Re: How do snakes breathe when they are eating?

Dear Jennifer:

Thank you for your question!  You are correct, some snakes do have movable 
windpipes.  When a snake opens its mouth wide and pulls its tongue back, you 
can see a hole down at the bottom of the mouth.  This hole is called the 
glottis, which is the opening and valve to the trachea, or windpipe.  When a 
snake breathes, it pulls air into the trachea and lung by expanding its rib 
cage, and pushes air back out of the lung by contracting its rib cage, 
because snakes have no diaphragm.  The diaphragm is the large muscle below 
our lungs that help us breathe.  As you pointed out in your question, when a 
snake eats large prey its mouth is totally filled and its airway can be 
blocked.  In order to still breathe, snakes can extend their glottis outward 
to the edge of the mouth beneath the prey.  The snake basically has a 
snorkel that it can stick out below its meal so it can still breathe while 
eating.  Snakes usually eat their prey by moving their bite forward on one 
side of their mouth, while holding on with the other side of their mouth.  
Once they get a good grip with the new side of the mouth, they use that side 
to hold and move their bite forward on the other side, and repeat until the 
prey is eaten.  Snakes need fewer breaths per minute than we do during 
eathing, due to their generally slower metabolism, but their movable glottis 
certainly helps. 

Take care!
Ingrid 

References:
Ernst, Carl H. and George R. Zug.  Snakes in Question: The Smithsonian 
Answer Book.  Washington: Smithsonian Institution Press, 1996.  This is a 
great basic guide to snakes.

Greene, Harry W.  Snakes: The Evolution of Mystery in Nature.  Berkeley: 
University of California Press, 1997.  This book has fantastic snake 
pictures.

Pope, Clifford H.  Snakes Alive and How They Live.  New York: Viking Press, 
1937.  An interesting picture of snakes from a naturalist's point of view.