Why can’t we swallow our food whole like snakes?

Snakes eat big meals and they don’t eat very often – a rattlesnake can eat a rat or a rabbit that weighs up to about one-and-a-half times its own weight, roughly the equivalent of me swallowing and digesting a 260-pound hamburger! Because the snake only needs to eat about three or four times its own weight every year, even if each meal is only about half its weight, five to ten meals a year are probably enough. And snakes don’t “unhinge” their jaws to do that!

The way this amazing feat works is easy to see when you watch a pet snake eat a mouse or see a snake feeding on TV. First, the skin stretches much more than ours does, and you can observe a bulge as a big meal moves from a snake’s throat down to its stomach. Second, our lower jaws are fixed together at the front, and you can feel where the two halves meet as a groove at the front of your chin (try it!). In snakes the two halves are not attached in front, so they can move separately, and their tips are visible as it swallows a meal. Finally, our jaws attach to our skulls (you can feel the joint move by pressing a finger right below an ear and opening your mouth), but in snakes there is an extra bone BETWEEN the jaw on each side and the skull, so that the mouth can open wider.

Rather than pulling or pushing food INTO its mouth like we do, a snake eats by walking its jaws OVER a meal in a side to side fashion. You can make a simple model to illustrate the difference by clasping your hands, holding your elbows against your sides, and moving your forearms up and down. This is like opening and closing our jaws, and the biggest thing we can eat has to go through the triangle formed by our body and our forearms. Now unclasp your hands (jaws not connected in front), unfold your arms at the elbows (your upper arm is now like that extra bone between a snake’s skull and its jaws), and you can move your forearms back and forth around a much bigger hole – just like a snake moves its jaws from side to side to pull its head over a big rat!