Abstract
Invasive alien species are one of the biggest threats to biodiversity today. One of the most successful invasive alien species in the world is the wild boar (Sus scrofa). During the last decades it has expanded its geographic range and increased in numbers in its natural range. The wild boar is an unwanted and blacklisted species in Norway but has started to expand into Norway from Sweden. We need methods to monitor and manage the species. I estimated wild boar density in Kolmården in Sweden using the Random Encounter Model (REM). REM is designed to estimate population densities of species without individual characteristics using randomly placed camera traps. The model parameters you need are trapping rate, movement speed / distance travelled per day, detection distance and detection angle. I had 44 randomly placed cameras covering an area of approximately 50 km2. The cameras were active for 2-3 months during the summer of 2019. The capture rate was 0.06, distance travelled per day was 5.3 km/day, effective detection distance was 7.78 meters and effective detection angle was 0.76 radians. This resulted in a density estimation of 1.69 wild boars per km2. The estimate is relatively low compared to other European studies, but it agrees well with expected densities in southern Scandinavia. My conclusion is that the REM is a viable monitoring method for wild boar.
