Table 1 Explanatory variables with a 50-m grid resolution for modeling ecological niches of terrestrial mammals in snowfall regions of northern Japan

(a) Regulation factors

Maximum snow depth (cm)

Mean values observed between 1991 to 2020

37–378

A

Solar radiation (KWh/m²)

Incoming solar radiation accumulated during the survey months (February and March)

60–199

B

(b) Disturbance factors

Distance to dwelling land (m)

Distance to areas occupied by artificial architecture

0–1994

C

Snowfield (250 m²)

Area without any vegetation cover available during winters (grassland, shrubland, paddies, or cropland)

0–1

C

West-facing slope (250 m²)

Slope land facing the bearing angle between 225° and 315°, affected by the winter monsoon (i.e., powerful and cold wind)

0–1

D

(c) Resources

Evergreen conifer (250 m²)

Area covered by evergreen conifer plantation, providing refuge from snowfall and cold wind

0–1

C

Deciduous broadleaf forest (250 m²)

Area covered by deciduous trees, providing plant food for herbivores

0–1

C

(d) Others

Elevation (m)

Mean elevation

16–782

D

Slope angle (°)

Mean slope angle

0–58

D