Chameleon
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? Chamaeleons |
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Genera
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| Bradypodion Calumma Chamaeleo Furcifer Brookesia Rhampholeon |
Chameleons (family Chamaeleonidae) are squamates that belong to one of the best known lizard families. They are famous for their ability to change their colour, and also because of their elongated tongue and their eyes which can be moved independently of each other. Their eyes are the most unique among the reptiles. Among other things they can rotate and focus separately to observe two different objects simultaneously. The name "Chameleon" means "earth lion" and is derived from the Greek words chamai (on the ground, on the earth) and leon (lion). They lack a vomeronasal organ. Like snakes, they don't have an outer or a middle ear and seem to be deaf; at least they cannot detect airborne sounds. But some, maybe all, can communicate via vibrations that travel through solid material like branches.
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, Sri Lanka, India and Asia Minor. 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 biotopes like tropical and montane rain forests, savannahs and sometimes semideserts 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. The Chameleon is "battling" humans for their space and habitat.
Behavior
All Chameleon species are diurnal. Their main activity is in the morning and in the evening. Chameleons are not active hunters but rather sit motionless for hours and wait for a prey to pass by. Although the Veiled Chameleon is an insectivore, they mainly feed on different arthropods and small vertebrates. Chameleons live mostly solitary lives and are quite aggressive toward other members of the same species.
Change of colour
Some Chameleon species are able to change their body colour, which has made them one of the most famous lizard families. Contrary to popular belief, this change of colour is not only an adaptation to the surroundings but also an expression of the physical and physiological condition of the lizard. The skin colour is changed under influence of mood, light and temperature. The skin colour also plays an important part in communication and rivalry fights.
Chameleons have specialised cells that lie in two layers under the chameleon's transparent outer skin. The cells in the upper layer, which are called chromatophores, contain yellow and red pigments. Below these chromatophores is another cell layer. Cells of this layer are called guanophores and they contain the colourless crystaline substance guanin. These guanophores reflect amongst others the blue part of incident light. If the upper layer of chromatophores is yellow, the reflected light becomes green (blue plus yellow). A layer of dark melanin containing melanophores is situated even deeper under these blue and white light reflecting guanophores. These melanophores influence the lightness of the reflected light. All these different pigment cells can relocate their pigments, thereby influencing the colour of light which is reflected.
Because they share the ability to change colour, anoles are sometimes confused with chameleons and are popularly known as "American chameleons".