Bait Sites Research Articles

The Effect of Climate on Strongly Disturbed Vegetation of Bait Sites in a Central European Lower Montane Zone, Hungary

Human landscape-transforming activities contribute to the global change in vegetation in different forms. Hunting is one of the most ancient human landscape-shaping activities. Feeders for hunting are particularly disruptive to vegetation. In the present study, we conducted a vegetation survey in these highly disturbed places. We investigated the vegetation dynamics over several years in the turkey oak–sessile oak zone, in two areas with different moisture and shade conditions (forest and clearing). Important background factors are the changes in precipitation and temperature. Our results confirm that weed infestation is detectable at bait sites over a long period. The seasonal changes in field weed vegetation, as well as the increase in the number and coverage of weed species at the end of summer, resulting from lifestyle characteristics, were generally detectable in all years and locations, especially in the case of open and more strongly degraded clearings. Meteorological factors played a role in the degree of weed infestation in each year. Degradation was more significant in drought years, while regeneration was also observed in wetter periods. At baits located in the clearing, we showed a positive correlation between the amount of summer precipitation and the total coverage of weed species, as well as between the average spring temperature and the coverage of certain weed species. With the drying of the climate, the disturbed areas are constantly losing their natural value, but wetter weather is not an automatic solution either. Considering that there are approx. 30,000 bait sites in the country, and they are used regularly and very intensively, they can serve as major infection hotspots for alien species in a network.

Seasonal efficacy and risks from a sodium nitrite toxic bait for wild pigs.

Wild pigs (Sus scrofa) are an invasive and destructive species throughout many regions of the world. A sodium nitrite (SN) toxic bait is currently used in Australia and being developed for use in the US and other countries to combat the increasing populations of wild pigs. In the US, efforts to modify the Australian SN-toxic bait and baiting strategy have focused on reducing issues with non-target animals accessing the SN-toxic bait spilled outside of bait stations by wild pigs. We tested and compared modifications for efficacy (with wild pigs) and hazards (with non-targets) in north-central Texas, US during summer (July 2021) and winter (March 2023) seasons. During both seasons we found that visitation to the bait sites declined 94-99% after deploying the SN-toxic bait, and we found a total of 106 dead wild pigs, indicating considerable lethality for the local population. Prior to deploying the SN-toxic bait, Global Positioning System (GPS)-collared wild pigs were more likely to cease visiting bait sites during summer when foraging resources were abundant. Farrowing decreased visitation to bait sites during the winter. We observed no dead non-targets during summer; winter results showed an average of 5.2 dead migrating birds per bait site (primarily Dark-eye juncos [Junco hyemalis]) from consuming SN-toxic bait spilled by wild pigs. The presence and winter-foraging behaviors of migrating birds appeared to increase hazards for those species. The current formulation of SN-toxic bait was effective at removing wild pigs during both seasons, however it is clear that different baiting strategies may be required in winter when migrating birds are present. Baiting wild pigs prior to farrowing during the winter, and during drier summers, may further improve efficacy of the bait. Reducing hazards to non-targets could be achieved by refining the SN-toxic bait or modifying bait stations to decrease the potential for spillage, decreasing environmental persistence if spilled, or decreasing attractiveness to migrating birds. © 2024 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Estimating red deer population size using vantage point counts at baited sites

AbstractAccurate estimates of population size are central to the management and conservation of wild ungulates. Counting animals from vantage points of baited sites is a method that is traditionally used in Europe to obtain abundance estimates of wild ungulates, but its reliability in forested landscapes is contested. We assessed the accuracy of vantage point counts (VPCs) for estimating population size in red deer (Cervus elaphus) at De Hoge Veluwe National Park, a fenced, partially forested game reserve in the Netherlands. We compared estimates from duplicated VPCs for 1977–2010 with population sizes reconstructed from cohort analyses of age‐specific mortality records, including and excluding supplementation with vehicular direct counts (VDCs) and field knowledge on herd composition and herd size from game wardens. Estimates from VPCs supplemented with VDCs matched the reconstructed population size well for 2001–2010. In addition, estimates based on ≥1 VPC site/11 km2 provided representative estimates of the reconstructed population size in that period. Simultaneous VPCs at multiple baited sites can yield precise population estimates for red deer in forests.

A comparison between above-ground bait stations and experimental caulk baits for elimination of field colonies of the Asian subterranean termite, Coptotermes gestroi (Blattodea: Rhinotermitidae).

Survey stakes and in-ground (IG) stations have failed to intercept underground tunnels of the Asian subterranean termite, Coptotermes gestroi (Wasmann), in southeastern Florida, rendering nearly useless the IG bait station that is the main tool of commercial baiting systems. When placed over an active infestation, above-ground (AG) bait stations were readily fed on by C. gestroi, resulting in colony elimination. A new experimental type of AG bait application being studied is an injectable caulk bait. In this study, we compared the efficacy of AG bait stations and an experimental AG caulk bait against field colonies of C. gestroi. Following the applications of AG bait stations at 3 sites with infested houses and trees, C. gestroi colonies were eliminated 7.1-28.1 wk later. The experimental AG caulk bait was applied at 7 sites including 4 houses, 2 office buildings, and 1 docked sailboat. Colony elimination times at caulk bait sites ranged from 3.1 to 13.6 wk, but there was no statistical difference in mean colony elimination time between AG station bait sites (17.4 ± 10.5 wk) and AG caulk bait sites (8.4 ± 3.8 wk). This study showed that AG caulk bait applications were equally efficacious in eliminating existing C. gestroi in structures as AG bait stations and will offer another tool for termite control professionals to better manage subterranean termites including C. gestroi.

Dry and unwary are best conditions for baiting wild pigs (Sus scrofa)

Wild pigs (Sus scrofa) are a highly destructive invasive species throughout North and South America, Australia, and many island nations. Where invasive, their populations are targeted for control to reduce damage. Controlling wild pigs often involves baiting to draw them into traps or entice them to consume a toxic bait. However, baiting can have mixed success in congregating wild pigs to focal areas long enough for control measures to ultimately be implemented. We sought to evaluate how environmental conditions (i.e., precipitation) and negative stimuli (i.e., proxy for exposure to previous control efforts) influenced use of bait sites by wild pigs. We compared visitation to bait sites during dry (2019–2020) and wet (2021) years, and between wild pigs that had been previously trapped and released in southcentral Alabama and northcentral Texas, USA. We found that drier years substantially increased use of bait sites by wild pigs (i.e., 119–136 % increase over 17 days). Similarly, wild pigs that did not experience negative stimuli had increased use of bait sites (i.e., 30–31 % increase over 17 days). We recommend that managers intensify their control efforts during drier periods to take advantage of susceptible behaviors of wild pigs during these times. We also recommend that control efforts focus on eliminating the potential for surviving wild pigs which may experience negative stimuli (e.g., narrow misses during trapping, shooting some wild pigs from a group, sub-lethal doses from toxic baits) and become educated against future efforts.

Changes in the Vegetation, Soil Seed Bank and Soil Properties at Bait Sites in a Protected Area of the Central European Lower Montane Zone

Feeding places for shooting wild boar (so-called bait sites) are spreading in some regions and they have a growing impact on natural ecosystems. Bait sites were investigated to detect the changes in vegetation, the soil seed bank and soil nutrients. The study area is situated in the Mátra Landscape Protection Area, representing a typical oak forest in the Central European lower montane zone (in Hungary). Two types of bait sites were selected: forests and clearings. A vegetation survey, a soil seed bank experiment and a soil analysis were conducted. The degree of degradation of vegetation was similar at the various bait sites, but only the abundance of weeds was higher in the clearings. The density of weed seeds in the soil varied regardless of type, clearly showing the effects of artificial seed sources. The number of weed species was, however, significantly higher in the clearings. The degree of Jaccard-similarity between the vegetation and the seed bank was the highest in the clearings. The dominance of long-term persistent seeds did not differ among bait sites, indicating frequent disturbances at these sites. The amount of soil nutrients was significantly (more than 10 times) higher in the clearings and this, along with their greater openness, may be responsible for the higher number of weed species in their seed banks. The vegetation and the soil of the clearings proved to be more degraded, mainly due to their habitat characteristics, but the seed bank was similarly infected in the less weedy forests; thus, all bait sites may equally be the focal points of a possible invasion. It means new challenges for the management, considering that climate change and the intensive logging and hunting activities can strengthen the effects of bait sites.

No panacea attractant for wild pigs (Sus scrofa), but season and location matter

Wild pigs (Sus scrofa) are a prolific invasive species throughout many regions of the world that cause extensive economic and environmental damage. Trapping is a common strategy for reducing their populations with baits (i.e., food) and attractants (e.g., scents) used to lure wild pigs into traps. However, there is little information on which scent attractants may attract wild pigs more readily and rapidly across regions and seasons. We examined 60 scent attractants for wild pigs that could be used to increase trapping success across three seasons (winter, spring, and fall) and in two geographic regions, including a warm and semi-arid rangeland (South Texas, USA) and a warm and moist mixture of upland and bottomland forests (South Carolina, USA). We found little evidence that most scents attracted wild pigs. Only strawberry extract and creosote bush oil increased the probabilities of visitation, and only in Texas during the fall season. No other scents attractants performed better than the control (i.e., no scent) in both study locations. More wild pigs visited sites during the fall season regardless of scent attractant used. The location of a site mattered more than which attractant was used, and a post hoc analysis revealed that distances to roads and water flowlines (i.e., permanent or ephemeral drainages, streams, and rivers) increased the probabilities of visitation during some seasons. We conclude there was no panacea scent that was more effective than controls in attracting wild pigs across regions and seasons. Placement of sites and seasonality were more important for attracting wild pigs, suggesting the location of traps or bait sites may be more important than the specific attractants used for management activities. Future research should include monitoring movements of wild pigs relative to scent attractants and evaluation of baits (e.g., food-rewards) for drawing wild pigs to sites.

Estimating Deep-Sea Fish Population Density From the Odour Extension Area: A Theoretical Basis and Comparison With the Conventional Methods

Accurately estimating the population density of deep-sea fish with a baited camera system has long been a significant challenge. Although several theoretical models have been developed using the first arrival time of an individual fish or time-varying fish abundance at the bait, none of the models allows for the spatio-temporal variability of the odour plume area extending from the bait. This study shows theoretically that the population density can be formulated as the inverse of the sample mean of the odour plume area extended until it reaches a first fish under the condition that fish at rest have a random dispersion. Each area estimate is governed by the homogeneous Poisson process and, hence, its probability density follows an exponential distribution. A large uncertainty can occur for each area estimate (sample), but the uncertainty decreases as the number of samples used to derive the sample mean increases by the law of large numbers. Numerical experiments conducted in the study indicate that the proposed method for inferring population density is also potentially applicable to cases in which the fish have a uniform or large-scale clumped dispersion. The experiments also show that the conventional method based on first arrival time fails to estimate the population density for any of the dispersion cases. This study also indicates that the reliability of the most popular inference method for estimating population density from the time-profile of fish abundance at the bait site was found to depend on the extension of the odour plume area and the dispersion pattern.

Come with me: experimental evidence for intentional recruitment in Tonkean macaques.

Recruitment is a process by which animals can initiate collective movements: the action of an individual prompts conspecifics to follow. Although it has been hypothesized that animals may be able to intentionally recruit others, there is no experimental evidence of this to date. We tested this hypothesis in two pairs of Tonkean macaques in a situation requiring the subjects to find a food site in a 2800 m2 area, and approach the site together to release rewards. Each subject was informed of the location of either highly or little-valued rewards. We recorded attention-action sequences in which an individual checked that his partner was attending to him before moving, and also simple departures (i.e., not preceded by eye contact). Analyses showed that sequences were more often followed by recruitment and leading the partner to a baited site than simple departures were. Moreover, subjects used attention-action sequences more frequently when informed of the location of the highly valued reward. This may be explained by the fact that the more motivated they were by the expected rewards, the more likely they were to actively recruit their partner. No such effect was found when subjects performed simple departures. We conclude that Tonkean macaques are capable of intentional recruitment because the subjects voluntarily behaved with the goal of influencing their partner's movement: they checked that the partner was paying attention to them and prompted him to follow by moving. Such performances can be accounted for either by associative learning or by intentional communication.

Assessment of weed invasion at bait sites in a Central European lower montane zone

The effects of wild game feeding on the local environment have been widely investigated in northern European countries but have received little consideration in Central Europe. Bait sites, that is, places where food is set out to entice wild boar for hunting are becoming ever more widespread, and they are having an increasing impact on surrounding vegetation. The aim of the present study was to assess the extent of weed invasion at different bait types. 3 bait sites located in forests, 3 baits in clearings and 3 baits on unpaved forest roads in the Central European lower montane zone, in Hungary. The field work was conducted in May and August. Four transects were laid out (at right angles to each other) from the centre of each bait, and consisted of 22 one meter square quadrats, in which vegetation survey were conducted. The application of multivariate statistical methods (PCA) and UPGMA analysis to the data collected revealed substantial differences between the bait types. The baits in the forest were the least degraded, with a sparse understory cover in both surveys. Road baits displayed a notable difference, as they varied depending on canopy closure, accessibility and exposure. Sites in clearings proved to be the most infected. Furthermore, there was a significant difference between the vegetation of the periods examined, arable weeds dominated in August. A stress gradient was detected along the transects, with the proportion of weeds decreasing from the centre, while the natural components of the vegetation increased. The effect was more noticeable in clearings, probably due to their greater openness. Invasion is typically limited to the immediate environment of the bait sites, but valuable patches of habitat can also be destroyed, and bait sites may serve as bridgeheads for biological invasions.

Untrapped potential: Do bear hunter cameras accurately index nontarget species?

AbstractRemote camera use by hunters offers the potential to collect citizen‐derived data on multiple species using hunter surveys, but the effectiveness of this approach is untested. We examine whether observations from remote cameras that hunters use at their black bear (Ursus americanus) bait sites and reported via hunter surveys are an effective method to monitor species. We compared data collected from pseudo‐bear bait sites established for this study to hunter established bear bait site observations from the same study area. We also quantified observations reported on hunter surveys as a landscape index alternative to white‐tailed deer (Odocoileus virginianus) hunter indices, gray wolf (Canis lupus) surveys, and mustelid (Mustelidae) trapper indices. We did not detect a difference in hunter‐reported camera observations versus our observations for four of the six species recorded at pseudo‐bear bait sites. Hunters were over nine times more likely to report photographing wolves and nearly one third as likely to report photographing mustelids. We observed a relationship between trapper survey‐derived mustelid indices and the camera‐derived index, but not for deer or wolves. Foremost, these results emphasize the need to further evaluate the utility of remote camera data derived from hunters. The widespread use of remote cameras by hunters, the low‐cost of hunter surveys, and the potential to collect accurate community composition and occurrence/presence indices, points to the value of adding questions to hunter surveys regarding multiple species of interest.

Deterring non-target birds from toxic bait sites for wild pigs

Toxic baiting of wild pigs (Sus scrofa) is a potential new tool for population control and damage reduction in the US. Field trials testing a prototype toxic bait (HOGGONE 2 containing 5% sodium nitrite [SN]), though, revealed that wild pigs spilled small particles of toxic bait outside of bait stations which subsequently created hazards for non-target species that consumed those particles, primarily passerine birds. To deter non-target birds from consuming particles of spilled bait, we tested four deterrents at mock bait sites (i.e., baited with bird seed) in north-central Colorado, USA during April–May 2020. We found a programable, inflatable deterrent device (scare dancer) reduced bird visitation by an average of 96%. Then, we evaluated the deterrent devices at SN-toxic bait sites in north-central Texas, USA during July 2020, where the devices were activated the morning following deployment of SN-toxic bait. Overall, we found 139 dead wild pigs at 10 bait sites following one night of toxic baiting, which represented an average of 91% reduction in wild pigs visiting bait sites. We found that deterrent devices were 100% effective at deterring birds from toxic bait sites. We found two dead non-target mice at bait sites without deterrent devices. We noted that deploying toxic bait in mid-summer rather than late-winter/early-spring reduced hazards to migrating birds because they were not present in our study area during July. We recommend using deterrent devices (i.e., novel, programmable, battery operated, continuous and erratic movement, and snapping sounds) to reduce hazards to non-target birds at SN-toxic bait sites. We further recommend deploying SN-toxic bait during seasons when migrating birds are not as abundant until further research demonstrates minimal risks to migrating birds.

Assessing the benefits of integrated introduced predator management for recovery of native predators

Increasingly threatened species and their habitats require multiple successful management actions to ensure persistence. Introduced predator exclusion and suppression programs are key conservation actions used to retain or restore Australian ecosystems. Nevertheless, few direct comparisons are made to ascertain the individual and combined efficacy of multiple introduced predator conservation actions to benefit biodiversity. When colocated, both management actions could generate additive conservation benefits that greatly assist the recovery or persistence of threatened native species. Varanid lizards are key functional components in Australian predator guilds and could benefit, via ecological release, when introduced predator management actions are successful. Here we tested the effects of a colocated predator‐exclusion fence and lethal fox baiting on varanid site occupancy in a semiarid protected area. Varanid site occupancy was higher at sites inside (Ψ = 0.90 ± 0.26) compared to sites outside (Ψ = 0.61 ± 0.28) the introduced predator‐proof fenced enclosure. There was only weak evidence of increased varanid site occupancy at fox baited sites (Ψ = 0.037 ± 0.024) compared to nonfox baited (Ψ = 0.00) sites. Overall, colocated introduced predator management actions achieved some additive benefits via possible spillover fencing effects for native mesopredator populations. However, most potential benefits to varanid populations outside of the predator‐proof fenced enclosure were absent due to unsuccessful lethal‐baiting effects on fox populations. The predator‐proof fenced enclosure nevertheless provides important habitat refugia for future source populations for reintroduction once adjacent protected areas become suitable.

The effect of competing carnivores on the feeding behaviour of leopards (Panthera pardus) in an African savanna.

Knowledge of competition dynamics among Africa’s large carnivores is important for conservation. However, investigating carnivore behaviour in the field can be challenging especially for species that are difficult to access. Methods that enable remote collection of data provide a means of recording natural behaviour and are therefore useful for studying elusive species such as leopards (Panthera pardus). Camera traps and Global Positioning System (GPS) collars are powerful tools often used independently to study animal behaviour but where their data are combined, the interpretation of a species’ behaviours is improved. In this study we used data from baited camera trap stations to investigate the feeding habits of leopards at Malilangwe Wildlife Reserve, Zimbabwe. We investigated the influence of spotted hyenas, lions and other competing leopards on the feeding duration of leopards using Generalized Linear Mixed Effects Modelling. To test the influence of competing predators on resting distances from bait sites, eight leopards were fitted with GPS collars. Results showed that leopards spent the shortest time feeding on the baits in the presence of competing male leopards compared to other predators while lion presence caused animals to rest farthest from bait sites. Interaction analysis indicated that small‐bodied leopards spent significantly shorter durations feeding when spotted hyenas were present. Our findings demonstrate that competition from guild carnivores has negative impacts on the food intake of leopards, which may have implications for fitness and survival. This study provides a snapshot of the competition dynamics at bait sites which may give insight to ecosystem level interactions among large carnivores in savanna ecosystems.

Daily and Landscape Influences of Species Visitation to Toxic Bait Sites for Wild Pigs

ABSTRACTToxic baiting of wild pigs (Sus scrofa) is a potential new tool for population control and damage reduction in the United States. Use of toxic bait sites by non‐target species is concerning because of the risks posed from exposure to a toxic bait. A 2018 field trial in northern Texas, USA, examining the efficacy of a prototype toxic bait (HOGGONE®, containing 10% sodium nitrite) revealed unexpected hazards to non‐target species, primarily passerine birds, from consuming toxic bait spilled outside of bait stations by wild pigs. The hazards jeopardize the ability to register HOGGONE as a tool for controlling wild pigs. We conducted apost hocanalysis from that 2018 trial to identify how daily and landscape factors influenced the use of bait sites by non‐target species, and subsequent hazards from consuming the toxic bait. We discovered that no single strategy can eliminate visitations by all non‐target species, but offering the toxic bait at night, in wild‐pig specific bait stations, and in more homogeneous landscapes appeared to be the best strategy for minimizing visits by passerine birds. We also found that use of bait sites by wild pigs were temporally clustered, and more pigs visited bait sites along linear features of the landscape (e.g., agricultural edges or riparian corridors). We recommend a baiting strategy where applicators do not place bait stations directly at sites where remnant particles of grain (from prebaiting) are available on the ground. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

Anthraquinone repellent seed treatment on corn reduces feeding by wild pigs

Wild pigs (Sus scrofa) are a destructive invasive species that cause extensive damage to agriculture throughout many regions of the world. In particular wild pigs damage corn more than any other crop, and most of that damage occurs immediately after planting when wild pigs excavate and consume planted seeds. We evaluated whether anthraquinone (AQ), a repellent, could be useful for protecting seed corn from consumption by wild pigs. Specifically, we conducted cafeteria-style tests at 16 bait sites for 6 nights using concentrations of: untreated, 0.5, 1.5, and 3.0% AQ by weight sprayed on whole-kernel corn in AL and TX, USA. We found that repellency for wild pigs was dependent on the AQ concentration, with the greatest repellencies of 95% (AL) and 59% (TX) observed using ~3% AQ. We also found that repellency decreased as the abundance of wild pigs increased at the bait sites. Raccoons (Procyon lotor) did not appear to be repelled by the AQ-coated corn, but white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) were. Overall, our results show promise for the development of a repellent for treating seeds to protect them from wild pigs. We recommend the next steps of testing of the 3% concentration of AQ on corn seeds that are planted underground to optimize the best potential protection against damage from wild pigs.

Efficacy and risks from a modified sodium nitrite toxic bait for wild pigs.

Wild pigs (Sus scrofa) are a destructive invasive species throughout many regions of the world. In 2018, a field evaluation of an early prototype of a sodium nitrite (SN) toxic bait in the United States revealed wild pigs dropped large amounts of the toxic bait outside the pig-specific bait stations while feeding, and thus subsequent hazards for non-target animals. We modified the SN-toxic bait formulation, the design of the bait station, and the baiting strategy to reduce dropped bait. We tested the modifications in Queensland, Australia (December 2018), Alabama, USA (August 2019), and Texas, USA (March 2020) under differing climatic and seasonal conditions for one night. Cumulatively we found 161 carcasses of all age classes of wild pigs using systematic transects. Remote camera indices indicated high lethality for wild pigs, achieving population reductions of 76.3 to 90.4%. Wild pigs dropped only small particles of SN-toxic bait (average = 55.5 g per bait site), which represented a 19-fold decrease from the previous trial. Despite this reduction, we found three Australian ravens (Corvus coronoides) in Queensland, two Virginia opossums (Didelphis virginiana) in Alabama, and 35 granivorous-passerine birds (mostly dark-eyed juncos [Junco hyemalis]) in Texas dead from consuming the dropped bait. We did not detect any population-level effects for those species. Our modifications were effective at reducing populations of wild pigs, but the deaths of non-target species require further steps to minimize these hazards. Next steps will include evaluating various deterrent devices for birds the morning after SN-toxic bait has been offered. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Measuring, evaluating and improving the effectiveness of invasive predator control programs: Feral cat baiting as a case study

Reducing the impacts of invasive predators is a key objective for conservation managers, livestock producers and human health agencies globally. The efficacy of invasive predator control programs, however, is highly variable. To improve control efficacy, managers require a fundamental understanding of the factors that contribute to the success or failure of a control program. Using a predator baiting program as a case study, we measured the efficacy of baiting as a control tool to significantly reduce feral cat (Felis catus) populations. We used camera traps and cat-borne GPS collars to monitor changes in feral cat populations at a baited site and an unbaited site, using a Before-After, Control-Impact (BACI) design. We also identified five key elements required for a successful baiting program (bait encounter rate, availability, attractiveness, palatability and lethality) and simultaneously measured these to identify areas for potential improvement. Baiting was ineffective at reducing feral cat populations; collared cat mortality was only 11% (1/9), with camera traps revealing negligible reductions in the number of cat detection events (9%), naïve occupancy (15%), and no significant change in the relative abundance of feral cats (F1,54 = 0.8641, P = 0.357). Several factors contributed to the poor control efficacy. Bait encounter rates were low, with cats active along tracks (where baits were laid) < 4% of the time. Cats encountered only 14% (7/50) of monitored baits, but none were eaten. Initially, baits appeared attractive to cats; however meat ants and desiccation rapidly decreased bait palatability. Bait availability to cats declined rapidly, with 36% of monitored baits (18/50) removed by non-target species within the first 48 h. The mortality of one collared cat and chemical assays confirmed that, on average, each bait contained sufficient 1080 to kill a large (>5 kg) feral cat. Our findings suggest that altering bait deployment patterns, increasing bait densities and improving bait palatability could potentially improve the efficacy of baiting programs to reduce feral cat populations. Our study provides a framework to measure and evaluate the key elements that contribute to efficacy of pest control programs, and to identify opportunities for improving outcomes of future control programs.

Factors and costs associated with removal of a newly established population of invasive wild pigs in Northern U.S.

The human-mediated spread of exotic and invasive species often leads to unintentional and harmful consequences. Invasive wild pigs (Sus scrofa) are one such species that have been repeatedly translocated throughout the United States and cause extensive damage to natural ecosystems, threatened and endangered species, agricultural resources, and private lands. In 2005, a newly established population of wild pigs was confirmed in Fulton County, Illinois, U.S. In 2011, a state-wide wild pig damage management program involving federal, state, and local government authorities directed a concerted effort to remove wild pigs from the county until the last wild pig (of 376 total) was successfully removed in 2016. We examined surveillance data from camera traps at bait sites and records of wild pig removals during this elimination program to identify environmental and anthropogenic factors that optimized removal of this population. Our results revealed that wild pigs used bait sites most during evening and nocturnal periods and on days with lower daily maximum temperatures. Increased removals of wild pigs coincided with periods of cold weather. We also identified that fidelity and time spent at bait sites by wild pigs was not influenced by increasing removals of wild pigs. Finally, the costs to remove wild pigs averaged $50 per wild pig (6.8 effort hours per wild pig) for removing the first 99% of the animals. Cost for removing the last 1% increased 84-fold, and averaged 122.8 effort hours per wild pig removed. Our results demonstrated that increased effort in removing wild pigs using bait sites should be focused during periods of environmental stress to maximize removal efficiency. These results inform elimination programs attempting to remove newly established populations of wild pigs, and ultimately prevent population and geographic expansion.

Factors Affecting Bait Site Visitation: Area of Influence of Baits

ABSTRACTBaiting is a fundamental strategy for the global management of wild pigs (Sus scrofa); however, little information exists on how anthropogenic bait affects wild pig movements on a landscape. We investigated factors that are important in determining the spatial area of attraction for wild pigs to bait (‘area of influence’ of a bait site) using data from Global Positioning System (GPS) collars and locations of bait sites. We monitored movements of wild pigs in 2 distinct study areas in the United States from February to September 2016 and used locational data using GPS collars to analyze the influence of habitat quality (dependent on site), home range size, number of bait sites in the home range, distance to a bait site, and sex in relation to movement in time and space. We determined the average area of influence by calculating the area of a circle with the radius as the average maximum distance travelled by wild pigs to reach a bait site. The average area of influence for our bait sites was 6.7 km2 (or a radius of approximately 1.5 km), suggesting a bait spacing of approximately 1.5 km would be adequate to capture visitation by most wild pigs and a spacing of 3 km could allow substantial visitation while minimizing redundant effort depending on the spatial structure of the populations. Eighty percent of wild pigs first visited bait sites within 8.9 days after bait deployment; and they visited earlier when their home range size was larger. As the number of bait sites in an individual's home range increased, individual pigs visited more bait sites, and the probability of a visit increased dramatically up to approximately 5 bait sites and much less thereafter. Wild pigs travelled farther distances to visit bait sites in lower quality habitat. Our results support the hypothesis that habitat quality can mediate the efficacy of baiting programs for wildlife by influencing their movement patterns and motivation to use anthropogenic resources. Our results suggest wild pigs will travel extensively within their home range to visit bait sites, and that in lower quality habitat, most animals will find bait sites more quickly. Determining the area of influence of bait sites can increase the efficacy of planning and monitoring management programs. Our study provides new information to help managers plan baiting designs to attract the greatest number of pigs. © 2020 The Wildlife Society.