What is the difference between a turtle and a tortoise?

Can you spot the differences between a water turtle (left) and a land turtle (right)? (Photo: LL28 and Francesco Riccardo Iacomino via Getty Images)

Turtles are reptiles with a protective shell, but there are important differences between species. How can you recognize these distinctive features? What fundamentally distinguishes common turtles from land turtles?

“All tortoises are turtles, but not all turtles are land turtles,” Sydney Fenn, a reptile keeper at the Columbus Zoo, told Live Science. Reptiles commonly referred to as turtles are mostly aquatic, while land turtles are terrestrial, according to Genius Vets in San Diego.

Many anatomical features of these animals are related to their habitat. For example, water turtles have flattened shells, which facilitates movement in rivers, lakes and oceans. In land species, as experts note, the shells are more often arched, which increases their stability on a hard surface.

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“When tortoises move, they sometimes roll over on their backs, and the domed shell helps them return to their original position,” Fenn added. “The shape also creates additional internal space, allowing some species to completely tuck their limbs under the protection of the shell.”

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There are exceptions to these rules, however. For example, “the African pancake turtle lacks the characteristic hard, dome-shaped shell,” said Brett Baldwin, curator of herpetology at the San Diego Zoo. “Its flexible, flattened shell, low in calcium, allows it to quickly hide in rocky crevices by expanding its shell to anchor itself.”

Species that live in both water and land have webbed feet for efficient swimming and walking on land. Fully aquatic species, such as sea turtles, have flipper-like limbs. In contrast, land-dwelling species have rounded feet and shortened limbs, according to the San Diego Zoo.

“Their short, powerful limbs help them support the weight of their shells when they live on land,” Baldwin said. Fenn added that desert tortoises have “wide, camel-like feet that help them move through the sand.”

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(Photo: David A. Northcott via Getty Images)

Unlike its domed-shelled relatives, the pancake turtle (Malacochersus tornieri) has a flat, thin, flexible shell.

(Photo: Mara Brandl via Getty Images)

The desert tortoise (Gopherus agassizii) uses its wide feet to move across sandy landscapes.

(Photo: wildestanimal via Getty Images)

A hawksbill turtle (Eretmochelys imbricata) displays a flat shell optimized for swimming in the waters of Kimbe Bay, Papua New Guinea.

According to Fenn, most aquatic turtles are omnivorous, while land species are primarily herbivorous. The high mobility of the former in the water allows them to hunt, while land species are limited to plant food due to their slowness.

However, “terrestrial turtles do occasionally consume animal matter,” Fenn said. “They don’t actively hunt, but they may eat insects or carrion when they have the opportunity.” Some aquatic species, such as green sea turtles (Chelonia mydas), are entirely herbivorous, according to NOAA.

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According to IFAW, turtles are found on every continent except Australia and Antarctica, preferring warm regions like deserts and the tropics. Marine species, as Genius Vets notes, are found everywhere except Antarctica. Fenn emphasized that aquatic environments help some species survive cold periods.

“They can dive into deeper waters with higher temperatures in winter,” she explained. “Some species can breathe underwater through a cloaca, which allows them to hide under the ice. This adaptation expands their habitat.”

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Charles K. Choi. Social Media. Live Science Contributor. Charles K. Choi is a freelance journalist who contributes to Live Science and Space.com. His work covers anthropology, astronomy, physics, zoology, and general science. He holds a master's degree in journalism from the University of Missouri and a bachelor's degree from the University of South Florida. He has visited every continent, including unique expeditions to Tibet, the Galapagos, and Antarctica.

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