Wild Pigs

Contributed Oral Presentations

SESSION NUMBER: 31

Contributed paper sessions will be available on-demand for the duration of the conference, then again at the conclusion of the conference.

 

Evaluating the Correlation between Wild Pig Behavior and Resource Selection
Lindsay M. Clontz; Kim M. Pepin; Kurt C. VerCauteren; James C. Beasley
Understanding movement patterns and associated behavioral states can provide insight regarding how animals use space and resources throughout the landscape. Invasive wild pigs (Sus scrofa) are generalists that have the potential to alter ecosystems across broad spatial scales. Thus, elucidating the correlation between wild pig behavior and landscape attributes can aid in the advancement of management strategies for controlling populations of this important invasive species. Using GPS data from 23 collared wild pigs in the southeastern U.S., our goal was to use movement characteristics of wild pigs to distinguish and define behavioral states and explore the connection between these behavioral states and resource selection. We analyzed GPS data with 30-minute resolution using hidden Markov models (HMM) to infer different behavioral states. Then, we developed a resource selection function (RSF) for each behavioral state to determine selection of habitat types and landscape attributes across behavioral states. From our data we were able to distinguish three behavioral states in wild pigs based on HMMs, which were inferred to represent disparate behavioral activities: (1) resting (short step-lengths and acute turning angles), (2) foraging (short to intermediate step-lengths and acute turning angles), and (3) traveling (long step-lengths and obtuse turn angles). Wild pigs selected for bottomland hardwoods and streams and avoided upland pines in all behavioral states. Wild pigs also selected for secondary roads during traveling but avoided these features while in resting and foraging states. Additionally, wild pigs demonstrated a significantly stronger selection pattern for canopy cover during the foraging behavioral state than either of the other states. Information on behavioral-based resource selection will aid wildlife managers in their ability to control wild pig populations more effectively and efficiently, ultimately reducing the negative environmental and economic impacts of this invasive species.
Rooting Out Genetic Structure of Invasive Wild Pigs in Texas
Anna M. Mangan; Antoinette J. Piaggio; Michael J. Bodenchuk; Timothy J. Smyser
Invasive wild pigs (Sus scrofa) are widely recognized as among the most destructive invasive species in the world. Throughout the US, invasive wild pigs (IWPs) have expanded rapidly over the past 30 years with populations now established in 38 states. Of the estimated 6.9 million IWPs distributed throughout the US, Texas supports approximately 40% of the population and similarly bears disproportionate ecological and economic costs. Genetic analyses are an effective tool for understanding invasion pathways and tracking dispersal of invasive species such as IWPs and have been utilized recently in California and Florida, two states with high densities of IWPs and long-established populations. Our objectives were to use molecular approaches to elucidate the biological processes shaping IWP populations throughout Texas, compare our results with patterns of genetic structure observed in California and Florida, and provide insights for effect management of this invasive species. We used a high density single nucleotide polymorphism (SNP) array to evaluate population genetic structure and isolation-by-distance. Genetic clusters of IWPs throughout Texas demonstrate 2 distinct patterns: 1) weakly-resolved, spatially-dispersed clusters and 2) well-resolved, spatially-localized clusters. The disparity in patterns of genetic structure suggests distinct biological processes are differentially shaping IWP populations throughout the state. Our results differed dramatically from the genetic structure observed in California and Florida, which where both characterized by high numbers of localized genetic clusters. These differences suggest distinct biological and perhaps anthropogenic processes are shaping genetic structure in Texas. Further, these disparities demonstrate the need for location-specific management strategies for mitigating IWPs and damage.
What Is a Sounder: Genomic Relatedness of Wild Pig Social Groups
Chelsea L. Titus; Courtney F. Pierce; Timothy J. Smyser; Stephen L. Webb; James C. Beasley
Wild pigs (Sus scrofa) display complex social structures with three main social units: sounders (multigenerational groups of presumably closely related, breeding-aged females with offspring), groups of dispersing breeding-aged males, and solitary breeding-aged males. However, recent studies have described varying group sizes and familial associations within social units. To elucidate the genetic composition of wild pig social units, we genotyped 778 wild pigs at 62,331 loci, sampled from 133 trap groups (124 sounders, 9 male social units) collected from 2014 to 2019 on the Savannah River Site, South Carolina, USA (SRS) and in Oklahoma, USA (OK). We estimated pairwise relatedness (R) and familial relationships for (1) all individuals within social units (sounders and male groups) and (2) just breeding-aged individuals, to remove bias associated with the presence or absence of dependent offspring within sounders. We then calculated mean R for social units and the local population within each study site. We found social unit size varied between SRS (range: 2-14 pigs; x̅ = 4 pigs) and OK (2-44 pigs; x̅ = 11 pigs), as well as the number of breeding-aged individuals within social units (SRS: 1-4 pigs, x̅ = 2 pigs; OK: 1-19 pigs, x̅ = 3 pigs). Most of the social units were composed exclusively of close relatives (1st– and 2nd-degree), and sounders were predominately composed of 1st-degree (parent/offspring, full sibling) females. However, approximately one-third of the sounders included a distantly related or unrelated female. Almost all male social units were composed only of close relatives. Our results provide the most comprehensive analysis to date of the genetic composition of wild pig sounders and male social units in North America. Although social units were largely composed of closely related individuals, sounders routinely contained unrelated females, suggesting there may be additional factors influencing sounder composition beyond familial relationships.
Assessment of Hoggone®Sodium Nitrite Feral Pig Bait Spillage Post Toxic Bait Deployment
John C. Kinsey; Justin A. Foster; Nathan P. Snow; Jason D. Wishart; Linton D. Staples; Janis K. Bush; Kurt C. VerCauteren
HOGGONE® has been identified as an effective sodium nitrite-based toxicant against wild pigs (Sus scrofa) in Australia, New Zealand, and the United States. Though HOGGONE is highly lethal to wild pigs, it is not species specific. Thus, to protect non-target species that may be attracted to HOGGONE, it must be deployed in a wild pig-specific bait station. Bait stations have effectively minimized non-target access to HOGGONE in both free-range and captive trials, but spillage of bait outside of bait stations caused by feeding wild pigs is a hazard for non-targets. Observations in associated studies have indicated that the method in which HOGGONE is presented in bait stations may affect spill rate. In Phase 1 of this study, we evaluated post-feeding spillage of three bait presentation methods (crumbled, extruded, and trays) against captive groups of wild pigs and conducted double-observer surveys to estimate spillage. Results indicated that the crumbled method produced significantly higher spillage (p <0.01) than the two alternate presentation methods. Though there was no statistical difference in spillage between trays and extruded presentations, differences in manufacturing and operational logistics led to the selection of trays for field use. In Phase 2 we further assessed the risk to non-target species in relation to consumption of spilled HOGGONE delivered in trays via bait stations. Here we estimated spillage across 12 additional replicates (N=16) in which trays were the only presentation method used. Results of Phase 2 maintained that HOGGONE presented in trays decreased total spillage with an estimated mean of 6.39g of spilled HOGGONE per 7 wild pigs per night. Further analyses will assess risk to potential non-target species through consumption of HOGGONE spillage by wild pigs. This study confirms that bait presentation method affects spill rate; and that spillage mitigation is possible and essential for risk management of non-target species.
Economic Analyses of Wild Hog Damage and Control Among Young Forest Plantations in Alabama
Micah Fern; Rebecca Barlow; John Kush; Jim Armstrong; Larry Teeter; Chris Slootmaker; Stephanie Shwiff
When estimating the cost of wild hogs (Sus scrofa) it is important to not only include the costs from the physical damage to the stand, but also the incurred costs from control measures aimed at preventing future damage. Private landowners are often less equipped to absorb financial losses from wild hog damage than their industrial counterparts. A survey was conducted to estimate the economic impact of wild hogs, namely costs of damage and control, to privately owned forestlands. The survey was distributed in the summer of 2016 to a sample of 1,200 private landowners across the State. A 35% response rate was achieved from the sampled group. Survey results indicated longleaf pine (Pinus palustris) and loblolly pine (Pinus taeda) were the most commonly reported tree species planted in 2013 to 2015. Wild hogs caused damage to 34 and 13% of forest acres in longleaf and loblolly plantations, respectively. Survey results suggest the southern half of Alabama holds the largest wild hog populations and sustained the most damage to forest stands. Consequently, landowners in this region invested the most capital on control methods. We then designed a stand level economic model to explore potential outcomes of private forest landowner’s responses to wild hog damage. Four scenarios were created to examine how profitability of the modeled stand might be affected by wild hog damage given the owner’s response. Lastly, we utilized sensitivity analyses to examine how varying discount rates and amounts of damage might affect the cost of wild hog damage and control. The results of these economic analyses are represented in a series of tables to help guide landowners in making informed management decisions based on their objectives. We hope the findings from this survey will provide a better understanding of the economic impact of wild hogs in young forest plantation.

 

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