Frogs breath with their mouths closed. Their throat movement pulls air through the nostrils to the lungs. Then breathe out with body contractions. The activity and temperature of an animal determine how important breathing is. Anurans have much more complex lungs then other amphibians, such as salamanders, because they're more active and have higher body temperature. Lungs can also help in water. Filling the lungs with air gives a frog better buoyancy, making it float more easily.Frogs can also breathe through their skin, with tiny blood vessels, capillaries, under the outer skin layers. The African 'Hairy' frog, Trichobatrachus robustus, has small lungs and during breeding seasons the males get hair like projections on their back legs. This is because of the high oxygen needs at this time.
Breathing, or respiration, is the process of exchanging oxygen for carbon dioxide to produce energy within a living organism. When a frog's life begins as a tadpole, it has gills, like a fish, under its skin and breathes through those, extracting oxygen from the water just as fish do. However, as it matures, it develops lungs and breathes through those, extracting oxygen from the air like land animals. This is the reason they are called "amphibians," as they exist first in an aquatic and then a terrestrial environment. Some species of frogs can continue to extract oxygen from the water, even as adults, through their skin when the hibernate.