Flying squirrels probably get water from foods they eat and rain, dew, and snow. It may change den trees at night and move to different ones more than 20 times over a year, staying in each for a varying numbers of days. Den trees with brooms are used more than twice as much as trees with cavities. High quality flying squirrel habitat can be a community mosaic of small stands of varying age classes in which there is a mix of tall conifers and hardwoods. Part of the mosaic must be old coniferous forest with den trees containing witches' brooms, woodpecker cavities, and natural cavities for nesting sites.
Riparian zones provide excellent habitat in all coniferous forest associations.
The female can breed before 11 months of age and give birth at about 1 year of age. Gestation requires about 37 days, so the young are born from May to early July. One litter of two per year is probably the usual case for Alaska, but they are known to have litters ranging from one to six in other parts of their range. Development is slow in comparison with other mammals of similar size. Their eyes open at about 25 days, and they nurse for about 60 to 70 days.