Woof, it's cold out there! So how come dogs' paws don't freeze up when they pad around on snow and ice - and what keeps dogs from minding the cold?
Japanese scientists say they've discovered why. First of all, they say in a new study published in the journal Veterinary Dermatology, dogs' pads contain lots of fatty tissue - which doesn't freeze as easily as other tissues. And the blood vessels in dogs' feet are arranged in a way that lets them act like living heat exchangers: arteries in the paws are very close to networks of tiny veins (venules), facilitating the transfer of heat from venous to arterial blood.
When a paw is cooled by contact with frozen ground, warmth from the arteries in the paw is transferred to the venules. This helps keep the paw at a tolerable temperature. In addition, it warms the blood before it flows back to the body - thus helping keep the dog's body temperature from falling uncomfortably low.
The so-called "counter-current" heat exchange mechanism sounds like a good one, and it's not unique to canines. Similar systems are seen in other animals, including penguins and foxes, physorg.com reported. The finding suggests that dogs may have evolved in cold environments.
Research has shown that dogs' feet are protected from freezing even in temperatures as low as -35 Celsuis, according to the BBC.
The research, carried out by Dr. Hiroysho Ninomiya and colleagues at Tokyo's Yamazaki Gakuen University, was conducted with the help of an electron microscope and four willing dogs.