Ava Williams
Even in freezing winter temperatures, dogs can touch the ground with their bare paws without suffering frostbite. They succeed thanks to a sophisticated heater, explain Japanese researchers in the “Veterinary Dermatology” journal. It works like a heat exchange system: warm, incoming blood heats the returning blood in the paws, keeping the dog warm and the paws constantly cool.
Heat pump in the paw
Using electron microscopy, the researchers found that the arteries and veins in dog paws are conspicuously close together. This allows the heat from the oxygenated blood in the arteries coming from the heart to easily transfer to the deoxygenated blood in the veins that previously came in contact with the cold surface. The blood from the veins runs back warmed up to the dog’s heart and from there into the central bloodstream.
Principle of dolphin and duck
“It was not previously known that the dog uses countercurrent heat exchange,” says Thomas Ruf from the Research Institute for Wildlife Ecology at the Vetmeduni Vienna. In other animals, however, the phenomenon is known – for example in the dolphin, which uses it in the fin, in the dog and deer nose, and also in the duck foot. “Otherwise, ducks would thaw if they stood on the ice for a long time. That’s how they keep their foot temperature at zero degrees.”
The animals have a unique trick to thank for the fact that the tissue is not damaged. “The composition of the affected parts of the body changes depending on the season. In autumn, the animals store more mono- and polyunsaturated fatty acids such as fish oil, which enable them to adapt accordingly,” explains Ruf. Animals that go into hibernation succeed in adapting the whole body according to a similar principle. In autumn, for example, marmots look specifically for plants with unsaturated fats – and in winter they have no problem cooling down to two degrees as a whole.
Some dogs are not winterized
According to the same principle as in the ancestor wolf, the paw temperature of dogs also drops to zero when it is cold. However, this does not apply to every breed of dog. “Some dogs are not suitable for snow and ice because they have been bred for other traits,” says the research leader. In this case, special winter boots for dogs can help. They provide additional insulation and not only offer protection from the cold, but also from road salt and grit.