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

5.1.4 Mustering
Commercial mustering <strong>of</strong> <strong>feral</strong> <strong>animals</strong> is commonly undertaken in <strong>the</strong> Rangel<strong>and</strong>s.
The <strong>animals</strong> can be mustered using helicopters, vehicles, motorbikes or by horseback.
A combination <strong>of</strong> ground <strong>and</strong> aerial mustering is an effective way <strong>of</strong> moving herds
<strong>and</strong> mobs over large distances into yards. The helicopter initially locates <strong>and</strong> musters
<strong>the</strong> <strong>animals</strong> away from inaccessible terrain towards where <strong>the</strong> yards are set. Once <strong>the</strong>
<strong>animals</strong> are near <strong>the</strong> yards <strong>the</strong> mustering is undertaken by <strong>the</strong> ground crew on horses
<strong>and</strong> motorbikes. One <strong>of</strong> <strong>the</strong> benefits <strong>of</strong> mustering is that <strong>animals</strong> can <strong>of</strong>ten be sold to
<strong>of</strong>fset <strong>the</strong> cost <strong>of</strong> <strong>the</strong> operation. However, mustering is usually only effective at
relatively high <strong>feral</strong> population densities. The use <strong>of</strong> Judas <strong>animals</strong> can help locate
<strong>feral</strong> groups <strong>and</strong> make <strong>the</strong> technique more effective. Olsen (1998) reports that
mustering efficiency <strong>of</strong> varies greatly. In Western Australia an average muster yield
between 30-40 percent <strong>of</strong> <strong>feral</strong> goats, whilst in <strong>the</strong> Flinders Ranges <strong>of</strong> South
Australia, approximately 80 percent <strong>of</strong> goats can be taken on an average muster.
Mustering is quite <strong>of</strong>ten used to reduce population numbers before beginning <strong>and</strong>
aerial cull, decreasing <strong>the</strong> expense <strong>of</strong> <strong>the</strong> operation.
5.1.5 Judas technique
The use <strong>of</strong> radio-telemetered individuals to locate <strong>animals</strong> with which <strong>the</strong>y associate
has been developed as a control technique for strongly gregarious species such as
goats, donkeys, camels, horses <strong>and</strong> water buffaloes (Henzell 1987, Taylor & Katahira
1988, Allen 1991, Williams & Henzell 1992, Dobbie et al. 1993, Olsen 1998). An
animal is captured through trapping, mustering or tranquiliser dart <strong>and</strong> a radio-collar
is fitted. The radio-collared ‘Judas’ animal is <strong>the</strong>n released <strong>and</strong> joins up with, <strong>and</strong> is
used to locate, groups in <strong>the</strong> area. Generally, it is best to use local <strong>feral</strong> <strong>animals</strong> as <strong>the</strong>
Judas because <strong>the</strong>y are familiar with <strong>the</strong> area <strong>and</strong> are already part <strong>of</strong> <strong>the</strong> social
structure <strong>of</strong> <strong>the</strong> target herds or mobs. The Judas animal is <strong>of</strong>ten clearly marked so that
during aerial culling it can be avoided. The technique is usually used for low density
populations or for survivors <strong>of</strong> o<strong>the</strong>r control campaigns that have become particularly
wary. The method is particularly useful when <strong>the</strong> <strong>management</strong> objective is local
eradication. It has been used to eradicate local populations <strong>of</strong> <strong>feral</strong> goats in Australia,
for example, in small areas <strong>of</strong> <strong>the</strong> Adelaide Hills in South Australia, (Henzell 1987,
Williams & Henzell 1992). The main disadvantage <strong>of</strong> <strong>the</strong> approach is that <strong>the</strong>
equipment is very expensive <strong>and</strong> requires skilled operators to work effectively
5.1.6 Fencing
Since <strong>the</strong> early days <strong>of</strong> European settlement, fencing has been <strong>the</strong> most common
method used to exclude <strong>feral</strong> <strong>animals</strong> from an area. Probably <strong>the</strong> best known fence is
<strong>the</strong> dingo fence that stretches 5614 kilometres from Queensl<strong>and</strong> through New South
Wales across South Australia to <strong>the</strong> Great Australian Bight. The fence divides <strong>the</strong>
sou<strong>the</strong>rn <strong>and</strong> eastern sheep grazing l<strong>and</strong>s from cattle <strong>and</strong> dingo country. Exclusion
fencing is increasingly being used as a tool to protect areas <strong>of</strong> high conservation value
from <strong>the</strong> threats posed by vertebrate pest species.
There are many types <strong>of</strong> fences used to exclude pests. They include conventional
stock fencing, electric fencing <strong>and</strong> purpose built fences to protect conservation
reserves. Fences have been used to break up areas into manageable blocks for control
<strong>and</strong> have been used to exclude <strong>animals</strong> from watering points <strong>and</strong> so concentrate <strong>the</strong>m
at watering points where traps have been set. They can also slow dispersal, making
control on <strong>the</strong> protected side more feasible <strong>and</strong> economic. Electric fencing is
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