Newts and salamanders (Caudata) are a group of amphibians that include about 10 subgroups and 470 species. Newts and salamanders have a long, slender body, a long tail, and usually two pairs of limbs. They inhabit cool, shady habitats and are most active during the night. Newts and salamanders are silent amphibians, they do not croak or make loud sounds liek frogs and toads. Of all amphibians, newts and salamanders most closely resemble the earliest fossil amphibians, the earliest animals to have adapted to life on land.
All salamanders and newts are carnivorous. They feed on small invertebrates such as insects, worms, snails, and slugs. Many species of newts and salamanders have poison glands in their skin which helps to protect them against predators.
The skin of newts and salamanders is smooth and lacks scales or hair. It acts as a surface through which respiration can take place (oxygen is absorbed, carbon dioxide is released) and for this reason it must stay moist. This means newts and salamanders are restricted to damp or wet habitats to ensure their skin never dries out.
During the larval stage, many species of newts and salamanders have feathery external gills that enable them to breath in water. These gills disappear when the animal matures into the adult form. Many adult newts and salamanders breath using lungs. Some species also absorb oxygen through the surfaces of their mouth and enhance the movement of air or water using buccal pumping, a rhythmic panting that is apparent by the vibration of the animal's chin. Moving air and water through the mouth also enables the newt or salamander to sample the odors in the surounding environment.
Newts and salamanders are divided into about ten subgroups including mole salamanders, amphiumas, giant salamanders and hellbenders, Pacific giant salamanders, Asiatic salamanders, lungless salamanders, mudpuppies and waterdogs, torrent salamanders, newts and salamanders and sirens.