Development of toxic bait to control invasive wild pigs and reduce damage

Abstract

Populations of invasive wild pigs (Sus scrofa) are increasing in many regions of the world, in particular the United States and Australia. Invasive wild pigs cause extensive damage to ecological resources and agriculture. Development and registration of a safe and humane toxic bait offers a practical and cost‐effective tool to control invasive species. Currently, no toxicants are approved for use on invasive wild pigs in the United States and those approved in Australia are under scrutiny because of concerns regarding humaneness and effects on nontarget species. We tested a newly formulated bait containing the micro‐encapsulated active ingredient, sodium nitrite (HOGGONE®; Animal Control Technologies Australia P/L, Victoria, Australia), that is considered humane and safer for nontarget species because it does not bioaccumulate. We examined palatability, lethality, and stability of the bait (i.e., fresh compared to 8‐month‐old bait) on groups of captive invasive wild pigs. We found HOGGONE® was a preferred food item, averaging 475 g of toxic bait consumed per animal during the first night offered. Consumption of HOGGONE® resulted in 95% mortality (53 of 56) in the treatment groups across 2 treatment nights. Most mortalities (98%) occurred during the first night the toxic bait was offered. Camera evidence suggested that deaths occurred within 3 hr post‐offering. The toxic bait was stable and effective up to 8 months post manufacture. Our results support current applications to register HOGGONE® for reducing damage from invasive wild pigs in the United States and Australia. Further research is required to evaluate HOGGONE® on free‐ranging invasive wild pigs using bait stations that exclude nontarget species. © 2017 The Wildlife Society.

Exposure of a population of invasive wild pigs to simulated toxic bait containing biomarker: implications for population reduction

“…Our findings build on previous research in New Zealand which found that 11 of 12 wild pigs (92%) succumbed to a similar SN toxic bait in a field setting . Similarly, a pen study in the USA found 95% efficacy for SN toxic bait on groups of wild pigs . For comparison with other toxic baiting strategies, a study in Australia found 63% consumption of biomarker baits by wild pigs using aerial baiting at 18 baits km −2 over an area of 70 km 2 .…”

“…Toxic baits offer a potentially cost‐effective option for controlling invasive wild pigs that could be broadly applied, provided that appropriate criteria are met for safety, humaneness, and efficacy . Specifically, a toxic bait containing the active ingredient sodium nitrite (SN), has been under development through a collaborative research effort between the National Wildlife Research Center (NWRC) of the United States Department of Agriculture, Texas Parks and Wildlife Department (TPWD), Invasive Animal Cooperative Research Center (IACRC), and Animal Control Technologies Australia Pty Ltd …”

“…Initial studies with SN toxic bait have demonstrated a high level of palatability and efficacy for wild pigs, and low secondary risks to non‐target scavenger species . A wild pig‐specific bait station has also been developed that successfully excludes non‐target species, including the capable and ubiquitous raccoon ( Procyon lotor ), preventing non‐target species from directly accessing the toxic bait inside the bait stations while still allowing access by wild pigs .…”

Evaluation of movement behaviors to inform toxic baiting strategies for invasive wild pigs (Sus scrofa)

“…The flash strategy, with the least amount of time for acclimation, achieved the lowest percentage of wild pigs that gained access to the bait station and should not be used operationally. The longer strategies resulted in nearly 90% of wild pigs accessing the bait stations, which when combined with a predicted lethality of 95% exceeds the estimated 52–70% population reduction needed to overcome the reproductive potential of wild pigs and keep their populations from increasing …”

Potential secondary poisoning risks to non‐targets from a sodium nitrite toxic bait for invasive wild pigs

“…Also, SN does not bio‐accumulate in tissues of animals because it is quickly metabolized or broken down, making SN an all‐or‐nothing toxin in which repeated sublethal exposures by scavenging animals are unlikely to have debilitating effects . Given these characteristics, a collaborative research effort between the Wildlife Services National Wildlife Research Center (NWRC, USA) of the United States Department of Agriculture, the Texas Parks and Wildlife Department (TPWD, USA), the Invasive Animal Cooperative Research Center (IACRC, Australia), Animal Control Technologies Australia (ACTA, Australia) Pty Ltd, and Connovation PTY Ltd (New Zealand) has developed an acutely toxic and highly effective lethal bait for wild pigs . This bait contains 100 mg/g (10%) of SN incorporated into an oil‐based matrix primarily comprised of peanut paste …”