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.
The blue can be to some extent an imperfect recessive or partially expressed recessive -- still showing blue but having some of the qualities of the seal/chocolate color. The dilute factor is even more difficult to deal with.
Of course it's a crap shoot -- that's what makes it so much fun! My younger dog's breeder had to laugh at the mathematical inclinations of Ruby's mom -- she was a Yellow bred to a yellow-factored Black, which should mean 50 percent yellow and 50 percent yellow-factored Black. She had TWO black males, TWO black females, TWO yellow males, and TWO yellow females. She really likes symmetry in her litters . . .
That's where they lost me. I've yet to see a remotely plausible evolutionary (gradualistic) explanation or mechanism for the rise of such a stupendously complex organ and its necessary support systems/structures.
The eye is one of the classic examples of irreducible complexity. (A Series of Eyes, by Michael Behe.)
When they look out the window at night...they can see Uranus.
I think you are right; but what’s great about it is they said it couldn’t be done. Until my breeder came along; it couldn’t; but she knows genetics really well. It took them 30 years. Even the breed founder has never done it. LOL
I never knew that about the blues and lilacs having had one of each. My lilac had the bluest eyes you have seen. They were just like the blues of the ocean. You learn something everyday.
I love it about the labs. My handler/trainer breeds blood hounds originating with a line going back to his grandfather. The grandfather’s dog had a star I believe on his hip and ever since then if you breed with that line; you are going to get a pup with a star on it’s hip.
That’s almost as good as DNA. LOL
Those are the folks who do what 'couldn't be done'. Congratulations to her.
It's hard to get a really good eye color in the Lilacs, so you had a really good kitty!
Talking about the star on the bloodhounds' hip, an interesting mark in Chocolate Labs is what they call "Bolo Spots" or "Bolo Pads". One of the main Chocolate foundation sires (who appears in almost all American field type Chocolate pedigrees) was a black English dog named Dual CH (dual = field & conformation) Banchory Bolo, whelped in 1915.
Not only did he throw the chocolate color, he also threw these funny little white spots on the bottom of the feet, in the hair behind the main paw pad.
My Shelley dog is descended via her grandsire NFC/AFC Storm's Riptide Star from Banchory Bolo. Sure enough, she has the white spots on her paws!
I know they don’t. I can call my friend anytime(I got both girls and my boy from her) and she will know the lines of any of this breed. It’s amazing. What was cute before she had this litter her daughter, 4 at the time told her she wanted a white puppy from white parents. The founder was there and said it couldn’t be done. Lindsay told her “miracles do happen”. Well it did.
I didn’t know that about lilacs. Her brother’s eyes were the same too. They were a beautiful litter.
That is one beautiful lab in the pic. I love the white spot. Amazing about genetics; isn’t it? I am going to ask my friend if her chocolate lab has one on his foot. LOL She’s probably going to tell me yes. Are they on all of the feet? That one is pretty. My friends two labs are field trial champions. I am not sure about conformation. But their mastiffs love to field trial. Both have been doing it since they were babies. And they have won. LOL It seems one day, the lab pups didn’t want to for some reason retrieve that thing; so Rumor went in a got it and won a big ribbon. It was so cute. And they all have such a good time. I believe Angus, who is my godson puppy, is 6th or 8th in the nation now and his uncle and Rumor’s father was the top mastiff in the country. I am so proud of them.
You won’t believe this but my guys are out of a kennel called Bolo and of course it’s in their name
Bolo’s Gallant Thunder(gallant watch is my kennel name)
Bolo’s Hi Stepin Keeley
Bolo’s Yellow Rose of Texas
What a handsome dog, I’m sorry for your loss. Our Shepherd will be ten in April and I have a hard time imagining life without him.
Their appearance is radically different.
Show dog:
That's my Shelley's dad, Dozer.
Field dog:
My Ruby the Egregious.
My Shelley -- she is an odd bird because her father is a show dog and her mother is a field dog. She is kind of a half-and-halfer -- she has the square shape and short back of a conformation dog, but she's very skinny and has a more pointed face. My Ruby's bloodline gets the show component from a very unusual kennel - that breeds in the English fashion for dogs that can both hunt and show. The only conformation thing about her is her head -- which is far more correct from a show standpoint than Shelley's.
Re: the Bolo pads. Shelley only has them on her front paws, but she also is starting to whiten up with age and she has a lot of white hairs generally on her back feet. No spots though.
Bolo is a great kennel name. It’s short and it’s easy to remember. And it stands for “Be On the Look Out”!
I once spoke with a couple who judge field trials. They wound up with an orphaned AmStaff (aka pit bull) puppy that was fostered by one of their Lab bitches. The AmStaff thought he was a Lab and did all the Lab stuff, including retrieving. They used to run him as a field trial test dog, which of course messed with the competitors' heads . . . .
Dogs drool cats rule
Headed out the door; but wanted to reply to part of your e-mail. I didn’t know that about the English; howwever, their labs were invited to participate in some event that the English you would know bring to America every year. They were very proud of that invitation.
I love it. Am familiar with the breed. They are with our NKC.
Mama Fuji at 4 months. Sorry about all the posts.
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