How wide is your gape?

Did you know that snakes are the only species that eat prey larger than their heads in one gulp?  True, there are many species that eat things in one gulp - like fish and amphibians.  These critters sneak up on prey and swallow without chewing.  However, they are what we call gape-limited: they can only eat things that fit in their mouth.  Fish eat smaller fish; frogs eat smaller frogs.  















And, there are many more species that eat things larger than their gape.  To overcome this difficulty some tear off bite-sized morsels.  Nature documentaries love to show eagles flaying the flesh off of helpless prey.  Still other predators liquefy their prey's insides and suck out the juices.  This is the method used by sea stars. They use their suction cup legs to pry open a mussel, insert their stomach into the opening, release their digestive juices thus liquefying the tissue, and finally bring their stomach, food and all, back inside their own body. 

While these methods of eating are fascinating, they still aren't as visually impressive as a feeding snake.
Snakes, don't chew, they don't suck up liquefied tissue, and they are not limited to small bite-sized prey.  Most people are familiar with the picture of a boa (or some other constrictor) wrapped around prey that looks too large to eat.  So how do they manage?  Snakes have a unique and very complex jaw.  A snake's skull contains multiple links and joints (kind of like being double jointed) which allows a high degree of flexibility, three-dimensional movement, and a very wide gape.  Interestingly, unlike humans, the jaws are not fused to the braincase (allowing for flexible upper jaw movement) and the two halves of the lower jaw are not fused together but rather are connected by muscle and skin; this means they don't have a bony chin and allows them to move each half of their mouth independently. 

Alfie, my corn snake, modeled this feat of feeding for me last week:

You can see the drastic change in jaw and neck width through this sequence of pics.  Amazing.  (She then curls up in her paper towel tube and enters a state of lethargy for about 3 days to digest.)