Feral Pig Problems in Australia

Feral pig herd

Feral Pig Herd

Pigs were introduced into Australia with the arrival of European settlers. As settlers moved around the country, pigs were common domesticated companions. When these animals escaped from captivity they quickly established wild populations.

Spotty pig

Feral pig distribution in Australia in 1996.
Darker colours are areas of higher population density. (Source: BRS)

There are now estimated to be over 23 million feral pigs in Australia, concentrated predominantly in NSW, Queensland and across the top of the Northern Territory. In other areas of the country, small isolated populations are present.

The distribution and abundance of feral pigs fluctuates markedly between years based on environmental conditions and availability of food and water.

Agricultural Impact

The agricultural impact of feral pigs alone has been estimated to be more than $100 million annually. Impacts include lamb predation, infrastructure damage, crop and pasture damage, water fouling, disease spread, erosion, competition with stock and the huge costs of control. Lamb and goat predation is so serious that vast areas infested with pigs have become unusable for sheep farming. Lamb losses of around 15% to pigs is common but losses as high as 38% have been reported.

Disease amplification and transfer

Spotty pig

Spotty feral pig

Feral pigs are known to be vectors for a number of serious endemic and exotic diseases that have the potential to devastate commercial pig operations as well as transmitting to other animals and humans. Examples include Foot and Mouth Disease Virus (FMD), leptospirosis, brucellosis, melloidosis and Japanese encephalitis.

The threat of an exotic disease outbreak such as Foot and Mouth Disease has led to an increased effort to control feral pigs. Should such a disease enter the feral pig population, it would prove difficult and extremely expensive to eliminate.

The disease risk posed by feral pigs is regarded by some as a "ticking time bomb" for Australia if a serious exotic disease gains access to the wide-ranging pig population.

Environmental Impact

boar in groundwater

Boar in groundwater

Rooting and digging behaviour of feral pigs effectively ploughs up riparian vegetation and destroys native ecosystems, leaving these areas susceptible to soil loss, weed establishment and to the spread of disease such as dieback (Phytophthora cinnamomi) through native vegetation.

Feral pigs are opportunistic scavengers and prey on invertebrates, bird eggs, small mammals, reptiles, amphibians and soil invertebrates. Their selective feeding habits also affect the biodiversity of vegetation and creates competition for food resources of native species.

Feral pigs have negative impacts on native ecological systems including changing species composition, disrupting species succession and by altering nutrient and water cycles. Impacts can be direct or indirect, acute or chronic, periodic or constant, and may be influenced by changing seasonal conditions.

Feral pigs tend to congregate around water as they are highly susceptible to heat. The impact of the pigs wallowing in wetlands and watercourses totally destroys these finely balanced ecosystems.

They also prey on ground dwelling mammals, reptiles and birds, in some cases putting extensive pressure on rare and endangered species.

Feral Pig Biology

Feral pigs are found in a range of habitats across the country. They will move in response to seasonal conditions, primarily following food and water availability. They are susceptible to heat, and as such require access to water and suitable harbour.

Piglets

Sows and piglets

Feral pigs are opportunistic omnivores, feeding on anything from grains, fruits and plant material to newborn lambs and carrion from dead livestock, changing their diet depending on availability of food types.

Feral pigs are often found in groups of sows with their piglets, juvenile pigs or as individual adult boars. The group size can range from one solitary boar to herds of over 100 pigs or more.

Sows have a 21-day oestrous cycle and a gestation period of 112-114 days. Breeding is determined by the quality and quantity of food available. The litter size of feral pigs generally averages between 5 and 6 piglets but may be as high as 10 under good breeding conditions. Under such conditions, feral pigs have the potential to produce two litters within 12 - 15 months.

Feral pig control options

Trapping

Trapping is most useful where pig numbers are small, or where the property is close to populated areas where baiting and shooting are too risky.

Simple traps can be constructed inexpensively, but the need to constantly monitor the traps make these control methods time consuming and expensive in the long term.

Animal welfare issues are also critical in relation to the time the animals are in the traps and the construction of the trap to ensure minimal risk of injury to the trapped animals.

The traps usually do not alter normal pig behaviour, are a humane method of control, allow for pig carcasses to be safely disposed of, and can be used to opportunistically target small numbers of pigs.

Since other non-target species also eat the foods used to bait pig traps, the trap should be designed so that it can only be activated by a pig.

Fencing

Fencing is an expensive option, but can effectively prevent feral pigs from reaching lambs or grain crops if used before feral pigs become habituated to the food source.

Once habituated to the source of feed, though, fences will be breeched unless they are strong enough to resist a charging pig. Once breeched, the fence becomes an ineffective control measure.

Shooting

Shooting from the air is effective, but can be expensive.

Ground-based feral pig hunting is considered by many to be good sport. and can be a useful control measure provided the shooting is carried out by experienced hunters. There are considerable safety concerns for the shooters and their dogs when hunting on the ground.

Baiting

Feral pigs have been baited with a range of poison substances including sodium fluoroacetate (‘1080’), yellow phosphorus and warfarin (an anticoagulant poison to which pigs are highly susceptible).

The use of yellow phosphorus in carcass material as a bait for pigs poses significant risks for non-target poisoning of other animals. The use of phosphorus and anticoagulant poisons are not supported by state governments on humaneness grounds.

Controlling feral pigs with baits containing sodium fluoroacatate or ‘1080’ is legal, and very effective. However strict protocols apply for accessing or making the baits in all states and territories. See the State 1080 Regulations page on this site for more information.

When used as part of a properly planned and coordinated baiting programme, baiting can be an effective feral pig control measure. Animal Control Technologies in collaboration with the Invasive Animals Cooperative Research Centre and Meat & Livestock Australia has developed an effective manufactured feral pig bait called PIGOUT® Feral Pig Bait.

More information

The Invasive Animals Cooperative Research Centre has produced more information accessible at:
http://www.feral.org.au/pest-species/pig/


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