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

Abstract

BACKGROUND An international effort to develop an acute and humane toxic bait for invasive wild pigs (Sus scrofa) is underway to curtail their expansion. We evaluated the ability to expose a population of wild pigs to a simulated toxic bait (i.e., placebo bait containing a biomarker, rhodamine B, in lieu of the toxic ingredient) to gain insight on potential population reduction. We used 28 GPS‐collars and sampled 428 wild pigs to examine their vibrissae for evidence of consuming the bait. RESULTS We estimated that 91% of wild pigs within 0.75 km of bait sites (total area = 16.8 km2) consumed the simulated toxic bait, exposing them to possible lethal effects. Bait sites spaced 0.75–1.5 km apart achieved optimal delivery of the bait, but wild pigs ranging ≥ 3 km away were susceptible. Use of wild pig‐specific bait stations resulted in no non‐target species directly accessing the bait. CONCLUSION Results demonstrate the potential for exposing a large proportion of wild pigs to a toxic bait in similar ecosystems. Toxic baits may be an effective tool for reducing wild pig populations especially if used as part of an integrated pest management strategy. Investigation of risks associated with a field‐deployment of the toxic bait is needed. © 2018 Society of Chemical Industry

Movement responses inform effectiveness and consequences of baiting wild pigs for population control

“…We deployed bait consistent with the baiting strategy developed for conditioning wild pigs for eventual deployment of toxic bait to meet objectives of a larger research objective (Lavelle et al, 2018b;Snow et al, 2018). This strategy was designed to maximize consistent and repeated visitation by wild pigs to bait sites while accustoming them to feeding from a wild pig-specific bait station (Snow et al, 2017b;Lavelle et al, 2018a).…”

“…Once wild pigs were observed visiting a site consistently or until 6 days, we introduced the bait station and started putting bait inside. After day 6, we started transitioning from whole-kernel corn to placebo HOGGONE ® (Animal Control Technologies Australia PTY Ltd, Victoria, AU; Snow et al, 2016) by slowly increasing the amount of placebo HOGGONE until a total of 20 kg of placebo and 1 kg of corn were offered, following Snow et al (2018). Placebo HOGGONE ® has been demonstrated to be equally attractive to wild pigs as whole-kernel corn (Snow et al, 2016).…”

“…Typically, baits stimulate both smell and taste for wild pigs, and provide sustenance (Lavelle et al, 2017). Prolonged applications of bait may be needed to overcome neophobic behaviors of some wild pigs (Muir and McEwen, 2007;Campbell et al, 2010;Lavelle et al, 2018b;Snow et al, 2018). As such, baiting programs usually rely on consistent and repeated visitations to bait sites before initiating population control activities (Campbell et al, 2006;Williams et al, 2011a;Snow et al, 2016;Lavelle et al 2018aLavelle et al , 2018b.…”

“…Application of bait may also be attempted to attract wild pigs from adjacent lands that cannot be easily accessed, to extend the reach of population control. Wild pigs reportedly respond to bait sites from radii of 1.5-1.7 km around the sites (Davis et al, 2017;Lavelle et al, 2018b;Snow et al, 2018). However, Lavelle et al (2018b) also demonstrated that the longer it takes for wild pigs to initially find bait sites, the lower their probability of repeated visitation to bait sites.…”

“…For example, trapping has been reported to remove only 62-83% of wild pigs that encountered traps (Choquenot et al, 1993;Saunders et al, 1993;Vernes et al, 2001;Williams et al, 2011b). Toxic baiting programs have reported higher potential for population control (e.g., 91-98%;Poch� e et al, 2018;Snow et al, 2018), but took >6 weeks to achieve in one study (Poch� e et al, 2018). Given that some wild pigs are not removed or not removed quickly, it is unclear how baiting programs impact the space-use and geographic distribution for the remaining population on the landscape.…”