Wild Pigs in Wildlife Habitat and Rangelands



Symposia will be available on-demand on their scheduled date, then again at the conclusion of the conference.

Wild pigs were introduced to the United States as early as the 1500s, but in the past few decades they have emerged as a major environmental and economic concern as populations have exploded in at least 35 states with estimates over six million. In addition to their adaptability and lack of natural predators, the explosion of invasive wild pigs in the United States can be traced to humans. Wild pigs inflict damage to everything they encounter, and no sector appears to be untouched. Damage to imperiled native wildlife and plant species could have lasting effects. Long term impacts to native game species may hamper future hunting opportunities. Conversely, wild pigs have emerged as a lucrative business for those offering equipment or access to land for recreational wild pig hunting. In addition to direct damage, wild pigs can carry a plethora of diseases that may potentially infect humans, livestock, and other wildlife. Recent research has been focused on effective wild pig removal methods, including trapping, shooting, and toxicants. Although hunting removes animals from the landscape, recreational hunting generally fails to make a significant reduction in wild pig populations. The critical first step to addressing the wild pig issue is public awareness and education. If left unchecked, the problem may become considerably worse and more difficult to address. How we tackle this issue will determine whether wild pigs emerge as a threat that is to be overcome or if they will continue to expand their destructive path.

The Wild Pig Situation
John J. Mayer; Kurt C. VerCauteren
Invasive wild pigs (Sus scrofa) have had a long history in the United States, with introduced populations dating back as early as 1220 CE in Hawaii and mid-1500s in the Lower 48 states. Initial introductions were contemporaneous with early exploration and colonization of the country and consisted of domestic swine that were brought along as a source of meat. Domestic stocks in Hawaii originated from Southeast Asia while the ones on the mainland came from Western Europe. In many early settlements, these domestic pigs were turned loose into unfenced areas to forage and fend for themselves, and many of these free-ranging pigs became wild-living or feral. Beginning in the late 1800s, Eurasian wild boar were introduced into the United States to provide a new huntable big game species. Though initially released into fenced shooting preserves, wild boar always eventually escape. Being conspecifics, in areas where populations of feral pigs and wild boar were sympatric, hybridization occurred. From 1900 up until the 1980s, populations of these invasive pigs remained fairly stable. Then, with growing interest in hunting them, the wild pigs in this country underwent an exponential increase in both numbers and distribution from 1990 through the mid-2010s. During this period populations went from being reported in 22 up to a maximum of 48 states and increased from 2 million up to almost 7 million animals nationally. Because of the increase in damage being caused by these pigs and the growing awareness that this generated, national, state and local control/management programs were implemented in the mid-2010s. Currently, there are 26 states with established populations, 7 states with emerging reports of wild pigs, using targeted removals and monitoring, 11 states that are “pig free” doing monitoring, and 6 states with no wild pigs.
Invasive Wild Pigs and Their Management in North America
Dale Nolte
Wild pigs were introduced to the United States as early as the 1500s, but in the past few decades they have emerged as a major environmental and economic concern as populations have exploded with populations estimates over six million spread across at least 35 states. This presentation provides an overview of damages inflicted by wild pigs and management strategies being implemented. Wild pigs inflict damage to everything they encounter, and no sector appears to be untouched. Economic impacts inflicted by wild pigs are being investigated but losses likely exceed early estimates of $1.5 billion annually. The World Conservation Union, Invasive Species Specialist Group labeled wild pigs as one of the “World’s Worst Invasive Alien Species.” Wild pigs consume large quantities of herbaceous and have been linked to 95% declines of understory vegetation in some eco-systems. Wallowing and rooting leads to soil erosion, weakens levees and earthen dams, and increases siltation of ponds and other water sources. Wild pigs are documented predators of livestock and other wildlife species and compete for foraging opportunities. USDA established a National Feral Swine Program in 2014. USDA/APHIS serves as the lead federal agency in a cooperative effort with other federal, state, tribal, and local entities that share a common interest in reducing or eliminating problems caused by wild pigs. Since environmental conditions and laws governing wild pigs vary considerably among states, APHIS’ strategy is to provide resources and expertise at a national level, while allowing flexibility to manage operational activities from a local or state perspective. Overall objective of the program is to minimize damage inflicted by wild pigs. In states where wild pigs are emerging or populations are low, strategies are to eliminate them. In states where wild pigs are abundant then the focus is to suppress wild pig populations to reduce damages.
Feral Swine Disease Surveillance and Target Projects
Vienna Brown
The National Feral Swine Program (NFSP) works with USDA APHIS Veterinary Services and USDA APHIS Wildlife Services National Wildlife Disease Program to conduct national disease surveillance in feral swine, specifically focused on classical swine fever, swine brucellosis, and pseudorabies. In addition to the diseases of national concern, the NFSP supports a number of pilot projects to address disease issues that arise at a local level. In close collaboration with Wildlife Services field personnel and others on the ground, the NFSP is able to quickly and robustly identify and sample for additional pathogens of zoonotic, domestic livestock, or companion animal concern. These projects are often multi-agency collaborative efforts and comprise a variety of diseases, including chronic wasting disease, bovine tuberculosis, hepatitis E, and leptospirosis.
Regulations and Role of Hunting to Control Wild Pigs
Mike Bodenchuck
Abstract Recreational hunting of wild pigs is permitted, with some restrictions, in 42 US states and prohibited in only 8 states. Recreational hunting, while removing wild pigs from the landscape, also creates demand for wild pigs, which perpetuates their presence on the landscape. The demand for wild pig hunting, inside and outside of confined shooting preserves, had led to the movement of wild pigs across the landscape and the establishment of new populations. In addition to demand brought about by the wild pig hunting culture, hunting has the potential to disrupt organized control through changes in movements of wild pigs and vandalism of pig control equipment. As an invasive species, applying the North American Wildlife Conservation Model is an inappropriate management philosophy, as several of the pillars of the model should not apply to wild pig management. The presentation will examine which states permit recreational hunting, bounty programs as a management tool, the role of shooting preserves as a source of wild pig populations and will present a few case histories regarding hunting and its relation to wild pig control.
Use of Genetic Tools to Elucidate Drivers of Expansion forInvasive Wild Pigs
Timothy J. Smyser; Antoinette J. Piaggio
Genetic tools can uniquely elucidate processes that have contributed to the rapid expansion of invasive wild pigs over the past 30 years and help inform management decisions. The National Feral Swine Genetics Archive was established to facilitate such genetic analyses in the midst of an ongoing invasion. By comparing high density SNP genotypes of wild pigs to commercial pig breeds, heritage pigs breeds, and wild boar, we determined that the increased distribution of wild pigs at a national scale has been attributable to the expansion of long-established populations as opposed to novel introductions of domestic pigs or wild boar. Further, patterns of range expansion demonstrate both incremental increases of established populations and long-distance translocation to previously uninvaded habitats. In building upon broad patterns of range expansion, we are developing novel techniques to map the fine-scale movement of wild pigs. By using supervised genetic clustering approaches, we have successfully delimited discrete genetic populations that can be interpreted as management units for prioritization of control efforts and allocation of control resources. Further, with the resolution provided by high density SNP genotypes, we are able to map movement among genetic populations – classifying residents, migrants, descendants of migrants, and grand descendants of migrants. Estimates of connectivity, integrated over multiple generations, suggest that translocation rates may be as high as 15% in some populations. In sum, the National Feral Swine Genetics Archive has demonstrated the importance of anthropogenic translocation in the recent and rapid expansion of wild pigs, documenting the movement of this ecologically destructive and economically costly invasive species both into uninvaded habitats and among established populations.
Toxicants as a Tool to Control Wild Pigs
Nathan P. Snow; Justin A. Foster; James C. Beasley; Kurt C. VerCauteren
Current methods for removing wild pigs (Sus scrofa) are labor intensive, costly, or difficult to apply over large regions (e.g., aerial shooting, ground shooting, or trapping). Consequently, wild pigs continue to expand their range and increase in number. Orally delivered toxic baits are being developed to provide additional tools for removing wild pigs from landscapes. A warfarin bait (Kaput®) is the only toxicant currently registered with the US EPA (since 2018) for controlling wild pigs. However, no states have yet approved its use because of concerns over non-target hazards. Meanwhile, a sodium nitrite bait (HOGGONE®) is being developed in the US and was recently registered for use in Australia. Both toxicants have advantages and disadvantages for use in the environment, and are yet to be established as safe and reliable tools for widespread control of wild pigs in the US. Ongoing research is aimed at enhancing safety while maximizing population reduction for wild pigs. In this talk we will discuss the latest research and developments for both toxic baits, and provide insight on their effectiveness and hazards.
A Wildpig’s Tale: Extending Management Information to the Public Through a Lattice Work Approach
James Cathey
Texas has the largest population of feral swine (Sus scrofa) in the U.S and with 83% of the state’s land mass categorized as privately-owned working lands, responsibility to manage this exotic species primarily falls on landowners. We observed a rapidly changing environment leaving property-owners searching for credible information to guide their management. Traditional outreach approaches like face-to-face meetings served us well in times past, but there is a need for educators to explore new options beyond this familiar practice. Because, in-person meetings require significant time and financial commitment it ultimately limits their potential, especially when facing exponential population growth of feral swine. To improve our outreach impact, we purposely developed an educational latticework to interconnect informative products to have more robust instructive offerings and we promoted them through multiple digital platforms each conveying a linked story tailored to their respective audiences. We re-imagined conventional items like Extension publications as phone applications and series of presentations as virtual lessons, accessible and shareable at any time, and able to cater to a variety of learning styles. In-person presentations were translated to social media posts, blogs, webinars, videos, newsletters, and a web-site, giving private landowners and a larger audience of web-users greater access to information. From 2015-2019, we reached 1.9M contacts primarily through digital media, whereas 15K people attended 229 programs and reported knowledge gained for feral hog biology, lethal control, trap/bait techniques and types of hog damage by 87, 84, 88 and 75%, respectively. Participants indicated willingness to adopt 2 practices and they anticipated a $2.7M reduction in damages in the upcoming year based on what they learned. This deliberate approach extended the shelf-life of knowledge pieces by connecting them together, resulting in a strong educational latticework that should be considered for future landowner outreach efforts.
Economic Numbers Behind the Destructive Behaviors of Wild Pigs
Stephanie Shwiff; Aaron Anderson; Sophie McKee
Wild pigs (Sus scrofa) are a non-native invasive species in the United States that transmit disease and inflict damage upon natural resources, agriculture, livestock, and property. Geographic distribution of wild pigs in the United States has nearly tripled since 1982, with anthropogenic influences playing a significant role in the expansion. The most widely cited aggregate estimate of wild pig damages in the U.S. comes from a 2007 study that conservatively estimates annual crop damages and control costs at $1.5 billion (Pimentel, 2007). The author based the estimate on a population of 5 million wild pigs in the U.S. and $300 in crop damages and control costs per swine (Pimentel, 2007). Wild pigs are seemingly unparalleled in their ability to inflict economic harm. While significant research efforts have been undertaken to comprehensively monetize the broad breadth of wild pig impacts, much remains unquantified. This presentation will explore published economic estimates of wild pig damage in the US to provide an updated understanding of the overall negative economic impacts of this invasive animal.
The Future of Wild Pigs in North America
Kurt VerCauteren; Stephen Ditchkoff; James Beasley; John Mayer; Gary Roloff; Bronson Strickland
As reiterated throughout this symposium, wild pigs (Sus scrofa) are a well-established ecological and economic villain in North America, causing considerable damage to both anthropogenic and ecological resources. Is there hope? Can the impacts of wild pigs be curtailed, or will they continue down their destructive path unimpeded? We are optimistic. Since the inception of the USDA/National Feral Swine Damage Management Program and associated efforts we have seen great progress; wild pigs have been eradicated from several states that had small populations, and in states where populations are well established their densities and distributions are being reduced. Of course, management strategies and tools, public support, and governmental support and legislative actions will need to continually evolve to keep the momentum going and further reduce populations and impacts of wild pigs across the continent. Keys to continued reductions in wild pig populations and damages include the development of unified goals, public education, improving our scientific knowledge to inform decision makers, and, realistically, the need to increase resources available for managing wild pigs. We will discuss ongoing strategies that are addressing each of these points and next steps. We will also send everyone home with action items.
TUESDAY 3:00PM – 4:00PM Panel Discussion

Organizers: Megan Clayton, Texas A&M AgriLife Extension Service, Corpus Christi, TX; Dale Nolte, USDA/APHIS/Wildlife Services, Fort Collins, CO; Russell Burton, Y2 Consultants, Jackson, WY; Kyle Schumacher, Northern Prairies Land Trust, Royal, NE; Carol Baldwin, Kansas State University, Manhattan, KS; Kurt Vercauteren, USDA/APHUS/Wildlife Services, Fort Collins, CO
Supported by: Rangeland Wildlife Working Group, Society for Range Management Wildlife Habitat Committee, USDA/APHIS/Wildlife Services

Location: Virtual Date: September 28, 2020 Time: -