Sea turtles are ancient marine reptiles globally distributed across tropical and temperate waters, known for their lengthy migrations and long lifespans. Their dietary habits are highly diverse, depending entirely on the species and the specific stage of the turtle’s life. Understanding what sea turtles eat requires recognizing the distinct ecological roles each of the seven species plays in the ocean.
The Simple Answer: Species-Specific Diets
The seven extant species of sea turtles are broadly categorized into three adult feeding groups: one herbivore, a group of specialized carnivores, and a group of generalist omnivores. The Green Sea Turtle (Chelonia mydas) is the single species that, as an adult, primarily consumes plants, making it the only herbivore in the group.
The specialized carnivores include the Leatherback and Hawksbill turtles, each focusing on a narrow range of animal prey. The remaining species, such as the Loggerhead, Kemp’s Ridley, Olive Ridley, and Flatback turtles, are considered generalist omnivores or carnivores. These turtles utilize a wider, more flexible diet of both animal and, occasionally, plant matter.
The Unique Case of the Green Sea Turtle
The Green Sea Turtle is the only adult sea turtle species that becomes almost exclusively herbivorous. Its common name is derived not from the color of its shell, but from the greenish hue of its body fat, caused by this plant-heavy diet. Adult Green Sea Turtles primarily graze on seagrasses and marine algae in shallow coastal areas and lagoons.
Instead of teeth, it has a finely serrated beak with sharp edges, which functions like a cutting blade to shear through fibrous seagrasses and scrape algae off rocks. This species also has a longer digestive tract compared to other sea turtles, allowing for the extended time needed to break down cellulose and efficiently absorb nutrients. This dietary preference allows the Green Sea Turtle to act as a grazer, actively maintaining the health and diversity of seagrass meadows.
Specialized Carnivores and Omnivores
The other six species have highly specific diets focused almost entirely on animal prey.
Leatherback and Hawksbill Turtles
The Leatherback Sea Turtle (Dermochelys coriacea), the largest of all sea turtles, is a specialized carnivore, feeding almost exclusively on soft-bodied invertebrates, primarily jellyfish and tunicates. Its mouth and esophagus are lined with backwards-pointing spines, called papillae, which help it capture and swallow slippery prey while expelling excess water. Leatherbacks may consume up to 73% of their own body weight in gelatinous prey daily.
The Hawksbill Sea Turtle (Eretmochelys imbricata) is known as a spongivore, feeding almost exclusively on sea sponges, which are toxic to most other animals. It uses its narrow, pointed beak to reach into coral reef crevices and tear off pieces of sponge.
Loggerhead and Ridley Turtles
The Loggerhead Sea Turtle (Caretta caretta) is a generalist carnivore with a preference for hard-shelled invertebrates. Its head and powerful jaw muscles are adapted for crushing the shells of prey like whelks, conchs, crabs, and horseshoe crabs.
The Kemp’s Ridley (Lepidochelys kempii) and Olive Ridley (Lepidochelys olivacea) sea turtles are both bottom-feeding omnivores that primarily target benthic invertebrates. Kemp’s Ridleys focus heavily on crustaceans, such as crabs and shrimp, utilizing their crushing jaws to access the soft meat inside the hard exoskeletons. Olive Ridleys are known for their broad, opportunistic diet that includes crabs, mollusks, shrimp, and occasionally algae and jellyfish.
Dietary Shifts Across the Lifespan
A significant factor in sea turtle diet is the concept of ontogenetic dietary shift. All sea turtle species begin their lives as small hatchlings that spend their early years in the open, or pelagic, ocean. During this time, every species, including the Green Sea Turtle, is carnivorous or omnivorous, feeding on small floating organisms like plankton, small crustaceans, and other soft-bodied invertebrates.
As the turtles grow, they move from the open ocean to coastal, or neritic, habitats, which triggers the shift to their specialized adult diets. For the Green Sea Turtle, this transition involves a gradual shift from a protein-rich carnivorous diet to the fibrous, herbivorous diet of seagrass and algae. The other species also transition from their generalist juvenile diets to the specific prey of adult life, such as the Loggerhead moving from small open-ocean prey to large, bottom-dwelling hard-shelled mollusks.