Abstract 137 – Current status of accidentally captured Asiatic black bears in traps for sika deer and wild boar in Nagano, Japan

Rumiko Nakashita, Akiko Takii, Hayato Iijima, Toshiaki Yamamoto, Hiroo Tamatani,
Misako Kuroe, Ryosuke Kishimoto, Shigeyuki Izumiyama

In recent years, the number of culled sika deer (Cervus nippon) and wild boar (Sus scrofa) has
increased as their abundance increased.　The increased culling effort simultaneously resulted
in a rise in the accidental capture of non-target mammal species via snare traps and box traps.
In Japan, the protocol mandates the release of accidentally captured animals. However, for
some mammals, especially Asiatic black bears (Ursus thibetanus), this poses a serious problem
due to the potential risks against workers being injured during the release of the captured bear
and the bear itself also being injured by the trap. Nagano Prefecture is one of the regions
experiencing an increase in accidentally captured bears. However, the frequency of accidental
capture and behaviour of captured bears has not been properly understood by localities. In this
study, we examined the actual situations of Asiatic black bears caught by accidental trapping in
two areas in Nagano (Ina and Karuizawa) in recent years, and investigated attributes
of　individuals which were accidentally captured. For those bears for which samples were
available, carbon and nitrogen stable isotope ratio analyses were conducted to determine the
diet of each bear. In the Ina area, many bears were trapped in box traps targeting wild boar
near corn-fields at the foot of the mountains, but only a few bears were found to be dependent
on crops. In the Karuizawa area, many bears were trapped in snare traps targeting sika deer in
national forests, and some of the individuals were captured repeatedly. Our study observed the
consumption of snared sika deer by bears, suggesting a potential link between bears learning to
eat snared sika deer and the accidental capture of bears in snare traps.