noun
harvest mouse; Eurasian harvest mouse
A very small rodent (Mus minutus) found in grassy areas; the Japanese name literally means 'reed mouse'.
カヤネズミは日本で一番小さなネズミです。
The harvest mouse is the smallest mouse in Japan.
河原の草むらでカヤネズミの巣を見つけた。
I found a harvest mouse nest in the grassy area by the river.
House mouse (Mus musculus), a common commensal rodent, while カヤネズミ is a wild species that builds nests in tall grass.
From 萱 (kaya, 'reed' or 'thatch grass') + 鼠 (nezumi, 'mouse'), referring to its habitat in grassy areas.