How do armadillos protect themselves by wedging into their burrows?

When threatened, some species of armadillo retreat to their burrows as a primary defensive strategy. Once inside, these animals flex their back plates to wedge themselves into the burrow so firmly that they become virtually impossible for a predator to pull out.1

This behavior is distinct from other defensive tactics used by armadillos, such as rolling into a ball, "playing dead," or, in the case of the pink fairy armadillo, using the vertical rear of its carapace as a flat plate to plug the burrow entrance entirely.1