It could have been a flying squirrel..
The southern flying squirrel is easily distinguished from other
Nebraska tree squirrels by its smaller size and by its gliding
membrane, or patagium, a fold of skin that extends from the wrist
of the front leg to the ankle of the hind leg. When the front and
hind legs are extended, the membrane forms a wing-like gliding
surface. The furred, broad and horizontally flattened tail serves
as a rudder and stabilizer during glides. The eyes are noticeably
large, an adaptation for its nocturnal habits. The ears are more
prominent than in other tree squirrels. Whiskers are also
prominent.
Southern flying squirrels are quite small. Adults usually are nine
to 10 inches long including the tail, and they weigh between two
and four ounces. Their fur is soft, silky and moderately long. The
upper body is grayish to brownish in color, and the underparts are
creamy white. The eyes are surrounded by a black ring, and a black
border extends along the edge of the gliding membrane.
Flying squirrels produce several vocalizations including a high
pitched "tseet" and other chirping sounds. Some vocalizations are
above the frequency range of the human ear. Some researchers have
speculated that flying squirrels use high-pitched sounds for
navigation, similar to the echolocation system of bats. Although
flying squirrels have an excellent sense of hearing, they do not
have the highly specialized hearing system of bats, and echo
location is unlikely.
Undoubtedly the most unusual habits of the southern flying squirrel
are its gliding ability and its nocturnal behavior. unlike fox
squirrels or gray squirrels that are active by day, the southern
flying squirrel is probably the most nocturnal of all mammals in
Nebraska. Other gliding mammals from various parts of the world
also tend to be nocturnal, and a possible explanation for this
association is that gliding in daylight might attract the attention
of hawks or other diurnal (daytime) predators.
