Why Horses Eat Tree Bark

If you own horses and have trees in your pasture you have probably witnessed the phenomenon of the bark disappearing from them.  After many hours of research on the web and reading through my selection of horse books I found that no one really knows why they do it. Until now...sort of.  I thought about this for a long time.  I pondered for days, observing them eating the bark.  I watched Snickers get let out his pen every morning only to walk over to the Russian Olive right outside his pen, the kind with very large thorns, and munch a few leaves and small branches.  Hmmm....he did this every day last summer. 

First they started with the larger trees, chewing the bark at chest height all the way around.  In our pasture a number of sucker trees have begun to grow and are now about 3 feet high.  When the pasture turned brown in the fall they finally began eating the sucker trees - thank you! This really confounded me.  Wouldn't the smaller trees be softer, more amenable to eating  than bark?  Wouldn't the bark be bitter?  Do they like bitter? 

Then, all at once it came to me:  it came to me as I was chewing on a pen cap which I tend to do when thinking...  all my pens and the ends of my sunglasses have been chewed and masticated until destroyed.  In school I chewed my pencils, which were much more satisfying!  That oh so wonderful crunch as the pencil wood gave way, the bitter taste of the paint, the occasional splinter.... hmmm.  In times of aggravation or deep thought I need to chew something, and gum just doesn't do it.  Hmmm....are you thinking what I'm thinking?  I think I can understand why horses eat tree bark and chew on wood.  Because it feels good!