Large Japanese field mouse

The large Japanese field mouse (Apodemus speciosus) is a nocturnal rodent of the family Muridae that is endemic to Japan, where it appears to be present on all the islands. It lives in forests, grasslands and cultivated fields, including rice paddies, at any altitude. It fills much the same broad niche as Apodemus argenteus, but the two prefer different microhabitats: A. argenteus favours dense canopy, while the large Japanese field mouse prefers open secondary forest. It is an omnivore, best known as a seed eater, especially in autumn and winter, when it hoards acorns and walnuts that make up between 13 and 100 percent of its food, which makes it an effective seed disperser. It forages mainly at night and, in brighter light, spends less time outside the nest and carries food home to eat. It copes with the high tannin of many acorns through specialised proteins and gut bacteria, and prefers acorns with less tannin. Individuals learn to open walnuts faster with experience, within 14 days. The IUCN lists the species as Least Concern.