This is impressive. Watch what happens when a very flustered squirrel makes a daring leap for freedom through the kitchen window of what looks to be a fourth-story apartment. The brief clip, captured on video by Finn83, raises an interesting question: how does a squirrel survive such a fall?
The conceptual explanation is straightforward enough: the wind resistance experienced by a body falling through the air is proportional to its projected area. Smaller bodies (like squirrels) tend to have greater surface-area-to-mass ratios than larger bodies (humans, for example), causing them to accelerate toward the ground at a decreased rate. From a sufficient height, the squirrel would achieve a slower (perhaps even non-lethal) terminal velocity, as well.
Thanks to drag, the squirrel survives; that much is obvious. Less clear is the importance of the squirrel's big, bushy tail when it comes to non-lethal plummets.
In a flyer entitled "Living With Wildlife: Tree Squirrels," the Oregon Department of Fish and Wildlife notes that "if a squirrel should fall," the tail can act as "a sort of parachute and cushion." Intrigued, I went searching for more information. I discovered that the tail-as-parachute/crash-pad claim has been reproduced in various forms around the internet (and in a handful of pretty adorable books), often alongside the statistic that squirrels can survive falls from as high as 100 feet. However, I've yet to come across any research that supports either of these claims. To the best of my knowledge, there have been no observational studies on the aerodynamics of free-falling squirrels. This, obviously, is a damn shame.
What I did find, however, was proof that the idea of squirrels using their tails like a drag chute has been around since as early as 1927, when, in a February issue of the Journal of Mammology, researcher A. Brooker Klugh wrote of red squirrels:
"That the tail acts not only as a rudder in leaping, but to a certain extent as a parachute in the case of a fall, is probably true."
Hear that? "Probably true." Pah! Does anyone know if there's been any research performed in the last 85 years that supports this assumption, or does tail-mediated squirrel descent remain an untested hypothesis? If you know, please feel free to speak up in the comments!