to their low numbers they did not pose a significant threat to devils
However, if the fox population surpasses the devil's, they will replace them and prevent any future devil re-population
Devil facial tumor disease (DFTD) is a deadly contagious cancer that leads to large tumors in the mouth and face of Tasmanian devils
(This carrying capacity is based on the red fox's carrying capacity for Tasmania ,as they are similar in size and have similar habitat and food needs)
This graph shows the general population of Tasmanian devils for the past years, averaging the common estimates
Prior to the disease, devil numbers had been steadily increasing
In areas where the disease was first seen, adult populations have been halving yearly
Devils live around six months after being infected
DFTD affects older devils (>2 years old) more often than younger ones, and since female devils breed for the first time at the age of two, they may not successfully raise a litter they die of DFTD
The tumors prevent devils from eating, leading to a slow and painful death
DTFT is very aggressive leading to graphic deformities and protrusions on the face
It is one of three recorded cancers that are contagious, spread from devil to devil by contact
It was wiped 80-90% of the remaining devil population in the last 20 years
The major threat affecting the Tasmanian devil's population is DFTD, accounting for around 90% of the recent population decline
It has an 100% mortality rate
The high latency period increases risks of transmission
DFTD affects the devil's face and mouth, which is problematic because devils commonly communicate by biting, increasing transmittance
Fairly high cannibalism rates also increase the species vulnerability to contagious diseases
Unfortunately there has been no sign of a devil developing immunity
Devil Facial Tumor Disease
A captured devil showing signs of DFTD
Roadkill
An estimated 2% of Tasmanian devils are killed on roads
Prior to DFTD, it was the leading cause of unnatural deaths of devils
A sign warning drivers to look out for wild devils on the road
A young Tasmanian devil
A Tasmanian devil joey
Effect of Road Fatalities on Devil Population
Confirmed Cases of DFTD in Tasmania 1996-2014
The disease has rapidly spread from the north-east to the rest of the island from one single infected female devil
As of now, it has affected almost all areas the island
Size relative to a 2m tall human
Only about 5% of devils are completely black, without their distinctive white stripe
devils will yawn or produce a strong odour to ward off predators
Food Web
The devil's favourite food is wombat meat since it is so fatty
Devils store their extra fat in their tails
The Tasmanian devil has the strongest bite of every mammal relative to jaw size
Places where DFTD is present
A devil suffering from DFTD
Habitat Destruction and Encroachment
Commercial Harvesting
Hunting
Pollution & Climate Change
Agricultural and Industrial Practices
Works Cited
Hawkins, C.E., McCallum, H., Mooney, N., Jones, M. & Holdsworth, M. 2008. Sarcophilus harrisii. The IUCN Red List of Threatened Species 2008 www.iucnredlist.org/details/40540/0

Department of the Environment (2015). Sarcophilus harrisii in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed Wed, 2 Dec 2015

Owen, David, and David Pemberton. Tasmanian Devil: A Unique and Threatened Animal. Crows Nest, N.S.W.: Allen & Unwin, 2005. Print.

"Tasmanian Devil, Sarcophilus Harrisii." San Diego Zoo Library. San Diego Zoo, 10 Feb. 2012. Web. 3 Dec. 2015. <http://library.sandiegozoo.org/factsheets/Tasmanian_devil/tasmanian_devil.html>.

Department of the Environment (2015). Sarcophilus harrisii in Species Profile and Threats Database, Department of the Environment, Canberra. www.environment.gov.au/sprat.

Save the Tasmanian Devil Website http://www.tassiedevil.com.au/tasdevil.nsf
Like many other animals, the Tasmanian devil has been impacted by urbanization
Though not a significant impact, the introduction of roads and reduction of the devil's natural habitat has facilitated the decrease in population
Deforestation in Tasmania has also affected the Tasmanian devil negatively
Positive Human Impact
Human settlement in Tasmania
Like most animals, the Tasmanian devil has been negatively impacted by pollution, especially in water
Water pollution has recently become a problem in Tasmania, and due to global warming, it has been experiencing more floods
These floods destroy their dens and hideouts and prevent them from finding shelter
It has been speculated that the reduction of the ozone layer encompassing Tasmania is what lead to the first cancerous mutation that caused DFTD, but its exact origins are still unknown
The Tasmanian devil is not commonly used commercially, and has therefore not suffered much from commercial harvesting
Their teeth and fur used to be collected and made into jewelry and clothes by humans hundreds of years ago
A necklace made up of over one hundred teeth from different devils
Before devils were protected by law in 1941, many locals would poison them in efforts to protect their livestock
During the early colonization of Tasmania, the Tasmanian devil was persecuted where 5000 devils were killed yearly
They were believed to be pests and "evil", hence the name "devil"
Current persecution is much reduced, but can still be locally intense with an excess of 500 devils thought to be killed per year
Since the discovery of DFTD and the extreme decline in population, a very large positive response to save the devils has been observed
In the short amount of time since being considered endangered, the Tasmanian devil has already received an enormous amount of help and support
Programs Underway
Action Plan
Immediate
Long-Term
1.
Making a donation/Volunteer
100% of proceeds go directly to help save the devils
2.
Adopt a devil
Help support a specific captive devil
3.
Raise awareness
Educating people is what leads to change
4.
Impose stricter laws
Particularly road fines and hunting laws
5.
Removal of infected devils
DFTD is a death sentence foe devils, they must be prevented from infecting others
1.
The Save the Tasmanian Devil Program (STDP)
researches DFTD, is establishing an insurance population, is trying to maintain the current genetic diversity
2.
Roadkill Project
reports devil roadkills to keep track of the distribution and movement of devils
3.
Taking Care of the Elders
specific enclosure for healthy aging devils who have a high chance of contracting the cancer in the wild
Devils often scavenge for food on roads and eat any of the roadkills
This leads to many devils being struck by oncoming traffic while feasting
Devil impacts are high in some areas where the speed limit is 20km/hr above the average
A Tasmanian devil roadkill beside its food
1.
Eradication of red foxes
They pose a threat to the remaining devil population
2.
Separate healthy devils from infected ones
Effectively decreasing chances of infections
3.
Development of a vaccine
Prevent further devils from infection
4.
Create a new separate population
Where no infected devils are present
5.
Selection for natural resistance
Look for a devil who is immune
In 5 years, the devil population will probably fall below 5000 individuals, if the current trend continues
4.
Devil Ark
largest breeding program for Tasmanian devils to create an insurance population
Like other wildlife in Tasmania, the Tasmanian devil is affected by agricultural/industrial practices
On devils, the impact is relatively small and indirect
Pesticides used in agriculture is hypothesized to promote the cancer
Recent dam building by industries is associated with excess flooding in areas where devils live
Some chemicals used by the agricultural industry have been linked to cancer in devils and are under suspicion of being carcinogenic to them
Age structures for specific regions in Tasmania
The amount of older devils has decreased significantly due to DFTD
These areas are representative of the entire island population therefore, the age structure of all Tasmanian devils would be similar, using percentages
Tasmanian devil joeys in their mothers pouch
By: Cristy Latalisa
Full transcript