Below is a southern flying squirrel.  Like many bats this squirrel is nocturnal.
 

This animal does not, of course, actually fly; it glides. There are
blanket-like membranes of  skin between its wrists and hindlegs
that give it the ability to glide far distances.  The flying squirrels
have dense, and soft fur.  They have long, flattened tails that are
used to guide their glides.  Notice the large eyes that helps them
see at night.