What Is an Amphibian? Frogs, Salamanders & Caecilians
Amphibians are vertebrates with moist skin that typically start life in water. Frogs, toads, salamanders, newts, and caecilians — traits, metamorphosis, and decline.
Global Animal Guide · July 10, 2026
Image sourcing: see credits & licences
Quick answer
Amphibians are vertebrates with permeable, usually moist skin and a life cycle that often includes an aquatic larval stage. Living groups are frogs and toads (Anura), salamanders and newts (Urodela), and limbless caecilians (Gymnophiona). Many undergo metamorphosis. They are ecological indicators — sensitive to pollution, disease, and habitat loss.
Last updated: July 2026.
Why “amphi”?
Greek amphi means “both sides” — historically, life in water and on land. Not every species fits the textbook pond-to-forest story, but the dual lifestyle is the classic pattern.
Skin as a superpower (and vulnerability)
Cutaneous respiration supplements lungs. The same permeable skin makes amphibians vulnerable to toxins, UV, and drying — one reason they signal ecosystem health.
Related reading
Frequently asked questions
Are frogs amphibians?
Yes — frogs and toads make up order Anura, the largest amphibian group.
Do all amphibians live in water?
No — many adults are terrestrial, but most still need moisture and often water for eggs or larvae.
What is metamorphosis in frogs?
The change from aquatic tadpole (gills, tail) to air-breathing frog with legs — see our metamorphosis guide.
Why are amphibians declining?
Habitat loss, chytrid fungus, pollution, climate change, and invasive species.