Animals like squirrels and small birds often move in short, rapid twitches. I’ve read that this is because their nervous systems are fairly simple, and don’t allow for much fluidity of motion. The other day I began to wonder if this might be a survival advantage for prey animals. Many predators react to movements rather than color or shape recognition, and so the less time a prey spends moving, the better for them.
Also, if you’ve ever wondered why squirrels are so indecisive when they’re in the middle of a road in front of a fast-approaching car, it’s because their first instinct at the sign of trouble is to freeze up and remain motionless. I’d also wager that a car’s fluidity of motion confuses them – they’re perhaps more accustomed to a predator bounding up and down as it runs toward them. Also, they’re most often oriented perpendicular to the car, so they only see the car with one eye, without depth perception. All they see is an object increasing in size somehow. I wonder if squirrels have depth perception at all, actually.
And in other zoological news, a great lesson I learned from Richard Dawkins’ The God Delusion is that moths and other insects are attracted to lamps and flames because their internal navigation systems are going haywire. Many flying insects use distant light sources like the moon as fixed reference points in their flight. But artificial light sources like street lamps make that impossible. We can keep the moon on our left and travel in a reasonably straight line, but a moth can’t keep a street lamp on its left; it will end up circling it forever. Or at least until daylight when the lamp turns off. Or until it plunges into the bulb and dies.
Last night a massive cicada was buzzing my porch, and I made the mistake of turning off the porch light with the door open. He zoomed into my living room and headed for my lamp, briefly stunning himself while I turned the lamp off and turned the porch light back on. He recovered and zoomed back outside. The poor bastard.
I don’t know about depth perception, but prey animals that have their eyes on the sides of their heads often have panoramic vision. Unlike animals with binocular vision, they can see who’s approaching them from behind, to some extent.
Then again, without depth perception, how could squirrels leap from branch to branch and tree to tree seemingly without ever missing? Are they just really lucky?
Someone ought to dredge up a biologist who specializes in squirrels to get these questions answered. And by “someone,” I mean “not me, perhaps Colter.”