Two Posts from Badger Run Wildlife Rehab

Ever wonder why birds can land on freezing metal in winter and their feet don’t get stuck to it?

Our fingers will get stuck on cold metal ice cube trays when pulling them out of the freezer. Our tongues freeze to cold metal ala A Christmas Story. That’s because the moisture on our skin freezes in contact with the icy metal.

Birds’ feet are covered with dry scales so there is no moisture to freeze to frigid metal. Birds have no sweat glands and essentially no secretory glands (not zero) so the skin does not secrete moisture through the skin on their feet.

The photo below of an Osprey’s foot shows these scales in the extreme.

Frigid temps can be hard on wildlife. How do they keep those bare feet from freezing? Countercurrent heat exchange.

Basically, the arteries carrying warm blood down to the feet are very close to, if not intertwined with, the veins carrying cooled blood back up to the body and the heart. So, the warm blood in the artery essentially rewarms the blood coming back up the leg’s vein so it does not cool the body’s core temperature.

And birds aren’t the only ones that use countercurrent heat exchange in their extremities to conserve body temperature. Other animals like arctic foxes and wolves use it, too. Deer species, as well. Also, beaver, muskrat, otters, and sea mammals.

  • anon6789@lemmy.worldOP
    3·
    18 hours ago

    I’m curious what the evolutionary tradeoff is for having this.

    Most of my life I was jealous we weren’t cold blooded as it sounded like a plus to be the ambient temp all the time. I eventually learned it was a great evolutionary leap to become warm blooded so our internal systems will generally always be operating at peak conditions despite our surroundings.

    It would really change life if a cold day would start shutting down your organ functions or leave you unable to digest food and you die of septic shock because you had a meal before going outside too long.