How do frogs and turtles hibernate for the winter without coming up to breathe?
Two mechanisms. Hibernation is defined as entering a state of sharply reduced metabolism during the winter. The result is that the need for oxygen is reduced to almost nothing. The second mechanism is that frogs can take in dissolved oxygen and excrete carbon dioxide through the skin. Some turtles can do much the same through the cloaca (softshelled turtles) or pharynx (snapping turtles).
