Who let the dogs out ... in the cold?
Dear Dr. John,
With the recent short-lived snowfall and the anticipation of more cold weather and snow, I have a question about my dog and any dog’s ability to walk in the snow, on ice, and in the cold. If I went out barefoot in the middle of the winter, I couldn’t last a minute, let alone hours like dogs do. What is it about their metabolism or their feet that allows dogs and other mammals to handle walking on cold surfaces with their bare footpads?
— Thanks. J.F.
Your question has long been a puzzle to me as well, so I did some homework. I knew that the footpads had a higher level of fat in them — just like polar bears have 2-3 inches of fat immediately under their skin that insulates them from the cold. The same holds true for any animals that seem to be able to tolerate extremely cold temperatures. Recently, scientists in Japan studied the pads of dogs’ feet and found out that not only does a high fat content exist that freezes less easily than other bodily tissues but dogs also lose heat easily from their pads because of a high surface-area-to-volume ratio. Using high-level microscopy, scientists found that the arteries supplying blood to the pads had numerous small veins to drain the area and that the design serves as a countercurrent heat exchange system. Warm blood arrives by arteries, and the heat is transferred to the veins keeping the blood warm as it returns to the body.
Similar systems are found in the arctic fox, polar bears, penguins, dolphins and other species. While dogs can stand the cold pretty well, prolonged exposure standing on ice can lead to splitting and bleeding, which are both painful. Some dogs, such as retrievers, enjoy swimming in icy cold water, but be sure to use proper judgment if your dog will be out for a long time in cold weather. While frostbite is rare in dogs, it can occur. Thanks for making me research the question.