Copyright © 2017 Desert Channels Queensland Incorporated

Parts or all of this publication may be reproduced, but only with the express prior permission of the publisher, unless otherwise exempted.

Raw content, expert guidance and technical advice by Dr Jim Mitchell of FeralFix; additional research and writing by Astrebla Services; layout design by JDesign. Images, apart from where acknowledged otherwise, are from the DCQ library.

If you would like more detailed information on feral pigs and their control, contact Dr Jim Mitchell of FeralFix on feralfixservices@bigpond.com.au or 0447 984 721, or refer to Threat Abatement Plan for predation, habitat degradation, competition and disease transmission by feral pigs (Sus scrofa) (2017) published by Department of Environment and Energy.

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The 510,000 square kilometre Desert Channels Region comprises the Queensland section of the Lake Eyre Basin - nearly one-third of the State.

Funded by the Queensland Feral Pest Initiative

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contents

Cover image and this image courtesy of Leigh Deutscher

Foreword 7Introduction 8Background 10History 11Description 12 Habits 12 Diet 13 Reproduction 13 Distribution 13Impacts 15 Production 15 Environmental 16 Disease 17Control 18 Landholder obligations 18 Hunting 19 Aerial shooting 19 Monitoring 21 Animal welfare 22 Trapping 24 Advantages and disadvantages of trapping 24 Strategy 26 Bait material 26 Trap design 27 Gate design 28 Disposal of trapped animals 31 Poisoning 32 Advantages and disadvantages of poisoning 33 Bait material 35 Bait distribution 36 Advantages and disadvantages of ground baiting 36 Bait abundance 38 Baiting timing 38 Reducing non-target impacts 38 Advantages and disadvantages of aerial baiting 40 Available toxins 40 Sodium fluoroacetate (1080): 41 Yellow phosphorus: 41 Sodium nitrite: 42

Overview of Queensland Government guidelines for 1080 use 42

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As a producer, it can be a challenge to balance the competing needs of running your business, managing your stock, maintaining your infrastructure and caring for your land. We have strong obligations to them all.

Striking the right balance is about more than simply managing and splitting your time, it’s about having access to the right information on which to base your management decisions.

That’s why I’m particularly proud of this booklet on feral pig control that Desert Channels Queensland has produced. Not only does the information come from renowned feral pig control expert, Dr Jim Mitchell, but it’s been written in plain English with the focus firmly on our region.

We have been running a feral pig control program, mainly in the mid to lower Channel Country, since 2011. Over that time, we have learnt a lot about feral pigs

from research, experience, observation and landholders. That information has been integrated into this publication.

So, whether you are a sheep producer in the northeast, or an extensive cattle producer in the southwest, between these covers you will find the information you need to effectively and efficiently control feral pigs on your land.

Thank you for being committed to reducing feral pig numbers and the impacts they have on our livestock and our land. I know you’ll find this booklet useful.

Dom Burden‘Macsland’ LongreachChairDesert Channels Queensland

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foreword

Desert Channels Queensland is a community-based group which sources funds and works with landholders, community groups, researchers, local government, agencies and industry to improve production and environmental outcomes across the Queensland section of the Lake Eyre Basin.

A major focus of our work has been feral animal control, particularly feral pigs. Our six year program to reduce feral pig populations on river systems that support the valuable Channel Country grazing country and wetlands, as well as the RAMSAR listed Coongie Lakes, and Lake Eyre itself, has seen more than 30,000 feral pigs removed from the landscape.

We have worked with landholders across the lower and middle reaches of Queensland’s Channel Country, collaborating on aerial shoots and long-term, remote monitoring stations. By reducing feral pig numbers in this strategic area, their spread down the

river systems to ecologically sensitive areas such as Coongie Lakes has been slowed.The program has involved extensive aerial and on-ground monitoring, as well as aerial shooting and complementary baiting of upstream areas.

This book has been designed to give landholders and others involved in feral pig control, useful and expert information to assist them in their efforts. Every effort has been made to avoid swamping the reader with non-essential information; rather, we have presented an overview of all aspects of feral pig control, along with enough practical detail to be useful in making future individual and collaborative pig control efforts even more successful.

While much of the information presented in this book is generic, it has, as much as possible, been tailored for the semi-arid and arid grazing lands of the Desert Channels region.

introduction

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reports...

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Large mob of feral pigs caught on a monitoring camera in the Channel Country.

Feral pigs in Australia are descended from escaped domestic stock. They are one of the most prolific, widespread and damaging pest animals in Queensland, and are found throughout most parts of the Desert Channels region. Feral pigs cause production and environmental losses through disease and weed distribution, crop destruction, predation, habitat degradation and reduction in species composition as a result of competition with, or replacement of, native species.

Estimated economic damage to Queensland agricultural industries from feral pigs is $80 million annually.

Because of their considerable economic impact on agricultural industries, and the environmental degradation they cause, feral pigs are classified as a restricted invasive animal under Queensland legislation (see Landholder Obligations section). They are also designated as a threatening process under the Commonwealth Environment Protection & Biodiversity Conservation Act 1999.

There are an estimated 12 to 23 million feral pigs across 38% of the continent, with most occurring in Queensland and New South Wales. The Queensland population is estimated at 3 to 6 million, the majority in north Queensland.

In the Desert Channels region - the Queensland section of the Lake Eyre Basin - population densities vary depending on the habitat. Most feral pigs are concentrated on the major river systems close to waterholes, but are also found around property dams. Without ongoing control measures, numbers can build to damaging levels in good seasons.

The semi-arid and arid environment of the Desert Channels region, coupled with feral pigs’ dependence on daily access to water, allows well-run, long-term, water-focused control programs to maintain ongoing low numbers.

background

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Extract of First Fleet provisions list shows 32 hogs.

historyDomestic pigs (Sus scrofa), (Linnaeus 1758), (Family Suidae, Order Artiodactyla) were brought to Australia on the First Fleet as a food source. They came to Queensland in 1865 when Brisbane was settled.

Inevitably, wherever settlement spread and pigs were taken, some escaped, quickly building a wild population that dispersed along watercourses and across the landscape. In New South Wales, feral pigs were considered a pest by the 1880s.

Feral pigs are now distributed throughout Queensland and are considered habitat generalists colonising all biogeographical regions, and even some urban areas. Population levels and distribution are influenced by availability of water, food and cover, and the effectiveness of control programs. Pigs are great survivors, physically very tough and with a higher intelligence than dogs. They can thrive in a variety of habitats and environmental conditions.

The general community attitude towards feral pigs varies from a major agricultural and environmental pest and an exotic disease liability, to a food, economic and recreational resource for Aboriginal and other rural communities. These contrasting opinions can lead to conflict within a community. However, multiple-use management of feral pigs is increasingly accepted as both practical and appropriate, provided activities are undertaken in accordance with state legislation.

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Boars typically lead a solitary life outside of the breeding season.

Feral pigs are generally smaller and leaner than domestic pigs; they have more muscular shoulders and necks, and smaller hindquarters. And while descended from domestic pigs, environmental constraints usually do not allow them to develop to their genetic potential. Their appearance may be anything from inferior domestic pigs to the so-called ‘razorbacks’ of the dry interior and the northern dry tropics.

They generally have longer snouts and legs than domestic pigs, a straight tail and well developed tusks, as well as keratinous shoulder shields in males (keratin is a fibrous protein constituting hair, hoofs and horns). Their hair is long, sparse and coarse and many have a crest running down the spine. Growth rates depend on environmental conditions, and while adult weights of 260 kilograms for males and 150 kilograms for females are possible, these are unlikely in drier country. Studies indicate

average adult body weights of 70 to 100 kilograms for males and 40 to 70 kilograms for females.

Black is by far the most common coat colour, but variations of red, white, browns and agouti (mixtures of colours as patches, spots or stripes) are also prevalent.

Reproduction

Mature females have a 21 day oestrus cycle, and a 113 day gestation period. In good conditions their population can increase by 90 percent or more in a single year. Often, many piglets are lost to predation (dingoes, wild dogs) and starvation; in tough times, juvenile mortality can reach 100 percent.

description

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While breeding can occur all year round, environmental conditions usually dictate a birth pulse during or just after the wet season. Sexual maturity is dependent on weight, with sows able to breed at 25 to 30 kilogram body weight, irrespective of their age.

Habits

Feral pigs are most active at dawn and dusk (crepuscular), or in overcast or rainy weather; they seek dense cover as protection against direct sunlight and high temperatures. To compensate for their limited sweat glands, they drink often and wallow to cool off.

Feral pigs have a matriarchal social structure where related sows (mothers, daughters, sisters, aunts, etc.) live together with their young, with males joining the group for mating. Bachelor groups form when sexually mature males leave or are chased from the group. Older boars live alone or in sibling pairs.

Groups usually range from 5 to 20 individuals, but this varies with age, gender, food and water availability and disturbances such as hunting. Numerous sightings of large groups (20 plus) is a good indication of a high density population, while many individuals, especially females, and small groups, usually indicate a low population density.

Diet

Feral pigs are opportunistic omnivores with a strong preference for succulent green vegetation, fruits and seeds, rhizomes and roots and animal material including marsupials, reptiles, ground-nesting birds and their eggs, carrion and invertebrates. Having a simple, single-chambered stomach (monogastric) means pigs are unable to efficiently extract energy from plant cellulose; they require supplements of other foods.

They tend to focus on a particular food source when it’s locally abundant, then shift to another food source when the first runs out. Pigs have a high-energy and protein requirement, particularly during lactation. They meet this however they can, whether that be with earthworms, carrion, insects, lambs, crustaceans, frogs or reptiles.

Gut content examined during autopsies of feral pigs shot during Desert Channels Queensland’s Channel Country aerial shooting programs indicate a varied diet including nardoo, freshwater mussels and crayfish, small mammals, and small ground dwelling birds.

Just before farrowing, sows may make ‘nests’ in dense lignum, or similar low bushes close to water. The piglets remain in the nest for several days. Sows produce one to two litters per year of around six, but up to 10, piglets which are weaned around 2 to 3 months.

Distribution

Feral pig groups generally have a defined home range making use of the same trails, shelter areas, feeding and watering areas (subject to availability), rubbing and tusking trees and wallows. While the home ranges of groups and individual boars may overlap considerably, there is no evidence that either gender is territorial.

Boars are typically solitary, with home ranges varying from 8 to 50 square kilometres, while females and juveniles tend to live in family groups over a 2 to 20 square kilometre range. Range size depends on the season and food availability.

Feral pigs need to drink every day, and are generally found within a few kilometres of water. However, individual boars have been known to travel more than 20 kilometres, yet soon return to their home range. Intense aerial shooting can displace feral pigs by over 100 kilometres.

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impactsThe impacts of feral pigs are not only economic, and they aren’t restricted to the agricultural sector. Their foraging habits mean they also have a severe impact on the environment, and their disease carrying propensity has major ramifications for human health. They are both amenable hosts and effective carriers (vectors) for a number of endemic and exotic diseases.

Production

While the bulk of the estimated $80 million annual losses to Queensland’s agricultural production from feral pigs occurs in the intensive agricultural areas, producers in the Desert Channels region do not escape impact.

Feral pigs commonly prey on lambs, with losses of 15% common, and as high as 40% reported. They also foul waterholes and dams, damage pasture, fences and watering

facilities, compete for pasture and access to water, and carry diseases and parasites detrimental to livestock production.

In semi-arid areas where feral pigs and livestock mix at high densities around waterholes, there is an increased likelihood of stock becoming infected through contaminated vegetation, soil, water, and even air.

Estimates put the cost of a small (controlled in 3 months) outbreak of Foot and Mouth Disease in Australia at more than $7 billion, while a large (12 months) outbreak would be in the vicinity of $16 billion in control costs, lost production and lost markets. Feral pigs are often referred to as the ‘ticking time bomb’ in relation to Foot and Mouth Disease... given their wide-ranging presence and high mobility across the landscape, they would be the prime carrier for this disease; their control would be critical to recovery efforts.

The wallowing and digging habits of feral pigs not only degrade waterholes and pasture, they provide an ideal habitat in which weed seeds carried by the pigs can become established plants. Research shows that around 14% of Mesquite seeds remain viable after passing through a pig’s gut, which can take 3 to 8 days. Mesquite is a Weed of National Significance and, given the extensive home range of boars in particular, the spread potential of this weed is significant.

Feral pigs come in close contact with cattle especially when competing for waterhole space on hot days.

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Environmental

Feral pigs have a number of negative impacts on the environment and, by extension, production. Their digging habit can deplete vulnerable plant species, destroy native vegetation and suppress new germinations, as well as change vegetation structure and composition, cause erosion, and create an ideal environment of loose soil in which weeds can quickly establish. They also disperse weed seeds and soil pathogens on their bodies or in their faeces.

Feral pigs prey on a wide range of native animals including earthworms, insects, amphibians, reptiles, ground birds and small mammals, freshwater mussels and crayfish, frogs and marine and freshwater turtles.

Predation, habitat degradation, resource competition and disease transmission by feral pigs adversely affect many native flora and fauna species, including four listed endangered species in the Desert Channels region:

• Red-finned Blue-Eye (Scaturiginichthys vermeilipinnis)

• Australian Painted Snipe (Rostratula australis)

• Bulloo Grey Grasswren (Amytornis barbatus barbatus)

• Salt Pipewort (Eriocaulon carsonii)

The Red-finned Blue-eye fish and Salt Pipewort plant both occur in small, shallow artesian springs in semi-arid and arid country. Understandably, these springs are also a focal point for local populations of feral pigs, which makes these endangered species extremely vulnerable to the pigs’ wallowing and digging habits.

While the Red-finned Blue-eye is only found in the Edgbaston Spring Group in the northeast of the Desert Channels region, Salt Pipewort is found in numerous spring groups across Queensland, western New South Wales and northern South Australia.

Because of their close association with water sources, foraging feral pigs have a dramatic detrimental effect on the biodiversity of wetlands and freshwater ecosystems, and are considered a threat to the habitat of the Australian Painted Snipe. They also degrade water quality, and destroy the aquatic vegetation habitats of a range of small aquatic and terrestrial animals.

Soil disturbance or digging while foraging for subterranean food (roots, tubers, soil invertebrates and fungi) can result in large expanses of deeply turned soil in highly fruitful foraging patches. Diggings can also cause hidden ecological damage such as disrupting soil nutrient and water cycles, changing soil micro-organism and invertebrate populations, changing plant succession and species composition patterns and causing erosion. This threatens the relatively small habitat area of the Bulloo Grey Grasswren, which straddles the Bulloo River and Cooper Creek.

Plant species richness declines to zero in the presence of extensive pig diggings: all species within the diggings are initially killed or severely damaged. While the loss of a few individual plants in diggings should have no impact on the survival of the species, when an individual species has a localized distribution, or is regarded as rare or endangered, pig diggings may influence the survival of that particular species.

Disease

Feral pigs are amenable hosts to a number of endemic and exotic diseases, they are also suitable carriers (vectors) for disease and parasite spread.

Brucellosis and Leptospirosis, the two most common diseases found in feral pigs in Australia, result in birth defects, abortion and infertility in both humans and livestock. Additional zoonoses (diseases that can be transmitted directly to humans) carried by feral pigs are Melioidosis, Q Fever, Ross River Fever and Dengue Fever. Leptospirosis and Q Fever can be fatal.

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Wallowing and digging damage can be clearly seen around this Channel Country waterhole. (image courtesy of Leigh Deutscher)

Most human infections occur through contact with pig blood, meat or urine or by inhalation of infectious airborne organisms during the butchering process (especially opening the abdominal cavity), or by eating undercooked feral pig meat. If you have to butcher feral pigs, wear suitable protective clothing (mask, goggles, strong rubber gloves and plastic apron and boots), and thoroughly wash your hands afterwards.

Feral pigs could also have a role in spreading exotic diseases and parasites that are transmittable to humans. These include Japanese Encephalitis, Rabies, Screw Worm Fly and Trichinosis.

Known parasites of feral pigs in Australia are Acariasis (biting and burrowing lice), Fascioliasis (liver fluke worm), Gastro-intestinal Helminthiasis (intestinal roundworm), Hydatidosis (hydatid tapeworm) and Sparganosis (spirometra erinacei tapeworm).

In regards to Foot and Mouth Disease, pigs are considered ‘amplifying hosts’ - they can excrete very large quantities of the virus in their exhaled breath. Cattle are very susceptible and can be infected by inhaling small quantities of the virus - there can be enough virus in a single exhaled pig breath to contaminate 400 cattle.

Blood samples taken at autopsies during Desert Channels Queensland’s Channel Country aerial shooting programs confirmed the presence of Meliodosis, Leptospirosis and Brucellosis. Parasites including thorn headed worms (Macracanthorhynchus hirudinaceus) were also found in several animals on the Barcoo River system.

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There is no silver bullet for feral pig control; the best results are achieved where the control program uses an integrated suite of control techniques. Each control technique has a role to play in managing this pest, depending on the season, environment, landscape, population and production systems involved. For example, fencing is only viable where high-value crops need to be protected; aerial shooting is not cost-effective when populations are low or vegetation is dense.

Because feral pigs roam the landscape, control activities on one property are of limited value if control is not undertaken on surrounding ones at the same time - coordination is key. The most effective control is achieved when all stakeholders are involved and timing and techniques match conditions and location.

Animal welfare is an ever-present issue with feral animal control programs. In this context, aerial shooting by trained and competent marksmen is probably the most humane method.

Landholder obligationsIn simple terms, a feral pig is a domestic animal running wild; when captured and penned in an escape-proof enclosure, it ceases to be a feral pig and is considered domestic. To keep domestic livestock you must be a registered biosecurity entity with an individual Property Identification Code (PIC) number. If you keep pigs, you must record them as you do other livestock; this is critical should there ever be a disease outbreak.

Under local government regulations there may be other restrictions and obligations on the keeping of pigs. Check with your local council.

The Queensland Biosecurity Act 2014 classifies the feral pig a restricted invasive animal, and states: It must not be moved, fed, given away, sold, or released into the environment without a permit. The Act requires everyone to take all reasonable and practical steps to minimise the risks associated with invasive plants and animals under their control.

At a local level, each local government must have a biosecurity plan that covers invasive plants and animals in its area. This plan may include actions to be taken on certain species. Some of these actions may be required under local laws. Contact your local government for more information.

An animal ceases being considered an invasive restricted animal (feral) if a person is keeping it and has become a registrable biosecurity entity to keep that designated animal. Feral pigs can be considered as designated animals if a person keeps them.

In relation to a pig, The Act defines feral as:

1. A feral animal is an animal that—(a) is living in a wild state; and(b) is not being farmed or kept for any other purpose.

2. For paragraph 1(b), an animal is being farmed or kept for another purpose only if it is kept in an escape-proof enclosure, cage or other structure.

The Queensland Biosecurity Act 2014 designation of feral pigs supersedes all designations and classifications under earlier Queensland legislation.

control

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Aerial shooting is a cost-effective way of quickly reducing a large population in relatively open country.

HuntingAs a control element, hunting is really only useful for mopping up remnants after a control program such as baiting, not in making the initial reduction in population numbers. Producers need to weigh up the limited population control benefits of allowing hunting, with the potential adverse impact of livestock disturbance.

Hunting feral pigs can be broken into three categories: game meat harvesting, recreational hunting and Aboriginal subsistence hunting.

The commercial returns of the game meat industry built on harvesting feral pigs is dwarfed by the dollar value of damage caused by feral pigs to both agriculture and the environment, not to mention potential human health implications from diseases.

Game meat harvesting depends on economic viability, and once populations are reduced or dispersed, it is no longer worth the harvesters’ while. In addition, game meat harvesters generally only target adult pigs: smaller pigs have similar input costs (time, fuel, bullets) for less return. Therefore, there is usually still a viable population remaining to quickly rebound when harvesters give up.

Recreational hunting with rifles, bows, and dogs is more likely to disperse the population

than make an appreciable effect on numbers; however, recreational hunters will sometimes scour the landscape for that elusive, solitary animal. On the other hand, lost dogs may lead to livestock predation if they establish a wild dog population.

While research shows that hunting, on its own, will only reduce numbers by 15 to 20 percent, the big advantage hunting has over baiting, for instance, is that it poses little threat to non-target species, and costs the landholder nothing.

Aerial shootingWhile aerial shooting can be expensive, it is an effective, efficient, all-year-round way to quickly reduce feral pig numbers, and is particularly useful in inaccessible areas. However, because it becomes more expensive as numbers reduce, it should be only one of a number of control methods used.

Generally, aerial shooting works best when the pigs are foraging in the open, away from cover. In summer, this is early morning and late afternoon, while in winter or on cooler, overcast days it can be all day.

However, in winter and overcast weather, feral pigs tend to spread out across the landscape,

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The batteries and memory cards need to be changed in monitoring cameras every couple of months.

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particularly if there has been rain and there is plenty of surface water. Although not always practical, waiting for a dry summer when the population congregates around the remaining waters is a good option: it reduces flying time and, consequently, the cost per pig. Conversely, flood time in the Channel Country can present a good aerial shooting opportunity as many feral pigs can become marooned on islands.

Desert Channels Queensland has used aerial shooting extensively during its six year Channel Country Feral Pig Program, and it has proven very successful, especially first time around when the pigs had not previously been exposed to this technique. Before pigs have developed any avoidance behaviour, they are easily flushed by the noise of the chopper; this makes dry season shooting around remaining waterholes a very cost-effective strategy.

Aerial shooting should be carried out by accredited marksmen using a large calibre rifle. Companies operating helicopters must be accredited for the task by the Civil Aviation Safety Authority, and the pilot must be endorsed for low level operations. Aircraft must be fit for purpose and planning of flights needs to account for payload and ambient temperatures, especially if control activities occur during hot weather. A helicopter with a smaller payload and less power may be cheaper to run per hour, but not as efficient in the long run because of less fuel load and shorter flying time between refueling.

To maximise kill rates, always shoot the pigs in sequence, starting at the tail of the mob, and moving forward. This allows the remaining pigs to be picked off as they continue to flee as a cohesive mob, following the leader.

In favourable terrain and conditions, 80 percent population reduction has been achieved with a single aerial shooting.

MonitoringMonitoring feral pig populations is a necessary part of strategic control. Initial surveys of population numbers and distribution provide important information on which to base strategic and operational decisions. Follow-up monitoring is critical for determining the effectiveness of control activities, and for informing the timing, and possible modifications, of future work.

Somewhat counter intuitively, direct observation is the least reliable method to ascertain the presence and numbers of feral pigs in an area. They tend to stay under cover during the day, particularly in the hot weather, moving out to forage in the evening and returning to cover soon after daylight.

Tracks, pads, dung, diggings and fence damage are far better indications of presence and numbers. In sheep country, a low lambing percentage with little or no sign of carcasses is a good indicator of feral pig predation - a few adult pigs can cause significant lamb mortality.

In relatively open country, like the Channel Country, aerial surveys can be conducted of areas where coordinated, large-scale control work has not previously been done. A high-wing, four-seater aircraft, which gives excellent visibility to a spotter at either side has proven effective, as has a voice recording device for each spotter. There is also an iPhone and iPad app called Distance Sampler which is specifically designed for surveying feral animals.

Aerial surveys in a dry summer when all the feral pig population is congregated around remaining waterhole and dams, have proven effective. The low-level flight will flush the pigs from cover, allowing spotters on each side of the aircraft to count and record numbers.

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Motion sensor cameras, strategically placed at key watering points by Desert Channels Queensland, have allowed ongoing monitoring to accurately predict the distribution and density of feral pigs encountered on subsequent shoots.

Desert Channels Queensland has also developed a smartphone and tablet weeds and feral animals app through Fulcrum. Access to this app is free for landholders, and it allows users to record sightings of feral animals in real time, even when there is no mobile phone service - really useful in most of the Desert Channels region. When a mobile phone or wi-fi service is available, the device uploads the data to the cloud-based Fulcrum server; it is then immediately visible to anyone with access. Contact info@dcq.org.au or 07 4658 0600 for your free login details and instructions.

FeralScan is another free, app-based, offline-capable, data collection tool. It was designed by the Invasive Animals Cooperative Research Centre (CRC) based on feedback from producers, and allows the sharing of data, alerts and notification within discrete groups. For more information or login details, contact FeralScan at peter.west@invasiveanimals.com or 0407 622 191.

Collecting and sharing data on feral pig distribution is the foundation on which successful control programs are built. Without good intelligence, even the best run activities may not be focussed and effective.

Animal welfareWhile Feral pigs are wild animals and cause great damage to production and the environment, and threaten human health, it is important to address animal welfare and human safety issues, no matter what feral pig control methods are used.

When ground shooting, head shots are preferred; with aerial shooting, chest shots are preferred, with a second chest or head shot to ensure a quick death. Shooting campaigns should be timed to avoid recently farrowed sows so dependant piglets are not left to die of starvation. Farrowing can generally be expected to coincide with the wet season when there is plentiful food.

If using dogs to locate pigs, they should be well trained and the operators should be skilled and experienced. Dogs should be protected from tusk injuries by neck, chest and body guards. Ideally, they should only be used to locate pigs, rather than attack and pull them down.

Poisoning is the most cost-effective control method. The success of a baiting campaign depends on the timing, bait material, the poison used and the placement of the baits, along with the availability of natural pig food - in a good season, feral pigs may not be inclined to take baits.

Trapping is generally considered the most humane method of feral pig control, as long as the traps are constructed so as to minimise injury, and regularly checked to ensure the animals are not food or water stressed. Trapped animals should be approached cautiously as their flight instinct causes them to become agitated and risk impact injury on the sides of the trap.

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Once trapped, feral pigs should be destroyed as soon as possible (image courtesy of FeralFix).

TrappingTrapping is a niche control method best suited to remove small, localised populations. It works best where there is limited natural food and water - limited natural food means feral pigs are more likely to enter a food-baited trap, and limited water means the environment is already concentrating the pigs in specific areas. Compared with other control methods, trapping has a high initial cost, but the material is generally long lasting and reusable, so the cost can be spread over many years. Grain for pre-feeding and trap baiting is another expense, and while meat can be used to bait traps, it must be contained in such a way (e.g. a mesh box) that the pigs can’t actually eat it. It is illegal to feed meat or meat products to feral pigs in traps.

Traps are also labour-intensive to establish and maintain. However, many landholders like the method as it can be incorporated into routine property work, and allows them to see how many pigs they are removing from the landscape. Trapped pigs are also a potential income source from the game meat industry.

Pigs have poor temperature regulation, which is why they wallow to keep cool, so traps should be set in shade where possible and checked at least once a day.

Improvements in trap design and a greater understanding of feeding behaviour have enabled trapping to become more species specific, posing minimal threat to non-target animals.

Trapping should be considered an ongoing process, not a discrete event like a shooting or baiting campaign. Because pigs are such intelligent animals, successfully trapping them requires patience, time and effort. And it is important to keep dogs away from the trap sites as feral pigs have a keen sense of smell and regard dogs as a predator. Also keep human activity to a minimum to avoid odour contamination.

An effective trapping program hinges on experience; patience; trap design, placement, quantity and maintenance; as well as palatable bait material with which to pre-feed (condition the pigs to the food source) and then tempt them into the traps.

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Pros

• environmentally friendly and humane

• suited to small areas of high value

• number controlled is known; carcasses can be removed

• flexible technique that can be fitted into routine property activities

• well-designed traps can be moved and reused as necessary

• offset costs through sale of pig carcasses

• non-target species can be released

• can be used when poisoning is impractical, or to follow up other techniques

• doesn’t interfere with normal pig behaviour

Cons

• initial cost of material and time to build and maintain

• large amount of bait material required

• labour intensive compared to other techniques

• enough traps required across the target area to ensure a high likelihood of all pigs encountering them

• slow way to reduce population

• may not keep up with breeding and migration

• not all pigs are trappable - some are wary, others conditioned by previous encounters

• likely ineffective if not well run

• each trap only has a drawing radius of about 800 metres

Advantages and disadvantages of trapping

A poor trapping strategy will not only fail to catch the target pigs, leaving them to continue causing damage and reproducing, but it also educates them about traps, making them more difficult to catch in the future. And, regardless of the quality of the baiting strategy, not all pigs can be trapped: some are super wary; some are trap escapees.

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A simple panel trap with molasses-laced grain as the bait food (image courtesy of FeralFix).

Common reasons for unsuccessful trapping programs are:

• unsuitable placement• insufficient traps• insufficient pre-feeding - including not

conditioning the full mob before setting the gate

• incorrect setting of the gate• trap too small for target group• no natural food shortage• large population, widely distributed

Bait material

Rotting fruits and fermenting grains are two highly attractive foods for pigs. Pigs’ sense of smell is similar to that of dogs, so the stronger the odour, the more widely the feral pigs will be attracted to the bait food. It may be necessary to experiment to get the best results, but soaking grain in water for a week gives it a very strong odour.

Strategy

Site selection is one of the most critical success factors for trapping. Areas of fresh diggings, on pig pads and close to water are ideal.

Before the traps are even brought on site, pre-feeding should occur to accustom the pigs to the bait material, and maximise the number attracted to the area. Remote monitoring cameras are useful for observing numbers and behaviour.

Once the target animals are settled with the bait food, the trap material can be dropped on site so they become accustomed to the smell. If the pigs remain settled, the trap can be partly erected, leaving the gate side wide open, and the bait food placed inside. When they are relaxed about taking food from the back of the trap, the gate side can be completed, but with the gate wired open. Before the gate is set, at least three nights of feeding inside the trap are required to ensure the whole group is captured.

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If the available bait food has low palatability, molasses or an animal food additive called Carasweet can be added to increase its attractiveness. Research has shown that black or green food dye added to grain reduces consumption by birds by as much as 80 percent.

Interestingly, a small amount of waste engine oil or creosote poured over the trap posts or nearby trees (the higher up, the further the smell travels) will sometimes attract feral pigs.

Trap design

Traps are made out of either panels or continuous rolls of steel mesh anchored with steel pickets or to trees. A variety of different trap gates can be used, depending on the construction method of the trap.

Mesh should be non-reflective to prevent reflected moonlight from discouraging pigs from entering. If you don’t have access to aged, galvanised mesh, the shine can be taken off by spraying it with cheap household vinegar or any weak acid solution.

For strength, the steel diameter should be at least 5 mm. PestSmart’s standard operating procedure for trapping feral pigs recommends a mesh grid size of no more than 75 mm by 100 mm to minimise snout injury to charging pigs. If a larger mesh size has to be used, chainwire should be securely attached to the inside to prevent injury and piglet escape.

If open top traps aren’t at least 1.5 metres high, a roof or roof bars will be required to prevent trapped pigs from jumping or climbing out. Steel pickets should be driven on the outside at corners and weak spots, otherwise at 1.5 metre intervals. In soft ground, they should be driven at 45 degrees to prevent trapped pigs from lifting the mesh. Securely wire the mesh to the pickets, particularly at ground level and at 200 mm as these are the highest stress points from charging pigs.

Branches and other vegetation placed around and over the trap can disguise it as well as provide some shade for trapped pigs. When placed over the gate, branches can discourage non-target animals.

There are three basic trap types: panel, silo and box. As the name suggests, the panel trap is made from steel mesh panels. The silo trap is made from a continuous roll of mesh, while the box trap is small, portable and fully enclosed.

Simple panel traps can be made by wiring together overlapping sheets of mesh. A more sophisticated version has each sheet framed with pipe and interlocking like portable cattle yards. Panel traps are relatively easy to construct, dismantle and move. They can be strengthened by wiring together the tops of steels pickets on opposite sides of the trap.

Silo traps, so named for their vague similarity to temporary grain silo construction, are made from a single 10 to 20 metre roll of steel mesh in a roughly circular layout. While they can accommodate a number of different trap gates, the ends of the mesh itself can form a sprung ‘gate’ similar to traditional cattle ‘spear’ traps. They have greater capacity and strength than panel traps, and can also be strengthened with cross wires.

The box trap is designed to fit on the back of a four-wheel-drive and can be quickly and easily transported and set up by one person. Ones with sides lower than 1.5 metres need a roof to prevent pigs from escaping. They are best suited to individual problem pigs and small groups.

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As the pig pushes through this funnel gate, the stick keeping it open to encourage entry will drop out, allowing the gate to close (image courtesy of FeralFix).

Opposite page: Parasite in autopsied feral pig (image courtesy Leigh Deutscher).

Gate design

Gate design and operation are critical components of successful trapping. While they range from the simple to the complex, they all fall into a few basic categories: panel, funnel, side-swinging and drop.

With panel and funnel gates, measures to discourage the entry or capture of non-target species may be needed. Cattle can be excluded with of a couple of horizontal steel pegs across the entrance, just high enough to allow pigs underneath. A side-swinging gate can be held open with stick notched either end to catch on the mesh of the gate and the side of the pen, and placed low enough in front of some feed so when a pig pushes under the stick to get at the feed, it lifts the stick and releases the gate.

Panel and funnel gates are easy to make, operate quietly, and are unlikely to jam if the sprung ends are kept at least 50 mm off the ground. Both are constructed by bringing parallel mesh together into a funnel shape and tying the top together, allowing the bottom to spread and let pigs squeeze through. Cutting sharp ends on the mesh and turning them slightly inwards will stop pigs trying to back out when they are part way in.

Tension should be just enough to bring the mesh back together; too much tension can make if difficult for pigs to push through and cause them to lose interest. Propping the mesh ends apart with a 150 mm long stick will make it easier for the first pig to push through. As it does, it will dislodge the stick and the gate will close, but the sight of it feeding inside the trap will entice others in.

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Simple drop gate propped open - the first pig pushes the gat up as it enters, allowing the prop to fall and the gate to close (image courtesy of FeralFix).

The side-swinging gate, when correctly adjusted, also operates quietly. It is considered by some as the best feral pig trap gate design as small pigs can easily push it open. These gates are designed to close under a counterweight, spring or bungee cord, into an angle iron door frame that prevents captured pigs opening the gate by getting their snouts behind it. This gate can also be propped open with a small stick to entice the initial pig through.

Drop gates fall into two distinct categories: target activated like all previously mentioned gates, and user activated. Target activated gates are hinged at the top to pivot up and in when pigs push under them, then immediately drop closed; user activated gates operate in slides like a guillotine, dropping on electronic command from a remote observer.

Target activated drop gates, while robust and easily propped open, are relatively noisy closers, which may frighten other pigs. They are also harder for small pigs to push open.

A variation of this gate uses individually swinging bars or pipes, 50 mm apart, that close onto a bottom bar. This version is easy for pigs to operate as they don’t have to lift the full weight of the gate to enter - small pigs only have to lift one or two bars. However, it needs a robust hinge structure to prevent distortion under pressure from pigs trying to escape. Additional strength can be achieved by incorporating receiving recesses into the bottom bar to resist sideways pressure on the swinging bars when they are closed.

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Compared with the gates above, all of which can be made on site or by a handyman, user activated drop gates are factory made and controlled by sophisticated technology. While they are comparatively expensive items they have a number of features that set them apart:

• 2.4 metres wide so pigs have unrestricted access and no sense of confinement;

• several can be fitted to the one large trap enclosure;

• cameras monitor pig activity and send images to a remote operator via the mobile phone network or UHF radio - the gates are triggered by a return signal;

• gates are only closed when all of the target mob is inside the trap; and

• non-target species are eliminated because you can see what’s in the trap before you trigger the gates.

Disposal of trapped animals

Trapped pigs must be shot as quickly and humanely as possible and removed from the trap. The trap should be approached quietly as even the strongest trap can be breached by panicked feral pigs. A .22 calibre rifle is adequate for head shooting trapped pigs.

Be aware of the brain’s location in both full frontal and profile views, and make allowances for differing angles and elevations.

Frontal method: when aiming horizontally, target the intersection of lines from the base of each ear to the opposite eye.

Temporal method: when aiming horizontally, target the midpoint between the base of the ear and the eye.

Poll method: aim directly down at the midpoint between the base of each ear - this method is often used with box traps where the shooter can get above the trapped animals.

Images sourced with permission from the PIG001: Trapping of feral pigs standard operating procedure developed by Trudy Sharp - www.pestsmart.org.au/trapping-of-feral-pigs

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Poisoning

When poison can be safely used, it is the most effective method of achieving large scale population reduction for least cost and effort. Aerial baiting is one of the few available methods to quickly reduce a feral pig population over a large area, especially if it is inaccessible or remote.

In some quarters, baiting is considered an indiscriminate killer of non-target species, yet research has shown that 1080 (sodium fluoroacetate) baits have no effect on scavenging bird populations. Sodium fluoroacetate is the principal pig control poison in Queensland, and the Australian Pesticides and Veterinary Medicines Authority’s 2008 review of it stated:

Although poisoning of individual non-target species may occur, the use of 1080 is not likely to cause widespread or serious impact on non-target fauna at the population level.

A new, more humane and target-specific toxin, sodium nitrite, has been developed, but not yet registered. This may lead to a new commercial bait with, potentially, a lower poison classification than 1080.

Landholders who have completed the following chemical handling safety courses may apply to the Health Department for endorsement to purchase baiting products containing 1080, direct from the manufacturer. These courses are AHCCHM303A – Prepare and apply chemicals, and AHCCHM304A – Transport, handle and store chemicals.

PIGOUT® factory-made 1080 baits loaded ready for aerial baiting (image courtesy FeralFix).

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The effectiveness of a baiting campaign depends on the timing, bait material, the poison used and the placement of the baits, along with the availability of natural pig food - in a good season, feral pigs may not be tempted by baits.

While population reductions of up to 90 percent have been reported for baiting programs, between 60 and 70 percent is considered normal.

Bait meat hung overnight to drain (image courtesy FeralFix).

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Pros

• cost effective - low cost of baits and distribution

• fast, effective population knockdown

• most cost-effective method for extensive or inaccessible grazing areas

• the least labour-intensive method

• socially accepted in rural communities

Cons

• risk to some non-target species

• strict legislative requirements

• loses effectiveness when there are abundant alternative food sources

• some pigs may develop bait shyness

• animal welfare implications

Bait material

The ease of detection and palatability of baits are crucial to poisoning success. The bait material used should be either as similar to the natural pig food of the area as possible so the pigs recognise it as food, or so appealing they can’t resist it. Cost and availability will also be deciding factors in the selection of bait material.

Meat baits are highly acceptable to feral pigs, particularly in the Desert Channels region where they are generally deficient in protein, which is essential to successful reproduction. Scrubbers, brumbies, injured or discarded livestock and kangaroos are all inexpensive and accessible sources of bait meat.

Meat should be hung overnight to drain, then cut into 500 gram pieces as regulated by Queensland legislation, before being injected with 1080 by a licenced operator, usually supplied by your local council. The meat must not contain any bone material.

Grain bait may not have high uptake by feral pigs in the west as, apart from Channel Country swamps, there is little chance of grain featuring in their natural diet. Grain is generally more expensive than the meat alternatives; however, if a cheap source is available, it may be worth

exploiting. Bear in mind that conditioning pigs to grain will require a period of pre-feeding.

Fermenting by submerging a bag of grain in a drum of water for a week will make highly attractive once pigs become used to the taste. Adding meat meal, molasses or vanilla essence increases the attractiveness and detection of the baits. A smear of creosote or sump oil on a nearby tree or post is a good attractant, and will also deter most non-target species.

The so called factory bait, PIGOUT®, is a 1080-based, fish-flavoured cereal matrix commercially produced for ease of handling, resilience to aerial baiting and resistance to non-target species. Such commercial baits would be cost prohibitive for extensive baiting campaigns, but may be suited to small-scale campaigns in inaccessible areas.

The Invasive Animals CRC, with financial support from Meat and Livestock Australia, is working on another factory bait, with the 1080 replaced by sodium nitrite, a rapidly-lethal, more humane and more pig-specific toxin. PIGOUT® Econobait, a bite sized 1080 bait specifically for use in the HogHopper® has also been developed.

Advantages and disadvantages of poisoning

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Bait distribution

The most important factor is ensuring the majority of the feral pigs in the target area find and eat the bait. This is influenced by bait density, pig movements and distribution, and seasonal conditions which may change feeding habits.

During the dry season, strategically placing baits in refuge areas where pigs concentrate, is much more effective than broad scale, blanket distribution. However, in the wet season, pigs are dispersed and have a greater likelihood of encountering more widely distributed baits.

Baits can be distributed from vehicles or aircraft, or made available to pigs in a specific area via bait stations like the HogHopper®. The most cost-effective distribution method varies by location: aerial for extensive or inaccessible areas; vehicles for moderate areas, and bait stations for small, discrete areas.

Ground baiting should target areas of recent feral pig activity such as near lignum swamps, along pig pads and drainage lines and under thick cover around property dams. Ground baiting allows reasonably accurate placement of baits under bushes or other cover to hide them from birds.

However, in extensive grazing areas, the distances covered and the time and labour required to do it, make ground baiting a less attractive option.

In smaller areas, such as where ewes are lambing, and when grain is a cost-effective option, pre-feeding with fermented grain will condition the pigs to that food and improve their uptake of the baits and the effectiveness of the campaign. When putting out the baited grain, place a bucket of grain every 100 to 500 metres along your track.

Pros

• cheap and cost effective

• good for small areas of where impact is current

• bait can be strategically placed

• pre-feeding can maximise uptake

• pre-feeding can inform bait requirements

Cons

• risk to non-target species

• labour intensive and time consuming in extensive situations

• wide distribution of baits might preclude bait exposure to all pigs

• is seasonal dependant

• requires vehicle access

Advantages and disadvantages of ground baiting

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Bait stations are a more targeted ground baiting alternative. With this technique, pre-feeding is required to condition pigs to both the food and the source. Before substituting poisoned bait material, the pre-feeding should continue until the pigs feed for three consecutive nights to ensure they view the site and the grain as a reliable food source. This will greatly increase the success of the baiting program.

A simple low cost pre-feeder can be made out of two large plastic garden pots joined together rim to rim and anchored between two steel pickets. A slot cut in the bottom allows grain to trickle out while preventing over consumption and encouraging pigs to linger, which attracts even more pigs.

Once poisoned bait material is introduced, some can be buried around the bait station to prevent non-target species from accessing it. Rain will dilute the poison’s strength so baits should be replaced after exposure.

Mechanical bait stations have been designed that rely on the pigs’ lifting response with their powerful nose - other species are either not powerful enough or lack the required lifting response. These types of bait stations also reduce the amount of bait material used as there is no non-target consumption.

The HogHopper®, an innovative mechanical feeder, can be used in any terrain and with any bait type. Developed by the Invasive Animals CRC with financial assistance from the Australian Pest Animal Management Program, this feral pig-specific bait delivery system is available for purchase from Animal Control Technologies Australia Pty Ltd. Not only does this unit prevent stock and wildlife from accessing the poisoned bait, it also helps to maintain bait freshness and palatability.

Homemade bait station made from two large garden pots (image courtesy FeralFix), and the factory made HogHopper®.

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Aerial baiting, while not considered as effective as strategic ground baiting, is the most cost-effective and efficient bait distribution method for extensive or inaccessible areas. Areas of high feral pig activity or suspected refuges can be identified and targeted during aerial baiting. These include lignum swamps, dense vegetation such as Prickly Acacia thickets or woody weeds around property dams, as well as drainage lines.

Often, in less extensive grazing areas, economies of scale can be achieved by groups of landholders banding together to aerial bait their combined holdings.

Aerial baiting is particularly effective when pigs are forced to concentrate in smaller areas, such as when a drought leads them to congregate around remaining water sources, or when flooding restricts them to islands. In both cases, they will be food stressed and will more readily accept baits.

Bait abundance

The most effective bait density depends on the season and the feral pig population, so getting an estimate of numbers by direct observation or monitoring cameras can inform bait requirements. Research from Cape York suggests 12 baits per pig in the dry season when pigs are concentrated around waters, and 52 baits per pig during the wet when the population is scattered.

Remembering that numbers can vary widely with local conditions, feral pigs densities in the Desert Channels region are estimated to range from approximately four per square kilometre along watercourses to less than one per square kilometre elsewhere. In most cases, 30 baits per square kilometre is considered adequate.

When aerial baiting at 100 knots, dropping a bait every second will result in a 35 metre

spacing of baits, which is considered sufficient for high pig visitation areas like water channels.

According to research, around 80 percent of baits are found by feral pigs within the first two nights. However, up to 57 percent may be encountered by non-target species - the majority of meat baits are found by scavenging birds which do not consume enough for a lethal dose. Most baits were moved less than 20 metres and, because they were only partially eaten, still available to feral pigs.

Baiting timing

The best time to bait is when food, water and cover resources become less abundant, and only available in limited areas. During the dry season when pigs are protein deficient is ideal; most will be concentrated around remaining waters, subsisting on low quality food, and far more likely to eat baits.

Reducing non-target impacts

Compared to shooting and trapping, baiting is largely imprecise; however, by using bait placement, strategic timing and bait stations, contact with non-target species can be minimised.

Accurate placement, in anything but the broadest sense, is not possible with aerial baiting. However, it is more achievable with vehicle baiting where a practiced operator can land them under bushes in passing. Burying baits or rubbing them in dirt to camouflage them is only practical in intensive situations.

Research has shown that dyeing baits green or black makes it difficult for birds to locate them. Bird take can also be minimised by distributing baits in the late afternoon, but this runs the risk of disturbing pigs that have already begun foraging for the evening.

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Fresh meat 1080 baits loaded ready for aerial baiting (image courtesy FeralFix).

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Cons

• high cost of aircraft hire

• inability to accurately place baits

• uneconomic for small areas

• risk to non-target species

• can’t be boosted by pre-feeding

Pros

• effective for large population over large area

• more cost-effective on larger properties or in remote areas

• small landholders can scale up by banding together

• creates economy of scale with very large quantity of bait material

• not constrained by ground inaccessibility

Bait stations, which use pre-feeding to condition feral pigs to the food and the site, rely on either a mechanical device, or the feral pig’s robust defence of a feeding site, to exclude non-target species.

Available toxins

The most commonly used toxin for feral pigs is sodium fluoroacetate (1080), which occurs naturally in some Australian plants. Phosphorus, marketed as CSSP is considered inhumane.

A major concern with 1080 is the effect on non-target species, particularly scavenging birds and some endangered carnivorous animals. The Australian Pesticides and Veterinary Medicines Authority conducted a review into 1080 and found that while poisoning of non-

target animals does occur, when appropriate bait material, placement, density and timing are used, the impacts can be limited and do not seem to have a significant effect on the populations of non-target animals.

Yellow phosphorus (CSSP), previously sold as SAP, a very popular rabbit poison, is considered inhumane. It is toxic to a wide range of animal and bird species and can cause secondary poisoning from vomit and carcasses of poisoned animals.

Sodium nitrite is a food preservative ingredient that, in a concentrated dose, exploits a metabolic Achilles heel in pigs: their inability to overcome the effects of hypoxia caused by the toxin. It prevents oxygen reaching the tissues, causing the pig to go to sleep and die. It is considered safe and humane, and is in the process of being developed.

Advantages and disadvantages of aerial baiting

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Sodium fluoroacetate (1080):

• the only toxin recommended by the State Government for feral pig control

• fresh meat baits can only be prepared and supplied by accredited State or local government officers

• dogs are the most susceptible of all animals• occurs naturally in over 30 native plants,

including Georgina Gidgee (Acacia georgina) and Heartleaf (Gastralobium grandiflorum), commonly called Poison Bush

• native wildlife is generally more tolerant to it than are feral pigs

• is water soluble and biodegradable - leached by rain and breaks down naturally in soil

• neutralised by 25 mm of rain (anecdotal only)

• does not accumulate in the food chain• causes death in 6 to 8 hours• is not toxic itself, but is metabolised

into fluorocitrate which blocks a vital biochemical pathway causing cells’ energy supply to expire

• toxic effects are delayed so pigs die some distance from the bait site

• death results from heart or central nervous system failures

• colourless, odourless, tasteless• is an S7 poison• high concentration required (72 mg per bait

- 10 times higher than for wild dogs)• vomit from poisoned pigs creates a

potential hazard for domestic dogs

Yellow phosphorus:

• commercially available as CSSP - previously sold as SAP

• yellow, wax-like substance• pronounced taste and garlic-like odour• is absorbed through the skin but primarily

through the gastro-intestinal tract• causes acute pains, convulsions, liver

damage, bloody diarrhoea, skin eruptions, coma, collapse and death

• generally slow acting and inhumane• death takes from 2 hours to 5 days• is not soluble in water and does not break

down readily in the environment• is toxic to a wide range of bird and animal

species• can cause secondary poisoning from the

vomit or carcass of poisoned animals• is an S7 poison

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Sodium nitrite:

• new toxin• causes hypoxia - oxygen starvation• target-specific - non-target risk extremely

small• exploits pigs’ inability to overcome hypoxia• is humane (painless) - pigs become

lethargic, go to sleep and die• death usually occurs within 2 hours• has an effective antidote (methylene blue)• bait stability is not yet perfected

Overview of Queensland Government guidelines for 1080 use

1. Baits can only be laid on land described in a written agreement.

2. No baits can be laid on any stock route or reserve for travelling stock without local government approval.

3. No baits can be laid within 5 m of a fenced boundary.

4. No baits can be laid within 50 m of the centre line of a declared road.

5. No baits can be laid within 20 m of permanent or flowing water bodies.

6. No baits can be laid within 150 m of a dwelling

7. All adjoining neighbours must be given 72 hours’ notice prior to commencement of baiting.

8. Warning signs must be placed at all property entrances and on the boundary fronting public roads. They must be erected immediately before baiting commences and left in place for one month after the baits have been laid.

9. Wild game harvesters should be notified of baits being laid for at least 28 days after the program as they are required to declare that they have not removed feral pigs from areas where baiting has occurred.

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