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| Regions > African Rainforest > Jackson’s chameleon

Jackson’s chameleon

Location at the Zoo: African Rainforest



Region:

Africa

Class:

Reptilia

Order:

Squamata

Family:

Chamaeleonidae

Genus:

Chamaeleo

Scientific Name:

Chamaeleo jacksonii

Description

: Jackson's chameleon is a medium sized member of the genus Chamaeleo. With its ovoid body shape, slightly flattened vertically, it gives a humpbacked appearance. The head is pyramidal with the widest part behind the eyes then tapering towards the snout. The tail when extended, equals the length of the body but when at rest, is curled up next to the cloaca. There is no inflatable skin flap at the throat. No external ears are visible. This chameleon when at ease is bright lime green. The lips are yellow, which also colours the base of the eyes, front of the head, the base of the horns and the tips of the dorsal crest. The entire lizard is covered by scales of various shapes and sizes. The dorsal crest, running the length of the spinal ridge is low and saw-toothed, becoming inconspicuous on the tail. The base of the head is crowned by a small, triangular, low dorsal casque. A ridge of prominent scales runs from the base of this helmet over the eyes and down to the snout (the head crest).

The male supports three prominent, upward curving horns. The largest one (the rostral) rises above the mouth tip. Two slightly shorter ones (the preorbitals) protrude from above the eyes. These are true horns with a bony core covered in keratin and marked with annulated rings. The female has none. She is smaller than the male in all respects. Only the male exhibits a swelling at the base of his tail which houses the hemipenes. He can display a wider array of colour patterns with greater intensity than the female. The prominent eyes are encased by turret-shaped lids which allow them to move independently and to swivel from 90 to 180 degrees. The lids do not completely close and the pupils are always visible through this opening (the turret-eye).

The interior of the mouth is pink. Small, sharp teeth are set in the ridges of the jaws. The tongue, when at rest, fills the mouth with a fleshy, clubbed-shaped tip, slightly concave at its end. When extended, it is one-and-a-half times the total length of the body and head. The fore limbs end in five digits with the outer two and the inner three bundled separately; on the hind limbs the arrangement is reversed. Each digit ends in a short yellowish-white claw. The pads of the feet and the ventral side of the tail at its tip are adhesive. The length is 152 - 356mm.

Distribution

: This chameleon is found in the central highlands of Kenya except for the eastern slopes of Mt. Kenya and on Mt. Meru and the Usambara mountain regions of northern Tanzania. A subspecies (C. merumontana) has been introduced to some of the Hawaiian Islands.

Habitat

: Enjoy humid, montane forests in elevations up to 2800 m with dense green foliage and optimal temperatures of 16 to 27 ˚C. Recently, coffee plantations and gardens are also chosen.

Food

: This is a mainly carnivorous lizard enjoying ants, butterflies, caterpillars, slugs, small arthropods, snails, worms, lizards, geckos, chameleons, and amphibians: anything small that moves. Leaves, young shoots, and berries may also be consumed.

Reproduction and Development

: Although Jackson's chameleons are relatively timid, they are nevertheless, strongly territorial and at mating time males become increasingly so. Upon seeing competitors, they become aggressive and quickly change into brighter colours of yellow and green, puff up their bodies, raise their fore limbs, gape their mouths, hiss, sway gently from side to side, and turn themselves crossways to an opponent, to increase the illusion of body size. These encounters usually intensify and rivals will then use their horns to joust with each other. However, these are little more than shoving matches; losers change colour, deflate their bodies and slink away. Sometimes they are pushed from their perch. When approaching females, males show their display colours and their profiles, moving their eyes quickly and swaying gently. If they are rejected, they will deflate, change colours and move to another female. Despite being receptive, she may at first make subdued threat gestures by opening her mouth and changing her colours to grey green. Or she may do nothing and the male will continue his approach. If the female is serious in her rejection, she hisses, gapes, raises her fore limbs, and shows her stress display by turning to grey with black blotches. When a male touches a willing female however, she turns to a light brown. He circles around to her back, holds her neck in his mouth and inserts one of his hemipenes into her cloaca. Copulation can last 15 minutes or longer at which time she becomes restless, changes colour and begins to move away. He too changes his colouration and deflates his body. Both go their separate ways.

She may mate several times during the next few days and by delaying fertilization, she can carry eggs fertilized by multiple partners. Gestation lasts for six to seven months depending on the amount of warmth. Since temperatures can drop to a night-time low of 5 ˚C, when basking during the day, she is careful to expose her eggs to the sun's warmth. Temperature and humidity seem to prompt birthing and this process is totally arboreal. This chameleon is ovoviviparous and as the female begins to expel live young, one at a time, still within their transparent, sticky yolk sacs, up to 30 in number, she presses them onto an arboreal substrate where they adhere. The gelatinous egg ruptures and after a short rest, the new born, using limbs and teeth, free themselves and move quickly into the foliage to hunt and avoid predation. She deposits her egg sacs at some distance from one another. There is no further parental care. She will not mate again for some time.

The young are coloured light to dark brown with white spots, dots, lines, and white with brown rings on the tail acting as camouflage on tree bark. They are alert and agile quickly becoming adept at hunting with their prehensile tongues, feeding voraciously on small prey: flies, spiders and insects. They innately understand the colour code. Predation from birds, snakes, carnivorous spiders, and adult chameleons is heavy and only a few of each generation survive to adulthood. Sexual maturity occurs at approximately nine to ten months. Life span in the wild is unclear.

Adaptations

: Jackson's chameleons are well suited to their slow moving, solitary life in the trees. Their resting colouration is excellent cryptic disguise and by swaying gently on branches they can mimic the movements of a leaf. Its safety lies in not moving quickly. This lizard does not vocalize beyond a hiss. Jackson's chameleons will hide from predators by keeping a tree branch or trunk between them and danger (shadowing). Communication is done through colour displays from special cells (chromatophores) lying beneath the epidermis. The upper layer of these contains yellow and red producing cells. White and blue reflector cells lie beneath and the deepest layer produces dark brown or black. By mixing, matching and reflecting these colours, chameleons have developed an intricate system for sharing information about feelings, physiological well-being, as well as gender and species identification. This last is important in avoiding hybridization. As well, each semaphore system is species specific. Colouring helps in thermoregulation; bright colours deflect heat and darker ones absorb it. The chameleon regularly replaces its clear epidermal layer by moulting throughout its life.

The male Jackson's horns clearly identify the sexes to each other and are a means of intimidation and attraction. The prehensile tail aids in balance and climbing and is strong enough to support this lizard on its own. The structure of the feet with their pincher-like opposable toes, adhesive pads and claws, makes the chameleon sure-footed. With no external ear openings, hearing is poor and picks up only vibrations. However, the large eyes set in swiveling, turret-shaped lids that are able to move from 90 to 180 degrees independently compensate for this, allowing the chameleon to see in any direction and with binocular vision to judge distance. Its telephoto vision makes distant objects appear close. The prehensile tongue, along with its eyes, is an effective hunting device for this slow moving lizard. The fleshy tip, slightly concave and sticky, traps prey easily. Connected to powerful muscles and a jointed hyoid bone, the tongue can be thrust forward with great speed and accuracy while the chameleon remains still.

The climate can be damp and cool with possible night-time temperatures of 5 ˚C. Being ovoviviparous; females keep eggs constantly warm, which is unlikely in a ground nest. The young are born in the relative safety of the trees and are released over a wide area allowing at least some to survive predation. Jackson's chameleons avoid dehydration by sipping dew from foliage and getting moisture from their food.

Threats to Survival

: This chameleon is much sought after by the pet trade. While it is illegal to collect it, poaching still occurs. Agricultural activities and human settlement are encroaching on montane forests. As a result, this lizard is trapped in a diminishing island of mountain habitat. Snakes, monkeys, birds, meat eating spiders, and parasites prey on it.

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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