Wild boar are now present on all continents except Antarctica and can greatly affect community structure and ecosystem function. Their destructive feeding habits, primarily rooting disturbance, can reduce plant cover, diversity, and regeneration. 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.

Impact of wild boar (Sus scrofa) in its introduced and native range: a review

The Middle Ebro Valley (MEV) is a semiarid area in northeast Iberia where the original riparian ecosystems are almost extinct and were replaced by intensive irrigated agricultural lands. To minimize crop damages and to understand the impact of wild boar on relict riparian ecosystems, a culling program was undertaken from 1994 until 2004. To assess the impact of wild boars, we analyzed stomach contents and surveyed crop damage. In the MEV, wild boars feed mainly on crops, particularly, maize. Other elements of the diet that are of agricultural origin include wheat, barley, and alfalfa, which are the alternatives to maize in the period between harvest and seeding, which is the basis of seasonal changes in diet. Results indicate that wild boar actively selected maize crops and consumed wheat in proportion to its abundance; barley and alfalfa fields were damaged less than expected based on their abundance. In the MEV, the wild boar population is limited by the availability of shelter areas found in the scarce riparian ecosystems, which do not provide important food items for this population. We conclude that in the region of this study, wild boars are not a significant threat to the flora and fauna of riparian ecosystems, although as these habitats are restored and areas are protected, the carrying capacity for wild boars might increase.

Diet of wild boar Sus scrofa L. and crop damage in an intensive agroecosystem

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.

A review of wild boar Sus scrofa diet and factors affecting food selection in native and introduced ranges

Wildlife species as reservoirs of infectious pathogens represent a serious constraint in the implementation of disease management strategies. In the Mediterranean island of Corsica, the dynamics of hepatitis E virus (HEV) and Aujeszky's disease virus (ADV) are suspected to be influenced by interactions between wild and domestic pigs. To improve our understanding of these influences, we first compared the seroprevalences of both viruses in domestic pig populations from different locations with contrasted levels of wild-domestic interactions, ADV vaccination, biosafety, and farm husbandry. Second, we performed an analysis at a more restricted geographical scale, to assess the matching of ADV or HEV prevalence between sympatric wild boar and outdoor pig farms most exposed to interactions with wildlife. Logistic models were adjusted to the observed data. A high seroprevalence of HEV (>80%) and ADV (40%) in pigs, with no significant difference according to the region, confirms that both pathogens are enzootic in Corsica. Vaccination against ADV had a strong protective effect, even when performed voluntarily by farmers. Farm biosafety had an additional effect on pigs' exposure, suggesting that contact between wild boars and pigs were involved in disease transmission. A strong correlation in HEV seroprevalence was observed between pigs and wild boars that were in close contact, and significantly lower seroprevalence was observed in pigs when they had little contact with wild boars due to spatial segregation. These results suggest a regular HEV circulation between sympatric wild boar and domestic pigs. The high HEV seroprevalence observed in domestic pigs (>80%) suggests a spillover of the virus from domestic to wild populations through environmental contamination, but this hypothesis has to be confirmed. Conversely, even though avoiding sows' release on pasture during estrus showed some protecting effect in the free ranging pig farms regarding ADV, ADV seroprevalence was not dependent on the swine populations (wild or domestic) or on the wild-domestic spatial overlap, suggesting two quasi-separate enzootic cycles. This information will prove useful for designing more efficient disease management strategies in Corsica and similar contexts.

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Aujeszky's Disease and Hepatitis E Viruses Transmission between Domestic Pigs and Wild Boars in Corsica: Evaluating the Importance of Wild/Domestic Interactions and the Efficacy of Management Measures.

In 2007 African swine fever (ASF) arrived at a Black Sea harbour in Georgia and in 2014 the infection reached the European Union (EU), where it still expands its territory. ASF is a fatal viral disease affecting domestic pigs and wild boar of all ages with clinical presentations ranging from per-acute to chronic disease, including apparently asymptomatic courses. Until the detection of the first case inside the EU, infections in the current epidemic were mainly seen among pig farms with generally low biosecurity, and with incidental spill over to the wild boar population. In the EU, however, the infection survived locally in the wild boar population independently from outbreaks in domestic pigs, with a steady and low prevalence. Apart from the wild boar population and the habitat, the current epidemic recognizes humans as the main responsible for both long distance transmission and virus introduction in the domestic pig farms. This underlines the importance to include social science when planning ASF-prevention, −control, or -eradication measures. Based on experiences, knowledge and data gained from the current epidemic this review highlights some recent developments in the epidemiological understanding of ASF, especially concerning the role of wild boar and their habitats in ASF epidemiology. In this regard, the qualities of three epidemiological traits: contagiousity, tenacity, and case fatality rate, and their impact on ASF persistence and transmission are especially discussed.

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Epidemiological considerations on African swine fever in Europe 2014–2018

Across Europe, wild boar numbers increased in the 1960s-1970s but stabilised in the 1980s; recent evidence suggests that the numbers and impact of wild boar has grown steadily since the 1980s. As hunting is the main cause of mortality for this species, we reviewed wild boar hunting bags and hunter population trends in 18 European countries from 1982 to 2012. Hunting statistics and numbers of hunters were used as indicators of animal numbers and hunting pressure. The results confirmed that wild boar increased consistently throughout Europe, while the number of hunters remained relatively stable or declined in most countries. We conclude that recreational hunting is insufficient to limit wild boar population growth and that the relative impact of hunting on wild boar mortality had decreased. Other factors, such as mild winters, reforestation, intensification of crop production, supplementary feeding and compensatory population responses of wild boar to hunting pressure might also explain population growth. As populations continue to grow, more human-wild boar conflicts are expected unless this trend is reversed. New interdisciplinary approaches are urgently required to mitigate human-wild boar conflicts, which are otherwise destined to grow further.

Wild boar populations up, numbers of hunters down? A review of trends and implications for Europe.

A population of wild boars (Sus scrofa) became established during the 1990s in the Natural Park of Aiguamolls de l’Emporda, a wetland on the western coast of the Mediterranean Sea (Catalonia, Spain). Between 2001 and 2004, a culling program was conducted to reduce the boar population. We collected and analyzed the contents of 142 stomachs to characterize boar diets, estimate impacts on ground-nesting birds, especially threatened species, and determine the relationships between boars and agricultural areas surrounding the park. The boar population consumed primarily plant material (94% by volume), particularly underground roots and rhizomes (33%). Agricultural (37%) and non-agricultural plants (49%) comprised very similar proportions of the diet. The primary foods were alkali bulrush (Scirpus maritimus) (24% by volume, and in 47% of the stomachs) and corn (Zea mais) (19% by volume and in 29% of the stomachs). Animal matter represented only 5.6% of the diet by volume, but occurred in 84% of the stomachs. The most important animal foods were, by volume, birds (2.3%) and crayfish (Procambarus clarkii) (1.7%) and, by frequency, snails (44%) and terrestrial arthropods (47%). Wild boar diets shifted seasonally between agricultural plants in summer and non-agricultural plants and acorns (Quercus sp.) in winter. Consumption of animal matter varied seasonally, crayfish were consumed primarily from May to October, terrestrial arthropods in May and June, and birds from March to April and September to October. Birds, especially ducks, were consumed most frequently while moulting, when vulnerable to predation. Given the high frequency of birds in the diet and the extensive rooting for underground parts of plants, the wild boar population might pose a threat to the coastal wetland ecosystem of the Natural Park of Aiguamolls de l’Emporda if allowed to become overabundant.

Food habits of wild boars (sus scrofa) in a mediterranean coastal wetland

Mamiferos - Orden Artiodactyla - Familia Suidae en la Enciclopedia Virtual de Vertebrados Espanoles, http://www.vertebradosibericos.org/. Versiones anteriores: 14-03-2006; 12-04-2007; 29-05-2008; 30-04-2014

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EL JABALÍ ( Sus scrofa LINNAEUS, 1758)

Roads, railways and other linear infrastructure are often filters or barriers to the movement of wildlife. Wildlife crossing structures (underpasses and overpasses) improve traffic safety and contribute to the conservation of biodiversity by allowing animals to move safely across roads, thereby reducing the risk of wildlife-vehicle collision. This connectivity between populations on opposite sides of the road allows animals to access resources and mates and facilitates gene flow, thereby improving the viability of wildlife populations. The effectiveness of crossing structures is significantly enhanced when combined with fences, and both measures are usually best implemented together. 1 Follow a logical sequence of steps to implement an effective mitigation strategy. 2 Wildlife crossing structures are diverse in their design, shape and size; and they must be fully described in plans and reports to avoid confusion. 3 Multi-use structures are a potentially effective approach to increase the permeability of roads for wildlife. 4 The selection of structure type depends on the goals of mitigation, target species and engineering constraints. 5 The detailed design of crossing structures is critical to success. 6 The location and spacing of crossing structures should be guided by the ecological and biological needs of the target species. 7 Maintenance, monitoring and adaptive management of crossing structures are needed to assure success. 8 Alternatives to wildlife crossing structures are more appropriate in some locations and situations. Wildlife crossing structures should be constructed when impacts cannot be avoided or minimised. There is a wide diversity in the type of wildlife crossing structures available. Selecting the appropriate design depends on the impacts to be mitigated, the target species, engineering and other location-related constraints and traffic safety considerations. In addition, effectiveness can be maximised by addressing a number of design, monitoring and maintenance issues.

Wildlife Crossing Structures

En las ultimas dos decadas, una poblacion de jabalies se ha establecido en el Parque Natural de los Aiguamolls de l'Emporda, una zona humeda costera del oeste de Cataluna. Como parte de un programa de monitorizacion en este area, se analizo el contenido del estomago de 38 animales para determinar la dieta de la especie, determinar su grado de dependencia de las areas agricolas limitrofes, e identificar el posible consumo de especies protegidas, como podrian ser algunas aves que nidifican en el suelo. Los resultados sugieren que los jabalies de este area tienen una dieta variada, en la que los elementos mas 
, . 
importantes son las plantas (92% del v6lumen total) y, particularmente (66%), sus partes aereas. Los 
recu~sos agricolas representan el 49% y los recursos subterraneos no agricolas representaban el 26%. La materia animal representaba solamente el 8% del volumen total, pero aparecia en mas del 80% de los estomagos examinados. En nuestra muestra, la mayoria eran aves (4,9"l~ del volumen, >30% de frecuencia) y cangrejo americano (Procambarus clarkii), una especie aloctona introducida (1% del volumen, 35% de frecuencia). La variacion estacional de la dieta refleja cambios entre las partes aereas (mayoritariamente agricola) y las partes subterraneas de las plantas, y estas ultimas representan la dieta del jabali en periodos de escasez. En el area de estudio, entre julio y octubre, los jabalies dependen mucho del componente agricola que crece cerca de la zona humeda costera. El jabali parece tener un impacto potencial importante en las comunidades de plantas y animales de las zonas humedas.

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Carme Rosell

Papers

Wild boar populations up, numbers of hunters down? A review of trends and implications for Europe.

Food habits of wild boars (sus scrofa) in a mediterranean coastal wetland

EL JABALÍ ( Sus scrofa LINNAEUS, 1758)

Wildlife Crossing Structures

Preliminary data on the diet of wild boar living in a mediterranean coastal wetland