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Thursday, January 19, 2012

Keeping your feet warm in the winter...

My thermometer said a brisk 15 Degree F morning when I prepared to leave my house this morning.  I took this into consideration as I dressed for the day, I put on a thin layer of socks and then a thick pair of wool socks.  I longingly eyed my battery powered foot warmers, but I thought they might be a moot point for only a couple of hours outside in the cold.  My friend and I rode by a pond with about ten mallards floating around, and she made the comment that their feet must be cold. Sure the down feathers work for the body, but what about those spindly legs?  No, battery powered foot warmers for ducks!  I spared her the lecture about the very interesting adaptations that birds have for surviving the cold weather, but I figured I would share it with you, since I'm sure inquiring minds wanted to know. 

The secret to ducks keeping their legs from freezing in the winter months is in the blood flow system.  They have a countercurrent exchange system in their veins and arteries.   Typicallyvenous blood transports cold blood back into the body from the feet--that cold blood would certainly cool down the body temperature and create hypothermia.  The warm arterial blood rushes from the heart.  Animals that are adapted to cold weather have their veins and arteries very close together.  The cold blood that comes from the feet towards the body, passes by the artery and picks up the heat from the arteries.  This effectively warms the blood heading back into the body, and cools the arterial blood so that it does not have that much heat to loose when it arrives at the foot.  This system keeps the blood in the foot cold at all times, and yet allows blood flow to keep the feet from freezing.     

This female common merganser is quite comfy on these cold days! On a side note, as more and more lakes start to freeze, keep your eyes out for these very cool ducks.  They tend to start hanging out in our neighboring waterways this time of the year.  The Brandywine Creek is always a good place to spot one or two.


Since I do not have such a spectacular adaptation, I'll stick with the battery powered foot warmers! You should try them if you are a inherently cold person, they do amazing things for you. 

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