Cats are lithe, athletic, remarkably graceful animals, and even the most sedentary couch cat can at moments remind us of their predatory wild cousins. Tortoises, however, not so much. So why the two together in one column? Last week I got asked two different and seemingly unrelated questions. Is it true that cats dropped from any height will land on their feet? If a tortoise tips over onto his back, is he a goner?
Tortoises are among those ancient animals who, like sharks and alligators, got things so right so long ago that there’s not been a great deal of pressure to keep racing down the evolution highway. If being upside down meant certain death then it’s not likely turtles and tortoises would have made it out of the Jurassic: sure, they’ve changed, some, but the basic body type has worked for more than 200 million years. Relatively flat aquatic species use their long and muscular necks to flip themselves upright but their big-domed stubby-necked landlubber counterparts have no such option. Instead, there’s a subtle geometry at work by which the shell’s actual shape, combined with the animal’s intuitive efforts at rocking and rolling, have evolved to assure what scientists call “self-righting.” You can find the math online but since it looks like k(R)=0.90R-1.01 and stuff like that, I suggest you just stick with this summary.
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