A bit of info on eyesight please?

[wadih]

After reading the cooked eggs thread, I selected 5 adult snakes (garter: 2 males and 1 female. Natrix: 1 Male and 1 female) and separated each one of them in different aquariums. I brought quail eggs broke one and painted the rest with its white to enhance the smell.
Nothing happened and they even did not consider it as food, one of them started playing with the egg as a ball :)

Any way, I tried another test: I kept the temperature of the room where the snakes are to 15C (57F-60F) which is the lowest degree (as I read) for this type of snake to be able to hunt. I brought several colored and transparent small plastic bowls and put small fish in each one of them, the bowls were high enough for the snake to see the fish through the plastic. And since the temp was low they are not interested in putting the effort except if they were sure it is worth it.
The important thing was that they were able to detect the movement inside the bowl regardless of the color (I even tried dark blue); however, none of them were able to detect the movement in the water with similar bowl-fish color test (in light or dark orange / red / brown) at all.
I am not sure if that can tell something or not ( I guess a forum moderator can give us final decision) but I think the snakes are not able to differentiate the color as much as human. They only tell the difference if it was big; otherwise, they will never tell if there was a fish or not.

I will be glad to hear more opinions about this...

[Charis]

I haven't really noticed whether mine have any preference for colors, will have to watch for that. I have noticed that both of mine, to begin with, hunts more by motion, after they have eaten 1 or 2 fish, they get more into a frenzy & seem to hunt more by touch. Neither of them seem to use their eyes much.

[guidofatherof5]

I once asked if garters can see color. I will they to find that thread and post a link. If I remember correctly they may be able to see limited color.

[aSnakeLovinBabe]

well, I don't know how much color they can or can not see, but even if they could not see any color at all, if you put an object on a background that is similar in color it is naturally going to be harder to distinguish because the shades themselves are similar.

[Lovok]

I did a search for "eye sight" and "vision", but didn't really come up with anything helpful. I'm reading conflicting info though, here and in some reference books.
Some stuff I've read says eastern garters have "excellent eyesight" and use it for hunting, while some people here have said their vision is no better (if not a little worse) than our own. In my/our case, when I know Scylla is awake, she doesn't always react to me, my hand, or my movements, at least up close. If I'm a few feet away from the tank, she'll duck for cover into a hide when I move closer. Yet when she's on her branches and I do the same thing, she couldn't seem to care a less. This leads me to think that they can't see well, and are "movement" based. but even that doesn't apply to her half the time. :confused: When I drop a worm into the tank, sometimes it barely hits the floor and she's on it (it never has a chance to move). Other times, she flicks & searches, and seems to have trouble finding a morsel, even if it's right under her tongue.

So, is their eyesight bad or not? If so, are they far-sighted (can see stuff better when it's farther away) or near-sighted? How dependent are they on movement vs smell vs sight? Does my girl need teeny specs on her snoot like the Incredible Mr. Limpett? :D

[guidofatherof5]

I think what you are seeing is selective vision. I think Scylla is reacting to what she wants to and when she wants to. I have had big radix females catch pinkies I've thrown towards them. I think garters have great vision all the way around.

[Lovok]

You know, I considered "selective vision", but didn't really think they could do that. I think I'm finding it hard to read her because I just can't tell what she's looking at and when. That "no blinking" somewhat expressionless thing snakes have going is NO road map to their thoughts! LOL

They must take in everything and evaluate it, because she rarely turns her head like she's zeroing in on something.

[wadih]

When I did the test i mentioned earlier I was not checking their eye sight at all. I tried once the same experience guidofatherof5 talked about (throwing the fish) and it worked perfectly specially if the snake is excited about food (usually happens after the first fish). In fact I think they have perfect eye sight.
However, the test was to know how good they differentiate colors. And what I reached was that they do not differ colors a lot. I mean they see for example orange, dark yellow and red as the same color and so on.
But I am not sure if these results can be generalized on all thamnophis, and that is why I asked if someone got more info about it.

[Lovok]

When I did the test i mentioned earlier I was not checking their eye sight at all. I tried once the same experience guidofatherof5 talked about (throwing the fish) and it worked perfectly specially if the snake is excited about food (usually happens after the first fish). In fact I think they have perfect eye sight.
However, the test was to know how good they differentiate colors. And what I reached was that they do not differ colors a lot. I mean they see for example orange, dark yellow and red as the same color and so on.
But I am not sure if these results can be generalized on all thamnophis, and that is why I asked if someone got more info about it.


Your thread about whether they see colors or not was what prompted me to finally ask my question, even though I've been thinking about it some time beforehand. Sounds to me like they have some definite kind of color-blindness. I guess questions like ours would be better answered by someone who's got some herpetophysiology--yeah, I just made that word up--knowledge, and know how their eyes are actually structured (rods? cones? both? more of one than the other?).

[guidofatherof5]

I know that someone from the forum put a link to a study for this color question. I looked in my records and couldn't find it. I'll keep looking.

[Stefan-A]

The photoreceptors and visual pigments of the garter snake
(Thamnophis sirtalis ): a microspectrophotometric, scanning
electron microscopic and immunocytochemical study
The presence of more than one cone pigment satis®es
the most basic retinal requirement for wavelength dis-
crimination or color vision. Unfortunately, we know of
no reports describing any color vision capability, or lack
thereof, in any snake species. Color vision is so common
among the vertebrates (Jacobs 1981) that it would not be
unreasonable to assume that the garter snake has color
vision. However, the assumption would be premature
without direct experimental data since a multipigment
system can serve other functions, such as simply
increasing sensitivity across a broad spectral range or
enhancing contrast (Lythgoe 1979).

[guidofatherof5]

The photoreceptors and visual pigments of the garter snake
(Thamnophis sirtalis ): a microspectrophotometric, scanning
electron microscopic and immunocytochemical study



Thanks Stefan. I thought it was you but didn't trust my memory.

[wadih]

Although I am new here (as my tag indicates :) ), I learned a very important thing about the forum. When stefan gives his opinion just agree with him :)

And since "the assumption would be premature without direct experimental data" how about an experiment that we can try as follow:
I am sure most of the people here knows how each snake acts upon their movement towards it. So if we just add a color plastic film (I guess available in all electrical hardware shops) with certain color and try wearing different colors of cloth. According to the results we can see if the snake is able to detect the movement in all colors or not...

[guidofatherof5]

Although I am new here (as my tag indicates :) ), I learned a very important thing about the forum. When stefan gives his opinion just agree with him :)

Now where would the fun be in that:D

[ConcinusMan]

oh no. It's way more fun to challenge it. Of course, this usually results in being shown the error of your ways, but still more fun.

[ConcinusMan]

I've had concinnus that almost seemed blind, especially at a distance. They only seemed to see things if they moved and only if they were close. Fish moving in the water bowl definitely grabs their attention, but once they get into the bowl it's as if they aren't using their eyes at all. Instead they just dive in and root around until they bump into a fish, then grab it. Same goes for pieces of fish. Once they smell it, they don't use their eyes at all, and will bite anything that smells like fish. I really think their eyesight isn't that great but is movement based. Mostly I think they rely on their sense of smell.

[Stefan-A]

Naturally some colours and contrasts blend in better with the background and are harder to detect. That applies to anything with vision of any kind.

Most of you should also already have noticed how easily distracted feeding garters are by movement. All it takes to draw a hungry snake away from a bowl full of food, is a wave of a finger. I've witnessed that countless times and I'm sure most of you have, too. It seems to me that vision tends to overrule smell, when both motion and smell are present. This doesn't of course imply that garters can't see stationary objects, they most certainly can detect shapes (e.g. eyes).

[Stefan-A]

And since "the assumption would be premature without direct experimental data" how about an experiment that we can try as follow:
I am sure most of the people here knows how each snake acts upon their movement towards it.
Yes, it varies from snake to snake, depending on personality, alertness level at the time as well as a myriad of environmental factors. Too many things can go wrong if we start assuming that we know our snakes that well. These factors need to be taken out of the equation and colour vision should be tested separately.

[ConcinusMan]

The man has spoken. That is all. Can't argue with the logic. It is sound.

[ConcinusMan]

I'm wondering if this should be merged with the 'color detection' thread located here: http://www.thamnophis.com/forum/husbandry/6403-color-detection-2.html

[Stefan-A]

It probably should, the topics have certainly been crossing over.

[ConcinusMan]

I thought so. They fit well together.

[wadih]

The man has spoken. That is all. Can't argue with the logic. It is sound.


You said it.... Guess that is right. Although that was the first thing that came to my mind in testing the color detection issue. I think if it was trivial or easy to test it a lot of reaserch results would have appered on the net.
I will try to think about a diffrent method but hopefully a more experianced snake owner might come up with effective ideas that we can try.

[drache]

my completely anecdotal observation leads me to believe that their distance vision is better than their close-range vision
I see them following movement and focusing with their eyes - they may not have facial expression, but with minimal observation skills one can often figure out what they're looking at; even someone with my relatively poor eyesight can see their pupils
and when they pop their heads up, it's pretty obviously a sign of interest
what and why catches their interest is an entire different area of study, but in the case of garters it seems that food and mating isn't all there is to it

[Stefan-A]

The man has spoken.
Yeah, cut that out. I'm no authority, I have little relevant education, even less experience and I've read about the same books as everybody else here.

[ConcinusMan]

Don't be so modest. (see, this the part where I suck up to a moderator)

[drache]

Don't be so modest. (see, this the part where I suck up to a moderator)
I can tell he totally loves it too

[Stefan-A]

I can tell he totally loves it too
Incorrect.

[Steven@HumboldtHerps]

Well, as far as I have found (Hello Y'All! Happy Holidays!)... uh... not much. Is there any newer research on snake vision? It seems there is common consensus on the fact that many snakes have variable preceptions of dark and light. Would this be "black and white" as we know it? Sharp? Blurred? No update on cones for color? I wonder if anyone has researched Boomslang vision as they are one of the only true, naturally occurring sexually dimorphic species. Do green boomslang males spy on their brown female mates? Or is it all pheromones? I am comfortable to say that many snakes do possess a unique vision that is sensitive to motion; although not the same (a shared derived characteristic of all snakes is the loss of ciliary eye muscles), a neat "visualization" (HA!) of this type of vision could be exemplified by Wiki's description of "blindsight".

Oh, the wonder! Most of my garters are very sight oriented, especially the little ones. Of course, the tongues are always flicking at the same time - Which is something else I have been trying to picture! Does the location of a scent molecule on a certain part of a snake's tongue register a direction?
Is that the advantage of a forked tongue? Add "blindsight" and "B&W", what else do you need? Infra-red? Oh, the specialization!

[drache]

Incorrect.
I guess I don't do facetious well in print

Does the location of a scent molecule on a certain part of a snake's tongue register a direction?
Is that the advantage of a forked tongue?
that's something they deduce from scent trail experiments, and yes - apparently the forked tongue is a directionally sensitive tool
read "The Snake Scientist" by Sy Montgomery and Nic Bishop - it's a cool book

[guidofatherof5]

I guess I don't do facetious well in print

that's something they deduce from scent trail experiments, and yes - apparently the forked tongue is a directionally sensitive tool
read "The Snake Scientist" by Sy Montgomery and Nic Bishop - it's a cool book

Good book, Reading it makes me want to go back to the Dens this Spring.