The wild boar Sus scrofa in northern Eurasia: a review of range expansion history, current distribution, factors affecting the northern distributional limit, and management strategies

Abstract

The wild boar Sus scrofa is one of the most widely distributed large mammal species in the world, existing on all continents except Antarctica. In the late 20th Century, its geographical range expanded naturally and through intentional releases. Despite the environmental, social, and economic importance of the wild boar, its current distribution in northern Eurasia remains uncertain, and the factors that limit and promote expansion in northern ecosystems are unknown. We aimed to summarise the history of wild boar range expansion and current distribution in the countries of northern Eurasia. We also assess the relative importance of climate (both harshness and warming), habitat (both current diversity and possible change), predators, releases, supplementary feeding, and hunting in limiting or promoting the distribution and range expansion of the species. We review hunting management and other regulations that may affect further northward expansion. Information on wild boar expansion and distribution was collated from available scientific publications, official statistics, volunteer reports, and expert knowledge. The effects of natural factors (climate harshness, habitat variation, predators) and anthropogenic factors (climate warming, habitat change, releases, supplementary feeding, hunting) on wild boar distribution were assessed using estimates (scores) provided by experts from the target regions. The wild boar in Europe is distributed up to 64°N. In Asia, the northern distributional limit is up to 61°N. The species' northern distributional limit is further north in the west than in the east of the geographic range. Experts regarded climate harshness, habitat, and hunting as the most important factors limiting wild boar distribution. Important factors that promote the expansion of the wild boar's range include climate warming and supplementary feeding. Our analysis of the official approaches to wild boar management suggests that the northern Eurasian countries do not have a united approach to the challenge of wild boar expansion. Collaboration between managers, policymakers, and researchers is needed for monitoring the wild boar distribution and range expansion throughout northern Eurasia. This data collection is especially important now, as parts of Europe and Asia are facing the challenge of African swine fever as well as other human–wildlife conflicts related to increasing wild boar populations.

Positive Selection on Rare Variants Underlying the Cold Adaptation of Wild Boar

“…Our comprehensive analysis revealed that 1.54% of genes (313 out of 20,306, Ensembl v105) were consistently identified across at least three distinct methods as being under selection, indicating a conservative estimation in this study. Additionally, 0.45% of genes (92 out of 20,306) were corroborated by all four analytical methods (Supplementary Table 7).…”

“…The severe low temperatures serve as a strong selective force, especially for species like the wild boar, necessitating adaptations for effective thermoregulation in these frigid zones. Beyond the cold, another major environmental challenge is the scarcity of food resources during the lengthy winter season (20). Thus, uncovering molecular adaptations enabling peripheral or derived populations of wild boar to survive and flourish in the cold Siberian climate and its neighboring regions is a subject of great scientific interest.…”

“…Given the species' tropical origins, we hypothesize that the genomes of cold-region populations could exhibit signals of adaptation to colder climates. However, this hypothesis has not yet been empirically tested (20). Here, we conducted the whole-genome sequencing of wild boar populations from both tropical Asian and Siberian regions.…”

“…In this study, we focus on the wild boar, Sus scrofa , a species with remarkable adaptive capabilities and wide distribution across diverse climatic regions in Eurasia. Their ecological niches encompass the humid tropics of Southeast Asia, extend through temperate zones, and reach the extreme area of the Qinghai-Tibet plateau as well as subarctic Siberia (19, 20). Phylogenetic analyses suggest that the Eurasian wild boar diverged from a clade of closely related Sus species at the onset of the Pliocene epoch (5.3-3.5 million years ago) within the tropical Asia (21).…”

Habitat suitability and crop damage risk caused by wild boar in Guizhou Plateau, China

“…Because species responses to environmental factors are scale‐dependent processes, factors related to wild boar habitat suitability and damage risk may manifest at different spatial scales (Falconi et al 2015, Rather et al 2020, Wang et al 2020). Climate is a major determinant of the suitability of wild boar's native habitats and their expansion into other areas (Markov et al 2019, 2022). For example, our results indicate the mean temperature of the coldest quarter and isothermality are most relevant for wild boar habitat suitability at 3.5‐km and 1‐km scales, respectively.…”