Box turtles, regardless of how many toes they have, are called “box turtles” because of one unique trait they all share in common.
That trait is quite amazing. Every box turtle is able to pull all of its body parts – head, tail, legs and feet and claws, all of it – inside its shell and lock it all inside.
When a box turtle decides to “close down” – for example, to hide from a predator or a perceived threat – it pulls its top shell (carapace) and its bottom shell (plastron) together so they meet at all points around the box turtle’s body.
The reason the box turtle can get its carapace and plastron to touch completely while other turtles can’t is because of a unique hinge that occurs about halfway down on the plastron. This hinge tilts each half of the plastron up just slightly to meet the carapace for a complete shell closure….kind of like a clam, only the occupant within has legs and a face.
This hinge muscle is very, very strong – it is said that once a box turtle decides to “clam up,” you can’t pry it open without causing the turtle significant harm (in other words, please don’t ever try this!!).