Dogs pant to regulate their body temperature. They have fewer sweat glands than humans, and most are located along the base of their feet; because of this, it is difficult for them to lose heat through sweating. By panting, a dog can cool its mouth and tongue, along with blood that is circulated through the head, keeping its body temperature at a safe and normal level. Although panting can help these animals stay cool, they cannot protect themselves against extreme heat, and owners should carefully monitor their pets during warm weather to prevent heatstroke. When a dog pants heavily during hot weather, it may be a sign of distress.
Methods of Keeping Cool
Animals try to keep themselves cool during hot weather by various methods, but they all involve evaporation. In a gas, the molecules are moving about more than they are in a liquid, so a gas has more energy. To convert a liquid into a gas, energy must be supplied, and this comes from heat. When a liquid evaporates, it carries heat away with it, cooling the surface from which it evaporated.
Humans have many sweat glands, located all over the skin, so they can cool themselves easily by secreting a liquid that evaporates, taking heat away with it. The absence of fur and the large surface area make this a very efficient method. Some other animals lick themselves so that they can cool down through the evaporation of saliva. In dogs, the main method of cooling is panting.
How Panting Works
The classic mouth open, tongue-lolling posture adopted when dogs pant helps to cool the mouth and tongue, but it also provides a draft of air to the major blood vessels of the head, which surround the nose. Panting helps to cool these blood vessels, keeping the brain from overheating and also circulating lower temperature blood through the rest of the body. The large surface area of the tongue, along with the rapid flow of air, maximizes cooling by evaporation, which is why dogs stick their tongues out when they pant. Panting also cools the respiratory system in the same way.
Overly rapid breathing can result in hyperventilation, but this does not normally happen with panting, as the breaths are shallow and do not involve exchange of gases in the lungs. A dog normally takes about 30-40 breaths per minute, but during panting, this increases to about 300-400. Dogs will switch from normal breathing to panting periodically in warm weather, but do not show any intermediate breathing pattern. Instead of increasing their breathing rate as the temperature rises, the switch to panting more frequently and for longer periods. Hyperventilation may occur, however, when the dog is unable to reduce its temperature through normal methods.
An apparent disadvantage of this method of keeping cool is that it involves using muscles. This movement produces heat as a byproduct, which could counteract the cooling effect. It seems, however, that the elastic properties of the respiratory system minimize the amount of muscle work that has to be done. Inhaling stretches the system, which then bounces back on exhaling. It has a natural frequency at which panting can take place with minimal muscular effort.
Signs of Distress
The normal body temperature for dogs hovers between 101° and 102°F (38° and 39°C). A temperature increase of merely three degrees, to 105°F (41°C), can lead to the early signs of heatstroke, and at this point, even if a dog pants, it may not be able to control its rising body temperature. At 108°F (42°C), dogs can suffer from major organ damage and death if the condition is not addressed immediately by a veterinarian.
Dogs pant after heavy exercise and during warm days, and this is entirely normal. Pet owners should watch out for other signs of heatstroke, which include accelerated or abnormal breathing and heart rate, a dry mouth and nose, heavy drooling, seizures, and pale or extremely dark gums. They should make sure that the dog has access to plenty of fresh, cool water, along with shade. Pets, and children, should never be left in a car, as the temperature inside can rise very rapidly.
If a dog is demonstrating symptoms of heatstroke, the owner should cool it down immediately with cool or tepid water and ice packs behind the legs, where large amounts of blood circulate. The pet should be given cool water to drink, but not too much, and should not be covered, as this traps heat. The owner should bring the dog to a veterinarian as soon as possible for additional treatment, as some of the signs of heatstroke will only appear after it is too late, and only quick professional attention will save the dog's life.
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