|
Author
|
Topic: Canine Vision
|
Rich Higgins
unknown comic
|
posted July 02, 2005 08:07 AM
"Until a few years ago, everyone thought that dogs' eyes all had the same basic structure and Dog A saw things the same way that Dog B did.
However, an Australian professor of veterinary science named Paul McGreevey started wondering about this and hooked up with a neuroscientist named Alison Harman, and they started studying the eyes of different kinds of dogs. Different kinds of dead dogs.
Dogs have something called a visual streak. It's a line of vision cells packed in there very densely and running across the retina. Scientists already knew this.
What McGreevey and Harman found out, however, was that some dogs don't have the visual streak. Nobody knew that before. Instead some dogs have something called an area centralis, which is a whole bunch of vision cells arranged in one spot, as opposed to stretched out in a streak.
Dogs with an area centralis probably see things more like we do than dogs equipped with visual streaks.
Visual-streak dogs tend to be hunters. They have long noses and good peripheral vision and can spot something moving out of the corners of their eyes and follow it with their eyes.
Area-centralis dogs tend to have shorter noses, and they have about three times as many nerve endings in the retina as do visual-streak dogs. That means they may not have great peripheral vision but they see things much more clearly, with greater definition, than other dogs.
Now I don't know if this has been absolutely proven, but the thinking is that maybe short-nosed, area-centralis dogs are more likely to watch TV than long-nosed, visual-streak dogs.
In the interview I read, McGreevey said this also might explain why short-nosed dogs can seem to be more attentive than long-nosed dogs. They are able to read your facial expressions better because of their ability to see up close. That's an interesting idea."
My daughter works at a pet resort in Scottsdale. $55 a night puts the doggy up in a suite with a bed and a TV that is on 24 hours. She says a lot of the dogs spend their time lying on the bed watching it.
IP: Logged
|
|
The Outdoor Tripp
Knows what it's all about
Member # 619
|
posted July 02, 2005 08:12 AM
Finally, it all makes sense.
I've got a long nose. I love to hunt. I watch very little TV.
Self actualization is mine!
Rich, you're a stinkin' genius.
--------------------
The Outdoor Tripp
www.theoutdoortripp.com
"All great truths begin as blasphemies."
Posts: 805 | From: Texas | Registered: Mar 2005
| IP: Logged
|
|
Leonard
HMFIC
Member # 2
|
posted July 02, 2005 08:36 AM
That's all I need, as to amenities. And, especially for Snottsdale; the price is right. Cancel my re$ at the Pointe.
Did they say that bobcats have the same type of "visual streak"? Maybe more so?
Good hunting. LB
--------------------
EL BEE Knows It All and Done It All.
Don't piss me off!
Posts: 31509 | From: Upland, CA | Registered: Jan 2003
| IP: Logged
|
|
2dogs
Knows what it's all about
Member # 649
|
posted July 02, 2005 08:58 AM
Very interesting. I found on the "WEB" awhile back. Some similiar info as well.
Basicially some breeds see different color hues, than others. Also read how a dog can visually tune in on cycles per sec. eg; They see every pic frame of a movie as compared to humans seeing only a constant movie w/o frame flicker ![[Eek!]](eek.gif) ![[Cool]](cool.gif) .
Posts: 1034 | From: central Iowa | Registered: Apr 2005
| IP: Logged
|
|
Cdog911
"There are some ideas so absurd only an intellectual could believe them."--George Orwell.
Member # 7
|
posted July 02, 2005 11:22 AM
Rich, I was right there with ya, man, until you started talking about the pet resort. What kinda fru-fru crap is that?
I got one dog. A huntin' dog. If he gets hungry, I just say, "Hunt."
On a more serious note, did they refer to the area of greater acuity as the area centralis or the foveal centralis? I've heard the latter referred to on many occasions as a cluster of densely packed rods in a specific area of the retina upon which the image is focused and which renders the best acuity. If I remember this correctly, the nerves connecting the rods to the optic nerve proper are wired one on one with each rod cell having its own nerve feeding to the ON and thus, to the brain. Cones, by comparison, have the nerves between the rod cell and the ON bundled. In other words, dozens of cone cells bundle to one common nerve that then feeds into the ON. If only one cone cell captures an image, the signal sent to the optic nerve and then to the brain is weak and attentuated. If a small image (or movement) falls upon a rod cell, the innervation structure sends a full strength signal to the brain, thus accounting for the greater acuity observed in rods, as compared to cones, ergo greater acuity and nighttime vision.
Now, I can definitely see the adaptive advantage of having a horizontal band of rod cells across the retina when you're a wild beast that depends upon its ability to see possible prey at long distance on a horizontal plane. With a domesticated animal that is not required to prey for its own earnings, it would not necessarily be an advantage to have that band, and since people are generally diurnal in nature (except for my teenaged son), it stands to reason that over time, their domesticated dogs would become diurnal as well and become less in need of visual acuity in the absence of light. They also don't have to see their game at long ranges and I bet over time, they have de-evolved the structure of their retinas relative to that fact.
As a home assignment respective to the retinal arrangement of rods and cones in your own eyes, go outside tonight and look at the stars. If you look directly at a dim star that is easily viewable in your peripheral fields of vision, it disappears. If you turn your head slightly, it re-appears. This is because the human retina has a fovea centralis comprised primarily of color-detecting cone cells. Around it is a densely packed ring of rod cells. Looking directly at a dim start focuses the image on cone cells that lack the acuity needed to deteect the faint amount of light, while the rod cells can easily "see" it.
On a related note, each of us has a blind spot created by a small dimple on the inner retinal surface - the retinal fossa - where the optic nerve attaches to the eyeball. Our brains have evolved to process visual signals in such a way as to ignore the absence of input in the images we see and just fills in the blanks.
At least, that's what someone told me once. Take it or leave it.
As far as cats go, I can only presume that they also possess the same retinal structures. Then again, what evolutionary advantage does the vertical eliptical pupil offer? Same goes for red foxes. Don't know.
--------------------
I am only one. But still, I am one. I cannot do everything, but still, I can do something; and, because I cannot do everything, I will not refuse to do something that I can do.
Posts: 5438 | From: The gun-lovin', gun-friendly wild, wild west | Registered: Jan 2003
| IP: Logged
|
|
Leonard
HMFIC
Member # 2
|
posted July 02, 2005 02:43 PM
No, that's completely true, Lance. Had to do that in a Biology class, once. Start at a certain spot and move a black dot around in another marked location and the black dot completely disappears where the optic nerve attaches to the retina.
But, I don't see why prey species couldn't benefit by having this lateral band? Especially since most tend to have their eyes on the sides of their head, especially birds. Maybe it allows the predator to compensate for his binocular vision?
Good hunting. LB
--------------------
EL BEE Knows It All and Done It All.
Don't piss me off!
Posts: 31509 | From: Upland, CA | Registered: Jan 2003
| IP: Logged
|
|
2dogs
Knows what it's all about
Member # 649
|
posted July 20, 2005 07:07 AM
I've had in wintertime snow. Some coyotes, busted me. Even while being motionless, while wearing all white camo.
Posts: 1034 | From: central Iowa | Registered: Apr 2005
| IP: Logged
|
|
Greenside
seems to know what he is talking about
Member # 10
|
posted July 20, 2005 10:18 AM
Kirby
Do you think coyotes can see better than man?
Dennis
Posts: 719 | From: IA | Registered: Jan 2003
| IP: Logged
|
|
2dogs
Knows what it's all about
Member # 649
|
posted July 20, 2005 10:51 AM
Quicker yes, better perhaps on some things.
Most of the one's I've stalked up on in fluff snow. That just happened to look my way, when I wasn't moving.
Could tell, something was not quite right. Most of them never turned their heads. Until a bullit[s] came there way[I like to motivate them, LOL!].
I've also had some, while stalking in on fluff snow from down or crosswind[out of sight]. Detect something was a miss. They quickly moved away, while looking back toward my position....Figure that one out. I never will.
------------
BTW, their not "smarter" just harder to call, around my areas ![[Big Grin]](biggrin.gif) . Invitation is still open
[ July 20, 2005, 11:01 AM: Message edited by: 2dogs ]
Posts: 1034 | From: central Iowa | Registered: Apr 2005
| IP: Logged
|
|
Greenside
seems to know what he is talking about
Member # 10
|
posted July 20, 2005 12:13 PM
Kirby
This is my opinion, but keep it in mind. Coyotes depth perception is not overly good. You can use that to your advantage when calling coyotes in IA and elsewhere. What I'm talking about is that you can do some of you setups in wide open corn and bean stubble and also grazed down pasture. All you need is a steep enough slope that your silhouette is below the horizon. When your in the bowl below the horizon coyotes, because of their lack of depth perception, will see you in only one plane. Basically all you look like is just a different shade of colot and more than likely not a human mass. If your above the horizon they will pick you up instantly as being a human and head out in a hurry. Before you sit down and call take a look behing you and see if you would be silhouetted. Keep it in mind and your going to be shooting more coyotes
Dennis
Posts: 719 | From: IA | Registered: Jan 2003
| IP: Logged
|
|
2dogs
Knows what it's all about
Member # 649
|
posted July 20, 2005 01:20 PM
Greenside,
Heres my opinion,
Mammals, fish, birds & reptiles see in 3-d as humans do. I was taught very well by my Dad, not to mention what I've learned & experienced on my own over the years. About Red Fox, & Coyotes.
Also, IMO...Coyotes have better senses than Red Fox.
I'm quite aware about cammo, ridgelines, wind, ect, ect.
Not to mention..."scent-cones"
[in the fire service, they call that a "plume-cloud"]whether visible or not.
Vapor density: Air = [1], anything, ie;[gaseous vapor]heavier than air, is given a number >1.
Human skin-cells & body hair, are heavier than air. So they'll fall to the ground. As for human sweat[liquid & vapor]. Sweat on a human, will put off airborne vapors. Which can/will be carried quite some distance in a wind.
---------------------
One thing that has stumped me yrs ago, & still does. Is how do some coyotes know, something bad is out there. When none of their senses are at play. I've seen/experienced it first hand.
-------------------
Another opinion on their depth perception.
If it was not that keen[IYO]. How is it, that they can[while flat-out running]. Judge a barbed fence..., the distance, spread of wires & any dip noted under the bottom strand. That they can slide through/under?...w/o slowing much if any?
[ July 22, 2005, 04:41 PM: Message edited by: 2dogs ]
Posts: 1034 | From: central Iowa | Registered: Apr 2005
| IP: Logged
|
|
Greenside
seems to know what he is talking about
Member # 10
|
posted July 20, 2005 01:50 PM
Kirby
I'm trying to help a fellow Iowan. Take my word on it. Lack of depth perception is a major cause of death in coyote. ![[Smile]](smile.gif)
Dennis
[ July 20, 2005, 01:51 PM: Message edited by: Greenside ]
Posts: 719 | From: IA | Registered: Jan 2003
| IP: Logged
|
|
2dogs
Knows what it's all about
Member # 649
|
posted July 20, 2005 02:50 PM
Greenside,
I know you are, I'm trying to hep ya back, eh.
Leading cause of death, where I hunt... is sometimes caused by not being faster than a bullit .
Posts: 1034 | From: central Iowa | Registered: Apr 2005
| IP: Logged
|
|
Az-Hunter
Hi, I'm Vic WELCOME TO THE U.S. Free baloney sandwiches here
Member # 17
|
posted July 20, 2005 03:23 PM
As I understand it, at least from the sources Ive dug up, coyotes have visual acuity of approx, 20/75....which is not better than normal human vision.
I suppose the hard part is getting the damned coyotes to read the chart:)
Posts: 1634 | From: 5 miles west of Tim | Registered: Jan 2003
| IP: Logged
|
|
2dogs
Knows what it's all about
Member # 649
|
posted July 20, 2005 03:57 PM
AZ-Hunter,
These tests, do you remember or know. How old these test animals were? Or how many they tested? Or what was the medium, they used? If you can find it. I'd like to read it as well.
Thanks
------------
As for comparing them to humans. I do believe we have the ability to pick out certain colors, shapes or sizes, better than them at certain distances.
Say for example, 20yrds away sits a human wearing camo, sitting in front of a bush[not moving].
Posts: 1034 | From: central Iowa | Registered: Apr 2005
| IP: Logged
|
|
Greenside
seems to know what he is talking about
Member # 10
|
posted July 20, 2005 05:46 PM
Kirby
Not trying to feed you any shit. The lack of depth perception in coyotes is your trump card or your ace in the hole. It should be a major factor in any of your setups. Pay attention.
Dennis
Posts: 719 | From: IA | Registered: Jan 2003
| IP: Logged
|
|
Leonard
HMFIC
Member # 2
|
posted July 20, 2005 06:23 PM
It's possible that the visual acuity in coyotes is not the limiting factor. If they had a human brain, they may be better able to pick out shapes and figure out what it might be. Like they say about turkeys, they assume every tree stump is a hunter with a shotgun. That's the problem with an animal with such a well developed sense of smell. Scent is reality, not shapes.
Good hunting. LB
--------------------
EL BEE Knows It All and Done It All.
Don't piss me off!
Posts: 31509 | From: Upland, CA | Registered: Jan 2003
| IP: Logged
|
|
2dogs
Knows what it's all about
Member # 649
|
posted July 20, 2005 06:23 PM
Greenside,
Chill...Never said ya was feeding me any.
I just disagree is all. I don't always believe test results or analogy's/summations from the "experts" who have done studies.
I'm no "doubting Thomas" either. I don't have to see something, in order to believe it. But scientific studies/opinions are often not 100% accurate or non-biased, IMHO. But I still consider their results.
I told a story, of "Clyde's dog" How many people you suppose believed it? Hmmmmm, perhaps just a couple maybe. Doesn't make it any less true, eh.
I've spent thousands of hrs in the field[40-winter's worth], watching coyotes & Red Fox. I've come to some of my own conclusions. I'm sure as you have as well, with your own experiences.
Posts: 1034 | From: central Iowa | Registered: Apr 2005
| IP: Logged
|
|
|
UBBFriend: Email this page to someone!
Printer-friendly view of this topic
