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.
