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Chameleons (family Chamaeleonidae) are squamates that belong to one of the best-known lizard families. The name "chameleon" means "Earth lion" and is derived from the Greek words chamai (on the ground, on the earth) and leon (lion).
Chameleons vary greatly in size and body structure, from approximately 1 in (2.5 cm) Brookesia minima, to the 24 in (60 cm) Calumma parsonii. There is even one species, thought to be unique to Malawi's Mount Mulanje, which is barely 1.5cm across when fully grown. Many have head or facial ornamentation, be it nasal protrusions or even horn-like projections in the case of Chamaeleo jacksonii, or large crests on top of their head, like Chamaeleo calyptratus. Many species are sexually dimorphic, and males are typically much more ornamented than the females.
The main things chameleon species do have in common is their foot structure, their eyes, their lack of ears, and their tongue.
Chameleons have feet that are split into two main "fingers", with a soft pad in between. Called "zygodactyl". These "fingers" are equipped with sharp claws to gain traction on surfaces such as bark when climbing. They have two claws on the outside of their front foot and three on the inside, but on the back feet this is reversed.
Their eyes are the most distinctive among the reptiles. The upper and lower eyelids are joined, with only a pinhole large enough for the pupil to see through. They can rotate and focus separately to observe two different objects simultaneously. It in effect gives them a full 360-degree arc of vision around their body. When prey is located, both eyes can be focused in the same direction, giving sharp stereoscopic vision and depth perception.
They lack a vomeronasal organ. Also, like snakes, they don't have an outer or a middle ear. This suggests that chameleons might be deaf, although it should be noted that snakes can hear using a bone called the quadrate to transmit sound to the inner ear. Furthermore, some or maybe all chameleons, can communicate via vibrations that travel through solid material like branches.
Chameleons have incredibly long tongues (sometimes longer than their own body length) which they are capable of rapidly and abruptly extending out of the mouth. The tongue has a sticky tip on the end, which serves to catch prey items that they would otherwise never be able to reach with their lack of locomotive speed. The tongue's tip is a bulbous ball of muscle, and as it hits its prey, it rapidly forms a small suction cup. Once the tongue sticks to a prey item, it is drawn quickly back into the mouth, where the chameleon's strong jaws crush it and it is consumed. Even a small chameleon is capable of eating a large locust or mantis.
Ultraviolet light is actually part of the visible spectrum for Chameleons. Primarily, this wavelength affects the way a chameleon perceives its environment and the resultant physiological effects. Chameleons exposed to ultraviolet light show increased social behaviour and activity levels, are more inclined to bask and feed and are also more likely to reproduce as it has a positive effect on the pineal gland.
 Distribution and habitat
The main distribution of Chameleons is Africa and Madagascar, and other tropical regions, although some species are also found in parts of southern Europe and Asia. There are introduced, feral populations of veiled and Jackson's chameleons in Hawaii and isolated pockets of feral Jackson's chameleons have been reported in California and Florida.
Different members of this family inhabit all kinds of tropical and montane rain forests, savannas and sometimes semi-deserts and steppes. Chameleons are mostly arboreal and are often found in trees or occasionally on smaller bushes. Some smaller species, however, live on the ground under foliage.
Most chameleons are oviparous, and lay eggs after a 3-6 week gestation period. Once the eggs are ready to be laid, the female will climb down to the ground and begin digging a hole, anywhere from 4-12 inches (10-30 cm) deep depending on the species. The female turns herself around at the bottom of the hole and deposits her eggs. Once finished, the female buries the eggs and leaves the nesting site. Clutch sizes vary greatly with species. Small Brookesia species may only lay 2-4 eggs, while large Veiled chameleons (Chamaeleo calyptratus) have been known to lay clutches of 80-100 eggs. Clutch sizes can also vary greatly among the same species. Eggs generally hatch after 4-12 months, again depending on species. The eggs of the rare Parson's chameleon (Calumma parsonii) are believed to take upwards of 24 months to hatch.
Some species of chameleons, such as Jackson's chameleon (Chamaeleo jacksonii) and the Flapjack chameleon (Chamaeleo fuelleborni), are ovoviviparous, giving birth to live young. This gestation takes 4-6 months depending on the species.
Chameleons generally eat locusts, mantids, crickets, and other insects, but larger chameleons have been known to eat small birds and other lizards. A few species, such as Chamaeleo calyptratus have been known to consume small amounts of plant matter. Chameleons prefer running water to still water.
It was commonly believed in the past that the chameleon lived on air, and didn't consume any food at all. This belief is today represented in symbolic form, with the chameleon often being used as a motif to signify air.
 Change of color
Some chameleon species are able to change their skin colour, which has made them one of the most famous lizard families. Changing colour is also an expression of the physical and physiological condition of the lizard. The colour also plays an important part in communication.
Chameleons have specialized cells, collectively called chromatophores, that lie in layers under their transparent outer skin. The cells in the upper layer, called xanthophores and erythrophores, contain yellow and red pigments respectively. Below these is another layer of cells called iridophores or guanophores, and they contain the colourless crystalline substance guanine. These reflect, among others, the blue part of incident light. If the upper layer of chromatophores appears mainly yellow, the reflected light becomes green (blue plus yellow). A layer of dark melanin containing melanophores is situated even deeper under the reflective iridophores. The melanophores influence the 'lightness' of the reflected light. All these different pigment cells can rapidly relocate their pigments, thereby influencing the colour of the chameleon.
Numerous species of chameleon are available in the exotic pet trade. Jacksonii ssp and calyptratus are by far the most common, and are frequently captive-bred. Most species of chameleons are listed on CITES, and therefore are either banned from exportation from their native countries or have strict quotas placed on the numbers exported. However, lack of enforcement in what are mostly poor countries reduces the effectiveness of this listing. However, captively bred animals of the most popular species (Panther, Veiled, and Jackson's) are readily found.
 External links
- EMBL Reptile Database
- Chameleons! Online E-zine
- Chameleon Care and Information Center website
- The African Herpetology Website
- The Chameleon Forums
- The Advanced Chameleon Keepers website
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