Posted on 11/08/2007 7:09:03 PM PST by blam
How Well Do Dogs See At Night?
ScienceDaily (Nov. 9, 2007) — A lot better than we do, says Paul Miller, clinical professor of comparative ophthalmology at University of Wisconsin-Madison.
Dogs have good night vision, due in large part to the tapetum, a mirror-like structure which reflects light, giving the retina a second chance to register light that has entered the eye. This is also what makes dogs eyes glow at night. The dog is holding a toy in her mouth. (Credit: Michele Hogan)
“Dogs have evolved to see well in both bright and dim light, whereas humans do best in bright light. No one is quite sure how much better a dog sees in dim light, but I would suspect that dogs are not quite as good as cats,” which can see in light that’s six times dimmer than our lower limit. Dogs, he says, “can probably see in light five times dimmer than a human can see in.”
Dogs have many adaptations for low-light vision, Miller says. A larger pupil lets in more light. The center of the retina has more of the light-sensitive cells (rods), which work better in dim light than the color-detecting cones. The light-sensitive compounds in the retina respond to lower light levels. And the lens is located closer to the retina, making the image on the retina brighter.
But the canine’s biggest advantage is called the tapetum. This mirror-like structure in the back of the eye reflects light, giving the retina a second chance to register light that has entered the eye. “Although the tapetum improves vision in dim light, it also scatters some light, degrading the dog’s vision from the 20:20 that you and I normally see to about 20:80,” Miller says.
The tapetum also causes dog eyes to glow at night.
Adapted from materials provided by University of Wisconsin - Madison.
Out of this world.
My guess would be species identification. The distinctive marks on turtles are often very subtle but involve color. Just a guess. The do pre-date the dinosaurs and it could be that they pre - date cones.
Thanks! That was fun!
It's hard to tell. He's been crying so much lately his eyes are blurry.
Keith Moon told him it would go over like a lead zeppelin.
About a year after Jeff Beck and Eric Clapton left Jimmy page as lead guitar in the group Yardbirds, they changed their name to Led Zepplein and I saw their first US performance at the Filmore west in San Francisco, April, 1969.
Be nice to us old timers, huh? Also, click on my name to see my dogs.
Jerry Lee Lewis ping
“Here’s a treat.”
And what it treat it was...thanks for sharing.
THAT was GREAT.....and my husband wonders what I do on FR.....LOL!
Just a little fun every once in a while. LOL
WOW!!!!!!!!!!!!!!!!!!!!
AWESOME!!! Thanks much!
You are welcome.
You are welcome.
I remember The Yardbirds. I remember Led Zeppelin too. Saw him in concert.
Yes, be nice to us oldtimers. We could atleast sing to our songs. LOL
I love your dogs. They are great.
That a rough-coat German Shepard?
ping
He was a Hurricane Katrina abandonee that I rescued, so I really don’t know what all courses through his veins. From his behavior and physical characteristics, I personally suspect he’s a GSD/Border Collie mix with a dash of cartoon thrown in for good measure.
Love it.
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