One of the really neat things about diving deep into a scientific problem is that you start to spot surprising things in images or videos that nobody else would see! My book on Falling Felines and Fundamental Physics got me really involved in studying videos of cats landing on their feet after a fall, and after the book came out I wrote a whole blog post about a cat flip video that I happened to see online where I spotted some really neat new dynamics in the falling felines problem.
Well, today I again spotted something remarkable in a falling animal video, and in fact I think it answered a question that I had been unable to answer ever since writing the book!
Let me give a little background: cats possess this remarkable reflex, often called the cat-righting reflex or just the cat flip, that allows them to change the orientation of their body in the air and land on their feet whenever they fall from a height. It is a true reflex, and something that comes naturally to them, and they can do it very fast — they can often land on their feet even if dropped from a height of one foot.
Clearly, cats have developed this instinct because they are natural climbers, and inevitably some of them fall from trees. Evolution has “trained” them to possess this reflex so that they can land safely. Even cats falling from skyscrapers at heights of 20 stories or more often survive with only minor injuries.
So it is easy to understand why a cat has developed this ability… but it turns out that rabbits can also do it! I found this gif on the internet that demonstrates the abilities of rabbits, cats, and dogs (source unknown, alas). It is quite clear that cats and rabbits have little problem landing on their feet, while the poor dog has a lot more trouble.
In the 1960s, one researcher on the righting reflex used rabbits instead of cats, as their capabilities are so strikingly similar.
The rabbit’s ability poses a bit of a puzzle, though: why would rabbits have developed a righting reflex? To the best of my knowledge, rabbits don’t spend a lot of time up in trees. I’ve mentioned this puzzle a number of times while giving talks on the cat-righting reflex. I made two guesses, both of which were a bit unsatisfying. The first guess is that rabbits, while fleeing from ground-based predators, occasionally run right off of ridges or small cliffs, and the reflex helps them land safely. The second guess is that rabbits, when picked up by aerial predators, wriggle themselves free often enough that the ability to land from a height became an important evolutionary selection process.
Well, thanks to the video I’ll show you, I think I’ve found the answer, and it’s different from my guesses!
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Skulls in the Stars 