Dogs come in many shapes and sizes. The smallest breeds include the toy and miniature varieties, such as the Toy Poodle, Papillon, Chihuahua, and Shih Tzu. These dogs usually weigh only 5 to 10 pounds (2.3 to 4.5 kilograms), or even less. Medium-sized dogs include many of the terriers and spaniels, which weigh in the 10 to 50 pound (4.5 to 23 kilograms) range. Larger still are the retrievers, shepherds, and setters, which often weigh 65 to 100 pounds (30 to 45 kilograms). Finally, the giant breeds, such as the Mastiff, Komondor, and Saint Bernard, can approach or exceed 200 pounds (91 kilograms). Of course, sizes vary within breeds, with males usually being larger than females. Mixed-breed dogs include all size ranges.
Dogs are generally much better at conserving heat than at cooling themselves. In sled dogs, who can survive outdoors even in bitterly cold temperatures, the fur acts as an insulating “blanket” that retains the heat generated by the dog’s high metabolism. However, in hot or humid weather, most dogs have difficulty. Dogs cannot sweat, which is an effective form of evaporative cooling. Instead, dogs lose heat primarily by panting. These rapid breaths (10 times faster than normal) are an attempt to lose heat through evaporation by moving hot, moisture-filled air in and out. During the short, shallow breaths in panting, little air can be exchanged in the lungs. In fact, dogs must stop panting periodically to take a good respiratory breath. Drinking water also helps dogs cool down, and the canine hair coat helps insulate from the sun.
Because the cooling system of dogs is relatively poor, certain summer situations can be dangerous and even life threatening. Sadly, many dogs die of heat stroke every year (see What to Do at the Scene and Transport). The most common problem is associated with being shut in a parked car. Even with the windows rolled down, the inside of a parked car can quickly reach 150°F (66°C) or more in the summer, which can cause heat stroke and death in a matter of minutes. Other dangerous situations involve being penned or tied out in the sun (without access to shade) or being locked in a poorly ventilated travel crate.
Ways to keep dogs cool during hot weather include air conditioning, spray misters, shade, dips in a wading pool, or gentle spraying with a garden hose. Keeping dogs wet during the heat of the day provides a method of evaporative cooling. Plenty of cool, fresh drinking water should be available at all times.
Dogs are generally much better at conserving heat than at cooling themselves. In sled dogs, who can survive outdoors even in bitterly cold temperatures, the fur acts as an insulating “blanket” that retains the heat generated by the dog’s high metabolism. However, in hot or humid weather, most dogs have difficulty. Dogs cannot sweat, which is an effective form of evaporative cooling. Instead, dogs lose heat primarily by panting. These rapid breaths (10 times faster than normal) are an attempt to lose heat through evaporation by moving hot, moisture-filled air in and out. During the short, shallow breaths in panting, little air can be exchanged in the lungs. In fact, dogs must stop panting periodically to take a good respiratory breath. Drinking water also helps dogs cool down, and the canine hair coat helps insulate from the sun.
Because the cooling system of dogs is relatively poor, certain summer situations can be dangerous and even life threatening. Sadly, many dogs die of heat stroke every year (see What to Do at the Scene and Transport). The most common problem is associated with being shut in a parked car. Even with the windows rolled down, the inside of a parked car can quickly reach 150°F (66°C) or more in the summer, which can cause heat stroke and death in a matter of minutes. Other dangerous situations involve being penned or tied out in the sun (without access to shade) or being locked in a poorly ventilated travel crate.
Ways to keep dogs cool during hot weather include air conditioning, spray misters, shade, dips in a wading pool, or gentle spraying with a garden hose. Keeping dogs wet during the heat of the day provides a method of evaporative cooling. Plenty of cool, fresh drinking water should be available at all times.
The Senses
Sight
Dogs can see movement and light much better than people. In the retina of the eye, dogs have more of a specific type of cell called a rod, which is good at collecting dim light, so they have better night vision. A reflective layer in the dog’s eye, called the tapetum lucidum, magnifies incoming light. This reflective layer lends a characteristic blue or greenish glint to dogs’ eyes when light (for example, headlights of passing cars) shines into them at night. However, dogs do not have as much visual acuity as people, meaning that they cannot distinguish fine details as well. They also cannot differentiate colors as well because they have fewer of the cells in the retina called cones, which are responsible for color vision. Contrary to popular belief, however, dogs are not completely colorblind.
Dogs can see movement and light much better than people. In the retina of the eye, dogs have more of a specific type of cell called a rod, which is good at collecting dim light, so they have better night vision. A reflective layer in the dog’s eye, called the tapetum lucidum, magnifies incoming light. This reflective layer lends a characteristic blue or greenish glint to dogs’ eyes when light (for example, headlights of passing cars) shines into them at night. However, dogs do not have as much visual acuity as people, meaning that they cannot distinguish fine details as well. They also cannot differentiate colors as well because they have fewer of the cells in the retina called cones, which are responsible for color vision. Contrary to popular belief, however, dogs are not completely colorblind.
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