In some areas, 35% of the Japanese squirrel's diet is made up of walnuts. The squirrel is more likely to hoard larger seeds/nuts and is more willing to carry them farther in order to cache them — this may have resulted in walnuts evolving larger sizes in areas where this squirrel lives.

The Japanese giant flying squirrel is one of the world's biggest squirrel species — weighing up to 1.3 kg (2.9 lbs) — but, using its flying membrane, it can still glide distances of over 100 metres (328 ft). Young squirrels learn to glide a few days after first emerging from their nests.