Why Don’t Ducks Freeze?

By Chalisa Nestell, Research Scientist

Between the high water levels and this bitter cold snap, there are thin sheets of ice across the shallower areas of Butler Creek. The mallards and other dabbling ducks are completely unfazed. How are the ducks able to withstand such chilly temperatures? Why don’t the ducks get hypothermia?

Those bright orange legs are equipped with an amazing counter current exchange system.

The counter current exchange system is a unique alignment of blood vessels, with veins and arteries lying next to each other, that allows for the exchange of materials. In this case, the system allows for the exchange of heat. In a nutshell, warm blood from the body, in the arteries, going into the duck’s feet is used to warm the blood coming from the feet and back into the body, in the veins. This has two advantages. First, it ensures blood going back into the body is warm. Second and more importantly, it conserves body heat by minimizing heat loss.

Physics tells us that the greater the difference in temperature between two things, such as duck feet and cold creek water, the greater the potential for heat loss. This is the beauty of the counter current exchange system. As the veins absorb heat and warmth, the temperature in the arteries decreases and the blood temperature in the feet becomes closer to the temperature outside. The reduced temperature difference results in reduced heat loss. Hence the duck isn’t continually losing large amounts of body heat while its dabbling bottoms-up for food in the water.

So the ducks’ toes do indeed get cold, several degrees colder than the body. But thanks to the counter current exchange system, the body stays nice and warm.

For more information http://askanaturalist.com/why-don%E2%80%99t-ducks%E2%80%99-feet-freeze/