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

• Have <strong>the</strong> non-target <strong>impact</strong>s <strong>of</strong> control been considered?
Many <strong>of</strong> <strong>the</strong> recommended control techniques have <strong>impact</strong>s on non-target species. For
example, poison baits are <strong>of</strong>ten consumed by native fauna. It is important that nontarget
<strong>impact</strong>s are carefully considered when selecting <strong>the</strong> <strong>feral</strong> animal control
techniques. This can be particularly important when implementing control to reduce
threats to endangered species. The most effective techniques may not be able to be
used due to <strong>the</strong> threat <strong>the</strong>y pose to <strong>the</strong>se species.
• What will be <strong>the</strong> consequences <strong>of</strong> target species eradication or population
depletion?
Sometimes <strong>the</strong> eradication <strong>of</strong> control <strong>of</strong> one <strong>feral</strong> species may have indirect <strong>impact</strong>s
on o<strong>the</strong>r <strong>feral</strong> <strong>animals</strong> or native species. These need to be carefully considered before
implementing control. For example, <strong>feral</strong> cat numbers have been observed to rise <strong>and</strong>
fall with fluctuations in rabbit numbers (Williams et al. 1995), <strong>and</strong> control <strong>of</strong> rabbits,
particularly in Rangel<strong>and</strong>s, is considered important in lowering <strong>feral</strong> cat numbers <strong>and</strong>
possibly reducing <strong>feral</strong> cat damage to conservation values (Newsome 1990). Thus
rabbit control may also help reduce <strong>the</strong> <strong>impact</strong>s <strong>of</strong> <strong>feral</strong> cats. However, in some areas
<strong>feral</strong> cats will increase <strong>the</strong>ir predation upon native <strong>animals</strong> when rabbit numbers
decline (Williams et al. 1995, Newsome et al. 1996). This can place extra pressure on
<strong>the</strong> <strong>the</strong> native fauna species that conservation efforts hope to protect. If such <strong>impact</strong>s
are expected, an integrated control program targeting both rabbits <strong>and</strong> cats is needed.
Similarly, dingoes may protect a range <strong>of</strong> native species by controlling exotic
predators like <strong>feral</strong> cats through direct predation (Palmer 1996a, 1996b) <strong>and</strong> by
excluding <strong>the</strong>m from carrion during droughts (Pettigrew 1993, Corbett 1995). Control
programs removing dingoes, deliberately or accidentally (non-target kill), are likely to
increase predation from <strong>feral</strong> predators. Pest <strong>animals</strong> that are controlled to some
extent by dingoes include pigs, goats, foxes, hares, overabundant kangaroos <strong>and</strong>
wallabies, <strong>and</strong> probably deer.
• Does <strong>the</strong> <strong>management</strong> plan contain adequate monitoring?
Most <strong>feral</strong> animal <strong>management</strong> programs in <strong>the</strong> Rangel<strong>and</strong>s have lacked adequate
monitoring. Monitoring tells you if your <strong>management</strong> actions are working, as well as
allowing variables such applicability to o<strong>the</strong>r regions to be evaluated.
‘Monitoring <strong>and</strong> evaluation’, says Braysher (1993), ‘are <strong>of</strong>ten forgotten aspects <strong>of</strong>
vertebrate pest <strong>management</strong>.’ Because <strong>the</strong>re is never enough money for optimal pest
control, most <strong>of</strong> <strong>the</strong> effort goes into actual control, <strong>and</strong> monitoring is neglected, or it is
very limited in scope. We are seldom able to say what has been achieved.
Monitoring is sometimes dismissed as an academic exercise, promoted by researchers
to provide <strong>the</strong>m with employment, <strong>of</strong> limited value compared to <strong>the</strong> ‘real’ work <strong>of</strong>
killing pests. Funding bodies are <strong>of</strong>ten reluctant to see pest control money ‘diverted’
into monitoring. People want action not words, results not observation. We thus
remain ignorant about <strong>the</strong> merit <strong>of</strong> many pest control operations. In some cases money
continues to be wasted on ineffective actions because no monitoring goes on.
Where monitoring is undertaken it is usually inadequate. It may consist only <strong>of</strong> counts
<strong>of</strong> <strong>animals</strong> killed or numbers <strong>of</strong> baits removed. But <strong>the</strong> number <strong>of</strong> dead pests may not
correlate with any benefit, because <strong>the</strong> pests may be multiplying fast enough to
replace any losses. Where pests are controlled for biodiversity, <strong>the</strong> focus <strong>of</strong>
monitoring should be on <strong>the</strong> benefit to biodiversity, when all too <strong>of</strong>ten it is on
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