http://cityroom.blogs.nytimes.com/2014/02/21/a-sharp-eyed-glider-leaping-into-darkness/

The flying squirrel (Glaucomys volans) does not actually fly — it
glides. When a squirrel leaps from its perch in a tall tree, it spreads its
limbs, stretching out its two patagia (thick, furred membranes that extend from
its wrists to its ankles). In this way, a squirrel less than 10 inches long
(including a tail almost half that length) can, in a single bound, cover 150
feet or more, gliding through the treetops effortlessly.

A nighttime jump through a dense canopy of leaves and branches requires keen
senses, and the squirrel is suitably equipped. The enormous, soft brown eyes
that make them so irresistible to humans are actually a significant part of the
squirrels’ survival strategy. A squirrel triangulates with movements of its head
before making its longest leaps, suggesting an advanced spatial sense.