Why dogs don't get cold paws

So, why don't dogs get cold paws? 

I asked this question in a recent YouTube video I made when we were snowed in at home (here) and I saw a dog charging around like a whirling dervish, seemingly completely unaware of the super-cold snow underfoot.

Well, several friends gave me...um...interesting answers, so I figured I'd find out and let you all know. Here goes.

Some animals, like dolphins and penguins have a highly developed set of blood vessels in certain areas which allows heat to be transferred efficiently between arteries bringing blood from the body to the veins going back to the heart; in dolphins the system is in the fins and in penguins, their legs and wings.

Research carried out in Japan (published in December 2011 - abstract here. If you're a student or academic you can get the full paper at that link) found for the first time that domestic dogs have this same system in their paws. Arctic foxes have been known to have this system for some time but it had previously been thought that there would be no evolutionary reason for domestic dogs to have such a developed system.

So, what do you know. In dogs paws, this set of vessels, called venules, allows heat from the arteries to pass to the veins before it moves back in the body. Interestingly, this process is sufficiently efficient to overcome the heat loss from the large surface area of the pads.

Cool huh.