Preventive Veterinary Medicine 124 (2016) 34–44 Contents lists available at ScienceDirect Preventive Veterinary Medicine jo ur nal ho me pag e: www.elsevier.com/locate/prevetmed Spatio-temporal modeling of the invasive potential of wild boar—a conflict-prone species—using multi-source citizen science data Astrid Moltke Jordt a , Martin Lange b , Stephanie Kramer-Schadt c , Lisbeth Harm Nielsen d , Søren Saxmose Nielsen e , Hans-Hermann Thulke b , Henrik Vejre a , Lis Alban d,∗ a Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, Denmark b Helmholtz Centre for Environmental Research Leipzig – UFZ, Department of Ecological Modelling, Leipzig, Germany c Department of Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research IZW, Berlin, Germany d Danish Agriculture & Food Council, Copenhagen, Denmark e Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark a r t i c l e i n f o Article history: Received 26 August 2015 Received in revised form 13 November 2015 Accepted 22 December 2015 Keywords: Habitat suitability model Landscape ecology Species distribution model Sus scrofa a b s t r a c t Denmark was considered not to have an established population of free-ranging wild boar. Today, sporadic observations of wild boar challenge that view. Due to its reservoir role for economic devastating swine diseases, wild boar represents a potential threat for Denmark’s position as a large pig- and pork-exporting country. This study assessed the prospects of wild boar invasion in Denmark. Multi-source citizen science data of wild boar observations were integrated into a multi-modelling approach linking habitat suitability models with agent-based, spatially-explicit simulations. We tested whether the currently observed presence of wild boar is due to natural immigration across the Danish–German border, or whether it is more likely that wild boar escaped fenced premises. Five obser- vational data sources served as evaluation data: (1) questionnaires sent to all 1625 registered owners of Danish farm land, located in the 60 parishes closest to the border, (2) an online questionnaire, (3) a mobile web-based GPS application, (4) reports in the media or by governmental agencies, and (5) geo-referenced locations of fenced wild boar populations. Data covering 2008–2013 included 195 observations of wild boar, including 16 observations of breeding sows. The data from the Danish Nature Agency and the mailed questionnaires were consistent regarding the location of wild boar observations, while data from the Danish Veterinary and Food Administration, the media and the electronic questionnaires documented individual scattered observations in the rest of Jutland. Most observations were made in the region bordering Germany. It is uncertain whether the relatively few observations represent an established population. Model outcomes suggested that the origin of wild boar in about half of the area with sporadic observations of wild boar could be attributed to spatial expansions from a local Danish population near the border and consisting of wild boar originally of German origin. However, the other half, located distant to the border, were likely a result of animals escaping fenced premises inside the country. The approach serves as a template to assess the status of an invading species and improve the knowledge base for risk assessment and management decision. © 2015 Elsevier B.V. All rights reserved. 1. Introduction In densely populated landscapes there is a potential conflict between human land use and the existence of large feral/wild mam- ∗ Corresponding author at: Risk Analysis Group, Department for Food and Veteri- nary Issues, Danish Agriculture & Food Council, Axeltorv 3, DK-1609 Copenhagen V, Denmark. E-mail address: lia@lf.dk (L. Alban). mals unless properly managed (Miller and Hobbs, 2002). In essence, such larger mammals compete with farmers for land, and in many cases ungulates browse on farm crops, and predators prey on live- stock. A balance may be reached, where large mammals can thrive even in rather intensively managed cultural landscapes such as in northern Europe where increasing numbers of wild boar are com- mon phenomena (Massei et al., 2011; Honda, 2009). Species invasions are typically divided into two groups; natu- ral dispersal and human-caused dispersal—intended or unintended (Mack et al., 2000). Understanding the mechanisms behind the http://dx.doi.org/10.1016/j.prevetmed.2015.12.017 0167-5877/© 2015 Elsevier B.V. All rights reserved.