The "Glowing" Eyes!

I was out late this evening and had a thought occur to me!  Wow!  Contrary to some folks idea, this is not that far-fetched...I do occasionally think!  No, seriously.  I was photographing a rabbit in the yard just about dusk when I noticed that the flash of the camera made the rabbit's eye glow.  Nothing unusual about that as rabbits' eyes "glow" when hit with a light source.  Usually, a bunny's eyes will glow red.  I learned that much way back in the day when we used to "spotlight" hunt rabbits. (Yes..I know that is illegal now but eons ago when I was a youngster, no one had thought about making a law against it.)  Anyway, the camera's flash just gave the rabbit's eye a sort of bluish white glow.  My thought..or question as it may be, was "Why?".  Just what causes some critters' eyes to glow?

 

First of all, this is not actually glowing.  Contrary to what all horror movies have taught us, ANIMALS' EYES DO NOT GLOW IN THE DARK!!!  They reflect light in the dark!  There is a vast difference in glowing and reflecting!  Anyway, I decided that after all these years, I needed to learn why animals' eyes do this.  After a bit of research, I found that it is all due to a reflective surface behind the retina.  This reflective surface is called Tapetum Lucidum (Which might be a great name for a rock band by the way!  It is one of those terms that just rolls off the tongue if you can pronounce it at all!  Tapetum Lucidum!)  Back to eyes and reflection...this reflective surface is there to help the critters see better in the dark.  It reflects any bit of light around and sort of magnifies it.  This allows critters to use every bit of light available.  Not all animals have this Tapetum Lucidum which accounts for why not all critters will shine back at you.

That, in itself was interesting to me..why?  Why do some have it and not others?   And which ones do?  It seems that the only logical answer to why some have it, is the fact that nocturnal animals have a need to see at night.  Well, duh, that seems to be reasonable!  Nocturnal animals are the only ones that really need to see in the dark! I suppose that diurnal critters do not need it much as they sleep at night. Although, it really would come in handy on those early morning treks to the pier!  Then I started looking at which have it and which do not.  According to most "experts", deer, rabbits, cats, dogs, raccoons, cattle, horses and ferrets all have the Tapetum Lucidum.  Their eyes will "glow".   Squirrels, hogs and kangaroos do not so they must sleep during the day!  Brilliant!  Except....I beg to differ with the so-called experts!  Aha!  How about those Flying Squirrels??  Those critters are definitely nocturnal!  Then again, perhaps they cannot see too well at night either at the rate they pelt the rooftop of the Little Bayou House with acorns all night.  Either they are clumsy, cannot see in the dark or just have a penchant for keeping me awake into the wee hours!    Seriously, Flying Squirrels eyes do reflect light.  Just go outside and shine a light up in any hickory, oak or pecan tree and you will more than likely see something staring back at you!  Now as for those kangaroos..there are not many of those hopping about the Bayou so I will just have to cede to the experts on that but at least we are all in the know about the "glowing" eyes and Tapetum Lucidum!