Why are dogs chill in heat and cold?

The full narration of the video.

The same dog rolls in the snow in winter, and trots around in a full fur coat all summer. Does it really not mind hot or cold? The answer hides in three things: a coat, four feet, and a mouth. Let's open them up one by one — there's a surprise at the end. Start with the coat. Many dogs have two layers: long, stiff hair outside, and soft, dense fuzz underneath.

That fuzz traps countless tiny pockets of air. Air is bad at passing heat along, so the coat works like an insulated box. In winter, it keeps body heat in. In summer, it blocks heat from the sun. So shaving a dog bare won't necessarily cool it. It can even get sunburned. Next, the feet. Dogs walk barefoot on ice and snow, yet their pads rarely get frostbite. Why?

Researchers in Japan looked at dog paw pads under a microscope. The vessels carrying warm blood down were pressed right against the ones carrying cold blood back. The warm blood warms the cold blood on the way. The heat loops back into the body instead of leaking out through the feet. When it gets colder, a dog curls into a ball with its tail over its nose. Less of it is exposed, so less heat escapes.

For the cold, most dogs come fully equipped — only small, short-haired and older dogs need extra care. But what about heat? When people get hot, we sweat all over. Dogs barely sweat at all. Only their paw pads and nose sweat a little, not enough to matter. Dogs rely on panting. In through the nose, out through the mouth, keeping air flowing over a wet tongue. As the water evaporates, it carries heat away.

At full speed, a dog can pant more than three hundred times a minute. It will also lie on a cool floor and hand its heat straight to the ground. Here's the surprise: panting can't shed heat as well as sweating does. A dog's real strength is handling cold; its weak spot is heat. A UK study looked at more than nine hundred thousand dogs. Over seventy percent of heat illness happened during exercise. On half of those days, it was under seventeen degrees Celsius.

Flat-faced dogs have it harder: short noses make panting hard work. English bulldogs are more than ten times as likely to get heat illness as Labradors. Before a summer walk, press the back of your hand to the ground for seven seconds. If you can't hold it, neither can your dog's paws. At noon outside your building, how many seconds can you last?