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Biomarkers have been used to quantify consumption of toxicants and other pharmaceutical baits by free ranging wildlife populations. Previous research has tested the efficacy and persistence of Rhodamine B (RB) as a biomarker in invasive wild pigs. However, little information is available about effects of RB on palatability of baits meant for invasive wild pigs, and studies have shown that the addition of RB to otherwise palatable baits reduces consumption by some species. HOGGONE® has been identified as an effective sodium nitrite-based oral toxicant for invasive wild pigs in trials conducted in captive pen trials. We simultaneously conducted five separate 2-choice tests to examine potential differences in consumption between HOGGONE® placebo paste (standard placebo) and HOGGONE® placebo paste containing 0.5% RB (RB placebo) in five groups of three invasive wild pigs. Each group was simultaneously presented with equal amounts of standard placebo and RB placebo paste for one night and monitored with remote cameras. Remaining bait was weighed and subtracted from the initial weight of both feed types to calculate consumption. There were no differences in the total amount of bait consumed or the time spent feeding between the two bait types across all five groups. Results of this study suggest that the addition of RB does not negatively impact consumption of HOGGONE® placebo paste by groups of invasive wild pigs. Thus, we provide more evidence that RB will be a useful tool for research on wild pigs, such as estimating proportions of free-ranging populations consuming baits that contain toxins or pharmaceuticals.

Invasive wild pigs (Sus scrofa) are a widely distributed and destructive invasive species throughout parts of North America, Australia, South America, Africa, and many island nations (Barrios-Garcia and Ballari 2012). The invasion of wild pigs is associated with extensive agricultural, ecological, and control costs (Hone 1995, Pimentel et al. 2000, Pimentel 2007). Wild pigs are expanding in distribution and population density throughout the United States and Australia (Bevins et al. 2014, Lewis et al. 2017, Snow et al. 2017b). These increases are attributed to intentional and accidental introductions by humans (Spencer and Hampton 2005, Barrios-Garcia and Ballari 2012), high reproductive potential (Mayer and Brisbin 2009), lack of predators (Bevins et al. 2014), human alterations to the landscape that improve suitability for wild pigs, and the adaptability of wild pigs to occupy a variety of landscapes and opportunistically feed on many food items (Seward et al. 2004). An international effort to develop an acute and humane toxic bait for invasive wild pigs is underway to assist in curtailing their expansion (Snow et al. 2017a). 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. Overall, we found that (74.1%) of wild pigs tested were positive for RB from consuming the RB bait. These wild pigs were sampled from an average distance of 0.61 km (SE = 0.04) from the nearest bait sites. 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. Most of the collared wild pigs visited >1 bait sites during the final night with biomarker deployment, leading to two relevant conclusions. First, the 18-day baiting strategy for locating, and accustoming wild pigs to the placebo bait and bait stations, was adequate for overcoming neophobic tendencies of wild pigs. Secondly, the spacing of the bait stations (i.e., 1 bait site per 0.75 km2) was adequate for exposing all wild pigs in between bait sites to the bait, and may have been expanded to expose more wild pigs. This study demonstrated the potential for exposing a large proportion of wild pigs to a toxic bait. Bait sites should be spaced 0.75-1.5 km apart, and closer will provide better efficacy. Approximately 18 days of coordinated pre-baiting should be sufficient for accustoming wild pigs to using the wild pig-specific bait stations and readily consuming a novel bait. Toxic baits may be an effective tool for reducing wild pigs 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.

BACKGROUND: Wild pigs (Sus scrofa) are an invasive and destructive species throughout many regions of the world. A sodium nitrite (SN) toxic bait is currently used in Australia and being developed for use in the US and other countries to combat the increasing populations of wild pigs. In the US, efforts to modify the Australian SN‐toxic bait and baiting strategy have focused on reducing issues with non‐target animals accessing the SN‐toxic bait spilled outside of bait stations by wild pigs. We tested and compared modifications for efficacy (with wild pigs) and hazards (with non‐targets) in north‐central Texas, US during summer (July 2021) and winter (March 2023) seasons. RESULTS: During both seasons we found that visitation to the bait sites declined 94–99% after deploying the SN‐toxic bait, and we found a total of 106 dead wild pigs, indicating considerable lethality for the local population. Prior to deploying the SN‐toxic bait, Global Positioning System (GPS)‐collared wild pigs were more likely to cease visiting bait sites during summer when foraging resources were abundant. Farrowing decreased visitation to bait sites during the winter. We observed no dead non‐targets during summer; winter results showed an average of 5.2 dead migrating birds per bait site (primarily Dark‐eye juncos [Junco hyemalis]) from consuming SN‐toxic bait spilled by wild pigs. The presence and winter‐foraging behaviors of migrating birds appeared to increase hazards for those species. CONCLUSION: The current formulation of SN‐toxic bait was effective at removing wild pigs during both seasons, however it is clear that different baiting strategies may be required in winter when migrating birds are present. Baiting wild pigs prior to farrowing during the winter, and during drier summers, may further improve efficacy of the bait. Reducing hazards to non‐targets could be achieved by refining the SN‐toxic bait or modifying bait stations to decrease the potential for spillage, decreasing environmental persistence if spilled, or decreasing attractiveness to migrating birds. © 2024 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Wild pigs (Sus scrofa) are a highly adaptable species that have invaded many regions and cause significant damage throughout the world. Ungulate‐proof fencing is increasingly used in conjunction with other control techniques to manage wild pig populations. However, little is known about how fencing affects wild pig space use behaviors and whether any changes may be exploited to increase efficacy of control activities. Our goal was to understand how wild pigs altered their space use behaviors in response to newly constructed fencing. Specifically, we examined for changes in space use area (home range and core area), increases in overlap with conspecifics, and shifts in space use as ungulate exclusion fencing was constructed on northern Guam from February 2021 to March 2022. Wild pigs closer to the fence had decreased space use. For every 200 m nearer newly constructed fence, home ranges and core areas decreased approximately 15% and 16%, respectively. When individual wild pigs were enclosed by the fence, those animals increased their home range overlap with conspecifics by approximately 76% compared to wild pigs outside the fence. Wild pigs shifted their home ranges 3 to 9 times more during the first part of fence construction when 68% of the fence was completed compared to all other time periods, with male wild pigs shifting greater distances than females by 1.15 times. The construction of ungulate fencing led to smaller space use areas of wild pigs on both sides of the fence and intensified use of the area inside the fence by wild pigs contained within (i.e., more overlap). Management activities nearer the fence should account for decreases in home range and core area size to maximize population control efforts (i.e., more densely spaced trap sites). Enclosed wild pigs should be eradicated quickly to minimize damages to sensitive flora and fauna and decrease disease risk from intensified movement behaviors inside the fence. [ABSTRACT FROM AUTHOR]

Contact among animals is crucial for various ecological processes, including social behaviors, disease transmission, and predator–prey interactions. However, the distribution of contact events across time and space is heterogeneous, influenced by environmental factors and biological purposes. Previous studies have assumed that areas with abundant resources and preferred habitats attract more individuals and, therefore, lead to more contact. To examine the accuracy of this assumption, we used a use-available framework to compare landscape factors influencing the location of contacts between wild pigs (Sus scrofa) in two study areas in Florida and Texas (USA) from those influencing non-contact space use. We employed a contact-resource selection function (RSF) model, where contact locations were defined as used points and locations without contact as available points. By comparing outputs from this contact RSF with a general, population-level RSF, we assessed the factors driving both habitat selection and contact. We found that the landscape predictors (e.g., wetland, linear features, and food resources) played different roles in habitat selection from contact processes for wild pigs in both study areas. This indicated that pigs interacted with their landscapes differently when choosing habitats compared to when they encountered other individuals. Consequently, relying solely on the spatial overlap of individual or population-level RSF models may lead to a misleading understanding of contact-related ecology. Our findings challenge prevailing assumptions about contact and introduce innovative approaches to better understand the ecological drivers of spatially explicit contact. By accurately predicting the spatial distribution of contact events, we can enhance our understanding of contact based ecological processes and their spatial dynamics. [ABSTRACT FROM AUTHOR]

Background: In 2018, a sodium nitrite (SN)‐based toxic bait for invasive wild pigs (hereafter wild pigs; Sus scrofa), was evaluated to determine its effectiveness in reducing local wild pig populations in Texas. Localized population reductions of >70% were achieved, but spillage of bait outside wild pig‐specific feeders (bait stations) caused by feeding wild pigs resulted in the deaths of non‐target animals. To evaluate risks to non‐target animals, we tested whether bait presentation influenced the total amount of bait spilled by wild pigs and estimated the associated risk to non‐target species. Results: We found that bait spilled outside bait stations could be reduced by >90% when compacted in trays, as opposed to being manually crumbled into pieces. We documented a mean spill rate of 0.913 g of bait per wild pig. Conservative risk assessments for nine non‐target species for which SN toxicity data exist indicate that there is relatively low risk of lethal exposure, apart from zebra finches (Taeniopygia guttata) and white mice. Our results indicate that there may be enough spilled bait per feeding wild pig to kill 9.5 or 3.5 individuals of these species, respectively. Other species assessed range from 0.002 to 0.406 potential mortalities per wild pig. Conclusion: We demonstrated that the amount of bait spilled by wild pigs during feeding and the associated risk to non‐target animals can be minimized by presenting the bait compacted in trays within bait stations. We recommend that baits be tightly compacted and secured in bait stations to minimize risks to non‐target animals from spilled bait by wild pigs. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Wild pigs (Sus scrofa) are invading many areas globally and impacting biodiversity and economies in their non‐native range. Thus, wild pigs are often targeted for eradication efforts. Age‐ and sex‐specific body measurements are important for informing these eradication efforts because they reflect body condition, resource availability, and fecundity, which are common indicators of population trajectory. However, body mass is often difficult to collect, especially on large individuals that require specialized equipment or multiple people to weigh. Measurements that can be rapidly taken by a single land or wildlife manager on any size wild pig without aid from specialized equipment would be beneficial if they accurately infer wild pig body mass. Our goals were to assess whether morphometric measurements could accurately predict wild pig body mass, and to provide tools to directly input these measures and estimate wild pig body mass. Using linear models, we quantified the relationship between body mass and morphometric measurements (i.e., body length, chest girth, ear length, eye to snout length, hindfoot length, shoulder length, and tail length) from a subset (n = 102) of wild pigs culled at the Mississippi Alluvial Valley, Mississippi, USA. We evaluated separate models for each individual morphometric measurement. We then used the model coefficients to develop equations to predict wild pig body mass. We validated these equations predicting body mass of 1592 individuals collected across eight areas in Australia, Guam, and the USA for cross‐validation. Each developed equation remained accurate when cross‐validated across regions. Body length, chest girth, and shoulder length were the morphometrics that best predicted wild pig body mass. Our analyses indicated it is possible to use the presented equations to infer wild pig body mass from simple metrics. [ABSTRACT FROM AUTHOR]

Toxic baiting of wild pigs (Sus scrofa) is a potential new tool for population control and damage reduction in the US. Field trials testing a prototype toxic bait (HOGGONE 2 containing 5% sodium nitrite [SN]), though, revealed that wild pigs spilled small particles of toxic bait outside of bait stations which subsequently created hazards for non-target species that consumed those particles, primarily passerine birds. To deter non-target birds from consuming particles of spilled bait, we tested four deterrents at mock bait sites (i.e., baited with bird seed) in north-central Colorado, USA during April–May 2020. We found a programable, inflatable deterrent device (scare dancer) reduced bird visitation by an average of 96%. Then, we evaluated the deterrent devices at SN-toxic bait sites in north-central Texas, USA during July 2020, where the devices were activated the morning following deployment of SN-toxic bait. Overall, we found 139 dead wild pigs at 10 bait sites following one night of toxic baiting, which represented an average of 91% reduction in wild pigs visiting bait sites. We found that deterrent devices were 100% effective at deterring birds from toxic bait sites. We found two dead non-target mice at bait sites without deterrent devices. We noted that deploying toxic bait in mid-summer rather than late-winter/early-spring reduced hazards to migrating birds because they were not present in our study area during July. We recommend using deterrent devices (i.e., novel, programmable, battery operated, continuous and erratic movement, and snapping sounds) to reduce hazards to non-target birds at SN-toxic bait sites. We further recommend deploying SN-toxic bait during seasons when migrating birds are not as abundant until further research demonstrates minimal risks to migrating birds. [ABSTRACT FROM AUTHOR]

BACKGROUND: Wild pigs (Sus scrofa) cause widespread environmental and economic damage, and as a result are subjected to extensive control. Current management strategies have proven insufficient, and there is growing interest in use of toxicants to control invasive populations of this species. In 2017 a low‐dose warfarin bait was federally approved for use in controlling wild pigs in the United States. However, no states have allowed use of this bait due to unanswered questions regarding welfare concerns, field efficacy, and non‐target impacts. RESULTS: All captive wild pigs fed 0.005% warfarin baits in no choice feeding trials succumbed in an average of 8 days from exposure. Behavioral symptoms of warfarin exposure included vomiting, external bleeding, abnormal breathing, incoordination, and limping. Postmortem examinations revealed hemorrhaging in organs and muscles, particularly the legs, gastrointestinal tract, and abdomen. Warfarin residues in tissues averaged 1.0 mg kg‐1 for muscle, 3.9 mg kg‐1 for liver, and 2.8 mg kg‐1 for small intestines. Field testing revealed wild pigs required extensive training to access bait within pig‐specific bait stations, and once acclimated, exhibited reluctance to consume toxic baits, resulting in no mortalities across two separate field deployments of toxic bait. CONCLUSION: Our results suggest wild pigs are susceptible to low‐dose warfarin, and warfarin residues in pig tissues postmortem are generally low. However, although warfarin‐based baits are currently approved for use by the US Environmental Protection Agency, further improvements to pig‐specific bait delivery systems and bait palatability are needed, as well as additional research to quantify efficacy, cost, and non‐target impacts prior to widespread implementation. © 2021 Society of Chemical Industry. This article has been contributed to by US Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

BACKGROUND: Wild pigs (Sus scrofa) are a destructive invasive species throughout many regions of the world. In 2018, a field evaluation of an early prototype of a sodium nitrite (SN) toxic bait in the United States revealed wild pigs dropped large amounts of the toxic bait outside the pig-specific bait stations while feeding, and thus subsequent hazards for non-target animals. We modified the SN-toxic bait formulation, the design of the bait station, and the baiting strategy to reduce dropped bait. We tested the modifications in Queensland, Australia (December 2018), Alabama, USA (August 2019), and Texas, USA (March 2020) under differing climatic and seasonal conditions for one night. RESULTS: Cumulatively we found 161 carcasses of all age classes of wild pigs using systematic transects. Remote camera indices indicated high lethality for wild pigs, achieving population reductions of 76.3 to 90.4%. Wild pigs dropped only small particles of SN-toxic bait (average = 55.5 g per bait site), which represented a 19-fold decrease from the previous trial. Despite this reduction, we found three Australian ravens (Corvus coronoides) in Queensland, two Virginia opossums (Didelphis virginiana) in Alabama, and 35 granivorous-passerine birds (mostly dark-eyed juncos [Junco hyemalis]) in Texas dead from consuming the dropped bait. We did not detect any population-level effects for those species. CONCLUSION: Our modifications were effective at reducing populations of wild pigs, but the deaths of non-target species require further steps to minimize these hazards. Next steps will include evaluating various deterrent devices for birds the morning after SN-toxic bait has been offered. [ABSTRACT FROM AUTHOR]

Oral baiting is a fundamental method for delivering toxicants to pest species. Planning baiting strategies is challenging because bait-consumption rates depend on dynamic processes including space use and demographics of the target species. To determine cost-effective strategies for optimizing baiting, we developed a spatially explicit model of population dynamics using field-based measures of wild-pig (Sus scrofa) space use, bait consumption, and mortality probabilities. The most cost-effective baiting strategy depended strongly on the population reduction objective and initial density. A wide range of baiting strategies were cost-effective when the objective was 80% population reduction. In contrast, only a narrow range of baiting strategies allowed for a 99% reduction. Cost-effectiveness was lower for low densities of wild pigs because of the increased effort for locating target animals. Bait avoidance due to aversive conditioning from sub-lethal dosing had only minor effects on cost-effectiveness when the objective was an 80% reduction, whereas the effect was much stronger when the objective was 99% population reduction. Our results showed that a bait-based toxicant could be cost-effective for substantially reducing populations of wild pigs, but for elimination it may be most cost-effective to integrate additional management techniques following initial toxicant deployment. The nonlinear interaction of cost-effectiveness, initial population size, and reduction objective also emphasized the importance of considering the dynamics of space use and bait consumption for predicting effective baiting strategies. Although we used data for an acute toxicant and wild-pig consumption rates, our framework can be readily adapted to other vertebrate pest species and toxicant characteristics. [ABSTRACT FROM AUTHOR]

Wild pigs (Sus scrofa; i.e., feral hogs, feral swine) are considered an invasive species in the United States. Where they occur, they damage agricultural crops and wildlife habitat. Wild pigs also depredate native wildlife, particularly ground‐nesting bird species during nesting season. In areas inhabited by wild turkeys (Meleagris gallopavo), nest destruction caused by wild pigs may affect recruitment. There is debate whether wild pigs actively seek ground‐nesting bird nests or depredate them opportunistically. To address this debate, in 2016 we examined the movements of wild pigs relative to artificial wild turkey nests (i.e., control [no artificial nests], moderate density [12.5–25 nests/km2], and high density [25–50 nests/km2]) throughout the nesting season (i.e., early, peak, and late) in south‐central Texas, USA. We found no evidence that wild pigs learned to seek and depredate wild turkey nests relative to nest density or nesting periods. Despite wild pigs being important nest predators, depredation was not a functional response to a pulsed food resource and can only be associated with overlapping densities of wild pigs and nests. Protecting reproductive success of wild turkeys will require reducing wild pig densities in nesting habitat prior to nesting season. © 2019 The Wildlife Society. Despite wild pigs being primary nest predators for wild turkeys, wild pigs did not show evidence of seeking nests and only depredated opportunistically. Reducing population densities of wild pigs is important in areas where wild turkey recruitment is low. [ABSTRACT FROM AUTHOR]

• Handling wild animals is risky and strategies to reduce risk should be considered. • Modified traps for the capture of wild pigs reduced trap-related injuries. • Enclosing occupied traps in shade cloth moderated flight behaviors. • Darting wild pigs in traps can be eased with trap modifications. Research on the ecology, behavior, and movements of wild pigs (Sus scrofa) often involves immobilization of study animals to attach GPS collars or other monitoring devices. In this process, it is important to minimize stress and injury to study subjects. Challenges in handling trapped wild pigs are common because multiple animals are often captured together, wild pigs exhibit intense fight-or-flight responses, large traps provide space for severe trap-related injuries, and immobilization drugs are less effective on excited wild pigs. We trapped and handled 148 wild pigs in corral traps in TX, USA, and evaluated two trap modifications for alleviating these issues, including: 1) using tightly spaced wire mesh for trap walls, and 2) enshrouding traps with a visual barrier prior to handling. We identified that the tightly spaced wire mesh of horse panels (10.2 × 5.1 cm) reduced injuries 88% compared to more widely spaced mesh sizes (10.2 × 10.2 cm or larger). We documented that it took an average of 71.6 s to enshroud traps, which corresponded to a rapid reduction in flight behaviors from wild pigs (i.e., ≤52.6 s until stationary). Enshrouding corral traps facilitated a 28% quicker delivery of chemical immobilization drugs via darting as wild pigs became inactive. We recommend using tightly spaced mesh of horse panels to reduce trap-related injuries and incorporation of trap shrouds to facilitate delivery of chemical immobilization drugs when handling wild pigs. [ABSTRACT FROM AUTHOR]

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 A new toxic bait is under development to curtail invasive wild pigs in the USA and Australia. Proper baiting strategy can expose most wild pigs in a large population to this bait. [ABSTRACT FROM AUTHOR]

BACKGROUND: Invasive wild pigs damage agriculture, property, and natural ecosystems. To curtail damage, an effective and humane toxic bait containing microencapsulated sodium nitrite is under development. Strategies for delivering the toxic bait are needed to establish adequate spacing of bait sites, and for simultaneously accustoming wild pigs to the novel bait and wild pig‐specific bait stations designed to exclude non‐target species. RESULTS: We monitored movements of 32 Global Positioning System (GPS)‐collared wild pigs relative to 41 bait sites containing placebo bait. Among the bait sites, we compared three experimental baiting strategies (and a control) to evaluate which strategy led to the most wild pigs accessing the placebo bait inside bait stations. We found that bait sites should be spaced 0.5–1 km apart to maximize opportunities for all wild pigs to find and utilize the bait sites. Baiting strategies that allowed ≥ 15 days for accustoming wild pigs to bait stations were most effective and resulted in nearly 90% of wild pigs accessing the placebo bait inside the bait stations. Bait stations excluded all non‐target animals, except one instance with a raccoon (Procyon lotor). CONCLUSION: These results demonstrate the potential for toxic bait to be an effective tool for reducing populations of wild pigs with minimal risks to non‐target species, if optimized delivery procedures are followed. © 2018 Society of Chemical Industry Strategies are needed for safe and efficient delivery of toxic bait to control damage by wild pigs. We present refined strategies for maximizing access to bait stations by wild pigs. [ABSTRACT FROM AUTHOR]

BACKGROUND An acute and orally delivered toxic bait containing micro-encapsulated sodium nitrite (MESN), is under development to provide a novel and humane technology to help curtail damage caused by invasive wild pigs ( Sus scrofa). We evaluated potential secondary risks for non-target species by: testing whether four different types of micro-encapsulation coatings could reduce vomiting by invasive wild pigs, testing the levels of residual sodium nitrite (SN) in tissues of invasive wild pigs, testing the environmental persistence of SN in vomitus, and conducting a risk assessment for scavengers. RESULTS Micro-encapsulation coatings did not affect the frequency of vomiting. We identified no risk of secondary poisoning for non-target scavengers that consume muscle, eyes, and livers of invasive wild pig carcasses because residual SN from the toxic bait was not detected in those tissues. The risk of secondary poisoning from consuming vomitus appeared low because ∼90% of the SN was metabolized or broken down prior to vomiting, and continued to degrade after being exposed to the environment. Secondary poisoning could occur for common scavengers that consume approximately ≥15% of their daily dietary requirements of digestive tract tissues or undigested bait from carcasses of invasive wild pigs in a rapid, single-feeding event. The likelihood of this occurring in a natural setting is unknown. The digestive tracts of poisoned invasive wild pigs contained an average of ∼4.35 mg/g of residual SN. CONCLUSION Data from this study suggest no risks of secondary poisoning for non-target species (including humans) that consume muscle, liver, or eyes of invasive wild pigs poisoned with a MESN toxic bait. More species-specific testing for scavengers that consume digestive tract tissues and undigested bait is needed to reduce uncertainty about these potential risks. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The eruption of invasive wild pigs ( IWPs) Sus scrofa throughout the world exemplifies the need to understand the influences of exotic and nonnative species expansions. In particular, the continental USA is precariously threatened by a rapid expansion of IWPs, and a better understanding of the rate and process of spread can inform strategies that will limit the expansion., We developed a spatially and temporally dynamic model to examine three decades (1982-2012) of IWP expansion, and predict the spread of IWPs throughout the continental USA, relative to where IWPs previously inhabited. We used the model to predict where IWPs are likely to invade next., The average rate of northward expansion increased from 6·5 to 12·6 km per year, suggesting most counties in the continental USA could be inhabited within the next 3-5 decades. The spread of IWPs was primarily associated with expansion into areas with similar environmental characteristics as their previous range, with the exception of spreading into colder regions. We identified that climate change may assist spread into northern regions by generating milder winters with less snow. Otherwise, the spread of IWPs was not dependent on agriculture, precipitation or biodiversity at the county level. The model correctly predicted 86% of counties that were invaded during 2012, and those predictions indicate that large portions of the USA are in immediate danger of invasion., Synthesis and applications. Anti-invasion efforts should focus along the boundaries of current occupied range to stop natural expansion, and anti-invasion policies should focus on stopping anthropogenic transport and release of invasive wild pigs. Our results demonstrate the utility of a spatio-temporal examination to inform strategies for limiting the spread of invasive wild pigs. [ABSTRACT FROM AUTHOR]

Wild pigs (Sus scrofa) are one of the most successful invasive species globally and are often implicated in agricultural damage. This damage is expected to increase as ranges of wild pigs expand, impacting the human food supply and increasing costs of food production. Our objective was to evaluate movement behaviors of wild pigs relative to resource availability and landscape features in an agriculture-dominated landscape, with a goal of informing management practices for reducing damage to corn. We monitored hourly movements of adult wild pigs relative to corn crops using GPS collars during the 2019 and 2020 growing seasons (Feb–Sept) in Delta County, Texas, USA. We generated movement metrics, home ranges for space-use analyses, and step selection functions to quantify selection for land cover types and landscape composition for each growth stage (i.e., pre-planting, establishment, vegetative, blister–milk, and dent–mature) and sex of wild pigs. We found that space-use and resource selection by wild pigs was dependent on corn growth stages and landscape composition, with more use as corn matured in fields closer to wooded areas. Most of the pigs had movement patterns that were categorized as residents with site fidelity near corn fields, yet some did make long-distance movements to select for corn. These results suggest that preventing damage is most important during the later stages of growth. If lethal control is not as effective or efficient before or during later growth stages of corn, managers should consider non-lethal methods, such as fencing to account for wild pigs that travel from afar, especially if corn fields are located near landcovers used as shelter for wild pigs. • Male wild pigs had significantly larger movements and home ranges than females. • Wild pig space-use changed with the progression of corn growth stages. • Most crop damage was caused by resident wild pigs living near the fields. • Wild pigs made long-distance movements to select corn in the later growth stages. • Corn growth stage and shelter adjacent to corn fields influenced selection of corn. [ABSTRACT FROM AUTHOR]

Wild pigs (Sus scrofa) are a highly destructive invasive species throughout North and South America, Australia, and many island nations. Where invasive, their populations are targeted for control to reduce damage. Controlling wild pigs often involves baiting to draw them into traps or entice them to consume a toxic bait. However, baiting can have mixed success in congregating wild pigs to focal areas long enough for control measures to ultimately be implemented. We sought to evaluate how environmental conditions (i.e., precipitation) and negative stimuli (i.e., proxy for exposure to previous control efforts) influenced use of bait sites by wild pigs. We compared visitation to bait sites during dry (2019–2020) and wet (2021) years, and between wild pigs that had been previously trapped and released in southcentral Alabama and northcentral Texas, USA. We found that drier years substantially increased use of bait sites by wild pigs (i.e., 119–136 % increase over 17 days). Similarly, wild pigs that did not experience negative stimuli had increased use of bait sites (i.e., 30–31 % increase over 17 days). We recommend that managers intensify their control efforts during drier periods to take advantage of susceptible behaviors of wild pigs during these times. We also recommend that control efforts focus on eliminating the potential for surviving wild pigs which may experience negative stimuli (e.g., narrow misses during trapping, shooting some wild pigs from a group, sub-lethal doses from toxic baits) and become educated against future efforts. • We evaluated how precipitation and negative stimuli influenced use of bait sites by wild pigs. • Drier years substantially increased use of bait sites. • Wild pigs that did not experience negative stimuli had increased use of bait sites. • We recommend intensifying control efforts during drier periods and using methods that do not aversely condition wild pigs. [ABSTRACT FROM AUTHOR]

Invasive feral swine (Sus scrofa) cause extensive damage to agricultural and wildlife resources throughout the United States. Development of sodium nitrite as a new, orally delivered toxicant is underway to provide an additional tool to curtail growth and expansion of feral swine populations. A micro-encapsulation coating around sodium nitrite is used to minimize detection by feral swine and maximize stability for the reactive molecule. To maximize uptake of this toxicant by feral swine, development a bait matrix is needed to 1) protect the micro-encapsulation coating so that sodium nitrite remains undetectable to feral swine, 2) achieve a high degree of acceptance by feral swine, and 3) be minimally appealing to non-target species. With these purposes, a field evaluation at 88 sites in south-central Texas was conducted using remote cameras to evaluate preferences by feral swine for several oil-based bait matrices including uncolored peanut paste, black-colored peanut paste, and peanut-based slurry mixed onto whole-kernel corn. These placebo baits were compared to a reference food, whole-kernel corn, known to be readily taken by feral swine (i.e., control). The amount of bait consumed by feral swine was also estimated using remote cameras and grid boards at 5 additional sites. On initial exposure, feral swine showed reduced visitations to the uncolored peanut paste and peanut slurry treatments. This reduced visitation subsided by the end of the treatment period, suggesting that feral swine needed time to accept these bait types. The black-colored peanut paste was visited equally to the control throughout the study, and enough of this matrix was consumed to deliver lethal doses of micro-encapsulated sodium nitrite to most feral swine during 1–2 feeding events. None of the treatment matrices reduced visitations by nontarget species, but feral swine dominated visitations for all matrices. It was concluded that black-colored peanut paste achieved satisfactory preference and consumption by feral swine, and no discernable preference by non-target species, compared to the other treatments. [ABSTRACT FROM AUTHOR]

Wild pigs (Sus scrofa) are a prolific invasive species throughout many regions of the world that cause extensive economic and environmental damage. Trapping is a common strategy for reducing their populations with baits (i.e., food) and attractants (e.g., scents) used to lure wild pigs into traps. However, there is little information on which scent attractants may attract wild pigs more readily and rapidly across regions and seasons. We examined 60 scent attractants for wild pigs that could be used to increase trapping success across three seasons (winter, spring, and fall) and in two geographic regions, including a warm and semi-arid rangeland (South Texas, USA) and a warm and moist mixture of upland and bottomland forests (South Carolina, USA). We found little evidence that most scents attracted wild pigs. Only strawberry extract and creosote bush oil increased the probabilities of visitation, and only in Texas during the fall season. No other scents attractants performed better than the control (i.e., no scent) in both study locations. More wild pigs visited sites during the fall season regardless of scent attractant used. The location of a site mattered more than which attractant was used, and a post hoc analysis revealed that distances to roads and water flowlines (i.e., permanent or ephemeral drainages, streams, and rivers) increased the probabilities of visitation during some seasons. We conclude there was no panacea scent that was more effective than controls in attracting wild pigs across regions and seasons. Placement of sites and seasonality were more important for attracting wild pigs, suggesting the location of traps or bait sites may be more important than the specific attractants used for management activities. Future research should include monitoring movements of wild pigs relative to scent attractants and evaluation of baits (e.g., food-rewards) for drawing wild pigs to sites. [Display omitted] • Sixty potential scent attractants were tested for ability to attract wild pigs across three seasons and 2 geographic regions. • There was no panacea scent that was more effective than controls in attracting wild pigs across regions and seasons. • More wild pigs visited during the fall season. • Location of the scents also increased wild pig visitation. [ABSTRACT FROM AUTHOR]

Wild pigs (Sus scrofa) are a destructive invasive species that cause extensive damage to agriculture throughout many regions of the world. In particular wild pigs damage corn more than any other crop, and most of that damage occurs immediately after planting when wild pigs excavate and consume planted seeds. We evaluated whether anthraquinone (AQ), a repellent, could be useful for protecting seed corn from consumption by wild pigs. Specifically, we conducted cafeteria-style tests at 16 bait sites for 6 nights using concentrations of: untreated, 0.5, 1.5, and 3.0% AQ by weight sprayed on whole-kernel corn in AL and TX, USA. We found that repellency for wild pigs was dependent on the AQ concentration, with the greatest repellencies of 95% (AL) and 59% (TX) observed using ~3% AQ. We also found that repellency decreased as the abundance of wild pigs increased at the bait sites. Raccoons (Procyon lotor) did not appear to be repelled by the AQ-coated corn, but white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) were. Overall, our results show promise for the development of a repellent for treating seeds to protect them from wild pigs. We recommend the next steps of testing of the 3% concentration of AQ on corn seeds that are planted underground to optimize the best potential protection against damage from wild pigs. • A 3% anthraquinone spray treatment on corn showed promise for reducing consumption by wild pigs. • Repellencies of 95% and 59% on treated corn were observed in Alabama, and Texas, respectively. • Repellency declined as larger groups of wild pigs fed on the treated corn. [ABSTRACT FROM AUTHOR]

Functional responses describe how changing resource availability affects consumer resource use, thus providing a mechanistic approach to prediction of the invasibility and potential damage of invasive alien species (IAS). However, functional responses can be context dependent, varying with resource characteristics and availability, consumer attributes, and environmental variables. Identifying context dependencies can allow invasion and damage risk to be predicted across different ecoregions. Understanding how ecological factors shape the functional response in agro‐ecosystems can improve predictions of hotspots of highest impact and inform strategies to mitigate damage across locations with varying crop types and availability. We linked heterogeneous movement data across different agro‐ecosystems to predict ecologically driven variability in the functional responses. We applied our approach to wild pigs (Sus scrofa), one of the most successful and detrimental IAS worldwide where agricultural resource depredation is an important driver of spread and establishment. We used continental‐scale movement data within agro‐ecosystems to quantify the functional response of agricultural resources relative to availability of crops and natural forage. We hypothesized that wild pigs would selectively use crops more often when natural forage resources were low. We also examined how individual attributes such as sex, crop type, and resource stimulus such as distance to crops altered the magnitude of the functional response. There was a strong agricultural functional response where crop use was an accelerating function of crop availability at low density (Type III) and was highly context dependent. As hypothesized, there was a reduced response of crop use with increasing crop availability when non‐agricultural resources were more available, emphasizing that crop damage levels are likely to be highly heterogeneous depending on surrounding natural resources and temporal availability of crops. We found significant effects of crop type and sex, with males spending 20% more time and visiting crops 58% more often than females, and both sexes showing different functional responses depending on crop type. Our application demonstrates how commonly collected animal movement data can be used to understand context dependencies in resource use to improve our understanding of pest foraging behavior, with implications for prioritizing spatiotemporal hotspots of potential economic loss in agro‐ecosystems. [ABSTRACT FROM AUTHOR]

Wild pigs (Sus scrofa) damage agricultural and natural resources throughout their nearly global distribution. Subsequently, population control activities (e.g., trapping, shooting, or toxic baiting) frequently involve the deployment of bait to attract wild pigs. A better understanding of how wild pigs respond to bait sites can help maximize efficiency of baiting programs and identify any potential pitfalls. We examined the movement behaviors of 68 wild pigs during three stages of intensive baiting programs (i.e., 15 days each: prior, during, and post baiting) spread across two distinct study areas in southern and northern Texas, USA. We found that bait sites needed to be within1 km of where females were located (1.25 km for males) to achieve ≥0.50 daily visitation rate. Deployment of bait increased movement distances and erratic movements for both sexes, but did not influence their foraging search area. Home range sizes increased and shifted during baiting, especially for wild pigs on the periphery of the baiting area. After baiting ceased, wild pigs moved away from bait sites and began using new space (i.e., less overlap with previously used home ranges), suggesting that baiting could facilitate the spread of wild pigs. We recommend that baiting programs should be coordinated to reduce the number of wild pigs left on the landscape following baiting. Bait sites should be spaced every 1–2 km, and should be actively relocated if visitation by wild pigs is not consistent. Uncoordinated and passive baiting for recreational hunting and trapping likely exacerbates the negative consequences of baiting identified in this study, such as expanding the space-use and facilitating the spread of wild pigs. • Bait sites should be 1–1.25 km from wild pigs for consistent visitation. • Baiting increases erratic movements for wild pigs. • Wild pigs not removed during baiting moved into previously unused areas. • Baiting programs should focus on removing all wild pigs. [ABSTRACT FROM AUTHOR]

Field immobilization of native or invasive wild pigs (Sus scrofa) is challenging. Drug combinations commonly used often result in unsatisfactory immobilization, poor recovery, and adverse side effects, leading to unsafe handling conditions for both animals and humans. We compared four chemical immobilization combinations, medetomidine–midazolam–butorphanol (MMB), butorphanol–azaperone–medetomidine (BAM™), nalbuphine–medetomidine–azaperone (NalMed-A), and tiletamine–zolazepam–xylazine (TZX), to determine which drug combinations might provide better chemical immobilization of wild pigs. We achieved adequate immobilization with no post-recovery morbidity with MMB. Adequate immobilization was achieved with BAM™; however, we observed post-recovery morbidity. Both MMB and BAM™ produced more optimal results relative to body temperature, recovery, and post-recovery morbidity and mortality compared to TZX. Adequate immobilization was not achieved with NalMed-A. Of the four drug combinations examined, we conclude that MMB performed most optimally for immobilization and recovery of wild pigs. [ABSTRACT FROM AUTHOR]