chameleon (thing)

Chameleons are old-world, arboreal lizards best known for their incredible morphological adaptations. Among the characteristics which distinguish them from other lizards are their independently moving eyes, their modified feet and their incredible tongues.

Chameleons have binocular vision, like many vertebrates including humans, but have the capacity to move their eyes independently in order to view nearly a 360^o arc around their bodies. When they search for prey, they rotate the two eyes in different directions. Once a suitable prey item is located, they fix both eyes on the object in order to gauge distance. There is some indication, from a 1995 paper in Nature, that chameleons may in fact be capable of judging distance not only with their bifocal vision, but also through the principle of negative refraction, making them unique among other vertebrates.

Chameleons have modified feet, giving the appearance of having two toes. In fact, like most lizards, they have in fact five toes on each foot, but these toes have been fused together to create two pads which are better able to grasp branches and twigs. On their front feet, two toes have fused to make the exterior pad, and the other three have fused to create the interior pad. Interestingly enough, this pattern is reversed in the hind feet.

Chameleons have long tongues with a sticky extremity, used to capture prey at a distance and then reel them back to the mouth. The tongue makes their 'sit-and-wait' predatory strategy highly effective. They can often reach prey items with great accuracy up to a distance of two to three body lengths (eg. a 15 cm chameleon may be able to strike prey as far as 40 cm away). Pressure is built by muscle action in the buccal cavity prior to a strike, such that the tongue can be projected forward with great speed. The tongue of a chameleon also contains specialized fibres permitting the animal to contract the extended tongue at great speed.

The chameleons have interesting heads, with a gular pouch under the lower mandible. Some species also have a gular crest (at the joint of the skull and vertebrae), particularly pronounced in the veiled chameleon, where the male may have a crest as high as his head is long.

Several species have between one and three horns adorning the head. There are in fact four kinds of horny protruberances found in the various species. First, the true horn, is a long and narrow bony protruberance jutting from the center of the forehead. Second, there are sometimes secondary bony protruberances of much smaller size. Third, some species have fleshy protruberances as opposed to bony ones. Finally, there are at times intermediary forms which fit between the false (second type) and fleshy horns.

Behaviour

Chameleons are generally solitary animals who move very slowly. As such, they rely on their ability to change their colouration and pattern to remain cryptic. This has the benefit of making them hard to detect for predators and prey alike. Chameleons generally adopt a stationary position in a tree (some species are terrestrial, but the same principle applies) and wait for a prey item to appear within their visual field. When the chameleon decides to move, they do so very slowly, rocking back and forth so as to blend in with the motion of leaves around them (as an interesting aside, this same behaviour is used by many insect species to avoid detection).

One of the most interesting features about chameleon behaviour surely must be their propensity and capacity for colour change. Chameleons can change colour using the chromatophores in their skin. Of considerable interest to ethologists is the observation that chameleons regularly change both their colours and patterns in nature in a manner seemingly unrelated to camouflage. It is believed that chameleons communicate with one another using these colour changes. One of the most brilliant sights in nature is apparently the mating season of the Panther chameleon, where males and females alike will attract each other and defend their territories with spectacular displays of green, yellow, red, blue and orange.

Finally, the veiled chameleon displays a behaviour quite unusual for reptiles. After the eggs hatch and the tiny neonates emerge, they climb on to the male and use his gular crest as a shelter. The male also uses this appendage to collect rainwater for consumption.

Taxonomic information Order: Squamata
Family: Chamaeleonidae
Genera:

• Bradypodion
• Brookesia
• Calumma
• Chamaeleo
• Chamaeleolis¹
• Chamaelinorops¹
• Furcifer
• Rhampholeon

A detailed list of species can be found at the end of this write-up, but here is a general description of the eight genera in the family Chamaeleonidae.

The genus Bradypodion are characterized by small bodied individuals with prehensile tails. They are found in southern Africa, and are all ovoviviparous.

The genus Brookesia, commonly referred to as the leaf chameleons, are extremely small-bodied chameleons found exclusively in Madagascar. They do not have prehensile tails, and are oviparous. They are also unusual members of the family given their terrestrial life-style.

The genus Calumma contains species of variable size again found exclusively in Madagascar. They are arboreal, have prehensile tails, and are oviparous. Parson's chameleon (C. parsonii) was once imported in great numbers into North America for the pet trade, and is among the most striking and colourful of all chameleon species.

The genus Chamaeleo consist of generally larger bodied individuals, and contains the best-known species to the general public (Veiled chameleon (C. calyptratus) and Jackson's chameleon (C. jacksonii)). The genus can be found throughout Africa. They are almost exclusively arboreal, have prehensile tails and are both ovoviviparous and oviparous.

The genus Chamaeleolis is restricted to Cuba, and are commonly referred to as crested anoles. These arboreal lizards lack prehensile tails and are oviparous.

The one species of the genus Chamaelinorops are restricted to Haiti. This species is also arboreal and lacking a prehensile tail.

The genus Furcifer is again a Malagasy genus containing oviparous, arboreal species with prehensile tails. The best known member of this genus is the panther chameleon (F. pardalis), which is a large specimen with incredible colouration.

The genus Rhampholeon consists of small-bodied terrestrial individuals. They are restricted to Africa, and are all oviparous.

Species list

Genera:

• Bradypodion
  Species:
  • adolfifriderici
  • caffrum
  • damaranum
  • dracomontanum
  • excubitor
  • fischeri
  • gutturale
  • karrooicum
  • melanocephalum
  • mlanjense
  • nemorale
  • occidentale
  • oxyrhinum
  • pumilum
  • setaroi
  • spinosum
  • taeniabronchum
  • tavetanum
  • tenue
  • thamnobates
  • transvaalense
  • uthmoelleri
  • ventrale
  • xenorhinum
• Brookesia
  Species:
  • ambreensis
  • antakarana
  • bekolosy
  • betschi
  • bonsi
  • brevicauda
  • brygooi
  • decaryi
  • dentata
  • ebenaui
  • exarmata
  • griveaudi
  • karchei
  • lambertoni
  • lineata
  • lolontany
  • minima
  • nasus
  • perarmeta
  • peyrierasi
  • spectrum
  • stumpfi
  • superciliaris
  • therezieni
  • thieli
  • vadoni
  • valerieae
• Calumma
  Species:
  • boettgeri
  • brevicornis
  • capuroni
  • cucculata
  • fallax
  • furcifer
  • gallus
  • gastrotaenia
  • globifer
  • guibei
  • hilleniusi
  • linota
  • malthe
  • nasuta
  • oshaughnessyi
  • parsonii
  • peyrierasi
  • tigris
  • tsaratananensis
• Chamaeleo
  Species
  • affinis
  • africanus
  • anchietae
  • arabicus
  • bitaeniatus
  • brevicornis
  • calcaricarens
  • calyptratus
  • camerunensis
  • chamaeleon
  • chapini
  • cristatus
  • deremensis
  • dilepis
  • eisentrauti
  • ellioti
  • etiennei
  • feae
  • fischeri
  • fuelleborni
  • goetzei
  • gracilis
  • harennae
  • hoehneli
  • incornutus
  • ituriensis
  • jacksonii
  • johnstoni
  • kinetensis
  • laevigatus
  • laterispinis
  • marsabitensis
  • melleri
  • microsaura
  • monachus
  • montium
  • namaquensis
  • oustaleti
  • oweni
  • pardalis
  • parsoni
  • pfefferi
  • pumilus
  • quadricornis
  • quilensis
  • roperi
  • rudis
  • ruspolii
  • schoutedeni
  • schubotzi
  • senegalensis
  • sternfeldi
  • tempeli
  • tremperi
  • werneri
  • wiedersheimi
  • zeylanicus
• Chamaeleolis¹
  Species:
  • barbatus
  • chamaeleontides
  • guamuhaya
  • porcus
• Chamaelinorops¹
  Species:
  • barbouri
• Furcifer
  Species:
  • angeli
  • antimena
  • balteatus
  • belalandaensis
  • bifidus
  • campani
  • cephalolepis
  • labordi
  • lateralis
  • minor
  • monoceras
  • oustaleti
  • pardalis
  • petteri
  • polleni
  • rhinoceratus
  • tutzetae
  • verrucosus
  • willsii
• Rhampholeon
  Species:
  • boulengeri
  • brachyurus
  • brevicaudatus
  • chapmanorum
  • kerstenii
  • marshalli
  • nchisiensis
  • platyceps
  • spectrum
  • temporalis
  • uluguruensis