Temperature Regulation

A common misconception is that dogs do not sweat. Primarily, dogs regulate their body temperature in a completely different way, through their tongue. That is why after a dog has been running or on a hot day, its mouth will be seen wide open with the tongue hanging out. This form of cooling maximizes heat lost while conserving moisture, because it carries heat from the hottest part of the body, the interior core of the thorax, unlike sweating, which cools the already coolest part of the body, the skin - or in less intuitive, more scientific terms, this higher efficiency of thermal loss relative to moisture conservation arises because heat flow is proportional to temperature gradient. In addition, dogs effectively sweat through the pads of their feet, since they are not furred. On a warm day and after exercise, a dog's naturally wet footprints might be visible on a smooth floor.

Dogs possess a rete mirabile in the carotid sinus at the base of their neck, a complex of intermingled small arteries and veins which acts as a heat exchanger to thermally isolate the head, containing the brain, the most temperature-sensitive organ, from the body, containing the muscles, where most of the heat is generated. The result is that dogs can sustain intense physical exertion over a prolonged time in a hot environment, compared to animals which lack this apparatus; thus, a dog chasing a jackrabbit through the desert may not be able to outrun the rabbit, but it can continue the chase until the rabbit literally drops dead from overheating.