Why do animals' eyes glow when light hits them?

Dude Here

New member
Just wondering what it is in their eyes that make predators' eyes glow and why they glow when light hits their eyes??? I've also noticed that most animals' eyes I've seen glow, and it seems like dogs, foxes and yotes are reddish/orange, deer and cattle are bluish/green, and cats are greenish/yellow. Why is that? What causes it and does it hinder the animal or help it? (In most of our cases, I'd imagine it hinders them because it gives them away.)
Just curious. Thanks for reading.
 
The retina of the eye is made up of cells called receptor cells. These receptor cells come in two different forms, rods and cones. These cells gather light and relay it to the brain to form the image seen. The “eye-shine” is simply light from your spotlight passing through the retina and being bounced back from these receptor cells. It’s called “refraction”. Different animals have different photochemical pigments in these cells and that’s why the different colors of shine.
 
Nasa? Isn't it also due to the fact that there are more of one of the types of receptor cells (rods and cones) in an animals eyes?

I can't remember which one at the moment.. CRS disease!! The more abaundant set is the reason that they can see better at night also???....James L.
 
True nocturnal animals have almost all rods. This actually makes their vision "fuzzy" and their eyes are usually very large to compensate.

The reason they shine is because the have a layer of cells called the tapetum lucidum. The tapetum is a thick reflective membrane under the retina. It gathers and bounces light back onto the retina, letting the rods work better at gathering the image. As light is reflected off the tapetum, the animal's eyes "glow".
 
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Nasa? Isn't it also due to the fact that there are more of one of the types of receptor cells (rods and cones) in an animals eyes?


The different colors are due to different ratios of rods to cones. Humans have the same issue, by the way -- it's what give us "red-eye" when our picture is taken with a flash.

This difference in the rod/cone ratio also explains why some animals see different parts of the color spectrum than others. Humans see less of the UV blue spectrum, but can easily discern more of the red/orange spectrum. That's why some animals see so much better at night.

Hope this helps -- good luck!

Specialized
 
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Why do animals' eyes glow when light hits them?


So you can see where to shoot. /ubbthreads/images/graemlins/grinning-smiley-003.gif
 
Not all nocturnal animals eyes shine. Ever see a feral hog or skunks eyes shine? Skunks go a little but not much. I've yet to really see a hogs eye shine.

Bobcats eyes almost seem to have their own light.

But, relative to their size spiders seem to have the brightest eyes. It can be hard to convince someone who has little experience spotlighting that those "eyes" (only appears to be one eye) belong to a spider.

I have also shined a whipporwill or chuck-wills-widow a long way across a clearcut or pasture.
 
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Yellowhammer, bobcats have bright eyes alright, but have you ever seen a badgers eyes? Now they got some bright eyes. Maybe they are related to spiders? lol, Good Hunting
 
Granger,
I believe same thing as you do. Only color blind animals have eyes that glow in the dark. I thought that I was wrong once, but it turned out that I was mistaken. /ubbthreads/images/graemlins/smile.gif
 
{/quote}I thought that I was wrong once, but it turned out that I was mistaken. /ubbthreads/images/graemlins/smile.gif



Rich, now you sound like my father!

OK the real reason Predator's eyes shine at night is so that we have something to aim at!

Skinner 2
 
Thats kinda what I was thinking Skinner2. How else would we shoot em? /ubbthreads/images/graemlins/confused1.gif /ubbthreads/images/graemlins/grinning-smiley-003.gif
 
It is called "Tapium lucidium." The cells in the back of the retinal walls are unique in that it allows light to bounce from the back of the eye to the front (inside) and then back again on the fovea as a means of amplifying the light. By magnifying it on the frontal wall of the inside eye it enhances quality (cones). The next science lesson.... it takes humans about 11 minutes to get their full night vision. Humans can only see Black and white at night unless enough light is shined to activate the rods. Red light preserves human night vision. All that work I need another beer, hiccup!
 
It is not the rods or cones it is the tapetum. A reflective membrane behind the retina. Behconsult was the first to get it right, but I think his spelling is wrong. I could be wrong I am a bad speller. I teach high school biology and cut up cow eyes every year.
 
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Slightly off topic but what causes red eye in pictures of humans? Is it a similar thing? I don't think it is because if I shine someone their eyes don't light up.
 
LeadPoison,
I have often wondered the same thing. I also wonder if people who are color blind have eyes that glow when light hits em.
 
Rich and LP, as far as color blind ppl go, no. Their eyes won't reflect because although they cannot discern color like a person with normal vision, they lack the tapetum membrane which is actually responsible for the reflection. The function of the TL is to act as a reflector to reflect the image being projected (via light) onto the retina back on the retina again and again, effectively superimposing the same image multiple times onto the rods in the retina, thus allowing for a better "look" at the image thus augmenting what we call "night vision". It's not that they see light better than we do. They just have the physiological adaptations to allow them to make better use of ambient light. The TL is reflective on both sides and the reflection that appears as glowing eyes is the same on the inside of the eyeball.

As far as red eye goes, it is caused by the flash illuminating the blood vessels of the retina as seen through a dilated iris. If you have a camera with the flash function that reduces red eye, you'll note that it flashes twice. The first being somewhat less than the second & a fraction of a second later. The purpose of the two flashes is that the first flash prompts the iris to constrict and the pupil to shrink making the retina inside the eye less visible (ergo less red). The second flash actually illuminates the subject for the photograph.
 


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