Distance in-between wildlife passages is a fundamental aspect when planning and designing efforts to mitigate barrier impacts along roads. Wildlife is confined to utilize passages within their home ranges. Therefore, distance in-between wildlife passages should consider home range areas for the target species. However, home ranges may be extended along road barriers, increasing the distance along the road where wildlife may have access to wildlife passages.
We analyzed the shape of home ranges in Scandinavian wild boars in relation to distance to adjacent major roads. We defined home ranges as 95% Kernel Density Estimates (KDE), based on 380 random GPS-fix positions for each of 52 individual wild boars. The maximum distance for each home range oriented parallel to the main direction of the road was estimated and labeled home range length. The maximum distance oriented perpendicular to the road was estimated and labeled home range width. The shape of the home range was derived from the ratio between its length and width. Nearest distance to major roads was derived from the centroid of the core area, defined as 50% KDE of individual home ranges. The relationship between the shape of each individual home range and the corresponding distance to the road was tested against a candidate set of linear models based on Akaike’s information-theoretic approach.
We found that wild boars that occur closer to a major road extend their home ranges along the adjacent road (HR ratio of length and width (β) = -1.2 for every meter farther away from the adjacent road, with 95% CI: -1.0 & -1.4). This suggests 1) that the adjacent road has an impact on wild boar habitat use, 2) that wild boars living closer to roads may encompass wildlife passages located farther away from their main areas of occupancy, and 3) that the impact may be due to a combination of barrier effect, disturbance, and habitat features such as spatial distribution of food and cover