This was originally posted June 8, 2010 and probably ten people read it. I hope you don’t mind my running it again. It reminds me of my favorite Abstruse Goose. The picture’s a little alarming, but justly so.
I had two trees in the front yard, and I’d watch the squirrels jump between them, across maybe a four-foot gap, and they did it at speed. They’d race out along the branch to its spindly end and the instant it bent under their weight, they’d go airborne and land on the other tree’s spindly end-branch, no hesitation, no wobble, no recovery, a fraction of a second, then tear down the next branch.
Squirrels – this is well-known – have tiny little brains specially evolved for this. They put the altitude of the starting point, the altitude of the target point, the distance between the points, air resistance, squirrel velocity, and the acceleration due to gravity into a kinematics equation that accounts for all three dimensions and probably contains some integrals and derivatives and for all I know, square roots. They solve the equation at the split second of the jump and they always nail it.
Another creature that does something like this is the paradise tree snake, which hangs off a branch in a J, accelerates up and out, widens its rib cage and flattens its round self into a sort of D, undulates through the air at 8 meters per second, can make 90 degree turns, and maintains the glide ratio of a flying squirrel; and I’d tell you all about their mental calculations but I’m too shaken by the prospect of airborne snakes and need to go nap.
Source for squirrel kinematics: my husband the physicist
Squirrel photo: Ray Eye
Snake photo: Magnus Manske