Feral Swine Damage Research Articles

Agricultural and Ecological Resources Safeguarded by the Prevention of Wild Pig Population Expansion.

Wild pigs (Sus scrofa) are one of the most destructive invasive species in the US, known for causing extensive damage to agricultural commodities, natural resources, and property, and for transmitting diseases to livestock. Following the establishment of the National Feral Swine Damage Management Program (NFSDMP) in 2014, the expansion of wild pig populations has been successfully slowed. This paper combines two modeling approaches across eight separate models to characterize the expansion of wild pig populations in the absence of intervention by the NFSDMP and forecasts the value of a subset of resources safeguarded from the threat of wild pigs. The results indicate that if wild pigs had continued spreading at pre-program levels, they would have spread extensively across the US, with significant geographic variation across modeling scenarios. Further, by averting the threat of wild pigs, a substantial amount of crops, land, property, and livestock was safeguarded by the NFSDMP. Cumulatively, between 2014 and 2021, wild pig populations were prevented from spreading to an average of 724 counties and an average of USD 40.2 billion in field crops, pasture, grasses, and hay was safeguarded. The results demonstrate that intervention by the NFSDMP has delivered significant ecological and economic benefits that were not previously known.

Assessing feral swine damage in the western gulf region of Arkansas, Louisiana, and Texas

Feral swine (Sus scrofa) as an invasive species in the U.S. have caused severe damage to natural resources through competing for food resources with domestic livestock and destroying habitat by rooting and wallowing. Given their increased population and wide distribution in the southern U.S., feral swine control is becoming an urgent issue for both natural resource managers and landowners. We conducted a three-state mail survey to examine feral swine damage in Arkansas, Louisiana, and East Texas in the western gulf region in 2021. Our results reveal that feral swine activities like rooting and wallowing can cause severe and widespread damage to agriculture and forestry. Among the most reported and concerned damage by feral swine were crops, pastures, livestock, and loss of land value. Soybean damage was the most important agricultural crop damage in both Arkansas and Louisiana while it was hay, silage, and forage crops in East Texas. In terms of livestock damage, beef cattle and calves were the most common and severe damage in all three states. Average economic loss due to feral swine damage was estimated at $67.13/ha, $42.96/ha, $27.31/ha, and $57.54/ha for landowners in the region who owned cropland, forestland, pastureland, and multiple land types, respectively. Those findings could help both landowners and wildlife management personnel understand the negative societal impact of feral swine, and they could also facilitate the comparison between expected benefits and costs of control programs/options for feral swine in the southern states.

Framework for assessing vertebrate invasive species damage: the case of feral swine in the United States

The aim of this study is to provide a general overview of the economic impacts associated with vertebrate invasive species (VIS) in the United States and suggests a methodology for differentiating types of damage. We identify a general framework for categorizing VIS damage that separates this damage into three main categories: destruction, depredation, and disease. We then examine how this framework fits into current published estimates of damage and management costs. Economic impacts associated with feral swine damage and management are plentiful enough to warrant separate treatment from other VIS and are observed in all three categories. For all VIS examined in this study, damage estimates associated with destruction provide the most evaluations of VIS impacts, especially destruction of crops. Evaluations of the losses associated with depredation are largely absent from the literature. We find that while published studies have estimated substantial economic impact associated with VIS, the current state of the literature focusing on VIS frequently fails to address all of the categories of damage, is difficult to compare or replicate, and is unsuited for extrapolation to nation-wide estimates of damage.

Invasive feral swine damage to globally imperiled steephead ravine habitats and influences from changes in population control effort, climate, and land use

Steephead ravines are unusual geological features primarily occurring in Florida’s panhandle, a biodiversity hotspot. The unique habitats formed by steepheads are extremely valuable biodiversity resources within this larger area of great biodiversity. Eglin Air Force Base (EAFB) is essential for global conservation of steepheads because this vast area holds the greatest number under single ownership. Steepheads are significantly threatened by feral swine rooting damage. A decade-long investigation of EAFB’s steepheads assessed the following: (1) severity of swine damage to steepheads, (2) changing levels of swine control on swine population and damage, (3) changing climatic conditions on damage, (4) changing military land use on damage (5) bioeconomics of damage. Swine damage to 21 EAFB steepheads was assessed 5 times over 10 years. Swine populations were indexed 8 times. Damage and population estimates were related to control effort, military land use, and climate variables to assess influences on damage levels. Monetary values were applied to estimates of total damage across all steepheads. Full control staffing rapidly reduced feral swine abundance and steephead damage. Reduced control staffing and reduced access from increased military activities allowed population rebound and increased damage. Drought possibly increased susceptibility to damage because steepheads provide a steady water source despite climatic circumstance. Estimated damage values across EAFB’s steepheads (excluding other resources damaged) was 1.5–11.3 times more than annual control costs. Effective swine control greatly reduces steephead damage. Technological advances may overcome access issues from changing land use. Swine control is a cost-effective steephead conservation approach.

Current status and future recommendations for feral swine disease surveillance in the United States.

USDA APHIS Wildlife Services (WS) responded to the threat of feral swine as a pathogen reservoir as early as 2004. To increase awareness and knowledge on that risk, WS began opportunistic sampling of animals harvested by its operational component to curtail swine damage to agriculture and property. Initially, pseudorabies and swine brucellosis were of most concern, as both serve as a potential threat to the domestic swine industry and the latter also possesses zoonotic implications. In 2006, classical swine fever, a foreign animal disease, became the main driver for feral swine pathogen surveillance. Subsequent years of surveillance identified numerous other disease risks inherent within populations of feral swine. Presently, feral swine surveillance falls under the purview of the APHIS National Feral Swine Damage Management Program, which began in 2014. In January 2018, a panel of animal disease experts representing industry, government, and academia were invited to Fort Collins, Colorado to discuss successes of this surveillance, identify any shortcomings or needs, and propose future feral swine surveillance. This manuscript serves to synthesize WS' surveillance and the future direction of these efforts.

Spatial dynamics of transmission and persistence of African swine fever in wild boar populations: insight for control

Spatial dynamics of transmission and persistence of African swine fever in wild boar populations: insight for control

Prevalence and amount of feral swine damage to three row crops at planting

Feral swine damage to corn, cotton and peanut crops at planting was assessed for 46 fields in Alabama. Damage was assessed on the basis of prevalence among fields and the quantity lost within each damaged field. Feral swine control by professionals dedicated to that task appeared to greatly reduce the prevalence of damage among fields, as the 14 fields which were within the areas where professional swine control operations took place were not damaged. For the 32 fields not receiving such protection, seven (21.9%) received some level of damage. Of those, 40% (four of 10) peanut fields, 15.4% (two of 13) cotton fields, and 11.1% (one of nine) corn fields were damaged. Damage levels were highly variable, both between and within crops. Losses were typically low <1.3%, but there were very notable exceptions where more substantial losses were incurred. One peanut field experienced a loss of 54.2% representing 32,401 kg of crop lost, valued at $15,779. Feral swine damage to freshly planted row crops has previously received little, if any, in-field quantification in the literature, with this study possibly being the first of its kind.

Economic estimates of feral swine damage and control in 11 US states

We report the results of one of the most comprehensive surveys on feral swine (Sus scrofa) damage and control in 11 US states (Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, Missouri, North Carolina, South Carolina and Texas). The survey was distributed by the USDA National Agricultural Statistical Service in the summer of 2015 to a sample of producers of corn (Zea mays), soybeans (Glycine max), wheat (Triticum), rice (Oryza sativa), peanuts (Arachis hypogaea), and sorghum (Sorghum bicolor) in the 11-state region. Producers that failed to respond to the initial mailing received multiple follow-up phone calls in an attempt to minimize non-response bias, and a total of 4377 responses were obtained. Findings indicate that damage can be substantial. The highest yield loss estimates occur in peanut and corn production in the Southeast and Texas. Control efforts are common, and producers incur considerable costs from shooting and trapping efforts. Extrapolating crop damage estimates to the state-level in 10 states with reportable damage yields an estimated crop loss of $190 million. Though large, this number likely represents only a small fraction of the total damage by feral swine in the 10 states because it only includes crop damage to six crops. We hope findings from this survey will help guide control efforts and research, as well as serve as a benchmark against which the effectiveness of future control efforts can be measured.

Feral swine damage to globally imperiled wetland plant communities in a significant biodiversity hotspot in Florida

We studied rooting damage during five-years of feral swine control at Avon Park Air Force Range, a significant botanical biodiversity hotspot in peninsular Florida with many globally imperiled plant species and communities. While control reduced swine abundance, remaining animals consistently rooted the 49 studied sites in both middle-dry season (MDS) and late-dry season (LDS) each year. At each study site, we measured rooting with sub-meter accuracy. Neither total nor proportional area rooted differed in either season, across study years, or among plant community types: herbaceous seepage slopes, wet pine savannas, wet grasslands. The proportion of sites with damage during MDS was at least 25 % less than pre-control baseline. During LDS, the proportion of sites with damage increased over years but remained below the initial 2 years’ MDS results. Fresh rooting frequency (rooting <1 week-old) across sites dropped precipitously from baseline and remained low for MDS. Fresh rooting frequency among sites during LDS was lower than MDS for all but year two of the study. Canopied habitat <50 m from a study site almost guaranteed rooting at the site each observation period. We propose actions for protecting wetlands, integrating swine control into other compatible land use practices, and improving swine control efficacy. While we measured damage amounts at each site very accurately, our approach of also considering frequency of rooting and frequency of fresh rooting across sites offers low-labor means to broadly assess swine damage and control efficacy at large geographic scales because in-field measurements of damage amounts are not needed.

A Survey of Feral Swine Damage in a Selection of U.S. States

We report the results of one of the most comprehensive surveys on feral swine damage and control in 11 U.S. states (Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, Missouri, North Carolina, South Carolina, and Texas). The survey was distributed by the USDA National Agricultural Statistical Service in the summer of 2015 to a sample of producers of corn, soybeans, wheat, rice, peanuts, and sorghum in the 11 states listed above. A total of 4,377 responses were obtained. Findings indicate that damage caused by feral swine can be substantial. The highest yield loss estimates occur in peanut and corn production in the Southeast U.S. and Texas. We hope findings from this survey will help guide control efforts and research, as well as serve as a benchmark against which the effectiveness of future control efforts can be measured.

Management of Feral Swine

Feral swine are an invasive species within the U.S. and cause millions of dollars in damage annually. The management of feral swine may contrast with traditional wildlife management objectives and provides an opportunity to review wildlife damage management in a new context. The authors examine feral swine damage management in the context of the North American Model for Wildlife Management and note where feral swine management departs from traditional management. While wildlife management agencies are actively engaged in feral swine management and control, the traditional approach will need to be modified to prevent populations from spreading. A model feral swine management program is presented for consideration.

Evaluating Feral Pig Management Strategies at Tejon Ranch, California

Author(s): White, Michael D; Kunkel, Kyran | Abstract: Feral swine are a serious management issue for natural resource managers, farmers, ranchers, and increasingly even suburban, private property owners. The 270,000-acre privately-owned Tejon Ranch in the Tehachapi Mountains of California, the subject of an historic conservation and land use agreement that conserved 90% of the property, supports a population of feral pigs that originally escaped from a private hunting ranch in the Tehachapi. Pigs now established on Tejon Ranch produce extensive ecological and economic damages, but are also a revenue source for the landowner’s hunting program. The Tejon Ranch Conservancy serves as steward of the conserved lands and is evaluating management options to reduce feral pig damages, while respecting the landowner’s right to maintain a hunting operation. To inform our management, we have modeled pig population responses to age- and sex-specific harvest scenarios. Consistent with previous studies, our models show that g70% of the population must be harvested annually to maintain or reduce the population, and that high harvest of adult females and juveniles is most effective at reducing abundance. Our analysis shows that population growth rates, which dictate harvest rates required for population control, are most sensitive to reproductive rates, and we have no site-specific data to estimate reproductive or mortality rates. As part of the National Feral Swine Damage Management Program, the Conservancy is partnering with the USDA Animal Plant Health Inspection Service on a research and monitoring project to estimate feral pig population size and demography; habitat use and home ranges; and damages at Tejon Ranch. The ultimate objective of the program is to evaluate techniques for reducing damages cause by feral swine.

Optimizing line intercept sampling and estimation for feral swine damage levels in ecologically sensitive wetland plant communities

Ecological sampling can be labor intensive, and logistically impractical in certain environments. We optimize line intercept sampling and compare estimation methods for assessing feral swine damage within fragile wetland ecosystems in Florida. Sensitive wetland sites, and the swine damage within them, were mapped using GPS technology. Evenly spaced parallel transect lines were simulated across a digital map of each site. The length of each transect and total swine damage under each transect were measured and percent swine damage within each site was estimated by two methods. The total length method (TLM) combined all transects as a single long transect, dividing the sum of all damage lengths across all transects by the combined length of all transect lines. The equal weight method (EWM) calculated the damage proportion for each transect line and averaged these proportions across all transects. Estimation was evaluated using transect spacings of 1, 3, 5, 10, 15, and 20 m. Based on relative root mean squared error and relative bias measures, the TLM produced higher quality estimates than EWM at all transect spacings. Estimation quality decreased as transect spacing increased, especially for TLM. Estimation quality also increased as the true proportion of swine damage increased. Diminishing improvements in estimation quality as transect spacings decreased suggested 5 m as an optimal tradeoff between estimation quality and labor. An inter-transect spacing of 5 m with TLM estimation appeared an optimal starting point when designing a plan for estimating swine damage, with practical, logistical, economic considerations determining final design details.

Preliminary Assessment of the HogHopper™ for Excluding Non-Target Wildlife

Feral swine populations are expanding throughout the U.S., where they are causing increasing amounts of damage to agriculture, natural resources, and property and threaten human health and safety. Methods to control feral swine damage in the U.S. consist of integrated fencing, trapping, snaring, and shooting (including hunting with dogs) efforts. New methods that are being developed to control feral swine damage include toxicants and fertility control agents. For these emerging technologies to be effective at the population-level, they must function through oral routes of delivery. Concurrent to the development of orally-delivered actives, a cost-effective system that delivers biologics to feral swine while restricting access to non-target wildlife, needs to be developed. Our objectives are to 1) describe historical efforts to develop a feral swine-specific oral delivery system in the U.S., 2) present preliminary findings from an ongoing collaborative evaluation of the Australian-made HogHopper™, and 3) outline future opportunities in developing a feral swine-specific oral delivery system. While there is a real need for a feral swine-specific oral delivery system, presently there is no universally effective system suitable for all applications and field scenarios. Each system has its advantages and disadvantages that must be assessed within its management context.

Evaluation of fences for containing feral swine under simulated depopulation conditions

AbstractPopulations of feral swine (Sus scrofa) are estimated to include &gt;2 million animals in the state of Texas, USA, alone. Feral swine damage to property, crops, and livestock exceeds $50 million annually. These figures do not include the increased risks and costs associated with the potential for feral swine to spread disease to domestic livestock. Thus, effective bio‐security measures will be needed to quickly isolate affected feral swine populations during disease outbreaks. We evaluated enclosures built of 0.86‐m‐tall traditional hog panels for containing feral swine during 35 trials, each involving 6 recently caught animals exposed to increasing levels of motivation. During trials, fences were 97% successful when enclosures were entered by humans for maintenance purposes; 83% effective when pursued by walking humans discharging paintball projectors; and in limited testing, 100% successful when pursued and removed by gunners in a helicopter. In addition to being effective in containing feral swine, enclosures constructed of hog panels required simple hand tools, took &lt;5 min/m to erect, and were inexpensive ($5.73/m excluding labor) relative to other fencing options. As such, hog‐panel fences are suitable for use by state and federal agencies for rapid deployment in disease response situations, but also exhibit utility for general control of other types of damage associated with feral swine. © 2011 The Wildlife Society.

Strawberry‐Flavored Baits for Pharmaceutical Delivery to Feral Swine

ABSTRACT More effective methods to control feral swine (Sus scrofa) damage are needed. We evaluated 8 oral delivery systems designed to deliver pharmaceuticals to feral swine on 2 properties in southern Texas, USA. We used modified PIGOUT® feral pig bait (Animal Control Technologies Australia P/L, Somerton, Victoria, Australia) throughout our trials to compare species‐specific visitation and removal rates. Given our consistent finding of high nontarget removal of baits intended for feral swine, we question whether a swine‐specific oral delivery system exists for this region.

Feral swine management for conservation of an imperiled wetland habitat: Florida’s vanishing seepage slopes

Only 1% of the original extent of Florida’s seepage slope habitat remains, with Eglin Air Force Base containing some of the largest tracts. Feral swine damage is one of the greatest threats to this wetland habitat. We conducted a multi-year study to evaluate the impacts of sport hunting and supplemental swine removal on damage to seepage slopes. Prior to initiation of removal in 2003, swine damage to seepage slopes in the portion of the base closed to hunting averaged 25.0%, over twice the 10.9% losses in the portion open to hunting. After less than one year of supplemental removal, damage in the closed-to-hunting area dropped to 7.2%. Although supplemental removal was not applied in the open hunting area, damage dropped significantly to 5.6%, statistically indistinguishable from the swine-controlled (closed) portion. After another year of removal, average damage in the closed hunting area dropped further to 5.6%, while the open hunting area dropped to 4.3%, again statistically indistinguishable. Even though removal was only applied to the area closed to hunting, it also produced damage reductions in the open hunting area, as swine were free to move among areas. Declines in damage following implementation of removal corresponded with large drops in swine population indices for the base. Economic valuations of seepage slope damage losses demonstrated substantial benefit–cost ratios for application of removal. Prior to removal, the combined value of swine damage to seepage slopes in areas open and closed to hunting was estimated at $5.3 million. After only 1.7 years of removal, the value of damage losses was reduced by nearly $4 million to $1.5 million. The benefit–cost ratio over the 1.7 years of removal was an impressive 27.5. Moreover, the economic benefits of removal exceeded the costs 55.2-fold for the first year, when management impact would be greatest.

The amount and economic cost of feral swine damage to the last remnant of a basin marsh system in Florida

Summary Swine ( Sus scrofa ) have been introduced into many natural habitats throughout the world, and they have adversely affected the environment in most of those places. Basin marshes are unique, but dwindling ecosystems in Florida that are especially vulnerable to damage by feral swine. We estimated the amount of swine damage to the last remnant of a basin marsh system in Savannas Preserve State Park (SPSP), and to ecotones within the marsh. We also applied an economic valuation method for the swine damage that was based on the dollar amounts that wetland regulators have allowed permit applicants to spend in mitigation attempts to replace lost wetland resources. We found that swine damaged 19% of the exposed portion of the basin marsh in our study area. Seventy percent of the sample sites showed swine damage at the shoreline and 58% showed damage at the interface with the upland vegetation of the adjacent mesic flatwoods. The area damaged within our study site alone was valued between $1,238,760 and $4,036,290. These damage valuation estimates were considered conservative, because it was impossible to incorporate values for such contingencies as swine impact to state and federally listed endangered plants in SPSP, some of which are found nowhere else in the world. We also could not extrapolate an economic quantity to describe the threat posed by the swine inhabiting SPSP as a reservoir for transmission of diseases to domestic livestock.

Prevalence and economic value of feral swine damage to native habitat in three Florida state parks

Feral swine (Sus scrofa) adversely affect the environment in many of the places where they have been introduced. Such is the case in Florida, but quantification and economic evaluation of the damage can provide objective bases for developing strategies to protect habitats. Swine damage to native wet pine-flatwoods at three state parks in Florida was monitored from winter 2002 to winter 2003. Economic valuations of damage were based on the US dollar amounts that wetland regulators have allowed permit applicants to spend in attempts to replace lost resources. The parks had different swine management histories and the damage patterns differed among them over time. Swine were intensively removed in 2000 from the first park, and it initially had the lowest habitat damage at 1.3%, but as a result of natural and artificial population growth this damage rose to 5.4% by the conclusion of the study, and was valued at US$ 19 193–36 498 ha−1. The second park had no history of swine harvest and, over the monitoring period, damage escalated from 2.6%–6.4%, with an associated value of US$ 22 747–43 257 ha−1. Swine were managed as game animals in the third park prior to its inclusion into the state parks system in 2000. Within this park, the proportion of area damaged decreased from 4.3%–1.5%, valued at US$ 5 331–10 138 ha−1. This decrease may be a result of human activities associated with development of the park's infrastructure causing dispersal of animals conditioned to avoid humans by hunting. Damage was highly scattered in each park, as evidenced by a much higher proportion of sampling sites showing damage than the actual proportion of land area damaged. The dispersed nature of small amounts of damage would increase the effort required to recover habitat and thus damage value estimates are probably conservative. It was also impossible to incorporate values for such contingencies as swine impact to state and federally listed endangered plants in the parks, some of which are found nowhere else in the world.