Why don’t ducks get frostbite when swimming in cold waters during the winter? Have you ever looked out into a cold pond and noticed the ducks playing happily in the water and wondered “How are they not freezing to death?” Well, it’s all due to the circulation in their feet!

Ducks in particular do not have a lot of body fat to protect themselves during the cold winter months. It is crucial for them to minimize heat loss as much as possible. They do this through a unique, countercurrent, heat exchange system. Other waterfowl such as geese, seagulls, have this adaptation too!

The countercurrent exchange system is an alignment of blood vessels. The veins and arteries lie next to one another and exchange materials, aka heat. To simplify this complex process, warm blood flows to the ducks’ feet and back into the body and into the veins. As the veins take in heat, the arteries’ internal temperature decreases. Thus, the temperature in their feet adapts to the temperature outside and reduces heat overall. This is efficient for the duck since there is a small temperature difference between the ice and their feet and they lose minimal body heat overall.  When the temperature of a Mallard’s foot is 33.8 degrees Fahrenheit, they only lose about 5% of body heat through their feet.

Ducks and other waterfowl aren’t the only animals that perform countercurrent heat exchange. Whales, turtles, beavers, and seals also benefit from this system.

This process doesn’t mean the animal never gets cold. Ducks will also lift one leg into their feathers or tuck in their bill to further conserve body heat.  By doing this, the duck draws in warm air.

If only humans were as lucky to have this amazing adaptation!

Photo credit: scienceabc.com