Differences in spatial niche of terrestrial mammals when facing extreme snowfall: the case in east Asian forests

Tracks of seven mammal species (wild boar [Sus scrofa], Japanese serow [Capricornis crispus]), red fox [Vulpes vulpes], raccoon dog [Nyctereutes procyonoides], Japanese marten [Martes melampus]), Japanese hare [Lepus brachyurus]), Japanese macaque [Macaca fuscata]) left on the snow surface in eastern Japan from 2015 to 2020.

Methods:

We set 55 survey transects in low-mountain forests with mosaic landscapes below 800 m above sea level within the Towada, Asahi, and Oguni regions, located in northern Japan. In most areas in these regions, maximum snowfall with > 2 m in depth was normally observed. The total length of the transects was 21 km in Towada, 180 km in Asahi, and 111 km in Oguni. We followed the transects on skis during the daytime when snowfall, which obliterated mammal tracks from the snow surface, had not been observed for > 24 hours before each survey. Then, we recorded a geolocation of distinct tracks only when those intersected transects. We conducted this survey once a mid-winter from 2016 to 2020 in Towada, from 2014 to 2019 in Asahi, and from 2015 to 2019 in Oguni. Although we could not follow all the transects every year because of limitations due to weather conditions, the total length of the transects that we explored reached 1,144 km. The mean completion percentage of transects surveyed each year was 90% in Towada, 52% in Asahi, and 87% in Oguni.