蝦夷 (Ezo, jukujikun (熟字訓)) + 栗鼠 (risu, “squirrel”, jukujikun (熟字訓))
蝦(え)夷(ぞ)栗(り)鼠(す) or 蝦夷栗鼠(エゾリス) • (Ezo risu)