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

for agricultural production, but is rarely at a level suitable for <strong>the</strong> conservation <strong>of</strong>
biodiversity, particularly when threatened or endangered species are involved.
Ano<strong>the</strong>r problem is that those contracted to harvest <strong>feral</strong> <strong>animals</strong> from national parks
may leave some behind as breeding stock, ra<strong>the</strong>r than removing <strong>the</strong>m all, to guarantee
<strong>the</strong>mselves a future supply. A third problem is that talk about income from harvesting
encourages l<strong>and</strong>holders to view <strong>feral</strong> <strong>animals</strong> as resources ra<strong>the</strong>r than problems. This
is particularly a problem on Indigenous l<strong>and</strong>s. Thus, commercial harvesting should
only be used as a tool within an integrated strategy ra<strong>the</strong>r than as a primary
<strong>management</strong> option. It is discussed fur<strong>the</strong>r in <strong>the</strong> sections on camels <strong>and</strong> Indigenous
l<strong>and</strong>s in Section 6.
5.1.13 Managing <strong>the</strong> <strong>impact</strong> not <strong>the</strong> <strong>feral</strong> number
In <strong>the</strong> past, much <strong>of</strong> <strong>the</strong> <strong>management</strong> efforts have been focussed on reducing <strong>the</strong> <strong>feral</strong>
animal population, with little heed paid to how effectively <strong>the</strong>ir <strong>impact</strong>s were
mitigated. A <strong>management</strong> strategy was considered successful if <strong>the</strong>re was a high
‘body count’ or if few <strong>feral</strong>s could be detected. Instead, <strong>the</strong> <strong>management</strong> <strong>of</strong> <strong>feral</strong>
<strong>animals</strong> should be undertaken to minimise or mitigate <strong>the</strong>ir <strong>impact</strong>s on biodiversity,
primary production or o<strong>the</strong>r socio-economic factors. By gaining a clear underst<strong>and</strong>ing
<strong>of</strong> <strong>the</strong> density-dependent <strong>impact</strong>s a <strong>feral</strong> species has on <strong>the</strong> environment, it is possible
to more cost-effectively manage that species. If density-dependent <strong>impact</strong> information
is available, a threshold level <strong>of</strong> population density can be set where <strong>the</strong> <strong>impact</strong> <strong>the</strong>
species has is acceptable if eradication is not feasible. Unfortunately, <strong>the</strong>
environmental <strong>impact</strong>s <strong>of</strong> <strong>feral</strong> <strong>animals</strong> are <strong>of</strong>ten poorly understood, <strong>and</strong> density
dependent damage curves are unavailable for <strong>the</strong> majority <strong>of</strong> species. Research into
this information is urgently required to enable <strong>the</strong> limited resources available for <strong>feral</strong>
animal control to be most effectively utilised.
5.1.14 Monitoring – assessing <strong>the</strong> effectiveness
Accurate monitoring is an essential component <strong>of</strong> any <strong>feral</strong> animal control program.
Monitoring <strong>the</strong> <strong>impact</strong>s <strong>of</strong> a program is necessary to determine <strong>the</strong> effectiveness <strong>of</strong>
<strong>the</strong> program in meeting its objectives <strong>and</strong> any incidental effects on non-target species.
The most commonly measured variable is <strong>feral</strong> animal population density <strong>and</strong> this
relates to <strong>the</strong> historical approach <strong>of</strong> managing <strong>the</strong> <strong>feral</strong> animal density <strong>and</strong> not <strong>impact</strong>.
Although a useful measure, monitoring <strong>of</strong> <strong>the</strong> <strong>feral</strong> animal population without
investigating its changing <strong>impact</strong>s on <strong>the</strong> environment may give misleading
conclusion <strong>of</strong> achievement <strong>of</strong> <strong>the</strong> programs goals. If <strong>the</strong> objective <strong>of</strong> <strong>the</strong> program is to
reduce <strong>the</strong> <strong>impact</strong> <strong>of</strong> a <strong>feral</strong> species, <strong>the</strong>n <strong>the</strong> <strong>impact</strong> <strong>of</strong> <strong>feral</strong> species is one <strong>of</strong> <strong>the</strong>
variables that must be measured. Unless density-dependent <strong>impact</strong> information is
available, o<strong>the</strong>r measures are required. One <strong>of</strong> <strong>the</strong> problems with monitoring
programs is that <strong>the</strong> results <strong>of</strong> a control program may not be clearly evident for years.
Quick measures <strong>of</strong> control program <strong>impact</strong> can include <strong>the</strong> change in <strong>the</strong> abundance
<strong>of</strong> <strong>feral</strong> <strong>animals</strong> in an area or changes in <strong>the</strong> population size <strong>of</strong> a threatened species.
However, monitoring needs to continue over a long time frame to ensure that sudden
changes in pest or fauna numbers are not due to some o<strong>the</strong>r factor (such as drought or
above average rains), <strong>and</strong> to detect long term improvements in ecosystem health <strong>and</strong>
viability. This requires that continual funding <strong>and</strong> support be available for monitoring
to detect <strong>the</strong> changes as <strong>the</strong>y occur.
Adequate monitoring also allows <strong>the</strong> cost effectiveness <strong>of</strong> different control techniques
to be assessed. By recording resource investments into each control technique or
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