Chameleon

Only partly, and it is not the main reason. The everyday image of a chameleon turning plaid to match a tartan blanket is a myth. A chameleon's normal resting colour, usually green or brown, already blends it into foliage, and it does make small adjustments toward its surroundings. But the large, fast colour changes people find so striking are mostly signals. A male facing a rival flares into bright, high-contrast colours to look dominant, and backs down by going dark and dull. A female signals whether she is receptive or already carrying eggs through colour. And a chameleon darkens to soak up warmth on a cool morning and pales to reflect heat when it is too hot. Camouflage is a background function, not the headline.

It is a projectile with a built-in catapult. At rest the tongue is folded on a stiff bone at the back of the throat, wrapped in a set of muscles, and around it is a sleeve of elastic collagen tissue. To fire, the chameleon contracts a ring of muscle that squeezes the tongue forward off the bone while the elastic sleeve, which has been stretched and loaded, suddenly releases, flinging the tongue tip out at high acceleration. The tip is a muscular pad that forms a suction cup and is coated in extremely sticky saliva, so it grabs the insect on contact, and then muscles reel the whole tongue and prey back into the mouth. The strike, hit, and return take a fraction of a second.

It gives a slow-moving animal a way to watch its whole surroundings without moving its body. Each eye is mounted in a turret and can rotate through a wide arc on its own, so a chameleon can scan for a hawk overhead with one eye while the other checks the branch ahead for an insect, covering a nearly complete circle of vision between them. When something worth catching is spotted, the chameleon turns its head to bring the target in front and then both eyes converge on it, switching to binocular vision to measure the exact distance, which is essential for aiming a tongue that only gets one shot. The brain is doing something unusual in handling two independent visual streams and then merging them.

They are popular but demanding, and not a good beginner reptile. The veiled, panther, and Jackson's chameleons are the species most often kept, and they need a tall, well-ventilated, heavily planted enclosure, precise gradients of heat and ultraviolet light, high humidity with a dripper or misting system for drinking, since chameleons rarely drink from a bowl, and a constant supply of varied, appropriately sized, gut-loaded live insects. They are easily stressed by handling, by seeing other chameleons, and by being watched, and stress shows quickly in their colour and health. Many die young in captivity from poor husbandry, so a chameleon suits an experienced keeper prepared to build the right setup.