General Information

There are two species of North American flying squirrel: the southern (Glaucomys volans) and northern (Glaucomys sabrinus) flying squirrels. There is little overlap in their habitats and they have slight physical differences. Both are members of the order Rodentia, family Sciuridae, and both are nocturnal animals.

Glaucomys volans	Glaucomys sabrinus

Photos courtesy of Animal Diversity Web, © Phil Meyers

Physical Description

Perhaps the most obvious difference between the two species is size. The northern variety is on average twice the size of the southern. In addition, the coloration of the ventral hairs of the two species varies – the southern flying squirrel has all white hairs while the northern has gray-based hairs. The northern species is also known to have a shorter lifespan in the wild (Whitaker, 1996).

Taxonomy

Evolution of Glaucomys

The flying squirrel is the oldest living example of the modern squirrel. Evidence of flying squirrel ancestors goes back between 38 and 55 million years, into the Eocene period, up to 25 million years before the first tree squirrels and 27 million years before the first ground squirrels. There is little evidence, however, of exactly how old North American flying squirrels are as their skeletal structure is so slight that it often does not fossilize. It is generally believed that the southern flying squirrel immigrated to North America from Asia via the Bering Strait some 25 million years ago. Similarly, the northern flying squirrel immigrated to North America the same way approximately 12 million years ago (Patterson, 2008).
There is some disagreement as to how related the two species of North American flying squirrel are. There is some speculation that the two species, because they moved into North America approximately 13 million years apart, are from two different families of Asian flying squirrels. However, in a paper published in 1984, Richard Thorington concludes that all flying squirrels are monophyletic. He uses the morphology of the wrist joint, which is consistent among all flying squirrels, as evidence that the group is monophyletic. He states that the most likely explanation, based on his research, is that all squirrels are a monophyletic group, and that flying squirrels evolved from tree squirrels during the Oligocene period (Thorington, 1984).

This website was completed by Kara Earle in partial fulfillment of the requirements for an undergraduate course -- Biology 323: Animal Behavior -- at Davidson College in the Spring Semester 2008.