Which turtle can completely close its shell using a hinged plastron?

The turtle that can completely close its shell with a hinged plastron is the box turtle. Its lower shell, or plastron, has movable sections that fold upward against the upper carapace, sealing the head, legs, and tail inside.

This unusual defense explains the name “box turtle.” When threatened, the turtle withdraws its limbs and pulls the hinged plastron tightly closed. The result is a hard, box-like shield that makes it difficult for predators to reach the soft body. North American box turtles generally belong to the genus Terrapene, while several Asian box turtles belong to different genera.

A common mistake is calling a box turtle a tortoise. Box turtles are turtles in the family Emydidae, not true tortoises, even though many are largely terrestrial. Sea turtles and snapping turtles cannot seal themselves inside their shells in the same way.

The shell is living bone covered by keratin scutes and is fused to the turtle’s ribs and vertebral column. Box turtles are slow-growing and long-lived; their vulnerability to roads, habitat loss, and collection makes many populations difficult to replace.