Toad Media
ABC Stateline
Transcript
Cane toads wiping out goannas in Kakadu
02/07/2004
PRESENTER: Michael Coggan
MICHAEL COGGAN, PRESENTER: There is fresh evidence
of native wildlife in the NT being destroyed by cane toads.
Research in Kakadu National Park has shown significant numbers
of goannas are dying after eating the toads.
With recent sightings 80km south of Darwin and as far west as the
Victoria River there's also evidence that other reptiles, including
snakes and freshwater crocodiles, will be threatened.
DR DAN HOLLAND, CENTRE FOR TROPICAL WILDLIFE MANAGEMENT:
The outlook at this point is relatively grim.
The mortality is significant and the rate of mortality actually
seems to be increasing.
MICHAEL COGGAN: The spectacular
diversity of wildlife in Kakadu National Park makes it worthy of
its World Heritage status.
That diversity is now seriously threatened.
Cane toads arrived in Kakadu in early 2001.
The toads have already delivered the local extinction of the endangered
northern quoll and there is new evidence that the toxic amphibians
are having a devastating impact on reptiles.
DR DAN HOLLAND: In the last month the rate of
mortality, adjusted for time, has increased almost 300 per cent
-- 277 per cent to be exact.
MICHAEL COGGAN: Dan Holland has been studying
goannas in an area known as the Buffalo Farm in the north of Kakadu
National Park since September 2002.
Covering about 70 square kilometres he has tracked, weighed and
tagged, two species of goannas.
The yellow spotted goanna can be found across northern Australia
but in this part of the Top End the lizard is disappearing.
DR DAN HOLLAND: We've seen somewhere between 55
per cent and 75 per cent decline in the population of yellow spotted
goannas, varanus panoptes, and somewhere around a 50 per cent decline
in the population of Gould's goannas or varanus gouldii.
MICHAEL COGGAN: In the first 10 months of his
study, Dr Holland found just one dead goanna.
Then the wet season arrived and cane toads began breeding in the
area.
Over the past eight months he has found a total of 38 dead goannas.
DR DAN HOLLAND: There's some evidence that death
by cane toad poisoning may be relatively quick, but in at least
a couple of the situations I've seen out here it may take several
days for the animal to succumb.
MICHAEL COGGAN: Dr Holland's research provides
an example of what can be expected in areas to the west and east
of Kakadu where the cane toad is advancing.
Just one bite of a toad is enough to kill a large reptile.
In the past month alone, Dan Holland has found 16 dead goannas.
DR DAN HOLLAND: If you consider that the yellow
spotted goanna is one of the largest remaining terrestrial predatory
species in this area, the loss of a significant proportion of the
population may well have unforseen and, at this point, unpredictable
affects upon the structure of the community as a whole.
DR ROD KENNETT, KAKADU NATIONAL PARK MANAGEMENT:
Cane toads are a problem for ALL of northern Australia Kakadu's
working with the other government agencies to try and understand
what the extent of that threat is.
MICHAEL COGGAN: Kakadu's Natural and Cultural
Resources Manager, Dr Rod Kennett, says the current research will
help to find ways of protecting vulnerable wildlife but at the moment
the march of the cane toad is unstoppable.
DR ROD KENNETT: There's no silver bullet for reducing
cane toad numbers.
You can go out and kill cane toads every night and they will continue
to come back.
It's a bit like trying to bail out the ocean with a thimble.
The traditional owners of Kakadu and other places in northern Australia
are already talking about the need to perhaps modify their hunting
reduce their level of hunting, in order to give goannas a chance
during these next few-to-many years.
MICHAEL COGGAN: Dr Hollands's research has been
backed up by PhD student, James Smith, from the Centre for Tropical
Wildlife at Charles Darwin University.
He has been studying the susceptibility of reptiles to cane toads,
with indications all but the hardy saltwater crocodile are vulnerable.
JAMES SMITH, CENTRE FOR TROPICAL WILDLIFE MANAGEMENT:
The animals we've looked at for this study are freshwater and saltwater
crocodiles, frilled neck lizards, some of the little dragons you
see around Darwin and four or five species of goannas.
It remains to be seen whether all those will encounter toads and
will actually try and eat them but it seems to be that if they do
eat them there's a high likelihood that they will kill them.
Graeme Sawyer has been working with the volunteer organisation
Frogwatch for the past 10 years.
He's developing a trap to help cut down on the number of large
adult breeding toads expected to arrive in Darwin within six months.
GRAEME SAWYER, FROGWATCH: It might not be a solution,
in terms of eradication but certainly there's enough evidence now
that cane toads are doing a lot of harm to our natural wildlife
and, from that point, Frogwatch is pushing people towards a minimisation
strategy.
MICHAEL COGGAN: Mr Sawyer believes governments
and parks should have done a lot more to prevent the northward advance
of the cane toad.
GRAEME SAWYER: If toad traps and stuff like that
can be made to work, is there a strategy where some of the national
parks and stuff could be protected or certain areas of them could
be protected where you could maintain remnant populations of other
wildlife that are really impacted?
DR ROD KENNETT: A number of people have suggested
traps.
They might work in a local situation, they're simply not going
to work in Kakadu.
It's too big an area, there are too many toads.
The places that traps and things like that might work is where
you have exclusion zones -- trying to keep animals from getting
on to islands, perhaps around local areas in the city, but for Kakadu
traps are not a feasible means of controlling toads.
MICHAEL COGGAN: There have been success stories
in the fight against cane toads.
A colony of northern quoll have been relocated to islands off the
coast of Arnhem Land and extensive quarantine measures have been
put in place for the Tiwi Islands.
While the work of Dr Dan Holland paints a grim picture, there is
anecdotal evidence that many species are able to adapt to the presence
of cane toads.
But with little or no data on the impact on other animals, including
fish and various bird species, only time will tell how much of the
NT's will be able to survive the arrival of the toad.
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