Turtles live in diverse habitats, thriving in both saltwater and freshwater environments. Some species spend their entire lives in the ocean, others are found exclusively in inland waterways, and a unique group occupies transitional zones where fresh and saltwater mix.
Ocean Dwellers
Sea turtles are marine reptiles that spend nearly their entire lives in the ocean, only returning to land for nesting. There are seven recognized species of sea turtles, including the green sea turtle, loggerhead, leatherback, hawksbill, Kemp’s ridley, olive ridley, and flatback. They possess specialized adaptations for aquatic existence. Their limbs have evolved into long, paddle-like flippers, providing powerful propulsion for swimming and diving.
Unlike their freshwater relatives, sea turtles cannot retract their heads or limbs into their shells. Their shells are streamlined and flattened, reducing drag as they move through water. Sea turtles have specialized salt glands near their eyes to excrete excess salt, often appearing as “tears.”
Inland Water Residents
Freshwater turtles inhabit a vast array of inland aquatic environments, such as rivers, lakes, ponds, and swamps. This group includes species like the painted turtle, snapping turtle, and red-eared slider. These turtles have webbed feet and claws, suited for navigating shallow waters and moving on land. Their shells are generally more domed than those of sea turtles, providing protection from predators.
Many freshwater species frequently leave the water to bask in the sun on logs or rocks to regulate body temperature. They are often omnivorous, consuming aquatic plants, invertebrates like snails and insects, and small fish. Freshwater turtles lay their eggs on land, typically in sandy or loose soil, and do not provide parental care to their offspring.
In-Between Habitats
Some turtle species have adapted to live in brackish water, which is a mixture of fresh and saltwater. These environments, often found in estuaries, mangrove swamps, and salt marshes, have fluctuating salinity levels. The diamondback terrapin (Malaclemys terrapin) is a key example thriving in these transitional zones.
Diamondback terrapins have specific physiological adaptations for varying salinity, including specialized salt glands to excrete excess salt. Their skin is also less permeable to salt compared to freshwater turtles, aiding ion balance. While they prefer intermediate salinities, these turtles can tolerate both freshwater and full-strength ocean water, showcasing flexibility in these dynamic habitats.