Invasive Wild Pigs in North America

Ecology, Impacts, and Management

Kurt C. VerCauteren, James C. Beasley, Stephen S. Ditchkoff, John J. Mayer, Gary J. Roloff, Bronson K. Strickland, Kurt C. VerCauteren, James C. Beasley, Stephen S. Ditchkoff, John J. Mayer, Gary J. Roloff, Bronson K. Strickland

• Publisher: CRC Press
• Year: 2019
• ISBN:
  9781351869898
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Ecology
• Index: Biological Sciences

Throughout North America, non-native wild pigs have become an ecologically and economically destructive invasive species. Though they are regarded as a popular game species by some, provide economic benefits to others, and are even engrained into societal heritage in some areas, wild pigs are responsible for an extraordinary amount of damage in both natural and anthropogenic systems throughout North America. As the density and range of wild pig habitat have substantially increased over the last several decades, the magnitude and diversity of their negative impacts are not yet fully realized or quantified. With various conflicts continually emerging, wild pig management is difficult and expensive to achieve. As a result, wild pigs represent one of the greatest wildlife management challenges North America faces in the 21st century.

Invasive Wild Pigs in North America: Ecology, Impacts, and Management addresses all aspects of wild pig biology, ecology, damage, and management in a single comprehensive volume. It assimilates and organizes information on the most destructive introduced vertebrate species in the United States, establishing a foundation from which managers, researchers, policy makers, and other stakeholders can build upon into the future. The book provides comprehensive coverage of wild pig biology and ecology, techniques for management and research, and regional chapters. It is an asset to readers interested in wild pigs, the resources they impact, and how to mitigate those impacts, and establishes a vision of the future of wild pigs in North America.

Features:

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• Compiles valuable knowledge for a broad audience including wild pig managers, researchers, adversaries, and enthusiasts from across North America

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• Addresses taxonomy, morphology, genetics, physiology, spatial ecology, population dynamics, diseases and parasites, and the naturalized niche of wild pigs

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• Includes chapters on damage to resources, management, research methods, human dimensions and education, and policy and legislation

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• Contains full color images and case studies of interesting and informative situations being created by wild pigs throughout North America

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• Includes a chapter on wild pigs at the wildland–urban interface, a more recent and especially challenging issue

1 Introduction

Kurt C. VerCauteren, John J. Mayer, James C. Beasley, Stephen S. Ditchkoff, Gary J. Roloff, and Bronson K. Strickland

Contents

1.1 Introduction

Acknowledgments

References

1.1 Introduction

If one wanted to design the perfect invasive animal species, i.e., a highly adaptable generalist (e.g., could live almost anywhere and eat almost anything), able to quickly increase population size and rapidly expand its range, difficult to control and manage, and causes extensive and diverse damage to natural and anthropogenic environments, one need look no further than wild pigs (Sus scrofa; Figure 1.1). As members of the species S. scrofa, wild pigs in North America share both a conspecific kinship with domestic pigs as well as folklore and mythology of native Eurasian wild boar of the Old World. In the scientific and public literature, individuals of the species are referred to as wild pigs, wild hogs, wild boar, feral swine, feral pigs, and other derivations of this theme. In this book, we call free-ranging suids “wild pigs” (Keiter et al. 2016). We use “wild boar” when discussing literature from the native range of S. scrofa, or when referring to recent introductions of pigs with European lineage.

Figure 1.1 Images of wild pigs: (a) depicts one of more pure Eurasian lineage, (b) is of typical, thin-haired wild pigs found in southern North America, (c) demonstrates characteristics of domestic pig pelage, and (d) shows typical pelage of young wild pigs. (Photos (a–c) by the US Department of Agriculture and (d) by J. Gaskamp. With permission.)

The history of wild pigs in continental North America dates back to the 15th century (Mayer 2018), corresponding to initial European exploration of the mainland, and possibly the 13th century in the Pacific Basin with human colonization of the Hawaiian Archipelago (see Chapter 17). Despite recognition as a destructive species in North America as early as 1505, wild pigs persisted, thrived, and gradually expanded their range, mostly occurring in the southeastern United States (Mayer 2018). However, over the last few decades the distribution of wild pigs substantially expanded to include all major geographical regions of continental North America (Figure 1.2), largely due to human-facilitated movements. With the exception of successful eradication efforts in a few areas, wild pigs now occur at greater densities and across greater portions of the continent than ever before.

Figure 1.2 Map of North America depicting general boundaries of regional chapters.

North America and its associated islands are not alone in dealing with ramifications of non-native wild pigs. Wild pigs have a long history of introduction and subsequent establishment throughout non-polar regions of the world. Hence, wild pigs are one of the widest-ranging mammals in the world, resulting in substantial impacts on ecosystems throughout their range (Melletti and Meijaard 2018). Even in their native range, wild boar populations have increased and individuals occur in historically unoccupied regions as a result of human activities such as deliberate releases for sport hunting, habitat alterations like reforestation, increased availability of certain agricultural crops such as corn, and changing climatic conditions to include milder winters and springs (Tack 2018).

Until the late 1980s, wild pigs successfully evaded focused attention of wildlife professionals. This occurred largely because range expansion and fostering of wild pig populations often happened secretly, thereby allowing wild pigs to infiltrate many North American ecosystems. At one time recently, wild pigs were found in 48 US states (Mayer and Beasley 2018), 6 Canadian provinces, at least 11 Mexican states (Mayer 2018), and numerous islands in the Caribbean and Pacific Basin (see Chapters 17, 18). These increases resulted in corresponding surges in the magnitude and scope of ecological and social damages being inflicted by wild pigs (Figure 1.3; see Chapter 7). Consequently, a multitude of far-reaching direct and indirect costs, some of which have yet to be realized, have been attributed to wild pigs.

Figure 1.3 Image (a) depicts typical damage to crop and (b) shows rooting damage to natural habitat. (Photos (a) by the US Department of Agriculture and (b) by J. Beasley. With permission.)

Costs generally outweigh benefits of wild pigs, but this debate is contentious in some regions of North America and can add to management complexities. For example, in some parts of North America, substantial industries exist relative to wild pig hunting and trapping, often adding significant financial and political incentives to retain and perpetuate wild pigs in these areas. Because wild pigs yield economic benefits to individuals that trap or process them for human consumption or other purposes, segments of society can have polarized views towards wild pigs, uniquely complicating management of this invasive species. Further, wild pigs in North America are second only to white-tailed deer (Odocoileus virginianus) in numbers harvested annually by recreational hunters pursuing large game (Kaufman et al. 2004), and in some US states wild pigs are legally classified as a game species. A broad divergence of opinions toward wild pigs even exists among governmental agencies with respect to classification (e.g., livestock, game animal, invasive species), and resultant management authority (e.g., departments of agriculture if classed as livestock, wildlife departments if classified as game species; see Chapter 11). This variation among administrative oversight confounds continent-wide management of wild pigs.

Wildlife professionals, the non-professional public, and numerous policy makers fortunately realize that wild pig populations are inflicting irreversible harm to some ecosystems in North America. Accordingly, support and urgency for controlling wild pigs increased substantially, but the tasks of control and eradication are monumental endeavors. In fact, some argue wild pigs in parts of North America (e.g., Florida) are naturalized (see Chapter 6) and substantial control or eradication is not feasible. Where wild pigs have existed for hundreds of years and local native species have adapted, management may more effectively focus on small-scale protection of critical resource areas (e.g., sea turtle nesting sites, unique ecological communities or areas). In contrast, newly occupied areas (e.g., northern latitudes of North America) where populations are relatively isolated hold greatest promise for eradication, likely warranting significant resource expenditures.

It is an exciting and challenging time to be a researcher or manager of wild pigs in North America. For researchers, the demand for applied results is high, with considerable knowledge gaps ranging from basic wild pig biology (e.g., reproductive rates, survival) and ecology (e.g., food habits, competition with native species), to development of new tools and strategies for control (e.g., toxicants; see Beasley et al. 2018). For managers, the integration of ecological, social, and economic factors affecting wild pig management poses substantial challenges, but impacts of wild pigs on natural and anthropogenic resources place an urgency on eliminating these animals where possible and reducing their densities and impacts elsewhere. Integrated management, innovative research, an informed and educated public, and effective policy and regulations against wild pigs will be imperative for successful management of this species. One objective of this book is to facilitate that process.

Our overarching goal with this book was to compile and synthesize current knowledge and understanding of wild pigs in North America, addressing all aspects of their life history, ecology, biology, strategies for management, and environmental and agricultural impacts. Information presented in this book builds upon previously published volumes focused on wild pigs in North America (e.g., Mayer and Brisbin 1991, reprinted 2008) and incorporates the large body of research and information produced in the last decade. It also updates and integrates important international resources (e.g., Tisdell 1982, Briedermann and Stöcker 2014, Melletti and Meijaard 2018) by including new literature or information relevant to North America. In total, 54 authors, all experts in their fields, from Canada, Mexico, the Pacific Islands, the continental United States, and elsewhere devoted valuable time to generate and summarize the extensive amount of information found within this book. We trust their efforts will be rewarded through improved understanding and management of wild pigs.

The book is structured in 3 broad sections, covering wild pig biology and ecology, techniques for management and research, and regional chapters. The first section includes an introduction and chapters related to taxonomy, spatial ecology, population dynamics, diseases and parasites, and the naturalized niche of wild pigs. The second section includes chapters on damage to resources, management, research methods, human dimensions and education, and policy and legislation. In the last section, we divided North America and associated islands into geographic areas, and each chapter provides greater region-specific information and detail (Figure 1.2). Wild pig researchers and practitioners provided detailed information and case studies specific to each region. The last section also includes a chapter on wild pigs at the wildland-urban interface, an especially challenging emerging issue. We conclude the book with our vision of the future of wild pigs in North America. We are confident that eradication is a reasonable goal in some locations (and perhaps regions) and believe that population control is achievable in the other areas, but both will require immense effort and political and social fortitude.

Acknowledgments

Contributions from K.C.V. were supported by the USDA. Contributions from J.J.M. were supported by the US Department of Energy Office of Environmental Management under Contract DE-AC09-0...