Wildlife triangle data, winter census Species-specific annual snow-track counts and average snow-track abundance indices in 50 × 50 km grid cells. The snow-track abundance index for a wildlife triangle (a ~12 km line transect) is calculated as N / (km_counted × snow_days). Here N is the number of snow-tracks crossing the transect line. The denominator stands for counting effort, consisting of the kilometers counted (km_counted) multiplied with the number of days during which tracks have accumulated (snow_days). The snow days are counted from last snowfall, or from the timing of a pre-mapping of snow-tracks, which prevents from recounting the tracks during the actual survey. The presented index for a given species, year and grid cell is calculated as the arithmetic mean index over all triangles, whose point of gravity are within the focal grid cell. In addition to the species-specific average abundance indices, also the number of snow tracks recorded, and the number of triangles counted are reported. The grid is constructed according to the ETRS-TM35FIN -coordinate system and the grid cell locations are given using the lower left corner coordinates (“lon” and “lat”). Coverage basis: threatened and invasive mammal species in the winter track counts, excluding the large carnivores. Data embargo period: 3 years Data quality: Professional / professionally curated (monitoring scheme) Methods: Line-transect census of snow tracks. The transect is ca 12 km long, shaped as an equilateral triangle and located in boreal forest landscape. The survey is done during one day by volunteers, mainly local hunters, skiing or walking along the transect. The survey period starts the 15th January and ends on the 28th February in the southern and central parts of Finland. In the northern parts of Finland (Oulu region and Lapland) the period continues until 15th March. Taxonomic coverage: Siberian flying squirrel (Pteromys volans); http://tun.fi/MX.48243 Muskrat (Ondatra zibethicus); http://tun.fi/MX.48537 Raccoon dog (Nyctereutes procyonoides); http://tun.fi/MX.46564 American mink (Neovison vison); http://tun.fi/MX.47243 European polecat (Mustela putorius); http://tun.fi/MX.47240 White-tailed deer (Odocoileus virginianus); http://tun.fi/MX.47629

2014