SRNL-RP-2009-00869 Wild Pigs BIOLOGY, DAMAGE, CONTROL TECHNIQUES AND MANAGEMENT Savannah River National Laboratory Aiken, South Carolina Paper and electronic copies of Wild Pigs: Biology, Damage, Control Techniques and Management SRNL-RP-2009-00869 can be obtained by contacting: Savannah River National Laboratory Savannah River Nuclear Solutions LLC Savannah River Site Aiken, SC 29808 SRNL-RP-2009-00869 Wild Pigs BIOLOGY, DAMAGE, CONTROL TECHNIQUES AND MANAGEMENT John J. Mayer and I. Lehr Brisbin, Jr. Editors Savannah River National Laboratory Aiken, South Carolina 2009 This document was prepared by Savannah River Nuclear Solutions, LLC, under contract number DE-AC09-08SR22470 with the United States of America, represented by the Department of Energy. Neither the U.S. Government nor Savannah River Nuclear Solutions, LLC nor any of their employees makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any apparatus, product, or process disclosed, or represents that its use would not infringe on privately owned rights. References herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U. S. Government or Savannah River Nuclear Solutions, LLC. Including Contributed Papers from the 2004 Wild Pig Symposium Augusta, Georgia Sponsored by U. S. Forest Service – Savannah River U. S. Department of Energy Westinghouse Savannah River Company, L.L.C. South Carolina Chapter of the Soil and Water Conservation Society University of Georgia - Savannah River Ecology Laboratory ii Wild Pigs Wild Pigs: Table of Contents Page Introduction 1 John J. Mayer and I. Lehr Brisbin, Jr. Part I. Biology of Wild Pigs 3 Taxonomy and History of Wild Pigs in the United States a 5 John J. Mayer Wild Pig Physical Characteristics 25 John J. Mayer Wild Pig Reproductive Biology a 51 Christopher E. Comer and John J. Mayer Wild Pig Behavior 77 John J. Mayer Wild Pig Food Habits 105 Stephen S. Ditchkoff and John J. Mayer Wild Pig Physiological Ecology 145 Stam M. Zervanos Wild Pig Population Biology 157 John J. Mayer Natural Predators of Wild Pigs in the United States 193 John J. Mayer Wild Pig Field Sign 205 John J. Mayer Part II. Wild Pig Damage 219 Overview of Wild Pig Damage a 221 John J. Mayer Diseases and Parasites of Wild/Feral Swine a 247 David E. Stallknecht and Susan E. Little Part III. Control Techniques for Wild Pigs 259 Wild Pig Trapping Techniques a 261 John J. Mayer and Paul E. Johns Use of Trained Hunting Dogs to Harvest or Control Wild Pigs a 275 John J. Mayer, Rollie E. Hamilton, and I. Lehr Brisbin, Jr. Efficacy of Shooting as a Control Method for Feral Hogs a 289 Doug M. Hoffman Contraception of Feral Pigs: A Potential Method for Population and Disease Control a 293 Lowell Miller, Gary Killian, Jack Rhyan and Tommy Dees Other Control Techniques for Wild Pigs 297 John J. Mayer Comparison of Five Harvest Techniques for Wild Pigs a 315 John J. Mayer iii SRNL-RP-2009-00869 Table of Contents (Continued) Page Part IV. Wild Pig Management Case Studies 329 Savannah River Site a 331 John J. Mayer and Laurel A. Moore-Barnhill Great Smoky Mountains National Park Wild Hog Control Program a 341 William H. Stiver and E. Kim Delozier Cumberland Island Feral Hog Management a 353 W. Edward O’Connell and John F. Fry Fort Benning Military Reservation a 357 Stephen S. Ditchkoff and Michael S. Mitchell The Pigs of Ossabaw Island: a Case Study of the Application of Long-term Data in 365 Management Plan Development a I. Lehr Brisbin, Jr., and Michael S. Sturek Prevalence of Antibodies to Selected Disease Agents in an Insular Population of Feral 379 Swine D. Bart Carter, Kyle K. Henderson, I. Lehr Brisbin, Jr., Clarence Bagshaw and Michael Sturek Influence of Habitat Attributes on Removal of Feral Hogs from Merritt Island National 387 Wildlife Refuge Arik Rosenfeld, C. Ross Hinkle and Marc Epstein a Papers presented at the 2004 Wild Pig Symposium in Augusta, Georgia iv Wild Pigs Wild Pigs: Introduction John J. Mayer and I. Lehr Brisbin, Jr. Savannah River National Laboratory, Savannah River Nuclear Solutions, LLC, Savannah River Site, Aiken, South Carolina 29808 (JJM) Savannah River Ecology Laboratory, P. O. Drawer E, Aiken, South Carolina 29803 (ILB) The existence of problems with wild pigs (Sus scrofa) is nothing new to the Western Hemisphere. Damage by these introduced animals was reported as far back as 1505 by the early Spanish colonies in the Caribbean, where wild pigs were killing the colonists’ cattle. Droves of these animals also ravaged cultivated crops of maize and sugarcane on islands in the West Indies during this same time period. These wild pigs reportedly were very aggressive and often attacked Spanish soldiers hunting rebellious Indians or escaped slaves on these islands, especially when these animals were cornered. The documentation of such impacts by introduced populations of this species in the United States has subsequently increased in recent years, and continued up through the present (Towne and Wentworth. 1950, Wood and Barrett 1979, Mayer and Brisbin 1991, Dickson et al. 2001). In spite of a fairly constant history in this country since the early 1900s, wild pigs have had a dramatic recent increase in both distribution and numbers in the United States. Between 1989 and 2009, the number of states reporting the presence of introduced wild pigs went from 19 up to as many as 44. This increase, in part natural, but largely manmade, has caused an increased workload and cost for land and resource managers in areas where these new populations are found. This is the direct result of the damage that these introduced animals do. The cost of both these impacts and control efforts has been estimated to exceed a billion dollars annually (Pimentel 2007). The complexity of this problem has been further complicated by the widespread appeal and economic potential of these animals as a big game species (Tisdell 1982, Degner 1989). Wild pigs are a controversial problem that is not going away and will likely only get worse with time. Not only do they cause damage, but wild pigs are also survivors. They reproduce at a rate faster than any other mammal of comparable size, native or introduced; they can eat just about anything; and, they can live just about anywhere. On top of that, wild pigs are both very difficult to control and, with the possible exception of island ecosystems, almost impossible to eradicate (Dickson et al. 2001, Sweeney et al. 2003). The solution to the wild pig problem has not been readily apparent. The ultimate answer as to how to control these animals has not been found to date. In many ways, wild pigs are America’s most successful large invasive species. All of which means that wild pigs are a veritable nightmare for land and resource managers trying to keep the numbers of these animals and the damage that they do under control. Since the more that one knows about an invasive species, the easier it is to deal with and hopefully control. For wild pigs then, it is better to “know thy enemy” than to not, especially if one expects to be able to successfully control them. In an effort to better “know thy enemy,” a two-day symposium was held in Augusta, Georgia, on April 21-22, 2004. This symposium was organized and sponsored by U.S.D.A. Forest Service-Savannah River (USFS-SR), U. S. Department of Energy-Savannah River Operations Office (DOE-SR), the Westinghouse Savannah River Company (WSRC), the South Carolina Chapter of the Soil & Water Conservation Society, and the Savannah River Ecology Laboratory (SREL). The goal of this symposium was to assemble researchers and land managers to first address various aspects of the biology and damage of wild pigs, and then review the control techniques and management of this invasive species. The result would then be a collected synopsis of what is known about wild pigs in the United States. Although the focus of the 1 SRNL-RP-2009-00869 symposium was primarily directed toward federal agencies, presenters also included professionals from academic institutions, and private-sector control contractors and land managers. Most of the organizations associated with implementing this symposium were affiliated with the Savannah River Site (SRS), a 803 km2 federal nuclear facility, located in western South Carolina along the Savannah River. The SRS was a very appropriate facility to host this symposium. The SRS has been dealing with its wild pig problem since the early 1950s. A lot has been learned about these animals at the site over the ensuing decades. Between the USFS-SR, DOE-SR, SREL, and the site’s management and operations contractor, which is currently Savannah River Nuclear Solutions, SRS organizations have conducted a wealth of research on this wild pig population, spanning a broad spectrum of topics and disciplines. In fact, the SRS wild pig population is among the most studied, and possibly is the best studied population of this invasive species found in the United States today. Unfortunately, with all of that work, the ultimate answer to controlling wild pigs and their impacts still has not been found. Over the years, control efforts at SRS have been successful in keeping the site’s wild pig numbers in check; but it’s an ongoing task that one cannot let up on. This volume represents the collected synopsis that was the goal of the aforementioned symposium. This edited report contains papers representing some of the symposium’s presentations, papers from researchers who were not able to attend the symposium, as well as several papers that were added to round out the volume to achieve the original symposium’s intended scope.