Study area
We studied the sika deer population inhabiting eastern Nagano and
western Gunma Prefectures in central Japan (Fig. 1). The landscape of
the study area is an agriculture-forest mosaic (Fig. 1), including
broad-leaved trees, such as Juglans sp., Quercus crispula ,
and Cornus controversa , and coniferous trees, includingCryptomeria japonica and Chamaecyparis obtusa . This area
also has mountainous areas with broad-leaved trees, such as Q.
crispula and Betula platyphylla , coniferous trees, includingLarix kaempferi and Abies mariesii , and an alpine zone
(Institute for Biodiversity Research and Education Earthworm, 2014).
Agricultural crop fields comprised both crop fields and sown grasslands
because deer consume vegetables and pasture grasses in this area
(Tsukada et al., 2012; Nagano Prefecture, 2016; Hata et al., 2019). The
elevation of the study area ranged from about 700 m to 2,500 m. The
maximum snow depth at the foothill of Mt. Asama was 16–99 cm in
2012–2019 (Japan Meteorological Agency, 2020). The estimated deer
density in this area was 31 individual/km2 in 2015
(Nagano Prefecture, 2016).