Cold feet, warm heart


Watching this snow-covered Canada Goose (Branta canadensis) swim around an icy lake, I thought “Brr”.

The core temperature of a goose, wrapped in its fluffy down coat, is ~104° Fahrenheit. But what about those feet? They must be freezing!

In a way, they are. The feet of this goose are only ~35°. As warm blood from the body travels to the toes, it transfers heat to the blood making the return trip. By the time the blood reaches the feet, it’s cold – so cold that little heat escapes through those exposed tootsies.

When the blood moves back toward the heart, it gathers heat from blood vessels traveling toe-ward. This process, called countercurrent heat exchange, keeps the goose nice and toasty.

7 thoughts on “Cold feet, warm heart

    • Cool! I’ll have to look that show up. Thanks for telling me about it.
      I think this type of circulation is common in most birds (correct me if I’m wrong). I first learned about it in mammals – arctic fox, for example.

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