About Sciurus lis Temminck, 1844
The Japanese squirrel (Sciurus lis) is a tree squirrel from the genus Sciurus that is endemic to Japan. It was formally described by Dutch zoologist Coenraad Jacob Temminck in 1844. Its native range covers large areas of the Japanese islands of Honshū, Shikoku, and Kyūshū. The species is not found on Hokkaido, where the closely related Eurasian red squirrel (Sciurus vulgaris) replaces it; the red squirrel is in turn not found anywhere in the Japanese archipelago outside of Hokkaido. In recent times, populations of Japanese squirrels have declined in south-western Honshū and Shikoku, and the species has been completely lost from Kyūshū. Human-caused forest fragmentation appears to be one factor contributing to these recent local extinctions of the species. In some regions, walnuts can make up as much as 35% of the Japanese squirrel’s diet. This squirrel-driven seed dispersal may have influenced the evolution of larger seed sizes in Japanese walnut populations where Japanese squirrels live. Additionally, Japanese walnut (Juglans ailanthifolia) is an important food source for Japanese squirrels living in lowland mixed-species forests of Japan. Japanese squirrels have a specific feeding technique for opening walnut shells: they chew along the shell’s natural crease, embed their teeth into the cleft, and pry the two shell halves apart. This method appears to be efficient, as it minimizes the total time needed to consume an entire walnut. Research has also found that fallen dead trees act as landmarks for Japanese squirrels during movement, and are used for vigilance and resting. Deadwood can also work as a food hoarding site for Japanese squirrels, a function that is critical to their survival. Increasing the amount of deadwood in a habitat can benefit small mammals like the Japanese squirrel, and significantly improves overall habitat quality.
