Yes, Japan is home to a population of squirrels and squirrel-like rodents that thrive across the archipelago’s varied forest ecosystems. The country features native tree squirrels and two distinct types of endemic flying squirrels found nowhere else in the world. These native species have adapted to the islands’ forested environment, with their distribution often tied to specific regions and elevations. Japan is a fascinating location for observing members of the Sciuridae family, from the tiny dwarf glider to the surprisingly large giant flying squirrel.
The Native Japanese Tree Squirrel
The native tree-dwelling species is the Japanese Squirrel, Sciurus lis, which is endemic to Japan and found predominantly on Honshu, Shikoku, and Kyushu. This diurnal creature is readily identified by its reddish-brown or dark brown coat on its back and stark white fur on its abdomen. Its body length typically ranges from 16 to 22 centimeters, with a long, bushy tail adding another 13 to 17 centimeters.
Its appearance changes subtly with the seasons; in winter, the fur becomes a grayer shade, and tufts of hair often grow on the tips of its large ears. This arboreal omnivore spends most of its time in trees, maintaining a varied diet. It feeds on seeds, buds, fruits, and fungi, and is known for its scatter-hoarding behavior, burying nuts and seeds for later retrieval.
This species does not hibernate, remaining active year-round to forage, with activity peaking in the early morning. Due to habitat loss and fragmentation, the Japanese Squirrel has faced local extinctions in parts of western Honshu and Kyushu, particularly in its southern range. Its survival is linked to the preservation of continuous stretches of lowland mixed-species forests and pinewoods.
Japan’s Endemic Flying Squirrels
Japan boasts two endemic species of flying squirrels. The Japanese Dwarf Flying Squirrel, Pteromys momonga, is the smaller, with a body length of 14 to 20 centimeters and a weight between 150 and 220 grams. This tiny creature possesses a patagium—a furry membrane of skin stretching between its wrists and ankles—allowing it to glide effectively between trees.
The dwarf flying squirrel inhabits sub-alpine and boreal evergreen forests on Honshu, Shikoku, and Kyushu, nesting in tree cavities often lined with moss. It is strictly nocturnal, emerging after dusk to forage for buds, leaves, bark, and seeds. In contrast, the Japanese Giant Flying Squirrel, Petaurista leucogenys, is one of the largest flying squirrel species globally, weighing up to 1.5 kilograms and reaching 25 to 50 centimeters in body length.
This giant species is found across Honshu, Shikoku, and Kyushu, preferring mature broadleaf or mixed forests. Its significantly larger patagium enables impressive glides, with recorded distances reaching up to 160 meters. Like the dwarf flying squirrel, it is nocturnal, relying on its large eyes and gliding ability to navigate the canopy while searching for leaves, seeds, and buds.
Ground Dwellers and Introduced Species
While tree and flying squirrels dominate arboreal niches, the Siberian Chipmunk, Tamias sibiricus, is Japan’s only native ground-dwelling squirrel-like rodent. This species is native exclusively to Hokkaido, where it is known as the Ezo-shimaris. The chipmunk is easily recognized by the alternating dark and light stripes running down its back and its habit of spending time on the forest floor.
Unlike the native tree squirrels, the Siberian Chipmunk prepares for winter by entering a period of torpor, relying on food caches stored in its burrow systems. A native subspecies of the Eurasian Red Squirrel, Sciurus vulgaris orientalis, is also found naturally in Hokkaido. This red squirrel does not hibernate and is an important part of the Hokkaido ecosystem.
Beyond native species, Japan has seen the establishment of non-native squirrels that pose ecological concerns. The Pallas’s squirrel, or Red-bellied Tree Squirrel (Callosciurus erythraeus), is a prominent invasive species in several localized areas, having escaped from captivity. This introduced species competes with the native Japanese Squirrel for resources and habitat, leading to conservation efforts to manage its spread.