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Regions > African Rainforest > Veiled chameleon

Veiled chameleon

Location at the Zoo: African Rainforest



Region:

Africa and Asia

Class:

Reptilia

Order:

Squamata

Family:

Chamaeleonidae

Genus:

Chamaeleo

Scientific Name:

Chamaeleo calyptratus

Description

: The veiled chameleon is large and very handsome. Both sexes have large plate-like scales covering the head and two lobes at the base of the neck (occipital). Just in front of these rises a prominent casque (helmet), more colourful in the male, thin and approx. five cm tall, the largest among all chameleons. A head crest fringes the edge of the helmet with granular scales and continues down the middle of the forehead to the snout (parietal crest). Another runs over the top of each eye (preorbital crests). Hanging from the throat is a flap of skin (the gular crest) which is edged with large conical scales that continue less conspicuously down the midline of the belly (the ventral crest). The length of the spine is capped with a low ridge of rough scales (dorsal crest). Females are stout-bodied; they are nevertheless, smaller than males in all other respects. The tail is as long as the length of the body when extended. At rest it is curled under towards the cloaca and the male exhibits a swollen pouch housing the hemipenes at its base.

Their eyes are raised and housed in turret-shaped lids that are surrounded at their base by a row of bead-like scales. The eyes see in all directions and can move independently, as well as focusing in tandem to allow for depth perception (binocular vision). The lids do not close completely (turret hole) with the pupils always visible. The interior of the mouth is yellowish-tan and filled with a pink, sometimes yellowish, fleshy, clubbed-shaped tongue. It is sticky and concave at its tip, which is anchored to powerful muscles in the mouth and throat and can be thrust forward with lightening speed to about 1.5 times the length of the head and body combined.

The forelimbs end in five fingers grouped in fleshy bundles of two (outer) and three (inner) which form pincher-like opposable digits (zygodactylism); the grouping is reversed on the hind limbs. As well, there are hook-like barbs above the ankle of the males (tarsal spurs), present from birth, that grow as they age. Males are more brightly coloured than females and their patterning is different as well. The veiled chameleon exhibits bright gold, green and blue mixed with yellow and orange. Many shades of these are boldly distributed in bands around the body and tail. Their average length is 35 - 45 cm.

Distribution

: These lizards are found in the greenest portions of the south western Arabian Peninsula from Asir province in Saudi Arabia to the border of South Yemen.

Habitat

: Tropical or subtropical climate on high, dry land plateaux, and mountain sides up to 900m; also in river valleys. They are partial to acacia trees and the lower branches of scrubs and bushes.

Food

: Veiled chameleons are mainly insectivores. They will consume anything that is small and moves. They are particularly fond of insects, flies, caterpillars, butterflies, slugs, and worms, along with leaves, young shoots, and blossoms when they need further hydrating. With suitable habitat shrinking, they have moved onto agricultural lands eating millet in particular.

Reproduction and Development

: Veiled chameleons generally live a solitary life style except at breeding times. Males are always fiercely territorial towards each other, females mildly so outside of mating seasons which occur when climatic conditions are right. Where there is little rainfall, breeding is limited to September and October so that hatching coincides with the spring rains. Where moisture is plentiful, impregnated (gravid) females appear all year long.

Males will strenuously confront intruders and try to drive them away by showing a flashy array of colours in sharply contrasting patterns (disincentive display) curl and uncurl their tails, then stand side by side with their opponents, flatten their bodies, inflate their throat crests and close their pincher feet on the other’s legs. Conflict can intensify and their occipital lobes will swell, making the helmets more threatening. This may proceed to head butting with severe biting and wounding. The loser concedes by darkening his colours, deflating his body and slinking away.

Disinterested females, usually those already impregnated, will also use intimidation to warn off approaching males by turning very dark green with blue and yellow spots, flattening their bodies, raising their gular crests, gaping their mouths, hissing and swaying from side to side, as will females with each other at mating time. Despite being receptive, females may move away at first, using similar, disincentive colour patterns to signal they are receptive. The male sits motionless near her, then approaches from the side in full display with swinging and twitching steps, inflates his body, shakes his head, uncurls his tail and butts her on the flanks with his snout (incentive display). Inexperienced males will sometimes bite. He secures himself on her back with his tarsal spurs and inserts one of his hemipenes. Coitus can last up to 20 minutes and females continue to be receptive for three or four more consecutive days, mating several times a day. When she is finished mating, she will change colour and show no further interest. She is capable of delayed fertilization and can have up to three clutches annually.

Eggs gestate from 20 to 30 days. As laying time approaches, she becomes restless and stops eating, climbs down to the ground and digs several shallow nest holes in warm sand out of which she will choose the most satisfactory. Into it she will deposit 20 - 70 white, oval, tough-skinned eggs usually in the evening to avoid extreme heat. Depending on temperature, eggs begin to hatch between 150 - 190 days later. Hatchlings can take up to a day to break free; after which they become arboreal and begin to hunt small prey: insects, snails, flies, anything that is small and moves. The young are pastel green; the future casque is a tiny swelling. They can interpret colour signals from birth and begin to use them in adolescence. Due to heavy predation, few survive to adulthood. They become sexually mature from three to four months.

Adaptations

: The veiled chameleon is well suited to its arboreal life in semi-desert conditions. Their resting colours mimic the treed surroundings and their slightly flattened bodies, which they sway from side to side, give the impression of a breeze-blown leaf. They are hide-and-wait predators, able to remain motionless for long periods while following prey in any direction with their swiveling eyes. Their safety lies in being still. The projectile tongue allows them to capture agile prey while they are motionless. The prehensile tail and zygodactylic feet aid in climbing and perching. The very large male helmet is both threatening and attractive; its size helps warn away males while charming the females.

The chameleon changes its colours quickly using layers of cells (chromatophores) found in the skin. Under the clear epidermis, which sloughs off in ragged pieces throughout life, is a layer of yellow and red cells below which are blue and white reflector cells. In a third layer are cells that produce brown and black. These are activated by nerve impulses and hormones and can be reflected and arrayed in numerous shades. How these are arranged into patterns is as important as the colours themselves. They allow chameleons to send many different messages: sexual identity, mating readiness, physical well-being, and emotional states.

Colour change is often a first line of defense. When irritated, chameleons will often emit a creaking sound. Also, when threatened, the gular crest is flattened, giving the impression that the head of the chameleon is too large to swallow. In mating displays and intimidation, however, it is raised to intimidate opponents or attract partners. In extreme cases of duress, when colour signals do not work, chameleons may drop from their perches, curl up and remain motionless. Newborns do so more frequently than stressed adults but few are injured in the fall. Body temperature is controlled by colouration (thermoregulation) as well.

The casque and facial crests collect moisture which then gathers around the mouth where it can be licked off. Hydration is also maintained by eating leaves during dry periods.

Threats to Survival

: Increased agricultural expansion and human settlement has greatly reduced the veiled chameleon’s habitat. Because they are slow moving creatures, these chameleons have evolved in a small pocket of greenery surrounded by desert which is rapidly being degraded. They are being pushed onto farm land and into trees along the sides of roads. While numbers are still plentiful, it is not clear how severely they will be affected by the use of pesticides. As well, this very colourful lizard is much sought after by the pet trade, and lizard parts are used in rituals and as curios. Veiled chameleons are preyed upon by birds and snakes in the wild.

Status

: IUCN: Not Listed; CITES: Appendix II.

Zoo Diet

: Kale, dandelion, romaine lettuce, bananas, tomatoes, apples, soft bill gelatine, prime supplement, crickets, and wax worms.


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