Eli5: Why do small animals like squirrels not lose appendages to frostbite when temperatures reach below freezing, and they walk around on ice and snow all day?
In: Biology
Bird legs work like the kidney’s Loop of **Henle**
Basically, warm blood going down into the foot is right next to the blood going up. The body stays warm but the foot is nearly frozen. The heat goes from one side to the other. Near the top of the loop, warm blood from the body loses heat to colder blood coming back from the foot. Here are a couple of pictures.
https://en.m.wikipedia.org/wiki/Countercurrent_exchange
https://images.app.goo.gl/mKbMbikocBAaXoJ88 (Kidney: loop of Henle)
Edited: thanks to folks below who corrected my spelling and apologies to Mr. Friedrich Gustav Jakob Henle It’s HENLE not HENLEY.
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