Cold’, ‘slimy’, ‘poisonous’: reptiles have never had a good press. But the popular perception of these fascinating creatures is often more myth than reality. If you want to know the truth, then Africa is the place to get started. At least 1600 species have been recorded on the continent – almost 50 per cent more than there are mammals – and new ones are being discovered every year.

First things first: reptiles hail from the Carboniferous Period, over 300 million years ago, when their amphibian ancestors evolved a covering of watertight scales that prevented rapid dehydration and so allowed them to survive on land. They are cold-blooded – which does not mean that they are constantly colder than us but that, unlike mammals or birds, they derive their body heat from their surroundings rather than generating it internally. This fuel-efficient process, more properly called endothermism, allows some reptiles to survive on just half a dozen meals a year and others to live more than a century.

Africa’s reptiles fall into three orders: the Chelonia (turtles and tortoises); the Crocodylia (crocodiles); and the Squamata (lizards and snakes – much the largest group). Most are hard to see, being small, shy and often hidden in foliage or crevices, but you’re bound to come across some of the larger and more obvious species – especially in early summer, when many are out and about establishing territories. So why not take a closer look?

Grabbing a bite
Pretty much everything edible features on one reptilian menu or another. Some species, such as the aptly named slug-eating snake, are specialists. Others, such as the monitors, are generalists. Tortoises, which are not nippy enough to overhaul moving prey, have simply turned veggie – though some may gnaw on an old bone for extra shell-strengthening calcium.

When it comes to finding prey, few animals are better equipped than snakes. Contrary to popular belief, that flickering forked tongue does not sting but ‘tastes’ the air by collecting scent particles and bringing them to a special sensory organ in the roof of the mouth, called Jacobson’s organ. The African rock python goes one further, using heat-sensitive scales around its lips to detect the body heat of passing prey.

Once located, a meal must still be captured. Chameleons ensnare their insect prey on a sticky saliva-coated tongue, shot forward longer than their own body length. Leatherback turtles have backward-pointing spines in their gullet to prevent their slippery jellyfish prey from escaping. And crocodile jaws slam shut on their victim – be it fish or wildebeest – with a pressure of more than 5000lbs per square inch, the strongest known bite of any animal.

Most food goes down whole. Snakes can dislocate their jaws to engulf enormous items – up to goat size, in the case of a large python. The African egg-eating snake swallows birds’ eggs three times the size of its own head, puncturing them with a tooth-like inner projection of its vertebrae before gulping down the contents and ejecting the crushed shell.
 

Getting around
Most reptiles are tetrapods – in other words, they get about on four legs. But technique varies with habitat. Chameleons, for instance, use tong-like toes to get a grip when clambering through flimsy foliage. Geckoes’ toes are lined with tiny, hairy scales called scansors that provide a sucker-like purchase on the steepest of rock faces. The shovel-snouted lizard of Namibia sprints on long legs over the desert dunes and, when standing still, avoids the burning sand by raising alternate legs in the curious ‘thermal dance’.

But limbs are not indispensible. Legless lizards, such as burrowing skinks, evolved because legs were no use when moving fast through long grass or loose soil. Their evolutionary descendants, snakes, have flourished on this adaptation. Most move in S-shaped undulations by pushing their coils against irregularities in the surface. But chunkier ones, including pythons and puff adders, may also use ‘rectilinear motion’, gripping the ground with their broad ventral scales and sliding forward caterpillar-fashion. Peringuey’s adder, another Namib Desert specialist, ‘sidewinds’ over the dunes in a series of lateral curves, lifting most of its body off the blistering sand.

Reptiles that make their living by burrowing, such as the shield-nosed snake, have evolved a spade-shaped front end for this purpose. The bizarre amphisbaenians, or ‘worm-lizards’, live permanently underground. Their cylindrical bodies are sheathed so loosely in their skin that they can generate a piston-like internal ramming motion when burrowing forward. 

Many aquatic reptiles, from crocodiles to sea snakes, have a flattened, oar-like tail that both propels and steers them through the water. The legs of sea turtles have evolved into powerful flippers, powering these marine giants over thousands of kilometres and to depths of 500m or more.
 

A deadly bite
The venomous bite of a snake is the ultimate reptilian weapon, both for attack and defence. Venom comes from the salivary juices and is delivered, syringe-like, via hollow fangs. There are three principal kinds: cytotoxic venom, found in vipers, causes blood vessel and tissue damage; neurotoxic venom, found in cobras and mambas, acts on the nervous system to cause paralysis; haemotoxic venom, found in boomslangs and vine snakes, prevents blood from clotting.

Small wonder, then, that we are so afraid of snakes. But the danger is greatly exaggerated. Only about 90 of the 400 or so African species are venomous to humans, and only 30 of these potentially lethal. All snakes – even the deadliest – do their utmost to avoid us. After all, why waste venom in a risky encounter with an animal that is far too big to eat? Also, a snakebite does not necessarily mean envenomation. Nearly all snakes can bite, and the shock of being bitten – even by a harmless species – can produce phantom poisoning symptoms. Envenomation occurs only when venom enters the bloodstream.

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Staying alive
Reptiles are as much hunted as hunters. Their predators range from large invertebrates, such as Scolopendra centipedes, which can overpower a small skink, to specialist raptors such as snake eagles. Some reptiles even prey on others: water monitors will often raid crocodile nests, for instance, while the Cape file snake is a voracious consumer of other snakes.

Defence strategies are as diverse as they are ingenious. First, there is simply not being seen. Camouflage adaptations range from the extraordinary flaps and fringes of Madagascar’s leaf-toed geckos, which flatten them into invisibility against a tree trunk, to the cryptic leaf-litter patterning of a gaboon viper. Then there is pretending to be something else. The harmless African egg-eating snake has markings that mimic those of the venomous night adder; to enhance the deception, it will even rub its coils together to produce a fake ‘hiss’.

Armour helps too. A leopard tortoise simply pulls its limbs and head into its shell and waits for its assailant to lose interest, while an armadillo girdled lizard grips its tail in its teeth and rolls into a biker’s bracelet of spiny scales that no self-respecting predator dare try to swallow. A giant plated lizard, with no armour of its own, wedges itself into a crevice and inflates its body, becoming impossible to extract.

And, if all else fails, then bluff it out: a cobra will rear up and spread its hood, while a chameleon will gape and inflate its body – both of them in order to appear bigger and more alarming. Blind snakes even wave their tail in the air as a false head, to divert the attention of a predator away from the important end.

New life
Reptiles also employ a bewildering range of reproduction strategies. Most lay eggs, the thick protective shell and yolk store allowing the embryo to develop independently of adults and water – as distinct from amphibians, whose young develop via an aquatic tadpole stage. A few squamates are viviparous: one captive Kenyan puff adder produced a world record 156 live babies.

Before making babies, reptiles must first get together. This often involves a show. The breeding season sees male agama lizards flaunt vivid colours in head-nodding displays to attract females and deter rivals. Nile crocodiles stake their territorial claims by bellowing deeply and blowing bubble fountains, while barking geckos chirrup out a chorus of clicks across the Kalahari dusk. Occasionally it comes to blows. Tortoises try to shove their opponent onto his back, and some snakes stage protracted wrestling matches, each combatant writhing and wriggling in order to gain the upper hand – or coil – on his rival.  

Eggs are generally laid in a warm, moist, sheltered place. Some reptiles go to greater lengths than others: a loggerhead turtle digs a sequence of deep pits on a beach, while a monitor lizard seals its clutch inside a termite mound, where it is incubated at the perfect temperature until it hatches when the rains come. Incubation temperature can even determine the sex of hatchlings: warmer temperatures produce males in crocodiles and females in chelonians.

And – as though to nail that myth about reptilian ‘coldness’ – some species make surprisingly devoted mothers. A female python, for instance, coils herself protectively around her clutch until it hatches. And a female Nile crocodile is the true reptile ‘supermum’, using her massive jaws to transport her tiny hatchlings to the water, before gently washing them and then releasing them.