| Q.
How many live in Tasmania?
A. It is very difficult to give an exact answer, with numbers
thought to be within the range of 10,000 - 100,000 individuals.
But if pressed to more precise, the best estimate based on
current data (December 2006) is between 20,000 – 50,000
mature individuals (which is assumed to be about half the
overall numbers).
There
are a variety of reasons why it is difficult to be more precise.
But one of the biggest challenges is that there are population
number estimates for only a few places across the State –
most of which were chosen for trapping because they were high
density before the Tasmanian devil disease. Good estimates
for anywhere in the World Heritage Area, for instance, aren’t
available because there are no roads and it’s hard to
check traps on a daily basis.
One
population figure has been based on the fact that estimates
in the mid '90s ranged between 130,000 -150,000 individuals.
Spotlighting data indicates an overall population decline
of 27 per cent from then until 2001-03. If this percentage
decline is applied to the mid ‘90s estimate, then the
population estimate for 2002 would be 51,000 mature individuals.
Another
method generated an estimate of total population size in 2004
as approximately 42,000 individuals. This estimate was derived
from density estimates from 10 sites (four disease-free sites,
six diseased sites) in the highest density areas (north-east
and south-east of the State) and from one disease free site
outside the high density area.
But,
with a high potential for error in these estimates, the most
accurate figure when determining Tasmanian devil numbers across
Tasmania would be between the range of 10,000 - 100,000 individuals.
Q.
Do they have diseases and parasites?
A. Yes they do. Tasmanian devils carry a number of internal
and external parasites. They often have small numbers of ticks,
tapeworms, and other parasites. Of great concern now is the
Devil Facial Tumour Disease.
Q.
What controls their numbers?
A: The greatest current threat to numbers across Tasmania
is the Devil Facial Tumour Disease (DFTD). It’s a fatal
condition that is restricted to devils, characterised by cancers
around the mouth and head.
In
1996, Tasmanian devils were photographed in north-east Tasmania
with what were apparently large tumours on their faces. Since
then, (as at December 2006), there has been a 90 per cent
decline of average spotlighting sightings in that region,
and a drop of 41 per cent across the State.
A
further potential, unquantified threat is the introduction
into Tasmania of the red fox, which would compete directly
with Tasmanian devil juveniles. Both species share preferences
for den sites and habitat, and are of similar size.
In
the past, competition and perhaps predation from thylacines
would partly control devil numbers. Other factors affecting
numbers included food availability, direct persecution, competition
from other devils and quolls, the loss of den sites to development,
and the toll of road kills.
Q.
Are Tasmanian devils endangered?
A: No, but they are due to be listed as endangered, In November
2007 the species was recommended for upgraded from the status
of vulnerable to endangered due to the Devil Facial Tumour
Disease (DFTD) wiping out much of the Devil Population in
half the State of Tasmania.. In February 2006, Tasmanian devils
were listed as a vulnerable species under the State’s
Threatened Species Protection Act 1995. More recently the
Federal Government included them under the Commonwealth Environment
and Biodiversity Act. They are wholly protected.
A decade ago, devil numbers seemed to be at a record high.
Then, in the mid 1990s, the first signs of the Tasmanian devil
disease were observed.
A
research program, which became known as the Devil Facial Tumour
Disease (DFTD) Program, or more simply the Devil Disease Program,
has been established to investigate the disease and identify
management options.
In
September 2006, Devil Facial Tumour Disease (DFTD) was gazetted
under the Animal Health Act as a List B notifiable disease.
What
is Devil Facial Tumour Disease?
A. Devil Facial Tumour Disease is a term used to describe
a fatal condition in Tasmanian devils which is characterised
by the appearance of obvious facial cancers. The tumours or
cancers are first noticed in and around the mouth as small
lesions or lumps. These develop into large tumours around
the face and neck and sometimes even in other parts of the
body. Adults appear to be most affected by the disease - males
the first affected, then females. Badly affected devils have
many cancers throughout the body.
As
the cancers develop in affected devils, they find it hard
to ingest food. The animal weakens further making it difficult
to compete with other animals for food. Affected animals appear
to die within three to five months of the lesions first appearing,
from starvation and the breakdown of body functions.
Q.
Could the devil facial tumours be caused by an accumulation
of exposure to the UV rays radiating through our ozone depleted
skies?
A. It’s true that there is growing evidence to suggest
that squamous cell carcinoma (SCC) and melanomas are initiated
by solar damage. Also, osteosarcoma of large breed dogs are
thought to be initiated or promoted by repetitive trauma.
Animals
in parks and zoos (including those in Tasmania) are less “shy”
and do sunbake. But there has been no evidence to date to
suggest that Devil Facial Tumour Disease (DFTD) has spontaneously
arisen in captive populations. We have also not had cases
of melanomas or SCCs.
Neoplasms
initiated/promoted from trauma and UV damage usually occur
as a result of having a degree of chronicity of exposure.
There was support for this hypothesis when it was found that
older animals were initially the only ones affected (three
to four year olds). But one to two year olds are now affected.
We
are still uncertain of the original cause of the Tasmanian
devil disease. But we have found evidence supporting our theory
that DFTD is acting as a contagious allograft – a “parasite”
in effect.
Do
you treat the Devil Facial Tumour Disease in individuals?
A: Treatment hasn’t yet been trialled for the following
reasons:
Initially we needed to make the best use of available resources
by investing time into the study of the disease.
Most
importantly, if a cure for this disease is found, we need
to be able to use it from a wildlife management point of view
rather than on individual animals - we want to keep the devils
wild and in the wild.
Surgery
and chemotherapy would be difficult, if not impossible, to
implement from a population point of view. Nevertheless, nothing
is ruled out that may help to save the devil, and research
is proposed to investigate the possibility and feasibility
of cancer treatment for devils in some limited situations.
Q.
Can the Devil disease spread to other animals?
A: The Mount Pleasant Laboratories, in Launceston, are the
only animal health laboratories in Tasmania, and handle all
cases concerning farmed and wild animals. To date, they have
found no evidence of the Tasmanian devil disease in other
animals.
The
field team is running surveillance with many traps and has
caught many species that showed no clinical signs of the disease.
Species include possums, quolls, cats and even a sausage dog.
General
Facts
Breeding
and Pups
Feeding
and Habitat
Information
from the DPIW Website
Further
Information:
Contact: Wildlife Management Branch
Wildlife Management Branch
Department of Primary Industries and Water
134 Macquarie Street, GPO Box 44
Hobart TAS 7001
Phone: 03 6233 6556
Fax: 03 6233 3477
Email: wildlife.enq@dpiw.tas.gov.au
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