There are around 5,000 species of frog and are found on every continent except Antarctica. They don't need to drink water as they absorb it through their skin – they have permeable skin, which means liquids and gases can pass through it. Each frog species has a distinct croak. They have vocal sacs, which fill with air, and can amplify the sound up to a mile away. There is evidence that frogs have roamed the Earth for more than 200 million years, at least as long as the dinosaurs.
