Proceedings of the Vertebrate Pest Conference

Wild pigs are among the most widespread invasive vertebrate species, having been introduced across the globe as a source of food and for sport hunting. Over the last few decades, the growing ecological and economic impacts of wild pigs have precipitated a shift in the perception and management of this species from a desired game animal to a destructive invasive species, resulting in substantial investments in wild pig management. Most notably, in 2014 the National Feral Swine Damage Management Program was established by the U.S. Congress, representing one of the most extensive management programs for a single invasive species in North America to date. This infusion of interest in wild pig control and resources to carry out these programs has spurred technological innovation, resulting in new and enhanced tools for locating, capturing, and removing wild pigs, as well as a surge in research on this species across its range. These investments have resulted in the elimination or presumed elimination of wild pigs from 12 U.S. States in the last decade. However, several significant hurdles remain that must be addressed to achieve long term success in the management of invasive wild pigs. The lack of unified management goals both within and between many agencies is probably the most important factor limiting widespread control efforts, as there is still no standardized legalized classification of this species in the U.S., and some states continue to actively manage wild pigs as a game species. The lack of concordance in management goals underscores the need for better educational programs targeting the public, legislators, and even wildlife professionals. Further, illegal movement of pigs remains a major contributor to the continued establishment of wild pig populations in new areas. As control efforts shift into states with abundant wild pig populations and an entrenched culture of wild pig hunting, new approaches to management, expanded educational campaigns, more unified management goals, and additional investments in control efforts will be needed. While complete elimination of wild pigs from their invasive range is unlikely, adoption of these strategies should facilitate further contraction of their range, benefiting native wildlife, ecosystems, and humans.

Roof rats (Rattus rattus) are invasive commensal rodents that pose a significant threat to both natural and manmade environments. Like other commensal rodents, roof rats are often controlled with rodenticides placed within bait stations, but rats can be slow to visit stations or avoid them altogether. We tested whether the addition of a scent lure (Airzonix; VM Products) would increase visitation and use of bait stations in 36 residential yards in Orange County, California. We placed two EZ-Secured (VM Products) stations, one containing a scent lure and non-toxic bait (treatment) and one containing bait only (control), in each yard, and monitored them continuously with digital game cameras for three weeks. We compared time to discovery and entry, bait consumption, and nightly roof rat activity between scent lure and control stations. The addition of a scent lure did not reduce time to discovery or entry significantly, nor did it increase bait consumption or rat activity, although rat behavior differed around scent lure and control bait stations. Overall, although roof rats discovered bait stations fairly quickly (median time to discovery 124-195 h), they entered and consumed bait in only a fraction (50-60%) of the stations, and were slow to enter stations (median time to entry 318-387 h), underscoring that additional techniques are still needed to improve the attractiveness and efficacy of bait stations.

Australia’s National Feral Pig Action Plan 2021-2031 is the first national strategy to reduce the extensive and diverse impacts caused by feral pigs to Australia’s environmental, agricultural, cultural and social assets by actively suppressing feral pig populations over time. Its development was instigated in response to growing threats of an exotic disease incursion, particularly African swine fever to the Australian pork industry. It provides a national framework for alignment of state, regional and local strategic feral pig management plans. The Plan was endorsed by Australia’s National Biosecurity Committee in October 2021 and aims to encourage land managers to work together in coordinated groups on a landscape scale, cross tenure basis, and strategically apply the most appropriate combinations of best practice management methods for their region (National Feral Pig Action Plan 2021). Its 10-year time frame reflects the long time required to reduce impacts from feral pigs, and their populations, as well as the enormity of the task. Many stakeholders, including governments, agricultural industries, natural resource management organisations, universities, Indigenous organisations, private land managers and not for profit environmental conservation managers are being engaged to support the Plan’s implementation. In Australia, how feral pig management is being undertaken needs to shift from being fragmented, ad hoc and reactive to be more coordinated, collaborative, strategic, and proactive; with activities supported by strong and trusted partnerships between all land managers. This paper discusses several initiatives being undertaken to support the implementation of the National Feral Pig Action Plan 2021-2031. These initiatives are principally directed at improving the efficacy and efficiency of on-ground best practice management actions by land managers by influencing practice and behaviour change and undertaking monitoring to fill significant data and knowledge gaps.

Monitoring devices are used extensively for wildlife applications including tracking, home-range identification, and facili­tating the recapture of animals. In the spring of 2021, Apple Inc., began marketing the AirTag™. This small device costing $20.00 - $25.00 can be attached to items and located remotely using iPhones. While Apple Inc. indicates the AirTag™ is not intended for use on pets, there may be applications for monitoring animals. The objective of this study was to evaluate the potential use of AirTags for animal tracking purposes on a college campus with urban and suburban-type environments. Initially, human subjects carried individ­ual AirTags (n=40) to 10 designated locations (n=40) within the 50-ha study area to simulate live tracking of individual devices. The actual location of the device compared to the location indicated on a stationary iPhone were recorded. In the second phase of the study, parameters related to the recovery of stationary devices (n=40) placed at randomly selected locations in the study area were collected. Finally, AirTags (n=4) were attached to domestic sheep via a collar in a more remote region of the campus to evaluate monitoring potential. Actual location of AirTags at designated sites compared to the location indicated on an iPhone varied from .09 ha - 5.4ha area. Recovery of AirTags hidden at various locations within the 50-ha area, took longer (p < 0.05) when using the iPhone visual locating method alone (78.4 ± 3.91 min) compared to using the visual display and an audio transmission from the AirTag™ (43.0 ± 1.21 min). Utilization of the AirTag™ to monitor free-ranging sheep in the more rural location was not effective. Results of this study suggest the use of Apple AirTag™ has some utility for monitoring animals remotely under certain physical and environ­mental conditions.

The brushtail possum, a marsupial native to Australia, was widely introduced in New Zealand (NZ) to develop a fur industry. Before the settlement of humans in NZ, there were no terrestrial mammals; therefore, the local species evolved without mammalian predators. This resulted in native species populations declining at alarming rates and many possibly facing extinction on the NZ mainland, especially large-bodied endemic birds. In response to this problem, private investors (supported by the NZ government) developed an initiative to eradicate key mammal predators (possums, rats, and stoats) on the NZ mainland by 2050 (PFNZ2050). As a result, control efforts have significantly expanded over the past decade, and there are now 17 PFNZ2050 landscape projects covering 757,000 ha. Research has looked at combining audio, visual and social lures to improve control efforts for possums. Early results indicate that a combination of lures increases both encounter and interaction rates around control devices. In particular, the combination of audio and visual lures was consistently the top performer in both captive and small-scale field trials. Large-scale field trials are currently underway to confirm these initial results, investigating the effectiveness of combination lures paired with multi-kill AT220 possum traps. Additionally, the lures are being assessed at different times of the year and with varying possum densities. With the drive to PFNZ2050, pest mammal monitoring has markedly increased as researchers attempt to evaluate competing management control strategies. Traditionally, this has relied on single-use plastic monitoring devices such as chewcards and tracking tunnels. An investigation of pest-animal interaction with chewcards indicates that approximately 12% of plastic deployed ends up as microplastic pollution. Another NZ government initiative seeks to ban all single-use plastics, and research is currently investigating the efficacy of non-plastic (biodegradable) alternatives. This research also includes a cost-effectiveness analysis and the reliability of identifying animal bite marks on both plastic and non-plastic chewcards.

Use of a contraceptive (i.e., fertility control) is attractive for rodent management where lethal control is unwanted. Although population reduction is generally unachievable with small-scale, short-term contraceptive use, reduced juvenile recruitment is achievable. The injectable immunocontraceptive vaccine GonaCon (active ingredient: gonadotropin releasing hormone [GnRH]) was registered in 2022 by the U.S. EPA for controlling fertility of female prairie dogs (Cynomys, a type of ground squirrel) in urban/suburban settings. Here we: 1) describe past research, including a replicated field study in Colorado (GonaCon treatment vs. control sites) testing efficacy of GonaCon in prairie dogs, which gave rise to the EPA registration of this product, 2) outline future research needs for prairie dog population management with GonaCon–Prairie Dogs, 3) describe the steps required to possibly register GonaCon for additional rodent species, and 4) describe the other fertility control pesticide products that are currently registered for use against rodents in the U.S. During the replicated field study in Colorado, prairie dogs were live-trapped in a portion (avg: 18.5%, range: 7-37%) of each colony’s total area. In treatment plots, every female captured ≥ 660 g was injected with 0.4 ml of GonaCon. GonaCon was highly effective in controlling female fertility during the first year (2019), as juvenile density was reduced 3×, but not in the second year (2020) following treatment. Treating whole colonies of prairie dogs is favored, yet if small or partial colony treatment is desired then annual GonaCon treatment may be needed. An amendment to the EPA label is in progress to allow treatment of both male and female prairie dogs. Due to recent interest from land and pest managers, other fertility control products and the steps required to possibly get GonaCon registered for additional rodent species are also outlined.

Free-roaming cats (Felis catus) are considered one of the most damaging invasive vertebrate pests in natural areas globally and are a major source of mortality for small animals in suburban and urban environments. Domestic cats are also considered to be a nuisance and a source of disease transmission to pet cats and to wildlife. Historically, the most common method of managing free-roaming cats has been euthanasia, but non-lethal approaches, such as trap-neuter-return (TNR), are increasing in popularity with the public. TNR-sterilized cats, subsidized by regular human feeding, remain in the environment and continue to prey upon wildlife and to be a source of disease and nuisance. However, the extent to which these cats depend on wild-caught prey vs. provisioned pet food is not clear. Moreover, if TNR colonies are located in areas of intensive human development, predation by these cats may be focused on commensal or widespread prey species rather than native species of conservation concern. Management of free-roaming cats aimed at protecting wildlife at the urban-wildland interface requires knowledge of the diet of cats across a gradient of land-use, from rural and natural open space to intensively developed suburban and urban areas. Our aim is to use stable isotope analysis to determine the diet of free-roaming cats in southern California, using ear tissue collected during TNR sterilization procedures. We will compare stable carbon and nitrogen isotope values of free-roaming cats, collected across a gradient of anthropogenic land use, to isotope values of potential prey and anthropogenic foods to determine whether they consume native or commensal prey, or rely on human-provisioned food. To date we have collected more than 300 cat ear tissue samples from veterinary clinics that perform spay and neuter procedures to support TNR programs in the greater Los Angeles metropolitan area. We have also coordinated with vector control agencies and wildlife rehabilitators in the region to collect samples of local commensal and non-commensal bird species, as well as collected samples of commercial pet food. Samples will be dried and homog­enized and sent to UC Davis Stable Isotope Facility for analysis using mass spectrometry. When results are received, we will use stable isotope mixing models to estimate the contributions of different food types to cat diets. Additionally, we will plot the capture locations of each cat in a geographic information system (GIS) and character­ize the landscape surrounding each cat using data layers depicting the type and amount of land use and degree of urbanization. We predict that free-roaming cats living in more urbanized areas will consume primarily pet food and commensal vertebrates such as rats and mice, pigeons, and house sparrows, whereas those living in less urbanized areas and closer to natural open spaces will consume more wild and native prey species. Preliminary data analyzed to date suggest that many trapped cats rely on anthropogenic foods, including pet food, rather than consuming wild-caught prey, and that consumption of these food resources increases with the degree of urbanization around cat capture locations. We hope that our results can help inform management decisions about how and where to permit the implementation of TNR, especially in areas likely to support native species of conservation concern.

The ability of coyotes (Canis latrans) to exploit resources in human-dominated environments has led them to increasingly come into conflict with people, for example by killing domestic animals or attacking children. Additionally, coyotes in these environments increase their exposure to anthropogenic threats, such as harassment, vehicle mortality, and rodenticides. Effective management of human-coyote conflicts requires a better understanding of how coyotes navigate the developed landscape. As part of a broader study of how the use of urban and suburban areas affects coyotes’ exposure to rodenticides, we examined movements and space use of coyotes across gradients of urbanization in Los Angeles and Orange County, California. We affixed GPS radio-collars to 12 coyotes (nine males, three females) and tracked them between August 2022 and December 2023. Radio-collars recorded location information approximately every 15 min, but we restricted our analyses to hourly locations. We used a 95% minimum-convex polygon (MCP) and 95%-kernel density estimate (KDE) to calculate the area used by each animal. Within each utilization area, we calculated the amount of impervious cover and the relative amount of open space and development, using publicly-available GIS data layers (National Land-Cover Database; U.S. Geological Survey 2021). Additionally, for each coyote, we calculated a measure of movement tortuosity (straightness index, SI; Batschelet 1981) to describe its tendency to take directed, straight-line movements or wander less linearly in the habitat. We calculated SI for nine coyotes for which we had hourly location data during the first 28 days after radio-collar deployment. SI values were calculated separately for diurnal and nocturnal movements of each coyote, and then for movements when it was traveling in areas with low (≤19%) vs. high amounts of impervious cover (Wurth et al. 2020), and in areas classified as open space vs. areas with human development. We used paired t-tests to compare mean SI values because movements and habitat use of individual coyotes were not independent. Utilization areas of coyotes (Table 1) ranged from 0.4 - 136.1 km2 (95% MCP) and 0.4 - 148.2 km2 (95% KDE). Excluding three coyotes that displayed wide-ranging, transient movements and considering only five animals that were tracked intensively (151-313 days) during the breeding and dispersal seasons, mean utilization area (95% MCP) was 2.16 km2 (SD = 1.79), which is our best estimate of home-range size. This estimate is about half the size of that typically reported for urban coyotes elsewhere (approximately 5 km2; Gehrt 2007, Gehrt et al. 2009, Franckowiak et al. 2019), including in the Santa Monica Mountains of southern California (Riley et al. 2003). However, it is similar to the estimate (2.1 km2) of Tigas et al. (2002) for coyotes living in fragmented coastal sage scrub and chaparral habitats in Los Angeles and Ventura County, where the urban landscape resembles our study area. Considering only the five non-transient coyotes that we tracked most intensively, on average, 67.2% of their home range was categorized as open space, whereas 32.8% had some level of human development (low-high intensity categories). On average, 68.3% of their home ranges were in areas with little impervious cover (<19%). In contrast, coyotes that displayed transient movements or that were tracked primarily during the dispersal season used areas with more human development (¯x = 55.5%) and more impervious cover (¯x = 50.8%). Coyotes in our study differed from those tracked by Riley et al. (2003), whose home ranges had only 15.6% developed area. In our study, coyotes still managed to use significant amounts of developed and semi-natural open space, despite the extensive degree of development in the region, although many limited their movements primarily to one or a few fragments of natural or modified open space. Diurnal movements were significantly more linear (higher SI) than nocturnal ones (t = 3.67, d.f. = 8, P = 0.006; Figure 1), suggesting that coyotes wander more at night, perhaps while foraging and engaged in conspecific interactions, and move in a more directed fashion during periods when people are active. However, for both diurnal and nocturnal movements, SI values did not differ significantly between movements in areas with low vs. high impervious cover, or in areas with large amounts of open space vs. human development. Both Tigas et al. (2002) and Riley et al. (2003) reported greater use of developed areas at night. Inclusion of data from longer time periods or using more refined categories of land use may increase our ability to detect differences in movements.

Recent increased regulatory restrictions on the use of a first-generation anticoagulant rodenticide, diphacinone, were put into place in California in January 2024 by the passage of California Assembly Bill 1322 in late 2023. Second-generation anticoagulant rodenticides were listed as California Restricted Materials in 2014, and their uses were further restricted in 2021 with the passage of California Assembly Bill 1788. As a result of the passage of AB 1322, diphacinone was added to the Restricted Materials list and prohibited for use in all areas of the state except for specific exceptional uses and sites. Specific requirements for rodenticide applicators using diphacinone are described, along with exceptions to restrictions, as well as other related regulatory requirements for rodenticide users.

Interspecific interactions are crucial in shaping ecosystem dynamics (Connell 1983, Tilman 1987, Barbosa and Castellanos 2005). Non-native ungulates have been introduced across the globe (Ferretti and Lovari 2014, Volery et al. 2021) and in environments where multiple invasives thrive, these co-occurring sympatric species may shift spatiotemporal patterns to minimize interspecific competition (Schoener 1974, Chesson 2000). Spatiotemporal shifts can lead to cascading effects to the native flora and fauna (Simberloff and Von Holle 1999). Given the potential negative impacts, understanding these interactions is vital for effective management of these ecosystems. Two invasive ungulates, the wild pig (Sus scrofa) and the Philippine deer (Rusa marianna), have inhabited much of Guam since their introduction in the 1600s and 1700s (Intoh 1986, Wiles et al. 1999) and both have been associated with significant ecological damage throughout the island (Conroy 1989). Despite sharing similar invasive roles, they seemingly coexist throughout areas of Guam. Subsequently, efforts are increasingly put forth to remove both species from partitioned areas at one time. To aid these efforts and understand invasive species interactions, we studied the seasonal spatiotemporal patterns of wild pigs and Philippine deer during February 2021-March 2022. Specifically, we used GPS collars from 39 wild pigs and 22 deer to examine spatial and temporal partitioning and assess dynamic spatiotemporal interactions between interspecific dyads at seasonal scales. We investigated spatial partitioning of wild pigs and deer by estimating the spatial overlap between home ranges and core areas of interspecific neighboring dyads. We estimated temporal overlap in diel activity to evaluate temporal partitioning between the species. Lastly, we examined dynamic spatiotemporal interactions, those that occur simultaneously in space and time, by estimating movement interactions between neighboring interspecific dyads to understand attraction and avoidance. We found spatial overlap between the species decreased significantly in core areas compared to home ranges in both seasons. Within home ranges, deer were approximately 3 times more likely to be within pig ranges than vice versa. This effect diminished at core areas such that deer were only 1.3× more likely to be within pig core ranges than vice versa. Temporal overlap of activity between wild pigs and deer was very high during dry and wet seasons, with overlapping activity peaks during crepuscular hours. At a critical distance threshold of 50m, we estimated 77 movement interactions from 58 dyad pairs over 3 seasons and found that only 2 (2.6%) and 4 (5.2%) movement interactions were considered avoidant and attractive, respectively, and the remaining 71 interactions (92.2%) were neutral.

Roof rats (Rattus rattus) are a successful invasive species worldwide because of their ability to exploit their commensal relationship with humans. They are opportunistic feeders that use a wide range of natural and anthropogenic food sources. Because some rodent control methods, such as traps and rodenticides, threaten non-target wildlife species, understanding the diets of roof rats can help develop targeted approaches to better control these pests. Our aim is to use stable isotope analysis and stomach contents analysis to determine the diets of roof rats collected in agricultural, urban, and suburban areas in California. We hypothesized that diets of roof rats trapped in agricultural areas would contain crop plants and food resources associated with the agricultural environ­ment (arthropods, mollusks), whereas those from urban and suburban areas, e.g., schools, residential zones, would consume a broader range of food sources, including anthropogenic foods such as pet food, trash, and produce from gardens and fruit trees. To date, we have obtained roof rat carcasses from control efforts across the state, including our own trapping in southern California. Rats were frozen until they could be dissected in the lab. From each rat, we removed the gastrointestinal tract and took a small sample of ear tissue for stable isotope analysis; all tissues were stored in 95% ethanol. Ear tissue samples were dried, cut into small pieces, and weighed before sending them to the UC Davis Stable Isotope Facility for stable carbon (C) and nitrogen (N) isotope analysis. Stomachs were dissected under a dissecting microscope and food items were identified using reference keys. Preliminary analyses of stomach contents revealed significant amounts of what appears to be plant material, seeds, arthropod parts, and rodenticide bait, as well as many roundworms. Isotopic analysis of ear tissue of 64 rats from four Central Valley counties and urban/suburban rats from three southern California counties (n = 65) and Yolo County (n = 14) showed that δ13C values of rats from urban settings were significantly enriched compared to rural rats (Figure 1; F = 4.52, d.f. = 1, 141, P = 0.053), which is consistent with an urban diet containing more anthropogenic foods. δ13C values of urban roof rats were also much more variable (coefficient-of-variation, CV = 8.7%) than that of rats from agricultural areas (CV = 3.6%), which showed remarkably little variation within a site, indicative of feeding on a concentrated, shared resource. δ15N of rats differed significantly between agricultural counties (F = 195.9, d.f. = 3, 60, P <0.0001), as well as between urban rats from Yolo County and southern California (F = 10.87, d.f. = 1, 77, P = 0.0015). Mean δ15N of rats from Kings and Yolo counties was 6.1‰ lower than that in Kern and Tulare counties (Figure 1), suggesting that Kings and Yolo County rats consume a mostly plant-based diet, whereas those from Kern and Tulare either consume more animal-based material or, possibly, feed on a food source that is enriched in heavy-nitrogen, e.g., fertilizer. We do not yet have sufficient samples of potential prey to identify what these rats might be eating or to estimate contributions of different food types to diet using a stable isotope mixing model, which is our ultimate aim.

The Agriculture Improvement Act of 2018 (the 2018 Farm Bill) established the Feral Swine Eradication and Control Pilot Program. The program funded $75M for 5 years, split evenly between the Natural Resources Conservation Service (NRCS) and the Animal and Plant Health Inspection Service (APHIS), both programs within the US Department of Agriculture. The agencies solicited joint programs from states with high densities of feral swine in two phases. In Texas, NRCS and APHIS submitted three multi-county project areas along watersheds for Phase I funding and one eradication effort along with two crop protection projects in Phase II. The eradication project was adjacent to a Phase I project area and after extensive surveillance, it was determined to be successful, the first such project in Texas. All the remaining projects were designed with a direct management effort, a self-help effort through trap loans and a damage assessment process. Landowner in-kind contributions were identified and captured to detail the effects of the program.

Wild pigs arrived on the Bankhead Ranger District in the late 1980s and ‘90s. They proliferated and control efforts began in the early 2000s. In 2011, intensive efforts began, centered around whole sounder removal. By 2020, pigs were controlled at low densities throughout the District except for the rugged and remote Sipsey Wilderness Area. The area is 25,810 acres and surrounding environs remained off limits until a minimum resource analysis was completed, allowing for active management. The Sipsey Pig Project was born. An interagency team was formed, comprised of United States Forest Service (USFS), Alabama Department of Conservation and Natural Resources (ADCNR), and Animal and Plant Health Inspection (APHIS) Wildlife Services personnel. Crucial funding and volunteer support was provided by several local organizations including the wilderness advocacy group. The project began in 2021, when ADCNR agreed to eliminate two special hog hunts on the District. Four technicians from the three agencies began control efforts focused primarily on trapping and whole sounder removal. Other techniques were utilized including aerial gunning and Judas pig with varying levels of success. The first year concluded with approximately 50% of the wilderness receiving control efforts and a record 421 pigs removed from the District, a three-fold increase over the previous year. The next year, 2022, saw the entirety of the wilderness receive control efforts and a marked decrease in pig densities. The initial battle is won but the war remains undecided. Initial control was achieved faster than expected, yet much work remains with four years left in the project. The Sipsey Pig Project is the most aggressive action to date undertaken against wild pigs in a USFS wilderness area east of the Mississippi River. The strategic application of management techniques combined with strong partnerships can achieve wild pig control in the remote regions of our country.

Hazing has been advocated as a non-lethal solution to human-predator conflicts, but the efficacy of hazing is not well documented, especially for mountain lions. We conducted a study of mountain lions throughout the state of California during 2001-2021 to determine if hazing with dogs has potential for deterring mountain lions from returning to sites of conflict. We used data on 76 mountain lions captured and equipped with radio collars; 34 lions were exposed to barking dogs during capture, then further exposed to barking dogs upon release (dog-exposed), and 42 lions were captured and released without exposure to dogs (control). We found that distance from the capture site was similar for dog-exposed and control mountain lions through 45 days following release, except for a slightly greater distance for dog-exposed lion shortly after release. Almost all mountain lions (94-98%) returned to within 6 km of the capture site during the 45 days following release, and most (77-88%) returned to within 1 km, with no significant difference between dog-exposed and control mountain lions. Therefore, aside from a modest short-term effect, we did not find evidence that hazing with dogs is an effective method for displacing mountain lions from a conflict location.

Invasive commensal rodents are the source of significant harms across diverse ecosystems globally, including biodi­versity loss on islands, economic damage in agricultural settings, and disease spread in urban areas. Genetic tools can provide unique insights and solutions for rodent management or eradication, adding to the toolbox of integrated pest management opera­tions. In real world conditions, the utility of genetic tools for rodent management is constrained by ecological factors such as mating and dispersal behavior, landscape variation, and ongoing management strategies. Here we describe two distinct uses of genetic tools for rodent management and their ecological considerations. First, we describe how patterns of genetic connectivity can inform the establishment of functional management units, discern among scenarios leading to island eradication failure, and provide insights into rodent management outcomes. Second, we discuss the utility and risks of using gene drive systems to eradicate invasive house mice from island environments. We describe aspects of risk assessment and mitigation as well as the utility of computational models for improving gene drive preparedness. Together, we outline the importance of ecologically-informed implementation strategies when using genetic tools, both currently available and in development, for the management of commensal rodents.

Anticoagulant rodenticides (ARs) have a long history of successful use in controlling vertebrate pest and invasive species. Despite regulatory efforts to mitigate risk, non-target wildlife may be unintentionally exposed to ARs through various trophic pathways, and depending on dose, exposure can result in adverse effects and mortality. Second-generation ARs (SGARs) are mixtures of cis- and trans-diastereoisomers (each including two stereoisomers) that exhibit similar in vitro inhibitory potency for vitamin K epoxide reductase in rodent microsomal assay systems. Some diastereoisomers and hence some individual stereoisomers are preferentially metabolized in vivo, resulting in residue patterns in exposed target rodents that differ from the bait formulations. Use of less persistent but equally potent SGAR stereoisomers in baits results in lower tissue residues in target rodents, which in turn constitutes lower risk when consumed by non-target wildlife. The toxicity of two brodifacoum formulations with stereoisomers having markedly different elimination half-lives in rats (Formulation A containing the two least persistent stereoisomers, and Formulation B containing the most persistent stereoisomer) were tested in a 7-day dietary feeding trial with American kestrels. Based on previous kestrel studies using commercially available brodifacoum, Formulations A and B were each provided at three dietary concentrations (0.05, 0.1 and 0.5 µg/g diet, 4 kestrels/dose level) predicted to cause a range of toxicity. Compared to unexposed controls, all kestrels that ingested 0.5 µg/g diet of the longer-lived Formulation B exhibited extreme coagulopathy. In contrast, the 0.5 µg/g diet of the shorter-lived Formulation A yielded only a modest lengthening of clotting time in just 1 of the 4 exposed kestrels. These findings support the notion that SGAR baits enriched with less persistent stereoisomers may pose lower hazard and ultimately risk to non-target wildlife.

Invasive house mice threaten native biodiversity on many of the world’s islands. Best practice for eradicating house mouse populations from islands currently relies on bait containing the anticoagulant rodenticide brodifacoum. These baits are typically either broadcast (by hand or by helicopter in natural areas) or placed in bait stations (in human infrastructure or in areas where open broadcast is not permitted). There have been many successful mouse eradications using these methods, including 29 of 36 attempts of islands being successful (81%) in New Zealand. Following recent failed mouse eradications on Gough Island (South Atlantic, 2021) and Midway Atoll (North Pacific, 2023), a workshop was convened with 24 people attending (16 in-person, 8 on-line) from 7 countries (Australia, Canada, France, NZ, South Africa, UK, US), to discuss some hypotheses for what may have contributed to these unsuccessful outcomes. The workshop was held in Palmerston North, New Zealand, between November 27 and 29, 2023. Discussions over the three days revolved around three hypotheses. We present the key factors hypothesized for why eradications failed on these two islands. We also outline research and operational needs that were identified in the workshop that can contribute to improved outcomes for future eradications of house mice from targeted islands.

Despite the lasting aversion many hold towards rats and mice owing to historical associations with diseases such as the plague, there exists a growing consensus among researchers advocating for a reappraisal of these creatures. A noticeable trend is emerging in Western Europe, wherein rodents are increasingly viewed as urban neighbors, challenging the prevailing negative perceptions. To explain the ongoing shift, we use examples from medicine, popular culture, science, and exhibitions. The recognition of rats and mice as sentient and intelligent beings necessitates human stewardship in the context of urban coexistence. We conclude that understanding the ecology and behavior of rats and mice in urban environments, as well as human behavior change, is a prerequisite for achieving harmonious urban coexistence.

Traps are one of the most commonly used products for controlling wild pig populations, but every trapping product and process produces different results. Early sexual maturity, extraordinary reproduction rate, and high piglet survivability gives feral pigs the capacity to recover quickly from inferior control efforts which do not target all age classes at the same time. Many trapping efforts fail to accomplish whole-sounder success, creating an industry need to evaluate efficiency and effectiveness. The 2018 Farm Bill provided funding for pilot projects in 10 states to collect feral swine harvest data. Researchers did not collect data points to measure work production or product efficiency and missed an important opportunity to numerically analyze Best Management Practices (BMPs). Our research compared four different trap products using their individual trapping processes to determine which, if any, was more efficient. This project eliminated the total wild pig population from a 20.23 km² (5,000-acre) Flint River property in Reynolds, Georgia. A total of 771 wild pigs were removed by one 57-year-old operator from 70 miles away while working only weekends (two days per week). Four different trapping products were tested and the best capture success rate over 32 months was 97.18% while using a mobile corral trap coupled with an automatic feeder with digital timer set to disburse bait at dusk. This method resulted in an average capture time of 29.65 minutes after sunset by incorporating an innovative conditioning process whereas the population dynamics and education level of each individual sounder dictated the time period between feeder conditioning and trap building. We continually observed several different sounder behaviors change, including predictable dusk feeding times, compared to the remaining three trapping products and methods tested.

Wild pigs have one of the widest global distributions of any invasive species, and damage associated with them has been documented for centuries. Previously, a field trial was performed in 2015 to evaluate the use of paraffin bait formulations containing warfarin to control wild pigs. While the results of this study were satisfactory, prior research suggests that a cracked corn-based alternative could successfully deliver warfarin to wild pigs and the authors indicated caveats associated with their study that should be addressed. For the current study, a field trial was conducted (2017), as a continuation of the prior research, to evaluate the use of a 0.005% warfarin cracked corn bait in reducing feral hogs, utilizing an alternative feeder type. Results indicated warfarin bait could reduce wild pig consumption and presence at feeders by 92-96.4%. The results also indicated that the feeder use during the current trial was superior in keeping non-targets from accessing the bait, yet potentially more difficult for wild pigs to utilize than previously used commercial feeders. Results further indicated that wild pig presence at feeders was noticeably greater during the current field trial. The availability of an alternative warfarin bait formulation could provide an additional tool to managers to control wild pigs in North Texas and the remainder of ever-expanding wild pig habitat in the U.S and potentially globally.

Since human arrival to the Hawaiian Islands, non-native predators have decimated native flora and fauna. In particular, native forest bird populations have suffered due to rat (Rattus sp.) depredation. To protect native species, conservation practitioners have been removing rats and other rodents from ecologically sensitive areas. Identifying reliable strategies for assessing the effectiveness of these control efforts is critical, particularly given limited resources for conservation. A common method used for monitoring rodents is baited ink-plates within a tunnel (hereafter ink-plates). While this method is widely used, its effectiveness has yet to be evaluated in many ecosystems, including montane rainforests. To evaluate the effectiveness of monitoring rat presence with ink-plates, we focused on the Alakai Plateau on the island of Kauai, which is home to several of Hawaii’s most critically endangered birds, and where over 300 Goodnature™A24 rat traps are currently in operation. The Alakai experiences approximately 11 m of annual precipitation, giving rise to areas of dense vegetation, which may affect how rats encounter and interact with ink-plates. We paired 116 Reconyx™ HyperFire cameras with individual ink-plates inside tracking tunnels in the summers of 2022 and 2023, at a site with an ungulate exclusion fence and at a site with no fencing, to monitor areas both with and without rat traps. Rats were detected on approximately twice as many cameras (34.5% presence) compared to ink-plates (16.4% presence). These results suggest that cameras could be a powerful tool for accurately assessing the efficacy of conservation interventions to mitigate the impact of invasive predators on Hawaii’s native birds. Increased investments in camera technologies are worth consideration, particularly in the case of critically endangered species. Further research into the cost-effectiveness versus the information gained by the two methods could help further refine conservation strategies.

Roof rats (Rattus rattus) are an invasive rodent that can cause substantial damage in citrus orchards. Their populations appear to be expanding throughout California, yet little is known about efficacious, cost-effective strategies to manage this invasive pest while minimizing pesticide use. Therefore, we developed two Integrated Pest Management (IPM) programs based on results of recent studies that incorporated observations of roof rat movement patterns, compared monitoring tools, and tested trapping and baiting options. Both IPM programs utilized elevated bait stations containing 0.005% diphacinone-treated oats and trapping, and we compared those programs to a bait-station only approach to determine which strategies were most practical. Initial IPM plots included a combination of elevated bait stations followed by a brief snap-trapping program and a longer-duration trapping program with Goodnature® A24 traps to hopefully keep rat numbers at low levels (Trial 1). Although initial bait applications were effective at reducing rat numbers, populations quickly rebounded within both the bait station only and IPM treatment areas within two-months following the completion of the baiting programs. Additionally, costs for this initial IPM approach were almost five times as much as a bait station approach. Our second IPM strategy (Trial 2) again incorporated an initial bait application period to knock down roof rat populations, followed by the use of trapping tunnels that contained two snap traps to further reduce/maintain rat numbers longer-term. We again observed effective knockdown with bait applications. However, in contrast to Trial 1, we observed substantial success with trapping tunnels at maintaining, and even increasing, overall efficacy within IPM plots, and IPM plots were always more efficacious than bait station only plots. Although the bait station only approach was less costly than the IPM approach used in Trial 2, the cost disparity was substantially less than that for Trial 1, and the cost difference disappeared during subsequent years, indicating long-term cost-effectiveness of this IPM approach. Collectively, the relatively low cost and high efficacy of a management program that incorporates initial bait applications to knock down roof rat populations, followed by a long-term snap-trapping program to maintain low densities, should provide an effective strategy for managing roof rats in citrus orchards.

The eradication of black rats from Dry Tortugas National Park (DRTO; 42 ha land mass) was completed in January 2022 through collaboration between USDA APHIS Wildlife Services and the National Park Service. Black rats had been documented throughout DRTO since the park was established in 1935. Rat predation of ground nesting birds at DRTO has included brown noddies and sooty terns. Additionally, black rats have damaged equipment and infrastructure throughout the park, and caused human health and safety issues in staff residences. For this eradication, WS chose to use a diphacinone-based rodenticide: Diphacinone-50 Conservation. Diphacinone was chosen instead of brodifacoum because it poses lower risks to non-target species (e.g., 100× less toxic to birds) and has less environmental accumulation over time. Diphacinone-50 Conservation was deployed throughout the park in bait stations placed on a 30m × 30m grid. Bait stations were baited and monitored daily for 14 days. Additionally, three hand broadcast applications were utilized during the eradication in areas of the park closed to visitors. Daily monitoring of the bait stations showed a high initial uptake of the toxicant. Also, monitoring using thermal imaging optics was used throughout the eradication to surveil bait uptake and rat activity. No rats were detected during the last four days of the eradication. Post-eradication monitoring was conducted quarterly for the first year following the eradication, and twice during the second year. Post eradication monitoring consisted of 120 snap traps and chew sachets placed throughout the park for four nights. In addition, track surveys were completed along the dune lines and thermal monitoring was conducted after dark during each monitoring period. The eradication was deemed a success in January 2024. National Park Service currently maintains a strict biosecurity plan for DRTO. This plan includes permanent bait stations and cameras placed in areas of likely reintroductions, monitoring of docking vessels, and checking cargo before distribution. Two weeks post eradication, NPS personnel observed a rat jump off a vessel onto DRTO. This rat was later found dead after consuming toxicant from the permanent bait stations. No rats have been detected at DRTO since.

The house mouse is a common indoor pest found in the urban environment. Low-income communities often have the highest house mouse infestation rates due to inadequate pest management practices. We conducted an 18-month long study evaluating the effectiveness of three house mouse management strategies in a low-income community in New Jersey, U.S. Six buildings containing 156 apartments were divided into three groups, T&B, T&B+E, and control. The T&B treatment included the installment of traps and rodenticide baits. The T&B+E treatment included using traps and rodenticide baits, plus interior and exterior exclusion of the buildings. Researchers applied baits and traps inside apartments, crawl spaces, and basements and followed up until no mouse activity was found. Exclusion was completed by contracted vendors with oversight from researchers. The apartments in the control group were serviced by an existing contractor which used rodenticides and glue boards for mouse control and their treatment was offered only to residents who complained about mouse infestations. Building-wide inspections were conducted at 0, 6, 12, and 18 months to evaluate the effectiveness of the programs. T&B and T&B+E were more effective than the control in reducing house mouse infestations. The infestation rate in T&B, T&B+E, and control at 12 months (May 2023) was 2, 2, and 44%, respectively. The infestation rate rebounded in all groups from 12 to 18 months, which was probably related to lower temperatures in winter. T&B+E treatment caused faster reduction of mouse infestations than T&B treatment, but did not result in lower new infestations than T&B. The palatability of different rodenticides varied significantly. Kitchens had a higher amount of mouse activity than living rooms. A median number of three mice were caught by snap traps per infested apartment. Additional studies are suggested to determine the benefit of rodent exclusion.

Superior rodent management is critical to preserve the diversity of wildlife, and to mitigate environmental and social damage. Pest management strategies can employ 21st century methods to balance the human-animal conflict, especially regarding rodents. Non-toxic fertility control has several advantages over the use of poison when the following parameters are true: 1) rate of removal exceeds rate of population increase; 2) compounds do not bioaccumulate in the rodents or the environment; 3) non-lethal method targets both males and females; 4) animals can be detected at low densities; 5) cost analysis favors fertility control over lethality; 6) method has socio-political acceptance. Our fertility control system meets each of these requirements. Utilizing plant-root-based extracts from Tripterygium wilfordii Hook F, we have formulated a proprietary rodent feed pellet that is efficacious in reducing mice and rat populations in multiple settings. The pellets target rodents with a population reduction capacity of 98% that is sustainable over 12 months. The cost of the pellet solution is less than 90% of other fertility control products, and less than 47% of poison products. The functional key to the success of fertility-control approaches is optimizing feeding protocols to achieve maximum population reduction. We have developed an application-based system to provide sustainable cost-effective management. The monitoring system captures consumption and feeder service data. Point-of-entry data validation is enforced. Compliance with the service program is monitored and configurable alerts are issued for outlying events. These data are ingested into a data analytics engine which generates real-time dashboards for oversight and analysis. Administrative features provide user management, project definition and configuration. In-line instructional documentation and pellet supply order forms provide support for field technicians. As a 501(c)3 non-profit charity we are funded by Open Philanthropy to provide the rigorous data sets presented: a 21st century solution to rodent management.

Wild birds pose unique food-safety risks to agriculture as they may carry multiple zoonotic pathogens, are difficult to exclude, and most are federally protected. As a result, the fresh produce industry regularly expresses concerns about these risks, and growers are sometimes instructed to not harvest crops around wild bird feces, potentially causing yield reductions and food waste. Farmers thus have financial incentives to reduce bird fecal contamination on their crops. However, existing bird deterrent methods can be expensive, have significant deleterious conservation implications, and/or are often ineffective. Thus, it is imperative to develop a holistic understanding of the true food-safety risks associated with wild bird communities and to inform growers and industry professionals about which birds, if any, represent substantive food safety concerns. Here, we evaluate the food-safety risks of wild birds, from the point of entering farms through harvest of the crop via three complementary approaches.

Expertise in wildlife and vertebrate pest management (VPM) within the U.S. University Land Grant system is increasingly rare, and very few Extension educators have the knowledge and tools to address VPM practices in this very specialized area. Yet, Extension educators (i.e., agents) receive a myriad of inquiries from the public searching for information on resolving conflicts associated with wildlife. Our team developed and launched an online survey to assess the needs of Extension educators in western region states and territories of the U.S. to determine the desired content and format of educational resources concerning VPM. We plan to review and compile current VPM educational materials (e.g., factsheets, videos, etc.), revealed in the needs assessment or recognized by our team, and determine their applications for wider use, or for revision/enhancement to address resource shortfalls. Our end goal is to use the survey data to identify current gaps in VPM resources and develop new or revised materials for Extension educators and volunteers. Because these educators frequently serve as “first responders” for people seeking solutions for conflicts with vertebrate pests, Extension staff need unbiased, science-based resources and training materials to counter the misinformation on the internet and fraudulent products in the marketplace. We will also determine how to best format and deliver this information to key audiences and stakeholders.

American barn owls (Tyto furcata; hereafter barn owls) are commonly attracted to breed on California farms for Integrated Pest Management; however, nesting barn owls face threats from the accelerating frequency and severity of heatwaves. Previous research has shown that the upper limit of a barn owl’s thermal neutral zone is 32°C (90°F) (Thouzeau et al. 1999). Negative effects of extreme temperatures on avian taxa include stunted nestling growth (Salaberria et al. 2014), delayed fledging (Cunningham et al. 2013), dehydration (Salaberria et al. 2014), hyperthermia (Thouzeau et al. 1999), and death (Hindmarch and Clegg 2024). We compared temperatures between two commonly used nest box designs to investigate heat mitigating attributes of size and shade panels. This study took place on a vineyard in the Central Valley of California, USA, with a Mediterranean climate where temperatures regularly rise above 38°C (100°F) in the summer (Table 1). The two box designs are freely available online. The smaller (hereafter, small) nest box’s dimensions are 57.8 × 40.6 × 31.4 cm (22.75" × 16" × 12.375") with a volume of 11,443 cm3 (4,505 in3). The larger (hereafter, large) nest box’s dimensions including the shades are 76.2 × 78.7 × 52.7 cm (30" × 31" × 20.75"), and without shades are 61 × 61 × 45.7 cm (24" × 24" × 18") with a volume of 26,334.7 cm3 (10,368 in3). We used Maxim Integrated iButtons (models: DS1921G, DS1923; Analog Devices, Inc., Wilmington, MA) to measure internal temperatures of the two nest box designs. Ambient temperature was extracted from an on-site weather station.

House mice and rats have been introduced to most countries and islands worldwide and represent serious threats to biodiversity, economic enterprise, and human health. Genome editing and gene drives are being explored as new genetic biocontrol methods to effectively suppress rodent pests. An essential step in the translation of this technology to field-ready tools is to administer breeding and behavioral trials with freely-interacting genetically modified (GM) rodents. Due to the potential impacts of unintended release of GM organisms, these trials will require biosecure animal facilities that are rigorously tested to ensure physical containment. This study was conducted to develop and evaluate the biosecurity of a physical containment facility for house mouse trials at USDA’s National Wildlife Research Center. First, we conducted >20 trials with 75 wild-caught (non-GM) house mice to test their ability to escape from small containment units (0.35 m2). During these trials that lasted >160 days, mouse behaviors and escape attempts were documented following exposure to attractants (high value foods and potential mates) as motivators for escape. Just two mice success­fully breached containment during early trials, and both were from chewing small holes in plastic walls that allowed escape to the other side of the containment unit. In a second series of trials, we assessed containment efficacy in a large (24 m2) arena intended to more closely replicate conditions of free-breeding wild mice. In these trials, mice were held in groups of six to 26 for up to 6 months. Across trials, only one mouse escaped the arena, an incident most likely attributable to human error during routine animal husbandry activities. This mouse was captured in the secondary containment (live-trap) within hours of breaching the primary containment. Overall, the containment strategy utilized here presents a robust design, with redundant containment mechanisms that should serve as a model for future behavioral trials using GM rodents. Additionally, our study highlights the need for rigorous staff training, careful attention to construction methods and materials, and adhering to biosecurity protocols to ensure the highest levels of containment that will be essential for testing efficacy of genetic biocontrols.