Turtles are ancient reptiles, with a lineage tracing back over 220 million years, predating crocodiles and snakes. They are recognized by their unique protective shell, an integral part of their skeleton formed from fused ribs. Their presence spans diverse environments globally, from vast oceans to arid deserts.
The Global Count of Turtle Species
The exact number of recognized turtle and tortoise species worldwide is dynamic, reflecting ongoing scientific discovery and reclassification. Currently, over 350 species are recognized, encompassing both land-dwelling tortoises and various aquatic turtles. This count is broadly categorized by their primary habitats.
Marine Turtles: Ocean Wanderers
Sea turtles are highly adapted for a life spent almost entirely in the ocean; only adult females typically return to land for nesting. Seven recognized species exist: the green, loggerhead, leatherback, hawksbill, olive ridley, Kemp’s ridley, and flatback sea turtles. They are distributed across all the world’s oceans, excluding polar regions, and many undertake extensive migratory journeys.
Their specialized adaptations include streamlined shells and powerful, paddle-like front flippers for agile swimming. Unlike terrestrial relatives, sea turtles cannot fully retract their heads or limbs, which facilitates rapid movement. They possess salt glands to excrete excess salt, allowing them to thrive in saltwater environments without needing freshwater sources. A slow metabolic rate and specialized respiratory systems enable them to remain submerged for extended periods. While some species are omnivorous, others have specialized diets; for instance, green sea turtles eat seagrass and algae, while leatherbacks feed on jellyfish.
Freshwater Turtles: Diverse Aquatic Life
Freshwater turtles are the most numerous and diverse chelonian group, inhabiting a wide array of aquatic environments such as rivers, lakes, ponds, and wetlands. Their adaptations include webbed feet for efficient swimming and diving. Many species possess flatter, more streamlined shells compared to tortoises, reducing drag. Some species, like the spiny softshell turtle, absorb oxygen through their skin, while others utilize cloacal respiration to extract oxygen from water.
This group exhibits significant diversity in size, appearance, and dietary preferences. The common snapping turtle is known for its powerful jaws, while the red-eared slider is often found basking. Other notable species include the painted turtle, with vibrant shell markings, and various mud and musk turtles. Most are omnivorous, consuming aquatic plants, insects, snails, and small fish, though some lean towards carnivorous or herbivorous diets. Like sea turtles, freshwater turtles lay their eggs on land, often burying them near water bodies.
Land Tortoises: Terrestrial Survivors
Tortoises are exclusively terrestrial, living their entire lives on land and not adapted for aquatic environments. They are found across diverse habitats, from arid deserts to humid forests, on every continent except Australia and Antarctica. Their physical characteristics are well-suited for terrestrial life. Tortoises typically have sturdy, elephant-like legs and unwebbed feet, supporting their heavy bodies and high-domed shells. These limbs are equipped with strong claws for digging burrows to escape extreme temperatures and predators.
Their shells are high-domed and thick, offering substantial protection. Prominent species include the giant Galapagos tortoises, known for their immense size and longevity, and the Sulcata tortoise, one of the largest mainland species. Other well-known examples are the Russian tortoise and Mediterranean tortoises like the Greek and Hermann’s. Most are herbivorous, feeding on grasses, leaves, flowers, and fruits, though some, like the red-footed tortoise, may occasionally consume animal matter. Tortoises are recognized for their remarkable longevity, often living for many decades, with some exceeding 150 years.