Tree squirrels, including flying squirrels, make their nests in hollow trees or limbs, or they sometimes build nests of twigs and leaves. They are extremely active and agile in the trees, and if they miss their hold and fall, they are seldom injured. There is a record of a Mexican tree squirrel leaping down a precipice and, as far as could be determined, landing unhurt on a ledge 180 meters below. Although this was a forced leap, it illustrates the remarkable agility of tree squirrels to ease or break a fall from a great height. Ernest P. Walker observed two tree squirrels fall at least 15 meters without apparent injury.
Most tree squirrels have a tendency to glide.
When they make flying leaps, they extend their legs widely, broaden and flatten their body, and stiffen and slightly curve their tail. This position presents to the air the broadest surface possible and partially neutralizes the force of gravity. Also, it is often carried over the back, especially when danger threatens, and probably misleads or baffles enemies. Flying squirrels are found in both the Old World and the New. At the outer edge sides of the body from the arms to the legs.