Predation and Flight
G. volans in “flight,” courtesy of FlyingSquirrels.com
Photo taken by Cy Hampson
Predation
The most dangerous predator of G. sabrinus is the owl, while for G. volans it is the house cat (Whitaker, 1996). The most common means of protection for a flying squirrel is to just stay in its den until nighttime, but once it does need to venture out it will escape predators by gliding away. Once it has landed at its target destination, the squirrel will quickly move from its landing spot to avoid any predators that may have been following closely. However, there is conflicting evidence on this behavior as a motivation for the evolution of gliding.
In a journal published in 1994, an article written by Holmes and Austad concluded that the lifespan of gliders is considerably higher than other similar, tree-dwelling mammals, and that they face less predation (Holmes and Austad, 1994). In that same issue, an article by Stapp refuted this claim by questioning the data presented by Holmes and Austad. While Stapp believes there could potentially be a correlation between gliding and predation, his research so far has shown that lifespan is consistent among tree-dwelling and gliding mammals, relative to body-size (Stapp, 1994).
Gliding
Regardless of the motivation behind the evolution of gliding among tree squirrels, this unique adaptation has proven to be highly advantageous. The presence of a patagium extending from the ankle to the wrist, and in to the shoulder, allows the squirrel to glide from a high tree branch to another tree or the ground. The squirrels are able to extend the styliform cartilage in their wrist to curve the tips of their wings, allowing for a great amount of maneuverability during “flight” (Thorington, Darrow, and Anderson, 1998). They are, because of this, one of the most aerodynamic of all flying mammals.
Braking posture and Landing Posture
Photos courtesy of FlyingSquirrel.com, taken by Cy Hampson
For video of squirrels gliding:
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.