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.
It’s funny blam....my current leisure read is Phil Lesh’s narrative of the history of the Grateful Dead and I confess that my Sirius radio is still tuned to their channel...36 I think.
You know.....them and Pink Floyd, Kinks, Skynyrd, Doors and Zepplin are bands I still enjoy just as much today.
regards....
that must have been fun....I caught the southern tail end of all that
GREAT pic! Thanks!
Boy O Boy, what a ride.
... but I would suspect that dogs are not quite as good as cats ...
Couldn’t help posting this great pic of yours.
Boy those chargers are expensive . . .
I just thought you might be interested. I checked with my friend who owns Angus and the mastiff you saw is Angus. I am so happy. I know that boy is going all the way.
Those kitties are absolute dolls. Are they related?
Good morning. I’ll forward your question to the one who’d know.
That’s interesting, because now that I am in my mid-fifties, I feel that I don’t see as well at night as I used to, but my husband doesn’t seem to have the same problem.
This getting older stuff really sucks.
Ask Michael Vick?
SO men have a rod...and women have...
Do we really need the final sentence in that caption?
Are there people stupid enough to believe that a dog could grow a tongue that in every respect resembles a candy cane?
Don’t know about how well they see at night...but my black lab sees SATAN every time somebody new comes to our house for the first 30 - 90 seconds....(chuckle)
The two on the right are both from a local breeder, they are great-uncle and grand-niece. Different sires because the one in the middle is a Blue Point and the one on the right is a Lilac. The one on the left is from a different local breeder and is not related to the other two.
Since they all hung out together, though, they all started looking and acting alike. Just like married folks!!
LOL. I was wavering back and forth between lilac and blue point. They are adorable. I have had 8 siamese myself; so you can tell I am a lover of the breed.
The big male, Finny (the one in the middle) was a "true Blue" -- if you have too much Seal or Chocolate in the background, the blue points acquire a brownish tint as does the body coat. He was solid Blue for 5 generations (with the exception of one Seal in the 5th - the infamous Thaibok Teriyaki), and his points were the correct slate blue with no brown notes, and his body color was a pure pale gray. He was one nice looking cat! The cat on the left, Trina, had a Chocolate mother and she always did have the brownish undertone in her points and a beige body. The little Lilac, who is still with us, has the prescribed glacial white body, lavender gray points, and mauve nose leather and paw pads. Hanging around with a bunch of dogs has made her a bit peculiar, though!
Siamese are definitely the best of the cats, although Burms and Tonks are nice too.
That is amazing. 5 generations and only one chocolate. I am impressed.
They all sound like wonderful babies. It’s definately hard to go to another breed once you have bitten by the Siamese bug. LOL
It's probably wise to keep those bloodlines separate -- just like keeping the Chocolate Labs out of your Yellow Lab bloodlines because of the risk of coming up with a "Dudley" (a Chocolate Lab with the dilute coat color gene that produces a Yellow Lab from a Black Lab. A "Dudley" is a Chocolate Lab with a yellow coat -- they have pink eye rims and a pink nose. Not a good thing for anybody, they're supposed to be more susceptible to sunburn and skin cancer, and disqualifying in the show ring).
Genetics be it kitties or doggies is fascinating. I have two white sable dogs and 1 silver sable dog. It’s amazing what you can come up with. They all have the same father who is a pure white. The girls mother is a white sable and the boy’s mother is a light gray sable. The father and mother of the girls produced an entire white sable litter which is the only one ever produced in this breed with a white father and white sable mother. They said it couldn’t be done. I think it was because the father had a lot of whites in his background and the mother had a lot of whites in her background. Probably a double recessive white gene there.
However, the father and the gray sable produced a litter of no whites and 4 silver sables.
Genetics is so cool; and you can predict what the pups might be; but then you get that occasional odd one that’s been hiding. LOL like the chocolate in your blue’s history.
So, it’s kind of a crap shoot.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.