Chapter 1

What is a Reptile?

Scaly, sun-loving survivors that have been on Earth longer than the dinosaurs.

Reptiles are a group of cold-blooded animals with backbones, lungs, and scaly skin. They include lizards, snakes, turtles, tortoises, crocodiles, and the tuatara — more than 11,000 species in total. Reptiles were the first vertebrates able to live their whole lives on land, thanks to their waterproof skin and shelled eggs. Today they live in almost every warm corner of the planet, from steaming rainforests to bone-dry deserts.

Sections

Characteristics

Reptiles are cold-blooded (ectothermic) vertebrates with a backbone, lungs for breathing air, and dry scaly skin. The main groups alive today are lizards and snakes (squamates), turtles and tortoises, crocodiles and alligators, and the tuatara from New Zealand. Together there are more than 11,000 known species living on every continent except Antarctica.

Evolution

Reptiles first appeared around 315 million years ago, long before the dinosaurs. They were the first vertebrates able to lay eggs on land instead of in water, which let them spread away from lakes and rivers. Dinosaurs and modern birds share the reptile family tree — in fact, scientists group birds inside the reptile family because they descended from small feathered dinosaurs.

Skin

Reptile skin is dry, tough, and covered in overlapping scales or bony plates made of keratin — the same material as your fingernails. This waterproof armour stops them drying out in hot places and protects them from bumps and bites. Most reptiles shed their skin as they grow: snakes usually peel it off in one long piece, while lizards shed it in flakes.

Thermoregulation

Because they are ectothermic, reptiles cannot make their own body heat. Instead they move around to control their temperature — basking on a warm rock in the morning to heat up, then slipping into shade or a burrow when it gets too hot. On cold nights many reptiles slow right down and rest until the sun returns.

Reproduction

Most reptiles reproduce by laying leathery-shelled eggs on land, hidden in sand, soil, or leaf litter. Some snakes and lizards give birth to live young instead. Baby reptiles usually look like tiny versions of their parents and have to look after themselves from the moment they hatch — although crocodiles and some pythons guard their eggs and hatchlings.

Habitats

Reptiles live almost everywhere: hot deserts, tropical rainforests, grasslands, mountains, rivers, and even the open ocean (sea turtles and sea snakes). They tend to prefer warm places because they rely on outside heat, which is why there are far more reptile species near the equator than near the poles.

Conservation

Around one in five reptile species is threatened with extinction. The biggest problems are habitat loss when forests are cut down or wetlands are drained, illegal collection for the pet trade, invasive predators like cats and rats, and a changing climate. National parks, breeding programmes, and laws like CITES help protect the most endangered species.

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