Naked mole rat
The naked mole rat is well adapted for the limited availability of oxygen within the tunnels that are its habitat: its lungs are very small and its blood has a very strong affinity for oxygen, increasing the efficiency of oxygen uptake.  It has a very low respiration and metabolic rate for an animal of its size, about two thirds that of a mouse of the same size. It only uses very little oxygen.  In long periods of hunger, such as a drought, its metabolic rate can reduce by up to twenty-five percent.