The incident happened many many moons ago......in Sri Lanka at home. We were wrapping up an ordinary day, past 9 o'clock in the night I think...... When our Bindu started barking somewhere in the garden. It was a bark with a certain alarm to it, as if saying "I'm not too sure what this thing is but I need to get some one's attention here!!!"
Now Bindu has always been a garden dog as he was never granted visa to enter the house by his superior, Bingo. So one would expect him to know his territory well, and he's not the kind of dog who barks at just about anything, so naturally this got us worried.
So torch in hand we approached the suspicious scene cautiously. The sight of 'back-up' sent Bindu into a frenzy! and he started jumping around this suspicious object and then looking towards us for an explanation.
Upon closer inspection the black rounded heap on the ground, turned out to be a tortoise with its head inside its shell!
Naturally we bursted out laughing! which seem to add to Bindu's confusion.
It wasn't the first time that we found a lonely wandering tortoise in the garden, but it has certainly never happened in Bindu's lifetime.
My father told us what they used to do (back in the good old days) when they found a tortoise like that. Light a candle and erect it on its shell, and send it on its way!
This was all good fun but somehow Bindu didn't seem to be convinced, so he decided to continue with his woofing and waffing. What with the tortoise going nowhere fast, we decided to lock Bindu up in a room, unknown to Bingo that is! ah the drama!.
And that's how we managed to get some sleep that night.
Our general idea of an eye is a round white ball with a black circle in the middle of it. However not all animals have this kind of geometrical arrangement. One example you would be most familiar with is the cats eye, which takes an elongated oval shape during the day time. But you probably wouldn't have come across some of these unusual pupil shapes that I've got below.
Most of us know the cat's version of the story. These cute fur balls have eyes that are able to see in dark conditions, increasing their sensitivity to light. Thus to protect their eyes from the glare of the sunlight during daytime the pupils contract to a mere thin vertical line. And if you see a cat lying around with droopy eyelids with that typical 'don't care' attitude, it's nothing more than trying to protect his eyes!
Next time you visit New Zealand, you can directly look in the eye of a local and see if this is true. Sheep and even horses (below) have a horizontally elongated pupil, increasing their field of view to around 290 degrees. Again another adaptation for a animal of prey.
I have no idea why these beasts have got a bean shaped pupil, the elongation is probably to do with being the hunted party.
Look at those heavy eyelashes! Would work very well for a mascara advertisement!!?
Seriously, the square shape is a very uncommon shape in nature. The heavy lashes are to protect their eyes against sand storms, but square pupil?? no idea.
That shape looks quite funny, but that bump in the pupil is to give the hippo the ability to see out over the surface of the water. So he can keep himself half immersed in his luxurious bath and gaze out over the water level.
The magnificent horse has a blind spot directly in front of it, so even if he can see a wide field of view, the image will have a dark slit at the front.
This half circle can be rotated. So when the deer is grazing the hemispheric pupil will come down, keeping level with the horizon.
I must mention that I borrowed these pictures from this site (what with all these allegations of photo theft going around in the blogosphere!) And if you do like to know some more interesting stuff about how frogs, birds etc use their vision you will find them here.
The location and structure of the human eyes enable us not only to see how long and wide an object is but also to see how far away it is from us and how thick it is. If we had 2D vision (like what you get when you close one eye and look through the other) we would still be able to see objects clearly but judging the distance would be a problem, so we would look rather clumsy trying to grab things that are further beyond our reach.
So for this reason nature has decided to give the natural predators/ carnivores the ability to see in 3D. Or else finding something to eat would be quite a challenge! Thus most of the predators have their eyes located at the front of their head, a feature of 3D or stereoscopic vision. So think of the big hunters like the tiger, cheetah, leopard, lion (lioness rather), wolf, hawk (more or less), bear, owl etc. all of these have their eyes located at the front of their heads. This gives them the ability to judge the distance to their food and pounce upon it at the right moment.
awww.......... purrr
And what about the prey? the hunted? Well, as far as they are concerned they would rather prefer to have the ability to scan a wide area than be able to see in 3D. Because ill judging the distance to the grass patch is not going to be fatal, but not being able to see the hunter creeping up from behind is! Therefore most of the hunted animals have their eyes located on either side of their heads giving them access to a panoramic view. Deer, antelope, horse, zebra, goat , sheep, buffalo and the like. These animals can only see in 2D, but they have a wide field of view almost close to 360 degrees enabling them to spot any suspicious activity around them.
Eyes focused on the grass
But of course nature is pretty diverse. And there are very many types of visionaries and all of them can't be categorised into these two classes. But at any time in your life if you do find some unidentifiable wild animal charging towards you, and if it has got its eyes at the front of its head, you are in deep trouble!
And what about us humans? does this mean that we are born predators? Well I'm not an expert in natural history but if you ask one he or she would probably argue that this has to do with humans being descendents of apes, if you believe in Darwin that is (the natural historian not the blogger). So for our predescessors it was vital to be able to judge the distance to the next swingable tree branch (I just made that word up I think). So we humans inherited the 3D vision due to this reason.
So you could say we were born to be Tarzan!
