Kurt C. VerCauteren

Context: Wild pigs (Sus scrofa) are an invasive species in many locations, where they cause extensive agricultural damage. Aerial operations, where animals are shot from a helicopter, is a widely used method for reducing the size of wild pig populations. However, information is limited on the behavioural responses of pigs. Aims: We used Before-After-Control-Impact (BACI) to quantify behavioural responses to two aerial operations in an agricultural matrix in northeastern Texas during spring 2020. Methods: Prior to aerial operations, we trapped and fitted 26 wild pigs with GPS radio-collars. After aerial operations, we classified wild pigs as low-impact pigs (i.e. pigs located >100 m from the flight path) and high-impact pigs (i.e. pigs located ≤100 m from the flight path). Results: Aerial operations did not affect resource selection; however, low-impact wild pigs were less likely to be in shelter land cover (i.e. riparian areas, forests, and shrublands) relative to high-impact pigs (selection coefficient = 0.89, 95% CI = 0.82–0.97). Helicopter tracklogs were mostly over shelter land cover (40%), which was similar to space use of high-impact pigs (50%) but higher than low-impact pigs (16%). We found no treatment effects on core and home range sizes nor interactions with conspecifics. Based on step lengths, high-impact wild pigs were 9% more nocturnal than low-impact wild pigs post operations (P < 0.01). No collared wild pigs emigrated from the area during or after aerial operations. Conclusions: Overall, wild pigs locally responded to aerial operations by moving more at night but did not make large escape movements. Wild pigs present in relatively low shelter land were apparently overlooked by helicopter crews. Combining aerial operations with other, night-time-oriented removal methods (e.g. trapping, night shooting, toxic baiting) within the same area as aerial operations should increase removal of cagey wild pigs and enhance population control. Implications: Aerial gunning is an effective way to rapidly reduce wild pig populations with a low risk of survivors relocating into new areas.

Understanding how animals respond to human disturbance associated with active removal operations is critical for improving the efficiency of wildlife damage management programs. Wild pigs ( Sus scrofa × domesticus ; also referred to as feral swine) represent one of the most ecologically damaging and widely distributed invasive mammals globally, yet little is known about how they behaviorally respond to the human activity generated by trapping‐based removal programs. In north‐central Texas, USA, we concurrently tracked wild pigs with global positioning system (GPS) collars ( n = 29) and field personnel who were conducting an intensive trapping removal program to simulate an emergency response to Transboundary Animal Disease introduction. We then used integrated step selection functions fit to individual GPS‐collared wild pigs to evaluate habitat selection and movement responses to human activity derived from the concurrent personnel tracking data. Contrary to classical disturbance‐avoidance predictions, all 29 wild pigs moved toward spaces used by humans rather than away from those spaces, with 86% (25/29) showing significant selection for areas closer to recent human activity (mean coefficient = −0.438, 95% reference range = −0.810 to −0.065). Similarly, wild pigs exhibited strong, consistent attraction to bait sites (mean coefficient = −0.624; all 29 individuals negative; 90% [26/29] significant). The presence of traps at bait sites did not reduce attraction to bait, and attraction to areas of recent human activity strengthened as time since personnel departure increased, suggesting wild pigs monitored human activity but timed their visits to bait sites after personnel had left the area. No sex‐specific differences were detected. Our findings suggest that bait‐conditioned wild pigs timed visits to bait sites in a way that limited direct contact with personnel, but that the value of bait at trap sites outweighed the risk associated with the traps themselves and with recent human activity during intensive trapping operations. Removal personnel should maintain consistent bait presence at trapping sites throughout removal programs and minimize time spent at bait sites during replenishment to maximize the window during which wild pigs are most likely to visit.

Wildlife managers across the United States face growing challenges associated with locally overabundant native species, invasive species, and increasing disease risks at wildlife–livestock–human interfaces. Drawing from field experience and emerging research, this opinion piece examines pressing issues for the profession: locally overabundant populations of white‑tailed deer and feral swine, and the diseases linked to these species. Traditional reliance on recreational hunting is often insufficient to meet population‑reduction goals for deer, particularly in suburban landscapes where hunting access and hunter participation limit effectiveness. Integrated strategies—including professional sharpshooting, private‐land access programs, venison donation programs, and exploration of regulated commercial harvest—may provide additional tools for agencies striving to reduce ecological impacts while enhancing societal benefits. For invasive feral swine, recreational hunting can exacerbate their spread, necessitating science‑based suppression led by trained professionals using targeted, highly effective removal methods. Disease concerns further highlight the need for interdisciplinary, One Health–oriented approaches to prevent and manage infections shared among wildlife, livestock, and humans. By embracing evolving technologies, strengthening human‑dimensions capacity, and engaging the public as partners, wildlife professionals can better address the multifaceted challenges of overabundance and disease in a changing management landscape.

Introduced species can disrupt trophic interactions by acting as novel predators, prey, or scavengers. Predicting the impacts of these disruptions can be integral to the conservation of native species and the maintenance of ecological function, but is challenging, especially for species involved in multiple trophic interactions. Wild pigs Sus scrofa are a widely introduced ungulate that can function as prey, predator, and scavenger, and disrupt ecosystems through many pathways. One underexplored avenue is how wild pigs alter predator–prey dynamics of mammalian carnivores. We explored how wild pigs affect cougar Puma concolor foraging ecology as both prey for cougars and scavengers of cougar kills. We monitored cougars in an area with wild pigs to evaluate impacts on cougar habitat selection, diet, and feeding behavior. We also monitored wild pigs scavenging at cougar kills to understand if scavenging by pigs affects cougar feeding behavior or kill rates. Habitat selection patterns indicated that cougars selected for areas based on both landscape factors and prey density, but selection was stronger for native black‐tailed deer Odocoileus hemionus columbianus than for pigs. We also documented that wild pigs, especially juveniles, were an important secondary prey item for cougars. Finally, we observed that wild pigs scavenged large prey items killed by cougars, which led to reduced feeding time by cougars at individual kills. However, wild pigs did not scavenge frequently enough to affect cougar kill rates. Our research highlights multiple impacts of wild pigs on cougar ecology, both as prey and as scavenger, to illustrate how wild pigs disrupt ecosystems. Areas with a higher density of pigs or lower density of native prey would likely see stronger impacts of wild pigs on predator–prey interactions, and management of wild pigs should account for these interactions, especially when native predators or prey are species of conservation concern.

Culling is frequently used to control animal diseases. Intensive culling can alter the movement behavior of surviving animals, especially in socially-structured wildlife species. These behavioral responses could have unexpected consequences on the spread of a disease. Thus, planning effective culling responses to diseases in wildlife hosts requires a thorough understanding of the potential impacts of culling on the target wildlife host species. We conducted a BACI design study of behavioral response to culling in wild pigs. We examined movement and contact responses in the populations using 122 GPS-collared wild pigs and three different culling methods (aerial operations, trapping, and an experimental toxic bait). Movement and contact metrics included home range area, net-squared displacement (i.e., home range shift), movement speed, distance, contact degree and contact duration. We observed increased movement distances during and after trapping treatments, and home range shifts and reduced area size after the toxicant treatment. We also observed increases in contact duration and number of unique contacts during trapping removals. Movement and contact responses varied by sex. Our results suggest that continued, intensive culling as with extensive trapping can substantially alter wild pig space use and contact. These behavioral responses could have important consequences for disease spread when managing an introduction of transboundary animal diseases or endemic diseases.

Introduction: Free-ranging white-tailed deer (Odocoileus virginianus) are a self-sustaining reservoir for bovine tuberculosis (bTB) in northeastern lower Michigan, (United States) continually putting the area’s cattle industry at risk. Liberal recreational deer harvest, baiting bans, and mitigation measures on farms have reduced but not eliminated bTB in deer nor have they eliminated transmission to cattle. With apparent prevalence in deer being low (1–2%) but constant, vaccination could be an additional tool to aid in addressing the problem and merits investigation. Mycobacterium tuberculosis Bacillus Calmette-Guérin (BCG) vaccine is a widely used human vaccine for tuberculosis that has also been well studied in domestic livestock and wildlife. It is the primary vaccine candidate, and oral delivery is the logical means for delivering it to free-ranging deer, although this has never previously been attempted.Materials and methods: Building off methods and strategies developed for vaccinating deer, we incorporated BCG vaccine into vaccine delivery units (DUs), consisting of a food-based matrix. We deployed DUs at sites in Michigan with a historically high prevalence of bTB. At each site, 100 DUs were placed systematically 2.5-m apart on 50-m x 10-m grids and monitored with still and video cameras. Consumption, still images, and video data were analyzed to assess uptake of vaccine DUs by deer.Results and discussion: Vaccine DUs were deployed in 2024 at 11 agricultural sites on private land which had previously demonstrated moderate to high deer activity and at all but two sites >50% of distributed vaccine DU’s were consumed, with 100% consumed at two sites. Deer learned to seek out and consume vaccine DU’s in just 1 to 3 days, with individuals often eating more than the 1 or 2 needed to vaccinate themselves. This high level of consumption was in spite of an exceptionally warm and dry winter, where deer were less food stressed than usual.

Understanding the epidemiology and transmission dynamics of transboundary animal diseases (TADs) among wild pigs (Sus scrofa) will aid in preventing the introduction or containment of TADs among wild populations. Given the challenges associated with studying TADs in free-ranging populations, a surrogate pathogen system may predict how pathogens may circulate and be maintained within wild free-ranging swine populations, how they may spill over into domestic populations, and how management actions may impact transmission. We assessed the suitability of Torque teno sus virus 1 (TTSuV1) to serve as a surrogate pathogen for molecular epidemiological studies in wild pigs by investigating the prevalence, persistence, correlation with host health status and genetic variability at two study areas: Archbold’s Buck Island Ranch in Florida and Savannah River Site in South Carolina. We then conducted a molecular epidemiological case study within Archbold’s Buck Island Ranch site to determine how analysis of this pathogen could inform transmission dynamics of a directly transmitted virus. Prevalence was high in both study areas (40%, n = 190), and phylogenetic analyses revealed high levels of genetic variability within and between study areas. Our case study showed that pairwise host relatedness and geographic distance were highly correlated to pairwise viral genetic similarity. Molecular epidemiological analyses revealed a distinct pattern of direct transmission from pig to pig occurring within and between family groups. Our results suggest that TTSuV1 is highly suitable for molecular epidemiological analyses and will be useful for future studies of transmission dynamics in wild free-ranging pigs.