Weird and wonderful

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Few African animals are more intriguing or, in their own way, more impressive than chameleons. These extraordinary lizards illustrate some of nature’s most ingenious adaptations to the challenges of survival, says Mike Unwin

ChameleonJust how bizarre can one animal be? Chameleons appear to be something straight from science fiction, with skin that changes colour on demand, eyes that swivel every which way, an outrageously extendable tongue and the horned, crested head of a dinosaur. Get close and it may inflate its body, gape its huge mouth and puff like a steam train.

Small wonder, perhaps, that these perfectly harmless lizards excite fear and superstition right across rural Africa. Myths vary from country to country. Some say that if a chameleon touches your skin it will become stuck there and can only be removed along with the skin itself. Others claim that a chameleon crossing your path will bring bad luck, or that a young woman will never find a husband if one looks into her eyes.

But chameleons have not evolved merely to give credulous people the jitters. These weird traits are all ingenious adaptations to a life lived largely among the leaves. Most inhabit low trees and shrubs, and their predominantly green colouration, combined with their general leaf-like shape — curved, ridged and laterally flattened — helps them blend into the foliage. Meanwhile, those horns, crests, flaps and other embellishments serve to break up the outline, helping further render these retiring reptiles invisible to predator and prey alike.

Watch the slow-motion progress of a chameleon and you can appreciate how much it values stealth and concealment. Not for it the frenetic dashing about of other lizards. Instead it takes one deliberate step at a time, often with its body swaying and trembling to resemble a windblown leaf. The feet work like tongs, with opposable, sharp-clawed toes fused into one set of three and one of two that provide a tenacious grip on the flimsiest twig. Assistance comes from the strong prehensile tail, with which it anchors itself while plotting its next move.

Chameleons, then, are supremely adapted ambush hunters. Their conical eyes can revolve independently of one another, like turrets, allowing a 360-degree arc of vision. Once the target is sighted — typically a fast-moving insect such as a cricket or mantis — both eyes swing round to focus together, providing the stereoscopic depth perception required for an accurate strike. And this strike is perhaps the most impressive trick of all: a chameleon can shoot out its tongue further than its own body length and at a speed of around three hundredths of a second. The sticky tip traps the unsuspecting victim, which is then whipped back into the chameleon’s maw.

So, no, there really is nothing to fear from these fascinating reptiles. They will not poison you, tear off your skin or damage your marriage prospects. Unless, of course, you happen to be a vulnerable insect in a chameleon’s sights — in which case, you ought perhaps to consider cancelling your honeymoon.

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Ground lion?
The word ‘chameleon’ is the Latinised form of the Ancient Greek ‘khamailéon‘, which derives from ‘khamai‘ (on the ground) and ‘léon‘ (lion) and translates loosely as ‘ground lion’. This refers to the reptile’s intimidating defensive display, in which it inflates its body, gapes wide, hisses and lunges at its assailant. This display, however, is all bluff: a captured chameleon might bite you but it won’t do any damage.

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All change
Contrary to popular belief, the famous colour changing of some species is not all about camouflage. A chameleon’s general hue does indeed match its surroundings and will adapt as these alter, from green to brown, for example, as it descends from tree to ground. But the patterns and vivid flashes of colour, including combinations of pink, blue, red, orange, black, light blue, yellow, turquoise and purple, are more to do with communication. They enable it to express aggression and alarm (usually a dark hue) or arousal (a more intense flush). Males, who perform sexual displays to females, are the brightest and also sport the more extravagant horns, crests and other embellishments.

The colour change mechanism involves two specialised layers of skin. The top one contains an adjustable lattice of nanocrystals. By manipulating the spacing of these, the chameleon affects which wavelengths of light are reflected and which are absorbed. When it is in a relaxed state the crystals reflect blue and green, but in an excited state they reflect longer wavelengths such as yellow, orange and red. The skin also contains yellow pigments that, when combined with the blue, produce the characteristic green of a calm chameleon. Colour change also has a role in thermoregulation (temperature control). The desert-dwelling Namaqua chameleon becomes black in the cooler morning to absorb heat more efficiently, and then a lighter grey to reflect light during the heat of the day.

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Fit for purpose

The anatomy of a chameleon is a living textbook of environmental adaptation. Each body part has evolved to do a specific job in meeting the challenges of concealment, communication and capturing a meal

Eyes
The conical eyes have fused eyelids, leaving just a pinhole through which to see. These revolve independently, allowing the chameleon all-round vision. Once a target is sighted, both eyes swing round to focus, providing the stereoscopic depth of perception required for an accurate strike.

Body
It is flattened laterally to resemble the leaves among which it clambers. Horns, crests and other projections help break up its outline, concealing it from predator and prey alike. Males sport the more extravagant embellishments to enhance their sexual displays to females.

Skin
Most species of chameleon can change colour at will, with vivid flashes of brighter or darker hues emblazoning its body.

Tail
The tail is generally about the same length as the body. Curled up when moving, it is strongly prehensile and can provide an anchor as the chameleon’s limbs seek out the next purchase on the route forward.

Limbs
A chameleon’s thin limbs often shake when it moves, mimicking the trembling of a leaf in the breeze and thus assisting its concealment.

Toes
The sharp-clawed toes are fused into one set of three and one of two to provide a zygodactylic grip (two toes forward and two facing back), grasping the foliage like tongs.

Tongue
A chameleon can shoot out its tongue further than its own body length to capture prey. A sticky ball of muscle on the tip forms a suction cup upon impact, trapping the victim, which the reptile then reels back into its mouth like a fish on a line.

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How to spot a chameleon
• Go on safari during the rainy season: this is when chameleons are more active and most often seen.
• Take a night drive: chameleons are surprisingly visible at night, when their body glows an eerie pale in the spotlight. Your driver will generally be adept at pointing them out, but it’s worth mentioning in advance that you would like to see one, if possible.
• Watch the road ahead: chameleons tend to stick to cover but cannot conceal themselves when crossing a road, which they are often obliged to do. Sadly, their shaking leaf trick is no defence against the wheels of a car. Drive slowly, stay alert and pull over and take a good look.
• Visit Madagascar: this extraordinary location is home to nearly half of the world’s chameleon species, all of which are endemic to the island; guides are skilled and experienced at finding them, particularly on torch-lit night walks.
• You don’t have to be on a game drive (or even in a national park) to spot a chameleon: take a walk around the grounds of your lodge, or even your suburban hotel, looking carefully among the bushes.

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Who’s who?
True chameleons belong to the family Chamaeleontidae and are confined to the Old World. They fall into 12 genera, containing in total some 180 species. Nearly half of these are endemic to Madagascar; most of the rest are found on mainland Africa, with a handful in Europe and southern Asia. They vary in size from the minuscule Madagascar dwarf chameleon (Brookesia minima), at just 2.8cm, to the impressive Oustalet’s chameleon (Furcifer oustaleti), which may reach 70cm. Although most occur in tropical forest, others have adapted to arid or mountainous terrain. Here is a selection of species you may (or may not) spot on your next safari:

• Flap-necked chameleon (Chamaeleo dilepis): Medium to large species (up to 32cm); generally green with a pale stripe along each flank; the most commonly seen chameleon across much of southern Africa.
• Parson’s chameleon (Calumma parsonii): This large chameleon (pictured below and top) can grow to 68cm; varies in background colour from green to turquoise and takes on vivid changes in hue; stumpy nose horn; found in the tropical rainforest of eastern Madagascar.
• Jackson’s chameleon (Trioceros jacksonii): A medium to large chameleon (up to 38cm) that is identified by three impressive triceratops-like facial horns (below); found in montane rainforests of southern Kenya and northern Tanzania.
• Namaqua chameleon (Chamaeleo namaquensis): Chunky but small (12cm-14cm) desert-dwelling species of southwest Africa that has evolved for a life on the stony ground, developing a shorter, non-prehensile tail and a unique thermoregulation capacity.
• Cape dwarf chameleon (Bradypodion pumilum): Small chameleon (up to 15cm), found in gardens and afro-temperate forest in coastal regions of South Africa’s Western Cape; one of multiple dwarf chameleon species.
• Pygmy leaf chameleon (Brookesia minima): One of several similar species of minuscule chameleon (as little as 3cm) confined to Madagascar; most are brown and live on the ground; many inhabit small ranges in remote areas and have only recently been identified by scientists.

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The next generation
A few chameleons give birth to live young but most are egg-layers. The female digs a hole in the ground and deposits her clutch at the bottom. This varies from just two to four eggs in some species to nearly a hundred in others. The hatching time is similarly changeable: generally from four to twelve months, but in some types up to two years. The Labord’s chameleon from Madagascar has a life cycle that is more akin to that of insects than other reptiles: its young spend eight to nine months in the egg before hatching in November. They then rush through a four- to five-month burst of eating and reproduction, after which they all die simultaneously. This makes them the shortest-lived of all four-limbed vertebrates.

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