Reptiles vs Amphibians: Key Differences With Examples

Key differences at a glance

Reptiles and amphibians are often studied together under the name herpetology, and both are ectotherms, sometimes called cold-blooded, which means they rely on outside heat to warm their bodies; see are reptiles cold-blooded?. But they are separate classes of vertebrates with very different ways of living.

There are about 12,000 known species of reptiles, in four groups: lizards and snakes, turtles and tortoises, crocodilians, and the tuatara of New Zealand. Amphibians number more than 8,000 species, in three groups: frogs and toads, which make up nearly nine in ten amphibian species, salamanders and newts, and the legless caecilians of the tropics.

Skin: scales versus moist skin

Reptile skin is tough and dry, covered with scales made of keratin. Turtles have large plates called scutes on their shells, and crocodiles have bony plates in the skin of the back. This armor holds water in, so reptiles can survive in the driest deserts. Reptiles shed the outer layer of skin as they grow, snakes in one piece and lizards usually in patches.

Amphibian skin is thin, smooth or warty, and kept moist by mucus glands. It has no scales on the surface. Water and oxygen pass straight through it, so the skin acts as an extra lung, and some amphibians drink by absorbing water through the skin. Many amphibians also have poison glands, from the mild toxins of common toads to the deadly skin of some poison frogs.

Eggs, larvae and metamorphosis

This is the deepest difference between the two classes. Reptiles lay amniotic eggs, which have protective membranes and a leathery or hard shell that keeps the embryo from drying out. The eggs can be laid in soil, sand or rotting plants on dry land, and baby reptiles hatch as miniature adults. Many lizards and snakes give birth to live young instead.

Amphibian eggs have no shell, only a coat of jelly, so they must be laid in water or in very damp places. In most species, the eggs hatch into aquatic larvae with gills, such as the tadpoles of frogs. The larvae then go through metamorphosis: a tadpole grows legs, absorbs its tail, develops lungs and turns into a small frog. Some amphibians skip the larval stage and hatch as tiny adults, and a few salamanders keep their larval form for life.

Breathing and body temperature

All reptiles breathe with lungs throughout their lives, even sea turtles and sea snakes, which must surface for air. Amphibian larvae breathe with gills, and adults use a mix of lungs, the lining of the mouth and the skin. Some salamanders have no lungs at all and breathe only through their skin and mouth.

Both groups control their temperature with behavior. Reptiles bask in the sun to warm up and retreat into shade or burrows to cool off, and many tolerate high temperatures. Amphibians usually avoid strong sun, because it dries their skin, and they are often most active on cool, wet nights. Both groups need far less food than mammals or birds of the same size, because they do not burn energy to stay warm.

Habitats: where reptiles and amphibians live

Because their skin and eggs hold water, reptiles can live almost anywhere warm enough, from deserts to rainforests and from mountains to the open ocean. Sea turtles, sea snakes and the marine iguana of the Galápagos spend much of their lives at sea.

Amphibians are tied to moisture. They live in ponds, streams, wetlands, damp forests and rainforests, and most return to water to breed. Almost no amphibians tolerate salt water, so they are missing from many oceanic islands. Neither reptiles nor amphibians live in Antarctica, and both groups reach their greatest variety in the tropics.

Examples of reptiles and amphibians

Reptiles you might see in Europe and North America include the sand lizard, the slow worm, the adder and the grass snake in Europe, and the green anole, the common garter snake, the painted turtle and the American alligator in North America.

Amphibians include the common frog, the common toad, the smooth newt and the fire salamander in Europe, and the American bullfrog, the spring peeper, the spotted salamander and the eastern newt in North America. To tell frogs from toads, see frog vs toad.

Common mix-ups

Salamanders and lizards are the classic confusion: both have four legs and a tail, but salamanders are amphibians with moist skin and no claws. The differences are explained in lizard vs salamander.

Caecilians look like large earthworms or small snakes, but they are amphibians. Turtles that live in water, such as snapping turtles, are still reptiles, and they lay their eggs on land. The tuatara of New Zealand looks like a lizard but is the last survivor of a separate ancient reptile order; see is a tuatara a lizard?.

Birds are another twist. In classification based on evolutionary relationships, birds are part of the reptile family tree because they descend from dinosaurs, though most schoolbooks still list them as a separate class.

Conservation: which group is more threatened?

Both groups are in trouble, but amphibians are the most threatened class of vertebrates. A global assessment published in 2023 found that about 41% of assessed amphibian species are threatened with extinction, driven by habitat loss, climate change and diseases such as chytrid fungus. The reasons are explained in why are amphibians declining?. A similar assessment of reptiles, published in 2022, found that about 21% of assessed reptile species are threatened, mainly by farming, logging and urban growth.

The difference partly reflects their biology. An amphibian’s thin skin absorbs pollutants and pathogens easily, and many species need both clean water and healthy land habitat to complete their life cycle, so damage to either can wipe out a local population. Reptiles are tougher in this respect, but slow-growing species such as tortoises and sea turtles recover very slowly from losses.