Scientists at Tokyo’s Yamazaki Gakuen University wondered why dogs do not seem to feel the cold in their paws, even though the paws have less insulating fur than their trunks. The paws have pads containing a high fat content, which freezes less easily than other tissues, but they also have a high surface area-to-volume ratio, which means they should lose heat easily.
Scientists in Japan have solved a long-standing veterinary mystery: how dogs can stand and walk for so long on snow and ice without apparent discomfort, and without freezing their paws.
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In humans exposed to frigid temperatures, vasoconstriction occurs in the extremities to reduce the blood flow and resultant heat loss, and ensure the blood returning to the rest of the body does not cool too much.
The research team, led by Dr. Hiroyoshi Ninomiya, used a scanning electron microscope to study the paws of four adult dogs, and discovered that the arteries supplying blood to the pads had networks of numerous small veins, or venules, closely associated with them, and that the system essentially acts as a counter-current heat exchanger.
