What Do Sea Turtles Eat? Diets From Seagrass to Jellyfish

Sea turtle diets at a glance

There are seven living species of sea turtle, and each has its own feeding niche. That is one reason several species can share the same coasts without competing much for food.

Green turtles: the seagrass grazers

The green sea turtle is the only sea turtle that is a herbivore as an adult. It feeds on seagrass meadows and on seaweeds (marine algae) growing on rocks and reefs. In the Caribbean, turtle grass is a staple; in Hawaii, where seagrass is scarce, green turtles feed mostly on algae.

Its beak has a finely serrated edge that cuts plants like a pair of shears. Green turtles crop seagrass close to the base and often return to the same patches, which keeps the young, tender, more nutritious leaves growing. Pigments from this plant diet are thought to tint the turtle’s body fat green, which is where the species gets its name.

A diet of seagrass is low in energy, so green turtles grow slowly and can take 20 years or more to mature. Their grazing matters to the ecosystem: well-grazed meadows stay healthy and support many fish and invertebrates.

Leatherbacks: jellyfish specialists

The leatherback sea turtle, the largest of all turtles, feeds almost entirely on jellyfish, salps, siphonophores and other soft, gelatinous animals. This food is mostly water and very low in calories, so a leatherback has to eat enormous amounts. A study of leatherbacks feeding off Nova Scotia, Canada, estimated that they can eat about three-quarters of their own body weight in jellyfish in a single day when prey is plentiful.

Leatherbacks have no crushing jaws. Instead they have a sharp, notched edge on the upper jaw and hundreds of backward-pointing spines lining the mouth and throat, which stop slippery prey from escaping. To find food, leatherbacks follow jellyfish blooms across whole oceans, from the tropics to cold waters off Canada, Norway and New Zealand, and dive hundreds of meters deep.

Hawksbills: sponge eaters of coral reefs

The hawksbill sea turtle is the only reptile known to specialize in sponges. In the Caribbean, sponges often make up 70–95% of its diet, even though many contain sharp, glass-like needles of silica and toxic chemicals. Hawksbills are picky and feed on a limited number of sponge species.

Their narrow head and pointed, hooked beak let them reach into cracks in the reef. They also eat soft corals, zoanthids, sea anemones, jellyfish, algae and other invertebrates. More detail is in what do hawksbill turtles eat?

Loggerheads, ridleys and flatbacks: shell crushers

The loggerhead sea turtle has a huge head and powerful jaw muscles, which it uses to crack hard-shelled prey such as crabs, horseshoe crabs, conchs, whelks, clams and sea urchins. It also eats jellyfish, fish, sponges and some seaweed. Loggerheads are flexible feeders and take whatever slow-moving animals are common where they live.

Kemp’s ridley, the smallest sea turtle, feeds mainly on crabs, especially blue crabs, in shallow waters of the Gulf of Mexico and the US Atlantic coast. The olive ridley is more of a generalist and eats crabs, shrimp, lobsters, jellyfish, fish and algae. The flatback, found only around Australia and New Guinea, eats sea cucumbers, soft corals, jellyfish, mollusks and other soft-bodied animals on the sea floor.

What do baby sea turtles eat?

Newly hatched sea turtles do not need to eat right away. They hatch with leftover yolk inside their bodies, which fuels their first few days of swimming as they head out to sea.

Once offshore, young turtles of most species drift with currents, often among floating mats of sargassum seaweed. There they eat small animals and plants they find near the surface, such as tiny crustaceans, fish eggs, small jellyfish, insects blown out to sea and bits of seaweed. Young green turtles are omnivores at this stage and only switch to a mostly plant diet when they move to coastal feeding grounds, usually at about 3–5 years old.

How sea turtles eat without teeth

Like all turtles, sea turtles have no teeth. They have a sharp, horny beak made of keratin, the same material as fingernails, and its shape matches each species’ diet. They also cannot pull their heads into their shells, and they swallow food without chewing.

Sea turtles drink seawater with their food. To get rid of the extra salt, they have large salt glands behind each eye that release a thick, salty fluid, which is why nesting turtles on a beach can look as if they are crying. The leatherback, which swallows great amounts of salty jellyfish, has especially large salt glands.

Myths and facts about sea turtle food

A common myth is that sea turtles only eat jellyfish. In fact only the leatherback depends on them almost completely; other species eat seagrass, sponges, crabs or clams. Another misconception is that sea turtles are immune to jellyfish venom. In reality, their tough, scaly skin and horny beak simply keep most stinging cells from reaching living tissue.

Plastic is a real and serious problem. Floating bags, balloons and sheets can look like jellyfish, and plastic that has been in the sea for a while grows a film of algae that may smell like food. Swallowed plastic can block a turtle’s gut. Plastic ingestion has been recorded in all seven species of sea turtle, and it is now seen as one of the threats these animals face worldwide.