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

as a refuge from predators. Removal <strong>of</strong> predators allows prey to utilise less protected
sites. Conversely, not changing habitat where susceptible species are present or
recreating necessary habitat may also prevent fox predation. Logging activities <strong>and</strong>
<strong>the</strong> establishment <strong>of</strong> roads through undisturbed habitat for example, may allow foxes
to colonise new areas which contain endangered or vulnerable species (Mansergh &
Marks 1993).
Fertility control
Targeting fox fertility may yield an effective long-term approach to reducing <strong>the</strong>ir
numbers <strong>and</strong> hence lower <strong>the</strong> need to use poison baits. Lethal control will be needed
to achieve a rapid reduction in fox numbers. Fertility control could <strong>the</strong>n be used
strategically to maintain reduced fox numbers to provide long-term protection for
threatened species. Fertility control is still at an experimental stage <strong>of</strong> development.
Hormone treatment is not considered a viable option for managing populations <strong>of</strong>
wild foxes as <strong>the</strong>re are no practical methods <strong>of</strong> ensuring effective treatment <strong>of</strong>
unrestrained <strong>animals</strong>. Research has, however, indicated that Cabergoline may have <strong>the</strong>
potential to control fox fertility in areas where poison baiting cannot be undertaken
(Marks et al. 1995a, 1995b). Immunocontraception has <strong>the</strong> potential to provide a
target specific form <strong>of</strong> fertility control which can be used on wild populations, but has
yet to be developed.
The Pest Animal Control CRC has been exploring <strong>the</strong> possibility <strong>of</strong> reducing <strong>the</strong> fox
population by anti-fertility vaccination. The canine herpesvirus has been identified as
potentially <strong>the</strong> most suitable virus carrier for <strong>the</strong> vaccine. Work on genetically altering
this virus in such a way as to cause an immune repsonse in foxes that supresses
reproduction has been conducted. A successful recombinant virus has yet to be
discovered <strong>and</strong> <strong>the</strong> research will be downsized <strong>and</strong> a briefing watch maintained.
Biocontrol
Some form <strong>of</strong> pathogen could conceivably affect foxes on a continental scale, but
currently none is known to be virulent, humane, specific to foxes <strong>and</strong> not transferable
to o<strong>the</strong>r species, especially domestic dogs. Research to develop an effective biocontrol
agent to manage foxes continues, however it has to address difficult scientific,
technical <strong>and</strong> biological problems.
Current <strong>management</strong>
NSW - Ground baiting with 1080 is by far <strong>the</strong> most commonly used technique in
NSW. In fact 78% <strong>of</strong> control efforts use this technique. Ground shooting is <strong>the</strong>
only o<strong>the</strong>r commonly used control technique (15%), although trapping,
exclusion fencing <strong>and</strong> den fumigation are used to a small degree. The most
widely used technique by NPWS is broad-scale baiting (both ground <strong>and</strong> aerial)
with 1080, which is <strong>the</strong> most effective <strong>and</strong> target-specific method <strong>of</strong> fox control
currently available. O<strong>the</strong>r less frequently used methods are trapping, shooting,
den fumigation <strong>and</strong> exclusion fencing. They are expensive, labour intensive,
requiring continuing <strong>management</strong> effort <strong>and</strong> can be effective in only limited
areas. Aerial baiting is used in western NSW to increase <strong>the</strong> cost-efficiency <strong>of</strong>
fox control over a very large area, with <strong>the</strong> aim <strong>of</strong> protecting endangered mallee
fowl populations. Aerial baiting <strong>of</strong> <strong>the</strong>se reserves is complemented by an
extensive ground baiting program on surrounding properties <strong>and</strong> state forests.
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