Exotic Animals - Major Pests
Feral Pig
Family: Suidae
Scientific names: Sus scrofa
Background
Feral pigs are large omnivorous mammals with powerful bodies and coarse hairy coats. Their thick necks, wedge-shaped heads and mobile snouts are used in feeding to uproot the ground and find prey or plant material.
Domestic pigs were first introduced to Australia during European settlement as a food source. Feral pig populations developed as a result of escapees or individuals that were allowed to wander in unfenced areas. In some areas, pigs were also introduced for hunting.
While the spread of feral pigs is not well documented, they were first identified as a pest in New South Wales in the 1880s. Today, it is estimated that there are between 13 million and 23 million feral pigs spread across approximately half of the continent (Victoria, New South Wales, Queensland and northern Australia).
Feral pigs require water daily and for this reason are generally located close to a permanent water source. Feral pigs reach sexual maturity at 7-12 months, and are able to produce one to two litters per year.
Impacts
Feral pigs are particularly destructive to the natural environment because they engage in ‘rooting’ behaviour to locate food. This rooting disrupts the seed bank, disturbs surface vegetation, alters soil composition, increases the growth of weeds, disperses the seeds of exotic plants, and destroys habitat utilised by native species. In addition, pigs are omnivorous, meaning that they eat a wide and varied diet including small animals and invertebrates. This reduces their availability as food for native species. Their rooting behaviour also increases soil erosion and increases siltation of rivers. Overseas, pigs have also been known to kill several species of tree ferns and epiphytes by felling or barking them.
Trampling and predation of eggs by feral pigs has also had significant impacts on native turtle species both overseas and in Australia. This damage is also likely to extend to the eggs and young of some bird species, however this has not yet been proven.
Feral pigs have also had a negative impact on agricultural systems because they trample cultivated crop species, destroy crops, damage irrigation systems and infrastructure, and reduce seedling recruitment. In addition, feral pigs have been associated with considerable losses of sugarcane each year. They have also been known to kill and eat up to 40% of newborn lambs.
In addition, feral pigs are capable of transmitting diseases including brucellosis, psuedorabies, leptospirosis, foot-and-mouth disease and Japanese encephalitis and the fungus Phytophthora cinnamomi.
Management Practices
There are a number of management strategies that may be implemented to control feral pigs, including:
- Baited trapping. This may be effective if traps are placed around waterholes where pigs congregate. This is relatively effective for smaller scale operations.
- Mustering. In the past pigs have been mustered for their meat.
- Aerial culling. This is an effective way of rapidly reducing feral pig populations if implemented correctly with appropriately trained personnel. Unfortunately, the effectiveness of aerial culling operations will vary across terrains, and it is often a very expensive procedure.
- Poison. In some instances, it may be appropriate to bait pigs using 1080. However, because of the foraging behaviour of feral pigs this is highly labour intensive and only effective over smaller localised areas. There are also risks of affecting non-target species using this method.
- Fencing may be used to prevent feral pig entry into particular areas, but it is not effective for population reduction.
