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

ensuring effective treatment <strong>of</strong> unrestrained <strong>animals</strong>. Immunocontraception has <strong>the</strong>
potential to provide a target specific form <strong>of</strong> fertility control which can be used on
wild goat populations. If <strong>the</strong> immunocontraception can be made to work, it may
provide a cheap, easily disseminated method for reducing fertility <strong>and</strong> populations <strong>of</strong>
some pest species on a continental scale. Broad scale control <strong>of</strong> goats using an
immunocontraceptive vaccine, if one were developed, would depend on developing a
suitable delivery mechanism for <strong>the</strong> vaccine <strong>and</strong> obtaining appropriate approvals to
release <strong>the</strong> vaccine into <strong>the</strong> wild. The development <strong>and</strong> initial employment <strong>of</strong> such a
vaccine would initially be very expensive; however <strong>the</strong> long-term cost <strong>of</strong> a successful
immunocontraception program would be low due to <strong>the</strong> low on-going costs. Currently
no immunocontraceptive research for <strong>feral</strong> goats is being undertaken.
Poisoning <strong>and</strong> baiting
The only poison that has been trialled for <strong>feral</strong> goat control in Australia is 1080
(sodium mon<strong>of</strong>luoroacetate). The main risk with this technique is consumption <strong>of</strong>
baits by non-target species. Three baiting techniques have been reported: pelletised
grain bait (Forsyth & Parkes, 1995); foliage baiting (Parkes 1983); <strong>and</strong> poisoning <strong>of</strong> a
water supply (Norbury 1993). This last technique to kill <strong>feral</strong> goats by adding 1080 to
water troughs, was trialled in Western Australia (Norbury 1993). The trial showed
that goats could be killed with minimal non target risks by designing <strong>the</strong> troughs to
exclude birds <strong>and</strong> providing <strong>the</strong>m with alternative water, by excluding domestic stock,
<strong>and</strong> by poisoning between 8.00am <strong>and</strong> noon to reduce <strong>the</strong> risk to macropods.
Following a public environment review (Agriculture Protection Board 1993), <strong>the</strong>
technique <strong>of</strong> adding 1080 to water troughs, under strict <strong>management</strong> conditions, is
now being used in Western Australia. This technique is not registered in any o<strong>the</strong>r
state. Goats free-fed on untreated bait material (such as grain) might be able to be
immobilised with bait to which a sedative such as Valium has been added. Initial trials
in South Australia have been promising, but fur<strong>the</strong>r development is needed (R.
Henzell, unpublished). If effective, this technique could avert many <strong>of</strong> <strong>the</strong> animal
welfare concerns associated with poisoning or trapping at water.
Biological control
Control <strong>of</strong> <strong>feral</strong> goats using a pathogen may be <strong>the</strong>oretically possible, but currently
none is known to be virulent, humane, specific to goats <strong>and</strong> not transferable to o<strong>the</strong>r
species. The potential risks to both <strong>the</strong> domestic goat industry <strong>and</strong> o<strong>the</strong>r livestock
industries from using a pathogen are too high to warrant any research on this
approach. Ano<strong>the</strong>r disadvantage is that <strong>animals</strong> are likely to develop resistance to <strong>the</strong>
pathogen <strong>and</strong> such resistance will eventually spread through <strong>the</strong> species.
Feral goats do not generally occur where <strong>the</strong>re are uncontrolled populations <strong>of</strong>
dingoes (Parkes et al. 1996). One <strong>feral</strong> goat population on an <strong>of</strong>fshore isl<strong>and</strong> was
successfully controlled by releasing dingoes onto <strong>the</strong> isl<strong>and</strong> (Allen & Lee 1995). It is
unlikely that dingoes would be acceptable as a 'biological control' in pastoral areas
where most <strong>feral</strong> goats occur, as predation by dingoes is not a target specific control
measure <strong>and</strong> o<strong>the</strong>r livestock would be at risk.
Bounties
Bounties on goats’ ears have been paid in Western Australia to induce people
mustering goats to kill unmarketable <strong>animals</strong> instead <strong>of</strong> releasing <strong>the</strong>m. Over 120 000
bounties were paid between 1977 <strong>and</strong> 1985, but discontinued in 1985 as <strong>the</strong> scheme
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