Snakes have a unique ability to unhinge their jaws, allowing them to open their mouths extremely wide. This, combined with flexible ligaments and muscles in their head, neck, and jaws, enables them to stretch their mouths around prey items that are much larger than their own heads. Once the prey is inside the snake's mouth, it uses a combination of muscular contractions and the movement of its lower jaw bones to slowly work the prey down its throat and into its stomach.
