Japanese squirrel
Refers specifically to Sciurus lis, a squirrel species native to Japan.
The Japanese squirrel inhabits Honshu and Shikoku.
I spotted a Japanese squirrel in the park.
Generic term for squirrel; ニホンリス specifies the Japanese species.
Formosan squirrel, another species sometimes seen in Japan, but not native.
Katakana spelling is standard for this animal name; usually written in kana.
Kanji spelling is uncommon; 栗鼠 is a rare ateji for 'squirrel'.
Compound of 日本 (Nihon, 'Japan') and 栗鼠 (risu, 'squirrel'). The kanji 栗鼠 is ateji; the word is usually written in katakana as ニホンリス.