The Rete mirabile: How Birds Stay Warm in the Winter

#christmas #winter #anatomy #learning #geese
As you walk past a pond, its surface covered by ice that looks slick in the rays of sunlight, you notice geese, that are just standing on the frozen surface with their big webbed scaly feet. Why don’t these geese seem affected by the cold, like you with your now numb nose and very cold hands?
Under the skin and scales of the goose’s leg is the answer. It has a tangled network of blood vessels called the Rete mirabile. These complexes of veins and arteries are quite common in vertebrates, being found from fish to mammals and used for all sorts of purposes like allowing giraffes to lower their heads to drink without internal hemorrhaging by equalizing blood pressure, but these geese have developed another ingenious way of using their retia mirabilia. Warm Blood being pumped into the feet through the arteries transfers much of its heat into the cold blood in the veins flowing back into the core of the bird. This means that there is very little heat loss with the warm blood warming up the cold body, keeping the bird’s core warm. With this system birds despite their reptilian feet and legs birds have been able to conquer some of the most extremely cold conditions on earth, the high arctic, high mountains, and the frigid waters surrounding the Antarctic. Penguins take this whole business further, they have these networks of blood vessels in their flippers and nasal passages since they spend their days submerged in icy water, keeping them from going hypothermic. This same principle is used by certain fish, like tuna, to be regionally endothermic, keeping heat generated by their muscles around their muscles or move it to the brain, allowing them to be faster than other fish in cold water.
Sources
Cech, J.J.; Laurs, R.M.; Graham, J.B. (1984). "Temperature-induced changes in blood gas equilibria in the albacore, Thunnus alalunga, a warm-bodied tuna" (PDF). Journal of Experimental Biology. 109 (1): 21–34.
Sepulveda, C.A.; Dickson, K.A.; Bernal, D.; Graham, J.B. (1 July 2008). "Elevated red myotomal muscle temperatures in the most basal tuna species, Allothunnus fallai" (PDF). Journal of Fish Biology. 73 (1): 241–249. doi:10.1111/j.1095-8649.2008.01931.x. Archived from the original (PDF) on February 7, 2013. Retrieved 2 November 2012.
Webb, J. (1 July 2014). "Deep dives of devil rays solve 'mystery' of warm brain". BBC. Archived from the original on 9 July 2014.

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This is Backyard Expeditions. Here you can find wildlife footage and short documentaries on the natural world. Nature is full of surprises, often amazing things are happening just feet from you door. I am a biology student who was inspired by the likes of the BBC natural history unit, PBS, and animal planet as a Child. I have also long been a hobbyist photographer, filming interesting things over time. My goal is to document interesting behavior and highlight interesting species I encounter both in exotic locations, and on backyard expeditions.

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[BeingBeverly]

Nice video 😃
I love learning about nature’s adaptations bc it’s always amazing.
I was watching the geese in the snowy grass today and they were there all day eating the grass.
However they left by dark and I wonder where do they spend the night? We’re located in a city .

[TheWildlifeBrothers]

As usual, another fascinating video and a ton of new information for me! Bird adaptations are among the most extreme of any animals on the planet, they never cease to amaze me. I had always wondered how they could stay warm given their anatomy, and this video explained it perfectly. Amazing work as always John!
- Harrison and Evan

[brigitteyim]

The intro made me think I was tuning into a Blue's Clues Holiday Special! So nostalgic <3
I'm studying for a Bio quiz and this has explained the concept so well. Thank you so much!

[rev]

Amoeba sisters brought me here! Subed🤩

[BuscandoFauna]

Hi friend. Excellent video explaining about the Rete mirabile, something key in the functioning of many animals. Thanks for sharing. Cheers

[BioBush]

Interesting! I didn't know the name for the structure, just the concept of countercurrent heat exchange. And I didn't know this same structure was used by so many types of animals! Cool facts, and your explanation was great. Thanks for digging up all this great information for us!

[tessa_xx]

Great video!


Isn't it a problem though, when the geese constantly lose body heat, warming up the cold blood?

[seharaliofficial]

n usual case what happens to arteries warm blood