Chameleon

Species

Chameleon is Greek for ground lion. Chameleons belong to four genera: Bradypodian, Brookesia, Chamaeleo and Rhampholeon. Some researchers also recognise a further 2 genera: Callumma and Furcifer. This article will focus mainly on the Jackson's chameleon, which is the chameleon I think I saw in Africa.

Chamaeleo jacksonii

Jackson's chameleon or three horned chameleon

Population

Unknown but IUCN classify the Jackson's chameleon as Least concern. Jackson's chameleon have been exported to the US for the pet trade and, in some places (Hawaii), have become an invasive pest species.
However, there are species of chameleon that are critically endangered like the Chapman's pygmy chameleon (Rhampholeon chapmanorum) that are only 6 cm long and only found in patches of rainforest in Malawi.

Size

The largest chameleons, Parson's chameleon (Calumma parsoni) can grow to 69.5 cm, including it's tail. it is about the size of a house cat and is found on Madagascar. Another Madagascan chameleon, the Malagasy giant chameleon, is similar size.
The smallest is only 21.6mm long called the nano-chameleon (Brookesia nana), also found on Madagascar.
Most chameleons are 17-25cm long.
The Jackson's chameleon can weigh 1 to 1.5kg. Male Jackson's chameleons have three horns: two preocular (by the eye) and one rostral (nose). Females don't usually have horns. If they do, they are poorly developed and often only a small rostral horn. The horns start growing at around 4 months old.

Habitat & distribution

Jackson's chameleon prefer forests (especially moist mountain forests) and woodlands. They are found in south-central Kenya and some parts of northern Tanzania.
There are some species of chameleon that are found in Asia (the Indian chameleon is found in India, Sri Lanka & other parts of Asia) and Europe (the common chameleon is found in Spain & Portugal). However, the majority are found in sub-Saharan Africa.
There are chameleon species that are ground dwelling and live in leaf litter, like the Namaqua chameleon found in southern Africa.

How do chameleons change colour?

Chameleons change the structure of their skin cells. This modifies the way light is reflected (and what colours we see). the top layer of skin contains pigment cells containing yellow and/or red pigments. Under this layer are specialised skin cells called iridophores, which contain crystals of guanine. (Guanine is one of the nucleotide bases that make up DNA). When the chameleon is relaxed, the crystals are tightly packed together. Shorter light waves i.e. blue light, go through the yellow pigments and give the chameleon a green appearance. If the chameleon is stressed or excited, the cells containing the crystals 'flex'. The crystals reflect longer wavelengths and we see brighter colours.
Under the layer of iridophores are melanophores. When a chameleon is frightened or submissive, melanin (a dark pigment) is transported to the surface of the skin giving a brown or black appearance.
Colour change is a way of communication or as a means of thermoregulation to dissipate heat in extreme desert conditions.

Diet

Most chameleons are insectivores. There are a few species that are cannibals - the common chameleon eats other lizards and some birds. Jackson's chameleons also eat plant matter, other reptiles and amphibians.

Interesting facts

From fossil analysis, scientists think chameleons originated in Africa and 'rafted' across to Madagascar.
Projectile tongue: a chameleon can fire out its tongue at 100 km/h in just 1/100 of a second. This is the fastest acceleration of any animal in the world.
Acrodont dentition: a chameleon's teeth are attached to the edge of the jaw, unlike mammals that have teeth with roots the are embedded in the jawbone.
Zygodactylous feet: toes are arranged in bundles of two or three and these bundles are fused together in opposite directions.
Eyes can move independently of each other.
Like snakes, chameleons shed their skin but not all at once (in sections).

Group

Chameleons are solitary, only coming together to breed. Jackson's chameleons prefer to stay hidden in trees.

Breeding & lifespan

Most chameleons are oviparous, which mean they lay eggs. 2-40 eggs are laid in the soil or rotting logs. The eggs hatch after about 3 months.
However, some chameleons (like the Jackson's chameleon) are viviparous, which means they give birth to live young. After a gestation period of 6-7 months, Jackson's chameleons give birth to 8-30 young. The babies are brown at first and start to turn green at around 4 months. The babies are precocial, which means they can look after themselves once they are born and don't rely on their parents (they find their own food).
Chameleons live to 5-11 years in the wild.

Predators & threats

Snakes, birds and some mammals (primates) prey on chameleons.
Deforestation is one of the main human threats to chameleons species.