Reptiles

Reptiles are vertebrates (they have a backbone) covered with dry scales. They replace their scales throughout their lifetime. Some reptiles molt, or shed their skin all at once. Others shed scales individually or in patches. They are cold blooded, which means they warm or cool their blood by moving to warmer or cooler places. They produce eggs with a shell to keep the embryo from drying out on land. Reptile eggs have large yolks that provide food for the embryo. Most reptiles lay their eggs, but some snakes and lizards are live-bearers. The female of live-bearer species carries the embryo, within its shell, inside until the egg hatches. All reptiles breathe with lungs. No reptile has gills. There are four classes of reptiles: turtles, Crocodilians (alligators and crocodiles), beaked reptiles, and Squamata (snakes and lizards).

The smallest reptiles are less than 2 inches long. The largest snakes, the Anacondas, are over 32 feet long. The largest lizard, the Komodo Dragon, grows to more than 10 feet long, and the Leatherback turtles reach lengths of more than 6 feet and weigh more than 1,100 pounds.

Turtles, Tortoises, and Tuatara

Most turtles live in freshwater habitats, but many spend time on land. The females come on shore during warm months to lay eggs. The tortoises live only on land, and many live in the desert. Most Crocodilians live in freshwater habitats. There is only one species of the beaked reptiles, the Tuatara, still in existence. The Tuatara has a scaly crest and lives on a few rocky islands in New Zealand. They are different from most reptiles because they are able to survive in cold temperatures.

Snakes and Lizards

Most reptiles belong to the order Squamata, which includes more than 2.500 species of snakes and more than 3,000 species of lizards. Most snakes and lizards live in the tropics, but many live in temperate zones and a few live near or above the Arctic Circle.

Snakes move by attaching their belly scales to rough surfaces and pulling themselves along. Most lizards walk on all fours, but some use only their hind legs when running. All lizards have claws. No modern reptiles can fly, but some tropical snakes and lizards can flatten their bodies and glide from tall trees.

Catching Food but Not Getting Caught

Snakes and lizards have a special organ, called Jacobson’s organ, in the roof of their mouths. They get information about their surroundings by flicking their tongues out and in rapidly, pressing the tongue against the organ. Some boas and pythons, and the pit vipers have heat-sensitive organs, too. They can find and strike their prey even in total darkness.

Most reptiles are carnivorous (meat eaters). A few lizards and turtles are herbivorous (plant eaters) as adults. Some reptiles stalk their prey. Others wait in ambush. Some have special ways to get food. African chameleons have a long, sticky tongue that they stick out rapidly to catch insects. The alligator snapper, a snapping turtle of the Southern United States, has a tongue that looks like an earthworm. The turtle uses it as a lure to attract fish into its open mouth. Most reptiles are adapted to protect themselves from predators. They use camouflage, flight, and threat displays, or hide underground or underwater. The rattling of rattlesnakes, the spreading neck displays of cobras, and the hissing and open mouth of alligators are examples of threat displays. Some snakes and the stinkpot turtle give off bad smells to discourage predators.

Amphibians

Almost all amphibians have features that fall between those of fishes and reptiles. The most commonly known amphibians are frogs, toads, and salamanders. They are cold-blooded vertebrates that spend their lives both in fresh water and on land. Their natural environments are shores, ponds, marshes, swamps, and low-lying meadows. Amphibians are found all over the world, except where there is snow all year long. Most amphibians breathe through their lungs and skin instead of through gills. Unlike reptiles, amphibians don’t have a scaly or armored covering and take in water and oxygen through their skin.

Metamorphosis

There are over 3,000 species of amphibians. They are divided into three orders: the Anurans (frogs and toads), the Urodeles (tailed amphibians, such as salamanders), and the rarely seen blind and limbless amphibians that look like worms or snakes. Most amphibians change from gill breathers to lung breathers as they grow from the larva stage to the adult. They also change from plant eaters to meat eaters. This process is called metamorphosis. Where dry and rainy seasons alternate, some amphibians become inactive until the rains come again. This is called aestivation. In cold regions, some amphibians go into hibernation.

All Anurans begin life as tadpoles. As they grow they lose their tails and gills and grow hind legs for jumping. There are more frogs than any other kind of amphibian. Most of the tailed amphibians are salamanders. They live in or near streams, and are sometimes found under rocks and logs. They have long tails, poorly developed legs, and smooth, moist skin. They do not have claws or ears. Some tailed amphibians live in water. They have tiny front legs, no hind legs, and feathery gills. They look like brown, gray, or greenish eels. They can live on dry land for a short time.

Eat or Be Eaten

Although amphibians have teeth, they do not chew with them. They use their long tongues to capture their prey, which they then swallow whole. The upper skin layer, called the epidermis, is regularly shed in a process called molting. The skin usually comes off in one piece and is then eaten by the animal. The lower skin layer, called the dermis, often has mucous and/or poison glands. These glands also make some amphibians stink. The skin can also change color so that the animal can hide when an enemy is near. Sometimes parts of the skin become brightly colored. The amphibian displays these colors to warn enemies to keep away. Other ways that amphibians protect themselves from predators is to puff up to look large and frightening, or to play dead.

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