10/6/2005: Zebras

[Undertoad]

Magilla suggested this one out of a gallery of zebras, and I think it's a fine choice. Partly because it's such a great photo.

It really shows off why zebras have stripes at all. We think zebras look strange, but we look at them from our understanding of the world, and it turns out they are adapted to the lion's view of the world. From Howstuffworks:

When all the zebras keep together as a big group, the pattern of each zebra's stripes blends in with the stripes of the zebras around it. This is confusing to the lion, who sees a large, moving, striped mass instead of many individual zebras. The lion has trouble picking out any one zebra, and so it doesn't have a very good plan of attack. It's hard for the lion to even recognize which way each zebra is moving: Imagine the difference in pursuing one animal and charging into an amorphous blob of animals moving every which way. The lion's inability to distinguish zebras also makes it more difficult for it to target and track weaker zebras in the herd.

So do zebra stripes confuse zebras as much as they confuse lions? Oddly enough, while making zebras indistinguishable to other animals, zebra stripes actually help zebras recognize one another. Stripe patterns are like zebra fingerprints: Every zebra has a slightly different arrangement. Zoologists believe this is how zebras distinguish who's who in a zebra herd.

So it's quite amazing, really! The zebra has developed two unique things: a pattern that confuses pattern recognition in lions, and a specific pattern recognition ability so they aren't as confused as the lion.

Human pattern recognition is very good - it's one of the things we are really known for - so we can tell that the above photo is different zebras, and not just one big mass of zebra-something. But try to count them.

Go ahead, try it, I'll wait.

No, really, how many zebras are in that picture?

OK. You counted the heads, and then you got confused in the bodies. That's your pattern recognition at work; because you are human, you're strongly biased towards finding differences in faces. You can recognize different people by tiny differences in their faces, and your brain is actually optimized for that task.

A zebra would look at that picture and say right away, oh sure, there are 11 zebras. A lion would look at it and say, I have no idea, it's a big pack, how annoying, the gazelle next door is easier.