Feral pigs trapped behind fence
Feral pigs are difficult to control for a number of reasons:
- they are intelligent, adaptable and secretive. As they are nocturnal, they camp through the day in thick, inaccessible vegetation wherever possible
- their reproduction potential is such that repeated control programs must be conducted before any sustained population reduction is achieved
- their omnivorous feeding habits give pigs a wide range of available food sources, making successful pre-feeding difficult
- their home ranges are large (2-50 km2) so control programs must be conducted over a large area (often including several properties) to be effective.
Developing a pig control strategy
The strategic management of feral pigs is aimed at minimising the damage they cause to primary production and conservation areas, not merely to kill pigs.
Strategic management involves four key components:
- definition of the problem. First you need to define the true impact of feral pigs on the valued resource. This sets a justifiable cost of control
- management plan. Next it is important to determine the best combination of control methods for your control program. Often the most effective approach is to coordinate on a local and regional level
- implementation. Actions often involve the cooperation with neighbouring land managers, both private and public
- monitoring and evaluation. Monitoring determines the cost effectiveness of each control method and the overall efficiency of the strategy. Evaluation determines if and how management should be changed.
Determining best control methods
The area in which pigs are to be controlled needs to be assessed for pig activity. Logistic, economic and environmental conditions within the area need to be taken into account to develop a control strategy.
If pigs are living and feeding in inaccessible areas (swamps, rough terrain or in broadacre crops) where vehicle access is impossible or impractical, and/or pre-feeding will not successfully attract enough pigs for trapping or baiting, helicopter shooting may be the only alternative.
However, most situations will lend themselves to either poisoning or trapping, or a combination of control techniques.
If poisons can be used safely, this is the best method of removing the bulk of the pig population with the least effort, time and expense. A poisoning program can be pig-specific if a sound poisoning strategy is followed.
Trapping can be an extremely good technique between poisoning campaigns when pig populations are low or poisons cannot be used safely.
Where economically viable, electrified pig fencing may prove worthwhile around key management areas, such as lambing paddocks or seed production areas.
Shooting and dogging often displaces feral pigs from a property but generally has little impact on total numbers, and simply moves the problem elsewhere.
Trapping is an important technique as it is most useful in populated areas, on smaller properties (less than 5000 ha) and where there are lower pig numbers. Trapping can be useful in 'mopping up' survivors from poisoning programs. It is most successful when food resources are limited.
Trigger mechanisms for pig traps can be made pig specific and, therefore, pose little or no danger to other wild or domestic animals.
Advantages of trapping
- It is the safest form of control and can be safely undertaken on closely populated areas.
- It is flexible and can be incorporated into routine property activities, as it makes economical use of labour and materials.
- Carcasses can be safely disposed of.
- Traps can be moved and re-used. Good trapping makes use of opportunities as they arise.
- The cost of traps can be offset by selling trapped pigs.
- It does not alter normal pig behaviour so it enables a greater number of the total population of an area to be removed.
- It is more humane to pigs and non-target species.
- It can be time consuming, and expensive to construct and maintain.
- It must be checked regularly.
- It is not practical for large-scale control.
- Some pigs are trap shy.
Steps to good trapping
- All activities that will disturb normal feeding should be stopped, i.e. no shooting or dogging.
- Free feeding prior to activating traps is an essential part of successful trapping.
- Feeding sites should be placed where feral pigs are active, i.e. water points, holes in fences and areas containing old carcasses on which pigs have been feeding.
- Bait for traps must be the usual food of the pigs in that area. Pigs feeding on one crop, such as sugar cane, will often not take to an alternative food, such as bananas. However sometimes new baits are attractive, i.e. fermented grains are often attractive to pigs.
- The trap can be built around the feeding site, with feeding within the trap undertaken for several nights before it is set.
- The trap should be set every night and checked each day. If the trap cannot be checked daily, shade and water must be provided.
- Trapping should continue until no more pigs are caught. A change of bait can be tried. Again feed for one or two nights before re-setting the trap.
- Traps may be left permanently in locations frequented by pigs, and pre-baited and activated when fresh pig signs appear.
- If the trap is to be moved, feeding at the new site should start before the trap is relocated.
Poisoning is the most effective control method available that can quickly reduce a pig population.
Sodium fluoroacetate (1080) is recommended only authorised persons can supply 1080 baits to landholders. Contact Biosecurity Queensland or your local government for more information.
Phosphorus-based poisons are available but not recommended as they are unnecessarily inhumane, less effective than 1080 and can result in secondary poisoning of non-target species. Pre-feeding is the most important step in poisoning operations. Free feeding with unpoisoned bait should be performed for a number of days prior to laying poisoned baits. The number of feral pigs killed by a poisoning program is determined by the number of pigs that find the poisoned bait and eat sufficient bait to ingest a lethal dose.
Through the wise selection and presentation of bait material, landholders can be species selective in their poisoning program and avoid many of the unintentional effects of secondary poisoning.
Bait material such as fermented grains are ideal, as they are very attractive to pigs but not to other animals. Feral pigs are one of the few animals that will dig up bait. You can establish a free feeding routine so that pigs are the only animals feeding. They keep other non-targets away from the feeding site.
Helicopter shooting is effective in inaccessible areas such as broadacre crops, swamps and marshes where pigs exist in reasonable numbers and are observable from the air. The cost of control varies with pig density and the efficiency of the operators.
The weapons recommended are shotguns with buckshot (SG) cartridges and high-powered .308 rifles with a bullet weight in excess of 150 grains, preferably hollow point or soft point projectiles.
Ground shooting is not effective in reducing the pig population unless intense shooting is undertaken on a small isolated and accessible population of pigs.
Though an expensive option, fencing can offer successful pig control. If the crop or livestock you are trying to protect is valuable such as macadamia, then the investment in a pig proof fence should be seriously considered. The effectiveness of a pig-proof fence is related to how much is spent. Research has indicated that the most successful pig-proof fences are also the most expensive.
The most effective pig-proof fences use fabricated sheep mesh held close to the ground by a plain or barbed wire and supported on steel posts.
Electrifying conventional, non pig-proof fences greatly improves their effectiveness, if used before pigs have established a path through the fence.
Pigs will often charge an electric fence to get through, and unless the fence incorporates fabricated netting pigs often successfully breach the fence.
For crop protection or to avoid lamb predation, pig-proof fences need to be constructed before the pigs are a problem. Once pigs have habituated to feeding on grain or lambs in a particular paddock, fencing may be ineffective.