Case study: Feral pig HOGGONE® baiting trials in Goondiwindi, Qld

Since 2005, the Invasive Animals Cooperative Research Centre (IA CRC) and primary partners Meat and Livestock Australia (MLA) and Animal Control Technologies Australia (ACTA) have been developing a new humane feral pig bait, HOGGONE®. The baits contain sodium nitrite — a common preservative for human food — which in pigs causes methaemoglobin formation and rapid depletion of oxygen to the brain and other vital organs. A relatively humane and rapid death results in 1—2 hours, depending on the dose consumed.

During the development of HOGGONE®, field trials were conducted in various Australian states and territories (Qld, NSW, ACT, SA and WA) to test the bait’s effectiveness in a range of feral pig-affected habitats. One of these trials took place near Goondiwindi, a cropping and beef production region of southwest Queensland. Study sites were located on private stations about 50km west of Goondiwindi, which according to historical records are home to the greatest feral pig densities in the area.

In Queensland, feral pigs are one of the most widespread and damaging invasive animal species. Feral pigs are a Class 2 Declared pest animal in this state and landowners must take reasonable steps to keep their properties free of feral pigs, according to Queensland’s Land Protection (Pest and Stock Route Management) Act 2002.

This is a major challenge in remote and inaccessible areas of the state, and might only be possible through the use of economically viable and species-targeted tools such as HOGGONE®.

Aims

The aim of the trial was to reduce the feral pig population by at least 70% at the trial sites, without affecting non-target species. This knockdown rate is the minimum target needed for registration of HOGGONE® as a vertebrate pest population control product, and is also needed to achieve a substantial and lasting decline of a feral pig population.

Partners and management

The project was jointly sponsored by MLA, the former Bureau of Rural Sciences and the Commonwealth Department of Sustainability, Environment, Water, Population and Communities. Queensland Murray–Darling Committee (QMDC) regional coordinator for pest management, Darren Marshall, and the managers at the two stations were key participants in the trial. The Goondiwindi region was approved as a site for HOGGONE® registration trials by the Australian Pesticides and Veterinary Medicines Authority5 (APVMA; Category 23 PER9968). The use of animals in this trial was approved by the Queensland Department of Primary Industries and Fisheries Animal Ethics Committee. All baits were manufactured by ACTA (Somerton, Victoria).

Process

The field performance of HOGGONE® was determined by measuring the difference in pre- and post-toxic baiting feral pig activity, mob size and bait uptake. The trial was conducted in march 2011 following flooding summer rains. The size of the trial was based on the experimental design guidelines of the APVMA, which determined that a minimum of 50 animals are needed for treatment and for non-treatment sites not exceeding 100km2.

Feral pig hotspots within the treatment and non-treatment areas were identified and free-feed fermented grain placed at these locations. Researchers then introduced non– toxic HOGGONE® baits, installed motion-sensing cameras and noted the feral pig hotspots as GPS waypoints. Treatment and non-treatment areas each had a total of 10–15 bait stations. A similar number of independent monitoring stations were set up around water points within each of the areas to record species visits. Once non-toxic bait feeding and the number of attending animals had plateaued, toxic HOGGONE® baiting was started and continued until the bait was no longer being taken by feral pigs. Bait uptake usually ceased by about the third day of toxic baiting. All remaining toxic baits were then removed from the site and destroyed.

The following techniques were used to indirectly measure reduction in the feral pig population:

  • Bait uptake — calculated as the proportion of total HOGGONE® baits set out per day that were consumed by pigs.
  • Photograph/resight — motion-sensing infrared cameras were used at each bait station to count and identify individual feral pigs (using coat patches, colour, size, mob affinity). Baiting efficacy was determined by the reduction in the number of individual feral pigs attending bait stations after toxic baiting.
  • Independent monitoring points — activity plots were created around all water points in the treatment and non-treatment areas and monitored for target and non target species visits to establish a daily activity percentage.

Features of the study

The trial used indirect measures — bait uptake, photography/resight and water point monitoring — to assess HOGGONE® effectiveness while avoiding direct influence of the feral pig population and potentially causing bias in the results.
These same measures had been successfully used during trials for the now registered PIGOUT® bait6 and previous HOGGONE® trials in other habitats.

Results

  • HOGGONE® statistically achieved an 83% reduction in the feral pig population at Station one, despite excellent pasture conditions. This result was replicated a week later at Station two (86% reduction). A total of 279 pigs were involved in the trials.
  • Feral pigs not killed were either piglets not on solids or a small proportion of mature pigs that were adverse to the taste of the nitrite bait. More recent formulations of the bait are hoping to overcome this.
  • There was minimal interest in or uptake of baits by other animals in trial areas (eg cows, birds, goannas or kangaroos), although it was thought that two apostle birds and an Australian magpie lark may have taken remaining crumbs of toxic baits. The use of bite-sized Econobaits in the HogHopper™ will prevent this in the future.
  • Most feral pig carcases that were found, were located within 250m of the bait stations. Carcases displayed no evidence of physical stress and mobs generally died together. Carcase nirite residue assessment showed that undigested stomach contents was the only risk for secondary poisoning of scavengers.

What worked and why

  • The cooperation between regional pest managers (QMDC), landholders and researchers meant there was good use of local knowledge and logistical assistance to get the most out of the trial. For example, identifying population hotspots and pre-trial free feeding ensured a large number of feral pigs were successfully targeted.
  • Regional land coordinator and station managers saw first-hand how effective HOGGONE® was at controlling feral pigs in Queensland. They were impressed with the free-feeding process and uptake of HOGGONE® baits.
  • Use of technologies like motion-sensing infrared imagery proved to be highly successful for unobtrusive remote monitoring of individual feral pigs and assessing the overall population decline.
  • The population reduction and large total number of pigs involved meant that the Goondiwindi trial results were able to form a solid part of HOGGONE®’s national registration dossier.

What didn’t work and why

Feral pig populations were harder than usual to target because unusually high rainfall meant they were not concentrated around permanent water. Additional pre-feeding was needed to concentrate feral pigs at the bait stations.

Conclusion

These field trials in southwest Queensland showed HOGGONE® baiting can effectively achieve a significant and rapid knockdown of a feral pig population. Even without deployment via a HogHopper™, HOGGONE® baits posed little risk to non target animals in these trials.

In this study, results exceeded the minimum knockdown required for registration of HOGGONE® as a vertebrate pest control product. The national product registration process has ensured, through multiple trials, that HOGGONE® baits work well on the ground and across a range of feral pig habitats.

HOGGONE® should provide a humane and broadscale means of controlling feral pigs in Australia. With proven efficacy and target specificity, HOGGONE® and HogHopper™ are already highly anticipated by the landholders who have seen these technologies in action.

 

Author Invasive Animals CRC
Year 2013
Publisher Invasive Animals CRC
Pages 4
ISBN/ISSN PestSmart code: FPCS1
Control method Baiting
Region QLD
Documents PestSmart Case Study: Feral pig HOGGONE® baiting trials in Goondiwindi, Qld [1.1mb PDF]
Links PestSmart toolkit for Feral Pigs: https://www.pestsmart.org.au/pest-animal-species/feral-pig/