Estimated to number only 30 at most, black bear in Shikoku have been found to be active beyond their sanctuary, forcing the state to come up with urgent steps to expand preserves and protect them.
Shikoku Institute of Natural History, a nonprofit organization in Kochi Prefecture, and the World Wildlife Fund Japan have tracked the bear's movements using transmitters attached to some of the animals.
According to institute executive Bungo Kanazawa, black bear used to inhabit wide areas of the mountains of Shikoku, but hunting and increased reforestation have reduced their habitats.
By the 1980s, they were only found near Mount Tsurugi on the Tokushima-Kochi border. Widely believed extinct in Kyushu, black bear are the most endangered animal in the country.
The institute captured five on Mount Tsurugi between 2005 and 2008, and released them after attaching transmitters to check on their range of activity.
The study found that the male could take in more than 100 sq. km and the female more than 40 sq. km for breeding and foraging.
"The field of activity is narrower in Tohoku and other regions, but a wider field is required in Shikoku because of limited food," Kanazawa said.
The animal's range in Shikoku mostly overlaps the state's sanctuary where hunting is restricted, and the "green corridor," which the Forestry Agency has created for animals to come and go, but two bears hibernated outside of these areas.
The habitat was mostly at more than 1,000 meters above sea level where broadleaf deciduous forests remain.