Swooping and Focusing


Chameleon Eyes

Chameleon, (Photo credit, somepets.com)

Chameleon, (Photo credit, somepets.com)

This week, as you probably guessed, I am going to inform you on Chameleon eyes.  It is widely believed that chameleons can look in two different directions at the same time, well, this turns out be only partially true.  Chameleons can scan their surroundings for danger or prey, but they cannot focus in two different directions.  When they hunt, they must look at their prey with both eyes before striking.  One thing that the chameleon has going for it are negative lens, meaning that the lens in their eyes are concave.  This increases the retinal image size, allowing more precise focusing.  In fact, image magnification in chameleons is higher in a scaled comparison than all other vertebrate’s eyes.  While the lens is negative, the cornea is positive or convex.  This also contributes to precise focusing by improving sight resolution in a narrower field of vision.  When you think about it, Chameleons don’t really need long range vision.  They usually live in an environment rich with bugs anyway, so they don’t need to look a long ways for their next meal.  And let’s face it.  They’re too slow to get out of the way of a swooping bird anyway.

To see some lizard with their eyes facing different directions, click here to watch my video.

Creepy Carnivores


Tarsier Eyes.

Tarsier (Photo credit, Ricky Garni)

Tarsier (Photo credit, Ricky Garni)

For the next couple weeks I am going to write about a very interesting subject, eyes.  First on the list we’ll head to the islands of Southeast Asia to take a look at the world’s only carnivorous primate.  The Tarsier.  The tarsier is a small animal with enormous eyes.  Each eyeball is as large as this creature’s entire brain.  The unique cranial anatomy of the tarsier results from the need to balance their large eyes and heavy head so they are able to wait silently for unsuspecting prey.  As you may have guessed, the tarsier has very acute eyesight, excellent night vision, and may also be able to see ultraviolet light!  The tarsier’s eyes are the largest of any mammal relative to body size. In fact, if a human’s eyes were proportionally as large as those of the tarsier, they would be the size of grapefruits. Its eyes are fixed to its skull and don’t turn in their sockets.  Fortunately, it has a very bendable neck and can rotate its head 180 degrees, just like an owl.  Not that that makes it any less creepy looking, but on the other hand it sort of looks like my dad so…  I guess it’s ok.

To watch my video, click here.