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

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warren structure amenable to recolonisation. On <strong>the</strong> o<strong>the</strong>r h<strong>and</strong>, skilled operators may destroy deep warrens effectively. Surface refugia destruction Rabbits in some parts <strong>of</strong> Australia prefer surface refugia even when warrens are present (Wheeler et al. 1981, Williams et al. 1995). Habitat destruction in <strong>the</strong>se situations may require <strong>the</strong> removal <strong>of</strong> <strong>the</strong> shrub layer, <strong>of</strong> exotic weeds such as blackberry <strong>and</strong> debris such as logs, <strong>and</strong> can greatly enhance <strong>the</strong> efficiency <strong>and</strong> effectiveness <strong>of</strong> control programs <strong>and</strong> slow recolonisation. This may be undesirable as such refugia also provide important habitat for amphibians, reptiles, small mammals, <strong>and</strong> ground dwelling or ground feeding birds. The relative benefits <strong>of</strong> this action for enhancing <strong>the</strong> recovery <strong>of</strong> endangered or vulnerable species would need to be carefully assessed against <strong>the</strong> risks to o<strong>the</strong>r native species if such action is proposed in areas being managed for conservation purposes. Shooting Shooting can be a humane way <strong>of</strong> destroying rabbits but is rarely an effective means <strong>of</strong> reducing populations. Shooting may be used by l<strong>and</strong> managers as a method for maintaining control once populations have been substantially reduced by o<strong>the</strong>r methods. Small numbers <strong>of</strong> survivors in difficult country can also be hunted with dogs <strong>and</strong> guns. Although not highly regarded as a game animal, wild rabbits are probably <strong>the</strong> largest hunting resource in sou<strong>the</strong>rn Australia. There are no published reports on <strong>the</strong> size <strong>and</strong> value <strong>of</strong> sport hunting <strong>of</strong> rabbits. The commercial rabbit industry depends largely on <strong>the</strong> supply <strong>of</strong> field-shot rabbits to processing works, however harvesting efforts have no significant <strong>impact</strong> rabbit populations (Ramsay 1994). To maximise returns, commercial hunters move to areas where rabbits are more abundant ra<strong>the</strong>r than continuing to shoot rabbits in a lower density population. Many <strong>of</strong> <strong>the</strong> areas now subject to commercial harvesting, mainly in <strong>the</strong> Rangel<strong>and</strong>s, are those where widescale effective <strong>management</strong> with conventional control techniques such as poisoning, fumigation <strong>and</strong> ripping are difficult to achieve in <strong>the</strong> short term, ei<strong>the</strong>r economically or logistically (Williams et al. 1995) Trapping Leg-hold traps have been used to catch <strong>feral</strong> rabbits for many years. The use <strong>of</strong> <strong>the</strong> traditional steel-jawed leg-hold trap for <strong>the</strong> control <strong>of</strong> rabbits is not advocated as <strong>the</strong>y subject <strong>animals</strong> to unnecessary pain <strong>and</strong> suffering <strong>and</strong> this technique does not reduce rabbit numbers significantly to be an effective control technique (Gibb et al.1969, Williams & Robson 1985). Exceptions to this are where small isolated populations are targeted, in which case barrel traps or s<strong>of</strong>t catch traps should be used (Korn & Hosie 1988). Fumigation There are two fumigation methods; pressure fumigation <strong>and</strong> diffusion fumigation (Cooke 1981, Williams & Moore 1995). Toxins used for fumigation include chloropicrin, carbon monoxide, carbon dioxide, calcium cyanide, <strong>and</strong> phosphine (Hayward & Lisson, 1978, Williams et al. 1995). Pressure fumigation requires <strong>the</strong> use <strong>of</strong> a pump to generate <strong>and</strong> force <strong>the</strong> fumigant throughout <strong>the</strong> warren. The fumigant usually comprises a mixture <strong>of</strong> thick smoke, carbon monoxide <strong>and</strong> chloropicrin (Parer & Milkovits 1994). During fumigation all warren entrances are sealed. Entrances 128
hidden in rocks or vegetation may be revealed by emerging smoke. Pressure fumigation is a slow <strong>and</strong> cumbersome process <strong>and</strong> is suitable only for small areas (Williams et al. 1995). In addition, <strong>the</strong> use <strong>of</strong> chloropicrin in pressure fumigation is both dangerous to operators <strong>and</strong> perceived to be inhumane (Oliver & Blackshaw 1979). Diffusion fumigation can use chloropicrin liquid, or aluminium-phosphide pellets, which give <strong>of</strong>f phosphine gas (Korn & Hosie 1988). Pellets are placed in absorbent paper towel or newspaper, <strong>the</strong>n moistened with water <strong>and</strong> sealed as far into <strong>the</strong> burrow as possible. Diffusion fumigation is useful for impromptu treatment <strong>of</strong> isolated warrens or re-openings detected by chance during normal property practices. Little equipment is required <strong>and</strong> it can be carried readily in a vehicle, on a motorbike, or by an operator walking in difficult terrain. The technique also allows for <strong>the</strong> use <strong>of</strong> an alternate toxin such as phosphine which is possibly more humane (Williams & Moore 1995; Williams et al. 1995). Both methods are labour-intensive <strong>and</strong> only small areas can be treated because <strong>of</strong> cost, <strong>the</strong> time required, <strong>and</strong> <strong>the</strong> intensity <strong>of</strong> <strong>the</strong> operation. The methods are useful where warrens cannot be ripped <strong>and</strong> for follow-up maintenance after large-scale programs such as warren ripping or baiting (Korn & Hosie 1988, Williams & Moore 1995). The efficiency <strong>of</strong> fumigation can be greatly increased by using dogs to drive rabbits into <strong>the</strong> warren. Fumigated warrens remain intact <strong>and</strong> <strong>the</strong>refore prone to recolonisation by rabbits. Once fumigated, warrens should be rendered unusable by securely blocking entrances. This is likely to be more cost-effective than repeated fumigation Poisoning Poisoning is ano<strong>the</strong>r commonly used rabbit <strong>management</strong> technique. If used alone, it is an expensive method <strong>of</strong> controlling rabbits because <strong>the</strong> treated areas are rapidly recolonised (Rowley 1968, Martin & Atkinson 1978, Foran et al. 1985, Williams & Moore 1995). Resources per rabbit are increased leading to increased survival <strong>and</strong> breeding, <strong>and</strong> <strong>the</strong> warren, <strong>the</strong> rabbit’s main form <strong>of</strong> shelter, remains intact <strong>and</strong> available for recolonisation. Frequent <strong>and</strong> ineffective poison baiting can lead to neophobia in rabbit populations that can reduce <strong>the</strong> effectiveness <strong>of</strong> baiting. Changing poisons does not overcome <strong>the</strong> problem (Williams et al. 1985). When used in conjunction with ripping or fumigation <strong>and</strong> follow-on control however, poisoning can be a cheap <strong>and</strong> effective component <strong>of</strong> integrated rabbit <strong>management</strong>. It is also an important <strong>management</strong> tool where rabbits are mainly surface dwelling, a common situation in several parts <strong>of</strong> Australia. Baits commonly used for rabbits include pieces <strong>of</strong> carrot, oat grains, or pellets manufactured from bran or pollard. Poison baits can be delivered from aircraft or from baitlayers towed by vehicles including four-wheeled motorcycles. Aerial bait laying is useful for broad-scale application but is less accurate. It should not be used where non-target <strong>animals</strong> occupy habitat close to <strong>the</strong> proposed treatment area. Vehicle-drawn baitlayers can broadcast <strong>the</strong> bait in a swa<strong>the</strong> or lay it in a shallow ploughed furrow. The choice <strong>of</strong> method depends primarily on <strong>the</strong> scale <strong>of</strong> <strong>the</strong> operation, <strong>the</strong> terrain, <strong>and</strong> <strong>the</strong> cost <strong>and</strong> availability <strong>of</strong> equipment. The selectivity <strong>of</strong> poisoning is enhanced by: (1) Pre-baiting with non-poisoned bait <strong>and</strong> ensuring that only rabbits are taking <strong>the</strong> bait (2) Using baits that are most attractive to rabbits (3) Using <strong>the</strong> minimal concentration <strong>of</strong> poison sufficient to kill rabbits (4) Placing <strong>the</strong> bait in <strong>the</strong> prime feeding areas <strong>of</strong> rabbits (5) Collecting carcasses <strong>of</strong> poisoned rabbits to minimise secondary poisoning. 129
Page 1:
Review of<
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Contributors Andrew Norris Pest Ani
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3.7.36 Common Myna (Acridot
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Table of figures F
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Section 2 Introduction Feral <stron
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Amanda Dimmock, QD
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Section 3 A status review o
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3.4 Birds Thirteen (or 14) species
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Information on the
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Summary A rodent that contributes t
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Dingoes can become a threat to wild
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The significance of</strong
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macropods and b<st
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^Lasiorhinus krefftii North
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Perceived threat Geopsittacus occid
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conservation areas. It is less clea
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Table 8 Rare species found in <stro
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Competition Several examples are re
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In truth, camels do substantial dam
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the Tanami. Buffal
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The situation today Buffalo numbers
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qualify under IUCN criteria as enda
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3.7.16 Goat (Capra hircus) Summary
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Drakonorchis drakeoides Hinged Drag
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3.7.19 Red Deer (Cervus elaphus) Su
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Impacts Much is known about <strong
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Distribution Ostriches have won <st
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nest in tree hollows along
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Distribution The skylark is found i
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Distribution The blackbird is wides
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Land, and<
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have been translocated to o
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esources. Significant investment in
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many native species (Clarke et al.
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spread across the
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Section 4 Legislative framework 4.1
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protection, as long as it falls wit
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Native Vegetation Conservation Act
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ehabilitate existing native vegetat
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suppression, which is the</
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al. 1986, 1987). The use of
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5.1.4 Mustering Commercial musterin
Page 86 and 87: etal. (1997) found that many native
Page 88 and 89: the vaccine <stron
Page 90 and 91: Where possible, integration <strong
Page 92 and 93: strategy, relative cost-effectivene
Page 94 and 95: Fencing Feral buffalo have a reputa
Page 96 and 97: 5.3 Management of
Page 98 and 99: Summary of <strong
Page 100 and 101: time comes for the
Page 104 and 105: Individual tracking Tracking is a l
Page 106 and 107: SA - Currently cats are not widely
Page 108 and 109: Method of control
Page 110 and 111: Aerial shooting Aerial shooting can
Page 114 and 115: 80% of export was
Page 116 and 117: ensuring effective treatment <stron
Page 118 and 119: the lower cost, wi
Page 122 and 123: conservation value rathe</s
Page 124 and 125: effort on the cont
Page 128 and 129: follow transect lines, one kilometr
Page 130 and 131: as a refuge from predators. Removal
Page 134 and 135: was completed it was the</s
Page 138 and 139: Poisons Traditionally, strychnine,
Page 140 and 141: infected and steri
Page 142 and 143: of high priority.
Page 144 and 145: Method of control
Page 148 and 149: technique can allow for cost-effect
Page 152 and 153: In South Australia, between 30 <str
Page 156 and 157: % respondents 100% 90% 80% 70% 60%
Page 158 and 159: a) b) Figure 3. a) Extent o
Page 160 and 161: Figure 4 Response frequency for lik
Page 162 and 163: distribution of <s
Page 164 and 165: Section 7 Key problems and<
Page 166 and 167: • Goats degrading temperate woodl
Page 168 and 169: conservation problems in Europe <st
Page 170 and 171: message that camels are a valuable
Page 172 and 173: In the Koolatong R
Page 174 and 175: environmental degradation’ (Nor<s
Page 176 and 177: ecause dingo and d
Page 178 and 179: Various control methods have been a
Page 180 and 181: Pascale Taplin, an Indigenous L<str
Page 182 and 183: Lack of a Strategi
Page 184 and 185: eradicated after seeing the
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In some situations, payment <strong
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could have led to better protocols
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Game hunting is a growing business,
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Much as we might like it, t
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conservation outcome. In such a sit
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community consultation and<
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• Have the non-t
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provide opportunities for strategic
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Section 9 Priorities for investment
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contacted for exact locations <stro
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way. Achilles heel research should
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efficient in any given situation. R
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west Queensland re
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Crossland, MR, 199
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Forsyth, DM, and P
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Lange, RT, and Gra
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Morgan, LA and But
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Parkes, JP, 1990, Feral goat contro
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Van Rensberg, PJJ, Skinner, JD, <st
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Appendix A Ferals animals</
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Indigenous lands I
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Appendix B Stakeholder survey form
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222
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224
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226
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Appendix C Database on past NHT fun
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Lachlan Rehabilitation of</
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Northern Territory
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Cape York Ambiilmungu-Ngarra tradit
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Wet Tropics Expansion and</
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Avon Protecting and</strong
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