Review of the management of feral animals and their impact on ...

5.3 Management <strong>of</strong> cane toads
Currently <strong>the</strong>re is no practical method for containing or eradicating cane toads. To
mitigate <strong>the</strong> <strong>impact</strong> <strong>of</strong> cane toads, a number <strong>of</strong> nor<strong>the</strong>rn quolls have been relocated to
toad-free <strong>of</strong>fshore isl<strong>and</strong>s. They will provide a breeding source for re-introduction if
<strong>the</strong> mainl<strong>and</strong> populations <strong>of</strong> nor<strong>the</strong>rn quoll succumb to <strong>the</strong> presence <strong>of</strong> <strong>the</strong> cane toads.
A publicity campaign has also been undertaken to educate <strong>and</strong> inform <strong>the</strong> public about
<strong>the</strong> cane toad problem. As part <strong>of</strong> this campaign, a competition is being run in <strong>the</strong>
Nor<strong>the</strong>rn Territory to design a new cane toad trap. In light <strong>of</strong> <strong>the</strong> lack <strong>of</strong> effective
control technologies, research is now underway on a new range <strong>of</strong> potential
techniques.
Traps <strong>and</strong> barriers
Present efforts to control cane toads are based on physical capture <strong>and</strong> destruction. A
range <strong>of</strong> cane toad traps have been commercially produced through <strong>the</strong> community
based organisation, Frogwatch. Current traps are <strong>of</strong> only limited effectiveness because
<strong>the</strong>y only work in a small area <strong>and</strong> require constant emptying. Research has
demonstrated that some <strong>of</strong> <strong>the</strong> pheromones produced by cane toads can be used as
effective attractants. Michael Tyler, at <strong>the</strong> University <strong>of</strong> Adelaide, has shown that
when a minute quantity <strong>of</strong> a male pheromone is placed on a pad, female toads will
move towards <strong>the</strong> pad <strong>and</strong> remain <strong>the</strong>re. Application <strong>of</strong> toad specific pheromones to
traps could greatly enhance <strong>the</strong>ir efficiency.
Cane toad-pro<strong>of</strong> exclusion fencing has been proposed to prevent <strong>the</strong> spread <strong>of</strong> toads
into <strong>the</strong> highly valued Coburg Peninsula <strong>and</strong> o<strong>the</strong>r areas. As with most <strong>feral</strong> exclusion
fencing, it would be expensive to install <strong>and</strong> maintain, may severely restrict <strong>the</strong>
movements <strong>of</strong> non-target species, <strong>and</strong> is very unlikely to prevent toad movement in
<strong>the</strong> long-term. Fur<strong>the</strong>rmore, it would be impractical to extend over large areas <strong>and</strong>
may only have value in helping conserve small, high-value, threatened communities
against <strong>the</strong> influx <strong>of</strong> cane toads.
Measures to prevent <strong>the</strong> expansion <strong>of</strong> cane toad range may include surrounding barge
l<strong>and</strong>ings with a cleared area combined with toad pro<strong>of</strong> fences (as has been done for
<strong>the</strong> Tiwi Isl<strong>and</strong>s) artificial refuges <strong>and</strong> watering points (that can be frequently
monitored), attractants such as lights or chemical attractants. Natural barriers or
bottlenecks should be identified to help control toads. On <strong>the</strong> mainl<strong>and</strong>, narrow points
for migration should be investigated to identify <strong>the</strong> most strategic points to efficiently
control cane toads.
Biocontrol
A range <strong>of</strong> biocontrol options are currently being investigated. CSIRO has extensively
investigated <strong>the</strong> possibility <strong>of</strong> a naturally occurring, toad-specific pathogen. Although
a highly desirable control solution, akin with myomatosis, ten years <strong>of</strong> research has
failed to identify a suitable c<strong>and</strong>idate pathogen. Ongoing support for biocontrol agents
should be continued, as this provides <strong>the</strong> most effective long term threat abatement
measure. Such a mechanism must undergo comprehensive testing to ensure that <strong>the</strong>
control is completely toad specific, with no risk <strong>of</strong> mutating to become virulent to
native anuran species. CSIRO is currently investigating a biocontrol for cane toads,
based on genetically engineering a gene to interfere with tadpole metamorphosis
(Robinson pers. comm.). This would <strong>the</strong>n be disseminated through <strong>the</strong> population via
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