i am tired and it is late and this will likely be posted in the morning but i saw something that was kind of inaccurate and now i'm teaching you all how duck feet don't get cold.
now. some people state they have "no nerves" and "no blood vessels" so they don't get cold. this is inaccurate of course because if it were true, their feet would be immobile (you need nerves to tell muscles to move and as referenced in the famous "duck test" ducks are known for walking) and dead (tissue dies without a blood supply and turns white or pallid). they have very few nerves and blood vessels, and their nerves are notably less heat-sensitive than ours are!
but that's not why they don't really get cold. the real reason is way fucking cooler.
as you know, blood goes all around the body. it takes veins on its trip back to the heart after giving our cells oxygen, and arteries all around the body to share the oxygen and nutrients it's picked up. duck feet have something special called a countercurrent heat exchange, or a rete mirable (latin for "miraculous net"), where the arteries and veins are woven together into what looks like a net and crisscross. thanks to the rete mirable, cold blood leaving the feet stays in contact with warm blood entering the feet, allowing for stasis of temperature. the warm blood is cooled, and the cool blood is warmed. thus, whatever coldness seeps into the duck through its small, limited number of blood vessels and thick foot scales doesn't really affect the duck!
additionally, as i've learned double-checking my duck facts, theyre not even the only critters that utilize the rete mirable. some animals, like sheep, use them in place of a carotid artery to help control blood pressure in their head. a useful little trick when so much of your time is spent looking down at the ground! plus, it helps keep their brain cool and can help prevent heat stroke as well as save water. this is also a mechanism which fish use to absorb oxygen from their gills, tuna and sharks can keep their muscles warm thanks to the rete, and aquatic mammals like seals and dolphins use a rete mirable for their flippers just like how ducks use theirs for their feet!
to circle back, the duck's feet still end up at around the same temperature as the water around it... there's not a lot of heat being lost. this is combined with how most of the foot's structure is stuff like tendons and bone (which doesn't freeze as easy as say, softer muscle mass or other soft tissues), even if it lost a lot of heat it'd be harder to freeze. human feet are much squishier than a duck's, so we're not as lucky.
this is all just a brief informative ramble, but i think this is an excellent example also of how nature is just. awesome. how animals are awesome. ducks are so common, no matter your local species, and yet when you look inside there's so much complexity. not even their feet- their feathers and the oil they groom them with form a complete watertight seal so that they stay entirely dry when they swim, insulated by their famously soft and warm downy feathers. the ancestors of ducks and geese ancestors once had teeth but lost them, so they sort of re-evolved teeth on their bills and tongues to filter food. there is so much going on inside that tiny little duck and all of that is the result of literal billions of years of blind flailing and sheer luck and just chance.
go appreciate a duck.
