Eastern Honshu is the only place in Japan where the black bears have any kind of a stronghold. The bears' home range is supposedly between 10 and 15 square miles, though this can vary depending on food supply and human encroachment. The more fragmented and degraded the bears' habitat becomes, the more distance they may be forced to travel to survive.
The bears in the mountainous areas hibernate where there is snow on the ground for most of the winter. The snow helps to keep them warm by serving as an insulating blanket over their dens. Black bears are excellent climbers. They build nests in trees and on steep slopes, called enza in Japanese, that they use for either eating, resting or sleeping in. They also den in hollow trees, under large rocks, or in the ground.
The Japanese black bears feed mainly on plant material year round. Depending on the time of year, their diet consists of acorns, beechnuts, oak nuts, green shoots, cherries, ants and other insects. Acorns are the most essential food to the bears in the fall, providing them with sufficient body fat before going into hibernation.
The Japanese black bear is an omnivorous creature. It will eat small animals such as frogs, lizards, crabs and carrion. However, it seldom hunts animals and feeds mainly on vegetation.
Something else that black bears in Japan do is gnaw off bark to get to the sapwood of valuable timber trees. Unfortunately, this damages and can even kill the trees, having a negative impact on the timber industry. Numerous bears are killed every year in attempt to reduce the problem.