Eyes and distance

[morpheon]

A friend and I were discussing about how far can chameleons see, and we couldn't find a definitive answer. I looked in a few things, and the only partial answer i found was in a French thesis that said this:

"Par ailleurs le caméléon a une très bonne acuité visuelle. Ses performances sont comparables à celles d’une lentille de téléobjectif de 100 à 150 millimètres de distance focale [LE BERRE (1995)]."

The quote is from "CAMÉLÉONS : BIOLOGIE, ÉLEVAGE
ET PRINCIPALES AFFECTIONS", by Fany JUNIUS-BOURDAIN in 2006.


Overall, what i understand in that, is that their eye performances are as good as a 100 to 150 millimeters telephoto len. However, in neophyte language, what does that mean?? How far can they really see?

Any help will be appreciated! Thank you in advance!

 

[Killjoy]

my best guess is something i came to learn through a discussion with the breeder i buy my chams from. it is speculated that at about 25-30 feet there is some generation loss or decreased vision. this is based on her keeping so many chameleons and learning the range / distance from oneanother where they seem to not even be to distinguish another chameleon across a very long room. She did go onto to say that they may recognize a chameleon, even if barely, but at that distance they tend to show no stress or immediate signs of concern. perhaps.... what they cant see clearly, cant hurt them. this is justmy educated opinion though, i would like to hear some other input also.

 

[morpheon]

Interesting anecdote! The way your breeder understood things seems logical and worth respect to say the least!

I guess we are now 3 waiting for other people's opinion!

 

[morpheon]

I went outside today with my little female Verrucosus. We were both on a 2nd floor balcony when a Volkswagen Golf black went in the street, about 30 meters away from us, and she obviously got scared. Of course, a car is bigger than a chameleon, but it gives a good idea of how far they can see. I'd add that nothing else was moving or could have caused her to be scared, as nothing else was moving and no sound happened before and after this car!

 

[MrCus]

well, I guess, first you need to understand, that there is no maximum distance you (or animals with similar eyes) can see. If the object is just big enough, you can see it even if it is Millions of kilometers away. The moon, for example. Or the milkyway. Of course, chameleons can see the moon (or they could if they wouldn't sleep at night...)

It is true, that chameleons eyes work similar to tele-lenses: the angle is not very wide, they need to turn the eye, if they want to see more. Unlike birds that can see about 270 degrees without moving the eye or the head. But what chameleons see seems close and they can focus the object very fine, even if the object is far away. Humas e.g. can only focus, if the object is within a quite close range: You cannot focus your hand and the house behind your hand at the same time. But if you focus a tree at the horizon and the rabbit 5 meters in front of the tree, all seems as sharp as the moon, that is millions of kilometers away. You cannot focus more detailled at this distance. It is all the same. And you cannot make a focus-difference between two needles that lay 30inches and 30.1 inches in front of your yes. It is all the same. For you. Not for chameleons: they can distinguish even this.
Since chameleons cannot see stereoscopic, they need to "guess" the distance using the lens-bend of the eye. (similar to you, if you look through a SLR camera and focus manually until the picture is sharp, and then read the distance from the scala of your lense) - And therefore, they can still focus the tree at the horizon and the rabbit differently. Or distinguish the distance of this two very close needles.
This is measured in "diopter". You maybe know this from eye-glasses.
Humas usually can focus by 10-15 diopter at maximum. (nearest and farest object) - And even less if they get old.
Chameleons can change their refraction power more than other animals by incredible 45 diopter! And this with a speed of 60 diopter per second! More than four times as fast as humans (you need a moment to focus from the tree to the newspaper).
So the fascinating thing at chameleons eyes is not the maximum distance since this is unlimited for every animal. It is the speed and power of its accomodation.

Try this: ask someone to fix two very thin twines with a tape somewhere so that they hang down. One of the twine should be a few millimeters closer to you (dont look during this person fix the twines of course). Then look at the twines from a distance of 5 meters with only one eye and guess which one is closer to you. - You cannot tell. The chameleon can. And they can even tell how far...

So you can be quite sure the chameloen can see another chameleon that is 10 meters away very clearly. But if it is that far away, it is just too far away to be stressed. If you place a female in your garden, and a male some meters away, it may took a while, but if the male sees the female, it will run very fast...

If you are interested in this stuff, look for papers from Dr Matthias Ott, and Lindesay Harkness.

Marcus

 

[morpheon]

Very interesting article Marcus! Thank you for your help!

Then, if we work with your idea of male watching a female, let's say the size for any given Furcifer Pardalis... How far do you think they could see each other? At what point would they not be able to see each other?

 

[MrCus]

Very interesting article Marcus! Thank you for your help!

Then, if we work with your idea of male watching a female, let's say the size for any given Furcifer Pardalis... How far do you think they could see each other? At what point would they not be able to see each other?

Well, i dont know exactly, but if e.g. a female sits on an exposed place and the male is not distraced by something, it recognize the female at about 15meters. This is what I wathed. I am sure they see each other at bigger distances.

 

[summoner12]

I don't know any actual distance... but i've seen my chams spot items of interest from long distance and demenstrate 'interest' in the item from some distance.

I think i've read on the forums that chams can 'zoom' their eyesight, not sure how true this is though. I wouldn't be surprised if they can.

Daily I have interaction with my melleri Henry. He is in our bedroom and will 'watch' us. he'll pear through and over branches to get a look at us. he is very interactive. he is also very aware of us and other people. I have found this to be true with my melleri and hearing from others who keep melleri.

 

[Killjoy]

Now this is how a thread should go, great opinions and input. Nice stuff!!!

 

[MrCus]

I know these postings talking about zoom. I guess this is a result of jumbling or misunderstanding the two things tele and zoom.
Tele is a fixed focal length that makes far waway things seeming closer/bigger. Zoom is the ability of some object lenses to change the focal length from tele to wide angle.
To do this, you need to move several lenses and change the distance between them. A Chameleoneye has only one lense and cannot change the distance to some other lenses. No animal can zoom with its eyes. All focal distances are fixed. Either tele or wide.
However, chameleons dont need zoom, since on the one hand, they use the whole retina to receive a "high resolution picture" like a cinema-screen, unlike most other animals or humans, that use only a small focal point with relatively less rods. - on the other hand they can turn their eyes and so dont need wide angel view. So a fixed tele with hig resolution retina is perfect for them.
As I sayed, try to find these papers. It is quite interesting - I am sure I have some of them on my harddisk, but currently im not at home- maybe when i am back i ll search for the whole title/description of the papers so that you can google it..