Spatiotemporal trends in Canadian domestic wild boar production and habitat predict wild pig distribution

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.