Never far from water
What Is an Amphibian?
Frogs, toads, newts and salamanders. All of them are still tied to the pond they came from.
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Step 1 of 5
The skin is bare, and it leaks.
There are no scales, no fur and no feathers — just thin damp skin. Left in dry air an amphibian loses water straight through it and cannot last the day.
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Step 2 of 5
But that same leaky skin is useful.
Oxygen crosses wet skin as easily as water leaves it. Amphibians take in a good share of their air through the skin, and some take in all of it that way.
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Step 3 of 5
The eggs have no shell at all.
They are laid in soft jelly with nothing waterproof around them. In dry air they shrivel within hours, so they must go into water or somewhere permanently wet.
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Step 4 of 5
Which is why the group is small and local.
Every amphibian lives within reach of somewhere wet — a pond, a stream, a damp forest floor. None of them crossed a desert, and none of them live in the sea.
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Step 5 of 5
And it is why they are the first to disappear.
Skin that lets oxygen in lets everything else in as well. When water is polluted or ponds dry up, amphibians go before anything else does — which makes them a warning worth watching.
About four in every ten amphibian species are now at risk — a worse share than for birds or mammals.
The short version
Amphibians are the bare-skinned, jelly-egg group — their skin must stay damp and their eggs need water, which keeps every one of them near a wet place.
Try it yourself
Leave one wet tissue and one in a sealed bag overnight. The open one is bone dry by morning. That is why a frog stays near the pond.