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Abstract

Understanding source dynamics of invasive species is crucial to their management. Free-ranging wild pigs (Sus scrofa) have caused considerable ecological and agricultural damage throughout their global range, including Canada. Objectives were to assess the spatial and temporal patterns in domestic wild boar and test the propagule pressure hypothesis to improve predictive ability of an existing habitat-based model of wild pigs. We reviewed spatiotemporal patterns in domestic wild boar production across ten Canadian provinces during 1991–2011 and evaluated the ability of wild boar farm distribution to improve predictive models of wild pig occurrence using a resource selection probability function for wild pigs in Saskatchewan. Domestic wild boar production in Canada increased from 1991 to 2001 followed by sharp declines in all provinces. The distribution of domestic wild boar farms in 2006 improved the fit and predictive ability of the habitat-based model, and the number of boar farms in adjacent rural municipalities had a relative variable importance of 0.84. Our results support the propagule pressure hypothesis, which states that establishment success is linked to source dynamics. Although eradication of wild pigs is rarely feasible after establishment over large areas, effective management will depend on strengthening regulations and enforcement of containment practices for Canadian domestic wild boar farms. Initiation of coordinated provincial and federal efforts to implement population control procedures for established wild pig populations are urgently needed to limit the spread of wild pigs and their impacts, and should focus on areas with existing or historic domestic wild boar farms.

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... Wild pigs were first introduced to Canada during a federal and provincial agriculture diversification initiative in the 1980's and 1990's to diversify livestock species and supplement producer incomes 17,18 . Escapes and intentional releases from domestic wild boar farms have led to the feral populations that are established on the Canadian Prairies 18,19 . Brook and van Beest 18 provided a coarse-scale distribution of wild pigs in Saskatchewan at the Rural Municipality level. ...
... This is consistent with the rapid expansion of wild pig populations in the United States 38,16 and most other areas of their native and introduced range 39,40,41 . Many areas in Canada are susceptible to wild pig expansion, especially those that are comprised of ample, energy-rich food resources from agriculture crops 10 , forest cover 42 , relatively low predator densities 42 , and repeated introduction/re-introduction events 19 . ...
... Our finding of wild pigs mainly concentrated in the Prairie Provinces with some of the coldest winters of all ten provinces and that the species is rare or absent in the warm coastal areas is inconsistent with studies that have found the opposite and have found that wild pig distribution is positively associated with warmer climates and have suggested cold winter temperatures to be highly limiting 10,21 . This likely reflects, in part, that domestic wild boar farms that are sources of free-ranging wild pigs were, and are, more concentrated on the Canadian Prairies 19 . The success of wild pigs in western Canada does highlight the capacity for wild pigs to thrive and expand in areas with long and extremely cold winters including some occurrences north of 55 o north latitude. ...
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Invasive species can spread rapidly at local and national scales, creating significant environmental and economic impacts. A central problem in mitigation efforts is identifying methods that can rapidly detect invasive species in a cost-effective and repeatable manner. This challenge is particularly acute for species that can spread over large areas (>1 million km2). Wild pigs (Sus scrofa) are one of the most prolific invasive mammals on Earth and cause extensive damage to agricultural crops, native ecosystems, and livestock, and are reservoirs of disease. They have spread from their native range in Eurasia and North Africa into large areas of Australia, Africa, South America, and North America. We show that the range of invasive wild pigs has increased exponentially in Canada over the last 30 years following initial and ongoing releases and escapes from domestic wild boar farms. We evaluate eight different methods for mapping invasive species over large areas and assess their benefits and limitations. Our findings effectively map the spread of a highly invasive large mammal and demonstrate that management efforts should ideally rely on a set of complementary independent monitoring methods. Mapping and evaluating resulting species occurrences provide baseline maps against which future changes can be rapidly evaluated.
... In many parts of North America, invasion by wild pigs into new areas is due to range expansion from existing populations (Snow et al., 2017), escapes from farms and high-fence shooting operations (e.g., Jackling et al., 2016), and illegal release of wild pigs by humans to establish hunting opportunities in new areas (McCann et al., 2018;Tabak et al., 2017;Waithman et al., 1999). In Saskatchewan, Canada, among the strongest predictors of wild pig distribution is proximity to Eurasian wild boar farms (Michel et al., 2017). ...
... We also note that there is variability among premises that we did not account for with respect to risk (e.g., number of swine and fence strength and security) because these data were unavailable. We did not include Census of Agriculture data in our analyses, which provides a count of many of the active wild boar farms at the scale of census subdivision up until census year 2011 (Michel et al., 2017;Statistics Canada, 2008); for this study, we required point locations of premises with wild boar at a finer resolution than census subdivision. ...
... Likewise, Michel et al. (2017) noted that a major escape or release of wild boar from a farm in Saskatchewan was the likely source of current populations of free-living wild boar nearby. Wild boar escaping captivity and establishing in the wild have also been documented in New Hampshire, Tennessee, North Carolina, and Texas, with anecdotal evidence of similar occurrences in other states (Mayer & Brisbin, 2008). ...
Article
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Invasive wild pigs (Sus scrofa) are considered one of the most damaging species globally, and once they become established in an area, they are notoriously difficult to eliminate. As such, identifying the potential pathways of invasion, especially in places with emerging populations, is critical for preventing new or continued invasion. Wild pigs have been reported in Ontario, Canada, in recent years. We tested four nonexclusive hypotheses about the source of wild pigs in Ontario: (a) escapees from captive sources within Ontario; (b) invasion from neighboring jurisdictions; (c) existing wild populations within Ontario; and (d) translocation and illegal release. We found that sightings of Eurasian wild boar were closer to premises with wild boar than were random locations; wild boar sightings were an average of 16.3 km (SD = 25.4 km, min = 0.2 km, n = 20) from premises with wild boar. We also found that sightings of domestic pigs were closer to domestic pig farms than expected. Sightings of wild pigs in groups of more than four animals were rare. Our results suggest that wild pigs observed in Ontario are recent escapes from captivity, recognizing that there may be established groups of wild pigs that we have not yet detected. While not common, we also received reports indicating that in the past, wild pigs have been translocated and illegally released. Other North American jurisdictions that have been successful at eliminating wild pigs have removed existing populations and changed regulations to limit future invasion, such as prohibiting possession and transport of wild boar and prohibiting hunting of wild pigs.
... Wild pigs (Sus scrofa) are an invasive species in North America and are descendants of Eurasian wild boar (S. s. scrofa) brought over from Europe and Asia, and domestic pigs (S .s. domesticus). Farmed wild boars either escaped captivity or were released and interbred with domestic pigs (Michel et al. 2017). Domestic wild boars (S. scrofa) were brought into Canada in the 1980s (Michel et al. 2017) to diversify agricultural production (Brook and van Beest 2014). ...
... Farmed wild boars either escaped captivity or were released and interbred with domestic pigs (Michel et al. 2017). Domestic wild boars (S. scrofa) were brought into Canada in the 1980s (Michel et al. 2017) to diversify agricultural production (Brook and van Beest 2014). The Prairie Provinces of Alberta, Saskatchewan, and Manitoba historically contained the highest number of domestic wild boar farms in Canada (Michel et al. 2017) in an agricultural landscape; both factors explain the successful establishment and rapid spread of free-ranging invasive wild pigs (Aschim and Brook 2019). ...
... Domestic wild boars (S. scrofa) were brought into Canada in the 1980s (Michel et al. 2017) to diversify agricultural production (Brook and van Beest 2014). The Prairie Provinces of Alberta, Saskatchewan, and Manitoba historically contained the highest number of domestic wild boar farms in Canada (Michel et al. 2017) in an agricultural landscape; both factors explain the successful establishment and rapid spread of free-ranging invasive wild pigs (Aschim and Brook 2019). The widespread success of wild pigs is the result of their extremely high fecundity in Canada (Koen et al. 2018), early sexual maturity (Gethôffer et al. 2007), flexible diet (Barrios-Garcia and Ballari 2012), and highly adaptive nature that allows them to thrive in a broad range of habitats (Seward et al. 2004). ...
Article
Full-text available
On March 4, 2022 we found the carcass of a wild pig (Sus scrofa) in a road ditch, approximately 12 km south of the Blackfoot Recreation Area (BFT), which is adjacent to the southern border of Elk Island National Park (EINP), in north-central Alberta. Thereafter, we found signs of wild pig activities in the pastures of the BFT. The expansion of wild pigs in the BFT-EINP Complex occurred soon after the culling of most of a wolf (Canis lupus) pack from 2014 to 2018 by the Alberta Government and local residents to allegedly protect livestock from depredation. Controlling established populations of wild pigs is a difficult challenge and managers must concurrently use the most effective methods, such as trapping combined with the use of Judas pigs and helicopter capture. However, grey wolves are known to feed on wild pigs, and along with large packs of coyotes (Canis latrans), they may decrease the density of invasive wild pigs. In this Point to Ponder, we make a series of recommendations to support active predation of wild pigs by wolves and coyotes in the agricultural-forest mosaics of north-central Alberta where wild pigs flourish.
... Originally, domesticated European wild boar were imported into western Canada from different parts of Europe in the 1980s and 1990s to diversify agriculture (Brook and van Beest, 2014). Indeed, domesticated wild boar farming remains common: in 2011 there were over 9000 domesticated wild boar on 150 farms across Canada (Michel et al., 2017). Farming for meat production and penned sport shooting operations are the original sources of free-living wild pig populations in Canada (Michel et al., 2017). ...
... Indeed, domesticated wild boar farming remains common: in 2011 there were over 9000 domesticated wild boar on 150 farms across Canada (Michel et al., 2017). Farming for meat production and penned sport shooting operations are the original sources of free-living wild pig populations in Canada (Michel et al., 2017). Wild pigs are extremely fecund in other parts of their native and introduced range (Comer and Mayer, 2009), making established populations notoriously difficult to control and almost impossible to eradicate (Cruz et al., 2005;Barrios-Garcia and Ballari, 2012). ...
Article
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An essential component of management efforts to control invasive species is the estimate of life history parameters, such as reproductive rate and litter size. Wild pigs (Sus scrofa), one of the most invasive terrestrial mammals worldwide, have recently become established on the Canadian prairies. We estimated life history traits in a population of wild pigs in Saskatchewan, Canada, at the current northern limit of their North American distribution. The average pregnant wild pig weighed 73.8 kg (46 – 130 kg; n = 7). Fifty-four percent of females ≥46 kg were pregnant in Feb., with an average of 5.6 fetuses per pregnant female (range 4 – 7; n = 7). Although small sample sizes precluded statistical significance, we found that larger females in better body condition tended to have more fetuses and that the sex ratio of fetuses tended to be female-biased. Based on the cohort that we sampled in Feb., we predicted parturition would occur between Feb. and May; this range of parturition dates may have been wider had we sampled wild pigs at other times of the year. We show that the number of fetuses of wild pigs in Saskatchewan is similar to other areas, suggesting that population growth and spread could be just as rapid. Our estimates represent the first empirical life history measures of wild pigs in Canada and are an essential step in developing science-based eradication plans for this highly invasive species.
... Wild pigs have more recently become established in parts of Canada (Brook and van Beest 2014;Aschim and Brook 2019), with escapes from farms and penned sport hunting operations thought to be the source (Michel et al. 2017). Observations of wild pigs in Ontario, Canada, suggests that wild pigs are present in the province (Aschim and Brook 2019). ...
... Although a key component of invasive species management is early detection to facilitate a rapid response, the first component is prevention. The recent invasion of wild pigs to new areas in North America is likely human-mediated in many cases; escapes from wild boar farms and captive hunting operations, and intentional release to establish new hunting opportunities are known to be driving factors (Waithman et al. 1999;Michel et al. 2017;McCann et al. 2018). As such, many states in the USA have made legislative changes, such as state-wide bans on possession of and hunting of Eurasian wild boar (Centner and Shuman 2015) to help prevent invasive wild pigs from invading or re-invading. ...
Article
Full-text available
Crowdsourcing can be a useful tool for the early detection of invasive species. Invasive wild pigs (Sus scrofa) have been reported in Ontario, Canada. We compared trends in reporting frequency of wild pig sightings to trends in media events that included directions for the public on where to submit their wild pig sightings. We found that media events occurring on the same week, and in up to two weeks before the sighting was reported significantly increased the number of wild pig reports we received. Our findings suggest that media can be used to increase participation by the public. Because of this relationship, our findings also imply that reporting frequency alone cannot accurately index real changes in wild pig numbers—participants were more likely to report sightings after they had been exposed to relevant media, and spikes in the number of reports tracked our outreach efforts. Despite this limitation, reports of wild pig sightings from community members remain a cost-effective tool to detect low-density invasive species across large regions, and participation in the program can be increased with periodic news media and social media blitzes.
... Our results are consistent with the rapid expansion of wild pig populations in the United States 16,39 and most other areas of their native and introduced range [40][41][42] . Many areas in Canada are susceptible to wild pig expansion, especially those that are comprised of ample, energy-rich food resources from agriculture crops 10 , forest cover 37 , relatively low predator densities 37 , and repeated introduction/re-introduction events 19 . ...
... Our finding of wild pigs mainly concentrated in the Prairie Provinces with some of the coldest winters of all ten provinces and that the species is rare or absent in the warm coastal areas is inconsistent with studies that have found that wild pig distribution is positively associated with warmer climates and have suggested cold winter temperatures to be highly limiting 10,37 . This likely reflects, in part, that domestic wild boar farms that are known sources of free-ranging wild pigs were, and are, more concentrated on the Canadian Prairies 19 . The success of wild pigs in western Canada does highlight the capacity for wild pigs to thrive and expand in areas with long and extremely cold winters including some occurrences north of 55° north latitude. ...
Article
Full-text available
Invasive species can spread rapidly at local and national scales, creating significant environmental and economic impacts. A central problem in mitigation efforts is identifying methods that can rapidly detect invasive species in a cost-effective and repeatable manner. This challenge is particularly acute for species that can spread over large areas (>1 million km2). Wild pigs (Sus scrofa) are one of the most prolific invasive mammals on Earth and cause extensive damage to agricultural crops, native ecosystems, and livestock, and are reservoirs of disease. They have spread from their native range in Eurasia and North Africa into large areas of Australia, Africa, South America, and North America. We show that the range of invasive wild pigs has increased exponentially in Canada over the last 27 years following initial and ongoing releases and escapes from domestic wild boar farms. The cumulative range of wild pigs across Canada is 777,783 km2, with the majority of wild pig distribution occurring in the Prairie Provinces. We evaluate eight different data collection and evaluation/validation methods for mapping invasive species over large areas, and assess their benefits and limitations. Our findings effectively map the spread of a highly invasive large mammal and demonstrate that management efforts should ideally rely on a set of complementary independent monitoring methods. Mapping and evaluating resulting species occurrences provide baseline maps against which future changes can be rapidly evaluated.
... It is well established that wild boar populations are growing almost exponentially throughout Europe, partly due to an insufficient hunting harvest (Massei et al., 2015). One of the drivers of wild boar (or feral pig) expansion to new ranges is hunting, specifically, introductions for hunting purposes and escapes from farms (Michel et al., 2017;Sales et al., 2017). Once new populations are established, feeding and insufficient hunting provide opportunities for further population growth. ...
Article
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EFSA assisted four countries in the analysis of epidemiological data on African swine fever (ASF), collected until September 2017. The temporal analysis demonstrated that the average proportions of PCR and antibody-ELISA positive samples from the hunted wild boar remained below 3.9 and 6.6, respectively. A peak in the ASF incidence was observed 6 months after the first observed case, followed by a significant reduction of the number of cases and low levels of African swine fever virus (ASFV) circulation at the end of 38 months follow-up period at different spatial resolutions. The spatial analysis concluded that human-mediated spread of ASFV continues to play a critical role in the ASF epidemiology, despite all measures currently taken. 'Wild boar density', 'total road length' (as proxy for human activity) and 'average suitable wild boar habitat availability' were identified as predictors for the occurrence of ASF in Estonia by a Bayesian hierarchical model, whereas 'wild boar density' and 'density of pig farms' were predictors according to a generalised additive model. To evaluate the preventive strategies proposed in EFSA's Scientific Opinion (2015) to stop the spread of ASFV in the wild boar population, a simulation model, building on expert knowledge and literature was used. It was concluded that reduction of wild boar population and carcass removal to stop the spread of ASFV in the wild boar population are more effective when applied preventively in the infected area. Drastic depopulation, targeted hunting of female wild boar and carcass removal solely implemented as measures to control ASF in the wild boar population need to be implemented in a highly effective manner (at or beyond the limit of reported effectivity in wild boar management) to sustainably halt the spread of ASF.
... Domestic wild boar were introduced to the Canadian Prairies as livestock in the 1980s and 1990s. Many of these animals escaped or were thought to have been released intentionally (Brook and van Beest 2014;Michel et al. 2017), founding the feral populations that are now reproducing in the wild (Koen et al. 2018). Studies on the impact of wild pigs in Canada are few 4 and their position in habitat space across their northern range is unknown. ...
Article
Invasive species are a major contributor to biodiversity loss worldwide. Wild pigs (Sus scrofa (L., 1758)) are highly invasive in their introduced ranges; they modify habitat and threaten native species. As recent invaders in Canada, it is unknown what habitats wild pigs occupy at the northern edge of their range and how they affect mammalian diversity. We examined habitat factors that we predicted would affect wild pigs’ co-occurrence with native mammals. We randomly placed 17 camera traps in 4 stratified habitat types (deciduous forest, grassland, cropland, and wetland) for two years to examine species co-occurrence in these habitats. We analyzed camera-trap data using non-metric multidimensional scaling. Wild pig detection during winter was greatest in wetland and cropland and positively associated with occurrence of moose (Alces alces (L., 1758)) and coyote (Canis latrans (Say, 1823)) and negatively associated with the presence of white-tailed deer (Odocoileus virginianus (Zimmerman, 1780)), mule deer (O. hemionus (Rafinesque, 1817)) and humans. In summer, we detected wild pigs only in grassland; these detections were positively associated with moose and mule deer, and negatively associated with domesticated cattle (Bos taurus (L., 1758)), elk (Cervus canadensis (Erxleben, 1777)), and humans. We conclude that invasive wild pig occurrence at the northern edge of their Canadian range varies seasonally, by habitat, and is negatively affected by the presence of humans. Moreover, apparent co-occurrence with native fauna and avoidance of domestic species provides early evidence for potential competitive interactions
... ( Bevins et al. 2014, Brook and Beest 2014, Michel et al. 2017, Miller et al. 2017). Environmental 65 and agricultural damage caused by IWPs is at least USD$1.5 billion annually (Pimental 2007, 66 Bevins et al. , Anderson et al. 2016). ...
Preprint
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Conflicts between wildlife, invasive species, and agricultural producers are increasing. Although direct management actions taken to mitigate these conflicts remain controversial, most stakeholders agree that better policies are needed to balance socio-economic considerations with invasive species management, wildlife conservation, and agriculture. However the interaction between societal and biological drivers that influence human-invasive species-wildlife conflict mitigation policy is poorly understood. We identify factors influencing policy leading to the establishment of a new federal program to control invasive wild pigs in the United States. We fit generalized linear models relating frequency of congressional policy activity, such as congressional hearings and reports, to frequency of print newspaper media and percent of the U.S. agricultural industry co-occurring with invasive wild pigs for 29 years preceding the establishment of the federal program in 2013. Our models explained 89% of the deviance in congressional policy activity indicating a strong linkage between congressional invasive wild pig policy activity and predictors representing the number of negative of newspaper articles, geographic distribution of print media, and percent of agricultural producers co-occurring with invasive wild pigs. These effects translated to 3.7% increase in the number of congressional policy actions for every additional five states with negative news media. Invasive wild pig congressional policy activity increased 6.7% for every additional 10 negative newspaper articles. Increases in co-occurrence of agriculture and invasive wild pigs had the largest effect, for every 1% increase in co-occurrence there was a 41% increase in congressional policy activity. Invasive wild pig congressional policy activity that explicitly addressed livestock increased at nearly twice the rate of policy activity addressing crop agriculture. These results suggest that agriculture and media coverage may act as determinants for invasive species policy. Our approach may provide early insight into emerging policy areas enabling proactive policy development by agencies or early engagement by scientists to find solutions before the policy area becomes grid locked. Our results can also support policy and program evaluation providing a means of determining if the implemented policies match the original policy determinants ensuring best alignment with public, environmental, and stakeholder interests.
... The invasive wild pig (IWP) Sus scrofa, often referred to as feral hog, feral pig, feral swine, or wild boar, are the most abundant free-ranging, exotic ungulate in the United States and are the descendants of Eurasian Russian boar (Sus scrofa linnaeus), feral domestic swine (Sus scrofa domestica), and hybrids between the two Brisbin 1991, Keiter et al. 2016). Since the 1960s, IWPs have expanded their range to at least 38 states and three provinces in Canada impacting ecosystems, wildlife, and agriculture (Bevins et al. 2014, Brook and Beest 2014, Michel et al. 2017, Miller et al. 2017). Environmental and agricultural damage caused by IWPs is at least US$1.5 billion annually (Pimental 2007, Bevins et al. 2014, Anderson et al. 2016. ...
Article
Full-text available
Conflicts between wildlife, invasive species, and agricultural producers are increasing. Although direct management actions taken to mitigate these conflicts remain controversial, most stakeholders agree that better policies are needed to balance socioeconomic considerations with invasive species management, wildlife conservation, and agriculture. However, the interaction between societal and biological drivers that influence human–invasive species–wildlife conflict mitigation policy is poorly understood. We identify factors influencing policy leading to the establishment of a new federal program to control invasive wild pigs (IWPs) in the United States. We fit generalized linear models relating frequency of congressional policy activity, such as congressional hearings and reports, to frequency of print newspaper media and percent of the U.S. agricultural industry co‐occurring with IWPs for 29 yr preceding the establishment of the federal program in 2013. Our models explained 89% of the deviance in congressional policy activity indicating a strong linkage between congressional IWP policy activity and predictors representing the number of negative of newspaper articles, geographic distribution of print media, and percent of agricultural producers co‐occurring with IWPs. These effects translated to 3.7% increase in the number of congressional policy actions for every additional five states with negative news media. Invasive wild pig congressional policy activity increased 6.7% for every additional 10 negative newspaper articles. Increases in co‐occurrence of agriculture and IWPs had the largest effect; for every 1% increase in co‐occurrence, there was a 41% increase in congressional policy activity. Invasive wild pig congressional policy activity that explicitly addressed livestock increased at nearly twice the rate of policy activity addressing crop agriculture. These results suggest that agriculture and media coverage may act as determinants for invasive species policy. Our approach may provide early insight into emerging policy areas enabling proactive policy development by agencies or early engagement by scientists to find solutions before the policy area becomes gridlocked. Our results can also support policy and program evaluation providing a means of determining if the implemented policies match the original policy determinants ensuring best alignment with public, environmental, and stakeholder interests.
... Especially in more northern regions, increased effort in removing wild pigs should be focused during colder periods to maximize efficiency. Although wild pigs appear to be expanding in Canada 21,67,68 and other northerly locations in North America 15 which do experience extreme periods of cold temperatures, eradication campaigns may benefit from operating during prolonged periods of cold temperatures. Wild pigs did not become conditioned to avoid using bait sites, thus baiting was a valuable tool for aiding removal even as population densities become low. ...
Article
Full-text available
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.
... In addition, forested areas provide shelter for the wild boar, where thermal regulation occurs during warm seasons, and serves as a hiding place and refuge. However, wetlands are places where animals find water to be ingested, as well as thermal comfort (Higginbotham 2013, Michel et al. 2017. ...
Article
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With the advancement of wild boar distribution in the rural environment, its impacts are not limited to health in the pig sector, but the requirements for monitoring and control of the species are requirements laid down by the OIE for the recognition of classical swine fever free zone status. The construction of ecological models of favorability or suitability for the occurrence of pest species are necessary tools for the decision making on priority areas of management aiming at risk management. This work aims to map the level of suitability for the occurrence of wild boar in the southern state of Mato Grosso do Sul, as well as to identify the main risk variables for contact with the wild boar and evaluate the biosecurity measures adopted by commercial farms integrated in the south of the State of Mato Grosso do Sul. To evaluate the risk potential of wild boar for commercial and subsistence swine farming in southern Mato Grosso do Sul, a model of environmental suitability was constructed for this species in the swine producing region. This model considered different environmental strata, being the selection of the layers considered the physiological and behavioral characteristics of the species. In parallel, interviews were carried out in a sample of commercial farms integrating the region to survey the perception of the presence of the invasive species and the biosafety measures adopted. The results of this work indicate that the risk of contact among wild boars and animals reared in closed production systems may be high in the study area and only establishment of appropriate biosecurity measures that consider the characteristics and habits of the boar may prevent the intrusion of this species and contact with domestic swine. The built model can be considered of high reliability and it is recommended to apply it to other areas of the state, being a useful tool for the productive sector, environmental agencies and decision makers.
... Wild pigs (Sus scrofa), also referred to as feral hogs, feral pigs, feral swine, invasive wild pigs, or wild boars (Keiter et al., 2016), are a widely distributed and destructive invasive species throughout parts of North America, Australia, South America, Africa, and many island nations (Barrios-Garcia and Ballari 2012). In particular, populations of wild pigs have been rapidly increasing and expanding throughout North America during the last 5 decades (Bevins et al., 2014;Michel et al., 2017;Snow et al., 2017). Wild pigs cause extensive damage to agricultural and ecological resources (Hone 1995;Pimentel 2007;Anderson et al., 2016), and these damages are expensive to mitigate (Pimentel 2007). ...
Article
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.
... Second, we used known locations of pigs in captivity as an index of the probability of undetected wild pigs on the landscape. A main source of wild pigs in Canada is escaped pigs from farms and high-fence hunting operations (Michel et al., 2017). While this practice became illegal in Ontario in 2004, closed-down captive hunting establishments could represent undetected wild pigs currently on the landscape (see Jackling et al., 2016). ...
Article
The probability of disease transmission among livestock premises via spillover from wildlife vectors depends on interacting ecological, demographic, and behavioural variables. Wild pigs (Sus scrofa) act as vectors and reservoirs of many diseases, including African Swine Fever (ASF), a highly lethal and contagious viral disease that affects both wild and domestic swine. Wild pigs play a significant role in the spread of ASF in geographic locations where the disease is present. Planning and preparedness will ensure that swift action can be taken to control ASF if it is introduced into North America. We used a network to predict the highest risk areas for ASF spread in Ontario, Canada given the distribution of wild pig sightings and other risk factors for wild pig presence and movement on the landscape. We used network nodes to represent the presence of domestic pig farms in a defined area, and we weighted network edges by the probability of ASF virus movement between farms via movement of wild pigs. Our network models predicted that central Ontario has relatively high network closeness, suggesting that this area has a relatively high risk of virus exposure. These highly connected areas tended to also have the highest domestic pig farm density within a node. Central and eastern Ontario had the highest predicted network betweenness, suggesting that these areas are important for controlling virus flow across the province. We detected 10 communities or clusters within the overall network, where nodes were highly connected locally and relatively less connected to the rest of the network. Predicting areas with a high risk of exposure to the ASF virus due to wild pig movement in Ontario will guide managers on where to focus surveillance for ASF in the wild pig population and where to heighten biosecurity within commercial and backyard pig farms, ensuring that managers are prepared to act quickly to limit spread of ASF if the virus is introduced.
... Since their introduction in the 1500s (Mayer and Brisbin 2008), wild pigs (i.e., domestic wild pigs who are likely a cross between Eurasian wild boar and traditional domestic pigs) have become established in 35 states in the USA (USDA 2020), showing a propensity to expand into areas with higher proportions of agriculture (Snow et al. 2017). In contrast, they have only been present in Canada since the 1980s, yet have rapidly expanded at rates greater than those in the USA (12.6 km 2 /year in the USA vs. 88 094 km 2 /year in Canada; Snow et al. 2017;Aschim and Brook 2019), particularly in the prairie provinces (i.e., Alberta, Saskatchewan, and Manitoba), due to accidental escapes and intentional releases (Brook and van Beest 2014;Michel et al. 2017). Currently, Canadian wild pig densities are unknown, but are likely lower than what is seen in many other parts of North America given that they are newly colonizing. ...
Article
Resource selection informs understanding of a species’ ecology and is especially pertinent for invasive species. Since introduced to Canada, wild pigs (Sus scrofa Linnaeus, 1978) remain understudied despite recognized negative impacts to native and agricultural systems globally. Elsewhere in North America, pigs typically use forests and forage in agricultural crops. We hypothesized Canadian wild pigs would behave similarly and using GPS locations from 15 individuals we examined diel and seasonal resource selection and movement in the Canadian prairie region. Forests were predominately selected during the day, while corn (Zea mays L.), oilseeds, and wheat (Triticum aestivum L.) were predominately selected at night. Forests and corn were consistently selected throughout the growing season. Wetlands and forests showed greater use rates than other habitats, with evident trade-offs as crop use increased with the timing of maturation. Activity was consistent with foraging in growing crops. Results indicate diel patterns were likely a function of short-term needs to avoid daytime anthropogenic risk, while seasonal patterns demonstrate how habitats that fill multiple functional roles – food, cover, and thermoregulation – can be optimized. Understanding selection by invasive species is an important step in understanding their potential environmental impacts in novel environments and informs their management.
... Wild pigs are native to Eurasia and Northern Africa, but have been widely introduced for centuries, often deliberately, and now occupy every continent except Antarctica (Mayer and Brisbin, 1991;Lewis et al., 2017). In North America it is an extremely destructive invasive species that is of concern for human and increased dramatically in recent years (Michel et al., 2017;Snow et al., 2017), and research suggests that a major mechanism for their spread is translocation of individuals to augment populations for recreational hunting (Tabak et al., 2016). Wild pigs evolved as pulsed resource consumers of mast crops; they have larger litter sizes and reproduce more often under favorable forage conditions, and have reduced fecundity under poor forage conditions (Ostfeld and Keesing, 2000). ...
Preprint
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Invasion of nonindigenous species is considered one of the most urgent problems affecting native ecosystems and agricultural systems. Mechanistic models that account for short-term population dynamics can improve prediction because they incorporate differing demographic processes that link the environmental conditions of a spatial location explicitly with the invasion process. Yet short-term population dynamics are rarely accounted for in spatial models of invasive species spread. Accounting for transient population dynamics, we predict the population growth rate and establishment probability of wild pigs following introduction into any location in North America. We compared predicted population growth rate with observed geographic rates of spread and found significant relationships between the annual rate of spread and population growth rates. We used geospatial data on the distribution of mast producing tree species (a principle forage resource of wild pigs) and agricultural crops that can replace mast in their diets to predict population dynamics using transient population simulations. We simulated populations under different initial population sizes (i.e. number of introduced individuals, often termed propagule size) and for different amounts of time following introduction. By varying the initial population size and simulation time, we were able to identify areas in North America with high probability for establishment of wild pigs if introduced. Our findings can be used to inform surveillance and removal efforts to reduce the potential for establishment and spread of wild pigs.
Technical Report
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This report describes the results of the first aerial survey attempt in the Northwest Territories conducted in November 2020 that looked for wild pigs. The survey was a proactive response to the threat of an expanding range of wild pigs in Alberta and Saskatchewan northwards, and an opportunity to judge the operational realities using a belly-mounted forward-looking infrared (FLIR) camera on a helicopter for future monitoring and management responses.
Article
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We compiled and analysed data from 1987-2004 on vegetation monitoring during feral ungulate management at Hakalau Forest National Wildlife Refuge, a tropical montane rainforest on the island of Hawai'i All areas in the study had previously been used by ungulates, but cattle (Bos taurus) were removed and feral pig (Sus scrofa) populations were reduced during the study period. We monitored six line-intercept transects, three in previously high ungulate use areas and three in previously low ungulate use areas. We measured nine cover categories with the line-intercept method: native ferns; native woody plants; bryophytes; lichens; alien grasses; alien herbs; litter; exposed soil; and coarse woody debris. Vegetation surveys were repeated four times over a 16-year period. Vegetation monitoring revealed a strong increase in native fern cover and slight decreases in cover of bryophytes and exposed soil. Mean cover of native plants was generally higher in locations that were formerly lightly grazed, while alien grass and herb cover was generally higher in areas that were heavily grazed, although these effects were not statistically significant. These responses may represent early serai processes in forest regeneration following the reduction of feral ungulate populations. In contrast to many other Hawaiian forests which have become invaded by alien grasses and herbs after ungulate removal, HFNWR has not experienced this effect.
Article
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Wild pigs (Sus scrofa), also known as wild swine, feral pigs, or feral hogs, are one of the most widespread and successful invasive species around the world. Wild pigs have been linked to extensive and costly agricultural damage and present a serious threat to plant and animal communities due to their rooting behavior and omnivorous diet. We modeled the current distribution of wild pigs in the United States to better understand the physiological and ecological factors that may determine their invasive potential and to guide future study and eradication efforts. Using national-scale wild pig occurrence data reported between 1982 and 2012 by wildlife management professionals, we estimated the probability of wild pig occurrence across the United States using a logistic discrimination function and environmental covariates hypothesized to influence the distribution of the species. Our results suggest the distribution of wild pigs in the U.S. was most strongly limited by cold temperatures and availability of water, and that they were most likely to occur where potential home ranges had higher habitat heterogeneity, providing access to multiple key resources including water, forage, and cover. High probability of occurrence was also associated with frequent high temperatures, up to a high threshold. However, this pattern is driven by pigs' historic distribution in warm climates of the southern U.S. Further study of pigs' ability to persist in cold northern climates is needed to better understand whether low temperatures actually limit their distribution. Our model highlights areas at risk of invasion as those with habitat conditions similar to those found in pigs' current range that are also near current populations. This study provides a macro-scale approach to generalist species distribution modeling that is applicable to other generalist and invasive species.
Article
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the Wild Boar (Sus scrofa) is invasive in western Canada and poses a significant ecological and socio-economic threat over much of the country. We sought to quantify their presence and to determine when they are most active and whether their activity patterns are influenced by group size. Digital trail cameras (n = 18) were placed in a stratified design in the four most dominant habitat types of central Saskatchewan, Canada, and activated between December 2011 and June 2013 for a total of 5715 trap-days. In 71 175 photographs, we obtained 22 individual visits of Wild Boars to the trail cameras. We found no differences in activity between night (1900–0700; 59% of all detections) and day (0701–1859; 41% of detections), and we did not detect any effect of group size. ongoing monitoring will be required to determine changing activity patterns in response to changing hunting pressure as Wild Boar continue to expand across Canada.
Article
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The wild boar Sus scrofa is an omnivore with one of the largest geographical ranges of all species. However, no synthesis exists on its diet, feeding behaviour and factors affecting food selection in its native and introduced ranges.A literature review and a test of effect size revealed significant differences in wild boar diet composition in native and introduced ranges. Wild boar diet is dominated by plant material (∼90%) in both ranges, but animal matter and fungi are consumed in greater proportions in the introduced range than in the native range. Food items frequently include agricultural crops (especially in the native range) and endangered animal species (especially in the introduced range). Energy requirements, food availability, and seasonal and geographical variations are major factors influencing food selection by wild boar. These factors may also interact with human activities (e.g. agricultural crops, supplementary feeding) to influence diet composition further.Dietary studies should be more rigorous and consistent across ranges to allow better comparisons. A detailed study of diet in combination with seasonal patterns of habitat use could provide key information such as target species and susceptible habitats on which management efforts should focus.
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Wild boar are now present on all conti-nents except Antarctica and can greatly affect com-munity structure and ecosystem function. Their destructive feeding habits, primarily rooting distur-bance, can reduce plant cover, diversity, and regener-ation. Furthermore, predation and habitat destruction by boar can greatly affect animal communities. Effects of wild boar on fungi and aquatic communities are scarcely studied, and soil properties and processes seem more resistant to disturbance. Wild boar also affect humans' economy as they cause crop damage and transmit diseases to livestock and wildlife. In this review, we found that most of the published literature examines boar effects in their introduced range and little is available from the native distribution. Because most of the research describes direct effects of wild boar on plant communities and predation on some animal communities, less is known about indirect effects on ecosystem function. Finally, predictive research and information on ecosystem recovery after wild boar removal are scarce. We identified research gaps and urge the need to lower wild boar densities. Identifying commonalities among wild boar impacts on native ecosystems across its introduced range will help in the design of management strategies.
Article
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Feral swine populations provide both benefits and liabilities to citizens of the United States. Their expanding range and increasing densities, however, have raised concern over the adverse environmental and agricultural effects and the increased risk of disease transmission between feral swine and livestock. We discuss the role of feral swine in the transmission of wildlife diseases and, in particular, in diseases of national significance to the livestock industry. We also discuss available management tools and strategies for reducing feral swine populations, minimizing damage or disease occurrences and eradicating populations when deemed appropriate. Finally, we note areas of research that may provide valuable management tools in the future.
Article
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Wild pigs (Sus scrofa) are considered opportunistic omnivores that consume primarily plant matter; vertebrates are thought to constitute only a minor component of their diets, primarily as carrion, but active predation on vertebrates has been suspected. We examined the stomach contents of 104 wild pigs collected during a 7-year period in oak woodlands of the Diablo Range, California, and found that 40.4% contained vertebrate prey comprising 20 species, including I I mammals, and totaling 167 individuals. Most stomachs with vertebrate prey included multiple individuals (<= 18) of >1 species (<= 6). Predation occurred in both male and female pigs and was most frequent during summer and fall, probably in response to protein deficiency in the diet. Wild pigs are a conservation concern because of their rooting behavior and consumption of mast; our results extend their potential impact to include predation on vertebrates, especially small mammals.
Article
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More than 30 species of exotic freeranging mammals have become established in the United States since European colonization (De Vos et al., 1956; McKnight, 1964; Roots, 1976). These species often become serious economic pests and can have grave consequences on their host environments (Cottam, 1956; De Vos et al., 1956; Mayer and Brisbin, 1991). True wild pigs (Suidae) are not native to the United States. Only the collared peccary (Tayassu tajacu; Tayassuidae) that inhabits the southwestern and south-central parts of the United States is native (Mayer and Brandt, 1982; Mayer and Wetzel, 1986). Feral swine (Sus scrofa) in the United States have originated from varieties of domestic swine, Eurasian wild boar, and their hybrids (Jones, 1959; Wood and Lynn, 1977; Rary et al., 1968; Mayer and Brisbin, 1991). Domestic swine were introduced to the United States as early as 750-1000 A.D. during the settlement of the Hawaiian Islands (Towne and Wentworth, 1950; Joesting, 1972; Smith and Diong, 1977). Christopher Columbus introduced domestic swine to the West Indies during the 1400s, where they proliferated and became pests. In the 1500s, Spanish explorers, such as DeSoto and Cortez, were the first to bring domestic swine to the United States mainland (Towne and Wentworth, 1950; Beldon and Frankenberger, 1977). By the 1960s, domestic swine and Eurasian wild boar were established in >20 states (McKnight, 1964). Swine introductions have intentionally or accidentally occurred by a variety of means, including: 1) translocation to establish populations for hunting, 2) escapees from shooting preserves or confinement operations, 3) avoidance of capture by domestic pigs in free-ranging livestock operations, 4) abandonment by their owners, and 5) dispersal from established feral populations (Gipson et al., 1997; Witmer et al., 2004). Feral swine are the most abundant free-ranging, exotic ungulate in the United States (McKnight, 1964; Decker, 1978) and have become widespread because of their reproductive potential and adaptability to a wide range of habitats. Like domestic swine, litter size depends on the sow’s age, nutrition, and time of year. Feral swine are capable of producing two litters per year with average litter size varying from 4.2 to 7.5 piglets (Taylor et al., 1998), but up to 10 piglets can be born during ideal conditions (Conquenot et al., 1996). Mayer and Brisbin (1991) and Mackey (1992) report feral swine populations in 23 states. A Southeastern Cooperative Disease Study (1994) and Nettles (1997) point out an additional 16 states with feral swine populations. An estimated population of 4 million feral swine currently occur in the United States (Pimentel et al., 2000) with the largest populations inhabiting Texas (1 to 1.5 million; Pimentel et al., 2000), Florida (>500,000; Layne, 1997), Hawaii (80,000; Mayer and Brisbin, 1991), and California (70,000; Barrett, 1993). Since 1965, feral swine have expanded their range from 15 (26%) to 45 (78%) of the 58 California counties (Frederick, 1998). Feral swine populations continue to increase (Gipson et al., 1997) because they possess the greatest reproductive potential of all free-ranging, large mammals in the United States (Wood and Barrett, 1979; Hellgren, 1999) and because of the absence of large native predators (e.g., mountain lion (Felis concolor) and wolves (Canis lupus) over much of the area occupied by feral swine. In southwest Florida where feral swine and a large predator coexist, feral swine is the most common food item (42%) in Florida panther (F. c. coryi) scats (Maehr et al., 1990), which may suggest that the presence of a large predator helps regulate feral swine density and associated damage.
Article
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We quantified the threats facing 488 species in Canada, categorized by COSEWIC (Committee on the Status of Endangered Wildlife in Canada) as extinct, extirpated, endangered, threatened, or of special concern. Habitat loss is the most prevalent threat (84%), followed by overexploitation (32%), native species interactions (31%), natural causes (27%), pollution (26%), and introduced species (22%). Agriculture (46%) and urbanization (44%) are the most common human activities causing habitat loss and pollution. For extant species, the number of threats per species increases with the level of endangerment. The prevalence of threat types varies among major habitats, with overexploitation being particularly important, and introduced species particularly unimportant, for marine species. Introduced species are a much less important threat in Canada than in the United States, but the causes of endangerment are broadly similar for Canadian and globally endangered species.
Article
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Over 120,000 non-native species of plants, animals and microbes have invaded the United States, United Kingdom, Australia, South Africa, India, and Brazil, and many have caused major economic losses in agriculture and forestry as well as negatively impacting ecological integrity. Some introduced species, like corn (Zea mays L.), wheat (Triticum spp.), rice (Oryza sativa L.), plantation forests, domestic chicken (Gallus spp.), cattle (Bos taurus), and others, are beneficial and provide more than 98% of the world’s food supply. Precise economic costs associated with some of the most ecologically damaging alien species are not available. Cats (Felis cattus) and pigs (Sus scrofa), for example, are responsible for the extinction of various animal species, however, it is impossible to assign monetary values to species forced to extinction. The estimate is that non-native species invasions in the six nations are causing more than US$ 314 billion per year in damages.
Article
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Aim To offer an objective approach to some of the problems associated with the development of logistic regression models: how to compare different models, determination of sample size adequacy, the influence of the ratio of positive to negative cells on model accuracy, and the appropriate scale at which the hypothesis of a non-random distribution should be tested. Location Test data were taken from Southern Africa. Methods The approach relies mainly on the use of the AUC (Area under the Curve) statistic, based on ROC (threshold Receiver Operating Characteristic) plots, for between-model comparisons. Data for the distribution of the bont tick Amblyomma hebraeum Koch (Acari: Ixodidae) are used to illustrate the methods. Results Methods for the estimation of minimum sample sizes and more accurate hypothesis-testing are outlined. Logistic regression is robust to the assumption that uncollected cells can be scored as negative, provided that the sample size of cells scored as positive is adequate. The variation in temperature and rainfall at localities where A. hebraeum has been collected is significantly lower than expected from a random sample of points across the data set, suggesting that within-site variation may be an important determinant of its distribution. Main conclusions Between-model comparisons relying on AUCs can be used to enhance objectivity in the development and refinement of logistic regression models. Both between-site and within-site variability should be considered as potentially important factors determining species distributions.
Article
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Biological invasions by nonindigenous species (NIS) can have adverse effects on economically important goods and services, and sometimes result in an ‘invisible tax’ on natural resources (e.g. reduced yield). The combined economic costs of NIS may be significant, with implications for environmental policy and resource management; yet economic impact assessments are rare at a national scale. Impacts of nuisance NIS may be direct (e.g. loss of hardwood trees) or indirect (e.g. alteration of ecosystem services provided by growing hardwoods). Moreover, costs associated with these effects may be accrued to resources and services with clear ‘market’ values (e.g. crop production) and to those with more ambiguous, ‘non-market’ values (e.g. aesthetic value of intact forest). We characterised and projected economic costs associated with nuisance NIS in Canada, through a combination of case-studies and an empirical model derived from 21 identified effects of 16 NIS. Despite a severe dearth of available data, characterised costs associated with ten NIS in Canadian fisheries, agriculture and forestry totalled $187 million Canadian (CDN) per year. These costs were dwarfed by the ‘invisible tax’ projected for sixteen nuisance NIS found in Canada, which was estimated at between $187 million Canadian (CDN) per year. These costs were dwarfed by the ‘invisible tax’ projected for sixteen nuisance NIS found in Canada, which was estimated at between 13.3 and $34.5 billion CDN per year. Canada remains highly vulnerable to new nuisance NIS, but available manpower and financial resources appear insufficient to deal with this problem.
Chapter
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One of the core goals of invasion biology is the identification of factors that increase the risk of establishment success of non-native species. Historically, marine invasions have been investigated through observational studies and surveys (Cohen and Carlton 1998; Ruiz et al. 2000). These have guided ecologists towards the processes most relevant to invasion, but researchers are becoming increasingly aware of the limitations of observational studies alone. It is clear that different factors may influence invasion success at different stages of the invasion process (Kolar and Lodge 2001) and a major challenge is to quantify the relative importance of these factors. Understanding the intricacies of invasion dynamics requires a rigorous approach, in which potentially important factors can be controlled, manipulated and tested (Ruiz et al. 2000). Particularly strong calls have been made for the inclusion of propagule pressure or invader supply into our models, experiments and surveys, and this chapter reviews recent progress in elucidating the role of propagule pressure on invasion success in marine ecosystems.
Article
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Species become invasive if they (i) are introduced to a new range, (ii) establish themselves, and (iii) spread. To address the global problems caused by invasive species, several studies investigated steps ii and iii of this invasion process. However, only one previous study looked at step i and examined the proportion of species that have been introduced beyond their native range. We extend this research by investigating all three steps for all freshwater fish, mammals, and birds native to Europe or North America. A higher proportion of European species entered North America than vice versa. However, the introduction rate from Europe to North America peaked in the late 19th century, whereas it is still rising in the other direction. There is no clear difference in invasion success between the two directions, so neither the imperialism dogma (that Eurasian species are exceptionally successful invaders) is supported, nor is the contradictory hypothesis that North America offers more biotic resistance to invaders than Europe because of its less disturbed and richer biota. Our results do not support the tens rule either: that ≈10% of all introduced species establish themselves and that ≈10% of established species spread. We find a success of ≈50% at each step. In comparison, only ≈5% of native vertebrates were introduced in either direction. These figures show that, once a vertebrate is introduced, it has a high potential to become invasive. Thus, it is crucial to minimize the number of species introductions to effectively control invasive vertebrates. • biotic resistance • ecological imperialism • invasive species • tens rule • time lags
Code
Tools for performing model selection and model averaging. Automated model selection through subsetting the maximum model, with optional constraints for model inclusion. Model parameter and prediction averaging based on model weights derived from information criteria (AICc and alike) or custom model weighting schemes. [Please do not request the full text - it is an R package. The up-to-date manual is available from CRAN].
Article
Since 1980, populations of wild boar (Sus scrofa) have increased over the species' entire European range. This increase has led to conflicts because wild boars cause crop damage amounting to several million U.S. dollars every year. Wildlife management agencies promote and financially support 3 major methods to reduce the loss: (1) intensive harvest, (2) supplemental feeding in forests to bait animals for easier shooting and to distract them from agricultural fields, and (3) building electrical fences around crops at risk. Our objective was to investigate how effective these methods were in reducing field damage by wild boars. Based on data from 44 hunting territories in the Canton Thurgau, Switzerland, we related damage frequency to harvest success, supplemental feeding, and fencing effort by means of 2 multiple regression analyses. The analysis of mean damage frequency among territories (averaged over 3 years) and changes in damage frequency within territories from 1994 to 1996 showed that only hunting reduced damage by wild boars. Because our results question the effectiveness of wild boar management practices and wild boar populations and damage are increasing throughout Europe, we suggest that control efforts and funds be reconsidered. Because only hunting seems to clearly reduce wild boar damage, we suggest more emphasis be put on the development and introduction of new harvest models among local hunting teams.
Article
Movements and home ranges of radio-collared wild boar (Sus scrofa) were monitored during February 1977-February 1979 in Great Smoky Mountains National Park, Tennessee. Seasonal home ranges of males ( $\overline{x}=3.5\text{km}^{2}$ ) were generally larger than those of females ( $\overline{x}=3.1\text{km}^{2}$ ). During a mast failure, winter home ranges were 3 times larger, mean hourly movement increased 5-fold, and seasonal migrations were more erratic than during winters following abundant mast production. One female reduced her seasonal ranges an average of 94% when suckling piglets. Certain males, possibly more dominant, aggressive, and sexually motivated, moved significantly greater distances per hour, and had larger seasonal ranges than other males. In summer, wild boar were primarily nocturnal feeders, and preferred American beech (Fagus grandifolia) northern hardwood, and cove hardwood forest types.
Article
The successful ‘Judas’ goat technique has been adapted for use with feral pigs. The ‘Judas’ goat technique involves releasing radio-collared goats into a control area and, after a sufficient period to allow them to join other goats, tracking them down and culling the other individuals associated with them. Trials with the technique on feral pigs in Namadgi National Park, ACT, indicated that it worked best with sows captured in the same area. Each of these sows established contact with 1–8 other pigs in the area within 1–7 days of release and was located with at least one other pig on 67–100% of occasions. In contrast, sows and boars from outside the study area took longer to come into contact with ‘local’ pigs and associated with them much less frequently. A subsequent control exercise in Namadgi, using ‘Judas’ pigs to indicate where to lay warfarin baits from a helicopter, resulted in a 75% reduction in the low-density population still present after a larger control exercise two years earlier. Since then, the technique has been used to eradicate a small colony of feral pigs in central Australia and is proving successful for control of feral pigs and other ungulates in other parts of Australia and New Zealand.
Article
Feral wild boar (Sus scrofa) are rapidly expanding their distribution and abundance globally and causing considerable socio-economic impacts. Prior to this study, the spatial distribution of feral boar on the Canada prairies was largely unknown. We surveyed all 296 rural municipalities in Saskatchewan, Canada, to determine the distribution of feral boar in the province and characterize community leader perceptions of risk. Of the respondents, over the past 3 years 48% never saw feral boar, 48% saw them at least occasionally, and 3% responded “I don't know,” indicating a few respondents were not confident in saying feral boar were present or absent. Feral boar were observed across a range of habitats, in all months, and at all times of day. Variables that best predicted the distribution of feral boar included % farmland (β = 6.46), % flaxseed crop (β = −8.63), density of paved roads (β = −1.92), % deciduous forest (β = 5.93), and % mustard seed crop (β = −12.63). Mapping the resource selection probability function (RSPF) across the landscape of rural Saskatchewan predicted 70% of municipalities had RSPF >0.7 (high probability of boar presence) and 12% had RSPF <0.3 (low probability of boar presence). At the scale of the individual municipalities, responses about management actions were positively associated with frequency of feral boar observations, whereas questions about the province as a whole were consistently positive regardless of frequency of feral boar observations. Control efforts in Canada are sporadic and limited in scope and scale, but the current distribution of feral boar in Saskatchewan, in combination with the life-history strategy of the species, indicates that aggressive and coordinated action is required. © 2014 The Wildlife Society.
Article
Since 1980, populations of wild boar (Sus scrofa) have increased over the species' entire European range. This increase has led to conflicts because wild boars cause crop damage amounting to several million U.S. dollars every year. Wildlife management agencies promote and financially support 3 major methods to reduce the loss: (1) intensive harvest, (2) supplemental feeding in forests to bait animals for easier shooting and to distract them from agricultural fields, and (3) building electrical fences around crops at risk. Our objective was to investigate how effective these methods were in reducing field damage by wild boars. Based on data from 44 hunting territories in the Canton Thurgau, Switzerland, we related damage frequency to harvest success, supplemental feeding, and fencing effort by means of 2 multiple regression analyses. The analysis of mean damage frequency among territories (averaged over 3 years) and changes in damage frequency within territories from 1994 to 1996 showed that only hunting reduced damage by wild boars. Because our results question the effectiveness of wild boar management practices and wild boar populations and damage are increasing throughout Europe, we suggest that control efforts and funds be reconsidered. Because only hunting seems to clearly reduce wild boar damage, we suggest more emphasis be put on the development and introduction of new harvest models among local hunting teams.
Article
Increasing reports of human/cougar conflicts may suggest that cougars are increasing in the Pacific Northwest. We determined minimum relative densities and average fecundity, survival, and growth rate of an apparently increasing cougar population in northeastern Washington, USA; northern Idaho, USA; and southern British Columbia, Canada, from 1998 to 2003. Minimum relative densities declined from 1.47 cougars/100 km2 to 0.85 cougars/100 km2. We estimated average litter size at 2.53 kittens, interbirth interval at 18 months, proportion of reproductively successful females at 75%, and age at first parturition at 18 months for a maternity rate of 1.27 kittens/adult female/yr. Average survival rate for all radiocollared cougars was 59%: 77% for adult females, 33% for adult males, 34% for yearlings, and 57% for kittens. Hunting accounted for 92% of mortalities of radiocollared cougars. The annual stochastic growth rate of this population was λ = 0.80 (95% CI = 0.11). Contrary to accepted belief, our findings suggest that cougars in the Pacific Northwest are currently declining. Increased conflicts between cougars and humans in this area could be the result of the 1) very young age structure of the population caused by heavy hunting, 2) increased human intrusion into cougar habitat, 3) low level of social acceptance of cougars in the area, or 4) habituation of cougars to humans. To help preserve this population, we recommend reduced levels of exploitation, particularly for adult females, continuous monitoring, and collaborative efforts of managers from adjacent states and provinces.
Article
In this paper the recent population changes of the Wild Boar in different European countries is analysed through the study of hunting statistics. A simultaneous increase in numbers is observed throughout the whole area during the period 1965–1975. From 1975 onwards the population stabilizes itself apart from in peripheral areas like Finland. Potentially favourable factors which play a part in this process are discussed and certain reproductive and dispersive characteristics which favour its invasive behaviour are discussed.
Article
Aim We reviewed 54 studies reporting population densities of wild boar (Sus scrofa) in western Eurasia in order to investigate the roles of vegetation productivity [fraction of photosynthetically active radiation (FPAR) index], winter harshness (mean January temperature) and presence/absence of wolves (Canis lupus) in shaping the biogeographical variation in population density of wild boar. Location We collected published data on the autumn–winter population density of wild boar (number of individuals km−2) in 54 locations in western Eurasia, from 1966 to 2003. Methods The mean January temperature, obtained from the World Climate data base (http://www.worldclimate.com), was taken as a measure of winter severity. We used monthly 4 × 4 km MODIS FPAR data sets covering January 2000 to June 2004 to calculate the vegetation productivity index. In addition, we collected literature data about the presence or absence of wolves from the study areas. Results In the geographical span of 37–60° N, the population densities of wild boar declined by three orders of magnitude, from 10 to 0.01 individuals km−2. The best multiple regression model (selected with the Akaike information criterion corrected for small samples) showed that mean January temperature and the vegetation productivity index were the most important factors explaining the biogeographical variation in population densities of wild boar. The impact of temperature was stronger than that of productivity. The presence of wolves had a weak limiting effect on population densities of wild boar at the biogeographical scale. Main conclusion We propose that winter harshness imposes density-independent mortality on wild boar populations at higher latitudes. Competition for food in less productive regions may cause stronger density dependence in birth and death rates of wild boar populations. We expect that wild boar will respond to global warming by both an increase in local population densities and an expansion of their geographical range north and north-eastwards.
Article
Summary • Humans have traded and transported alien species for millennia with two notable step-changes: the end of the Middle Ages and beginning of the Industrial Revolution. However, in recent decades the world has entered a new phase in the magnitude and diversity of biological invasions: the Era of Globalization. This Special Profile reviews the links between the main drivers of globalization and biological invasions and examines state-of-the-art approaches to pathway risk assessment to illustrate new opportunities for managing invasive species. • Income growth is a primary driver of globalization and a clear association exists between Gross Domestic Product and the richness of alien floras and faunas for many regions of the world. In many cases, the exposure of these economies to trade is highlighted by the significant role of merchandise imports in biological invasions, especially for island ecosystems. • Post-1950, technical and logistic improvements have accelerated the ease with which commodities are transported across the globe and hindered the traceability of goods and the ease of intercepting pests. New sea, land and air links in international trade and human transport have established novel pathways for the spread of alien species. Increasingly, the science advances underpinning invasive species management must move at the speed of commerce. • Increasing transport networks and demand for commodities have led to pathway risk assessments becoming the frontline in the prevention of biological invasions. The diverse routes of introduction arising from contaminant, stowaway, corridor and unaided pathways, in both aquatic and terrestrial biomes are complex. Nevertheless, common features enable comparable approaches to risk assessment. By bringing together spatial data on climate suitability, habitat availability and points of entry, as well a demographic models that include species dispersal (both natural and human-mediated) and measures of propagule pressure, it is possible to generate risk maps highlighting potential invasion hotspots that can inform prevention strategies. • Synthesis and applications. To date, most attempts to model pathways have focused on describing the likelihood of invader establishment. Few have modelled explicit management strategies such as optimal detection and inspection strategies and assessments of the effectiveness of different management measures. A future focus in these areas will ensure research informs response.
Article
Invading alien species in the United States cause major environmental damages and losses adding up to almost $120 billion per year. There are approximately 50,000 foreign species and the number is increasing. About 42% of the species on the Threatened or Endangered species lists are at risk primarily because of alien-invasive species.
Article
ROCR is a package for evaluating and visualizing the performance of scoring classifiers in the statistical language R. It features over 25 performance measures that can be freely combined to create two-dimensional performance curves. Standard methods for investigating trade-offs between specific performance measures are available within a uniform framework, including receiver operating characteristic (ROC) graphs, precision/recall plots, lift charts and cost curves. ROCR integrates tightly with R's powerful graphics capabilities, thus allowing for highly adjustable plots. Being equipped with only three commands and reasonable default values for optional parameters, ROCR combines flexibility with ease of usage. Availability: http://rocr.bioinf.mpi-sb.mpg.de. ROCR can be used under the terms of the GNU General Public License. Running within R, it is platform-independent. Contact: tobias.sing{at}mpi-sb.mpg.de
PigTrace/PorcTrace Canada
  • Canadian Pork Council
Canadian Pork Council (2015). PigTrace/PorcTrace Canada. http://pigtrace.ca/. [Accessed 20 September 2015].
U.S. wild pig problem irks state officials
  • K Murphy
Murphy, K. (2013). U.S. wild pig problem irks state officials. Reuters. http://www. huffingtonpost.com/2013/08/24/us-wild-pigs_n_3809182.html. [Accessed 15 15 September 2015].
Exotic swine ban in Michigan brings backlash
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