Blakiston's Line

Thomas Blakiston, who lived in Japan from 1861 to 1884 and who spent much of that time in Hakodate, Hokkaido, was the first person to notice that animals in Hokkaidō, Japan's northern island, were related to northern Asian species, whereas those on Honshū to the south were related to those from southern Asia.

[3][4] Sakhalin, the island just north of Japan, and Hokkaido may even have been connected to the mainland as recently as 10,000 years ago or less.

[5] Apart from these former land bridges, there are more factors that play a role in why there is a difference in the fauna north and south of the line: Besides birds, animals that are of different origins north and south of the Blakiston Line include wolves, bears and chipmunks.

[3] On the contrary to major hypothesis that terrestrial animals couldn't move across Blakiston's Line, excavations of fossils of Palaeoloxodon naumanni and Sinomegaceros yabei (Japanese) from Hokkaidō, and moose and Ussuri brown bear from Honshū indicate a new assumption that terrestrial animals could have crossed the strait periodically.

Andrew Davis, who has been a professor at Hokkaido University for four years, argued that this may have been because of his unusual position in Japanese society as a European.