noun
squirrel
General term for any squirrel (family Sciuridae).
公園でリスが木の実を食べている。
A squirrel is eating nuts in the park.
noun
Japanese squirrel
Specifically the Japanese squirrel (Sciurus lis), a species native to Japan. Often distinguished as ニホンリス in scientific contexts.
See also: 日本栗鼠
ニホンリスは本州と四国に生息している。
The Japanese squirrel inhabits Honshu and Shikoku.
The kanji 栗鼠 literally means 'chestnut mouse/rat', reflecting the squirrel's appearance and diet. The reading りす is likely a native Japanese word, but its exact origin is uncertain.