Sea turtles are ancient marine reptiles. Unlike their terrestrial and freshwater counterparts, sea turtles have evolved specialized diets tied to their diverse marine habitats. Each species has distinct feeding preferences, adapting to resources in their specific ocean environments. Their varied diets highlight that there is no single answer to what all sea turtles eat.
Diets of Sea Turtle Species
Sea turtle diets vary significantly, reflecting their ecological niches.
Adult green sea turtles are primarily herbivores, consuming seagrasses, seaweeds, and algae. Their serrated beaks scrape algae from rocks and tear marine vegetation. Juveniles are omnivores, feeding on plants and small invertebrates like crustaceans and worms.
Loggerhead sea turtles are carnivores with powerful jaws for crushing hard-shelled prey. Their diet consists of bottom-dwelling invertebrates like crabs, conchs, whelks, and horseshoe crabs. Young loggerheads are opportunistic feeders, consuming organisms in floating Sargassum algae, including small crustaceans and mollusks.
Hawksbill sea turtles are specialized “spongivores,” feeding almost exclusively on sea sponges. Their narrow, bird-like beaks reach into coral reef crevices to extract sponges. They may also consume marine algae, corals, and small invertebrates.
Leatherback sea turtles are “gelatinivores,” feeding almost entirely on soft-bodied, gelatinous prey. Their diet includes jellyfish and other invertebrates like tunicates and sea squirts. These deep-diving turtles forage in pelagic environments where these organisms are abundant.
Kemp’s Ridley sea turtles are carnivores, preferring crabs. They also consume other invertebrates like shrimp, mollusks, and jellyfish. As adults, they are benthic feeders, searching for food on the seabed.
Olive Ridley sea turtles are omnivores, consuming a variety of food. Their diet includes crabs, shrimp, lobster, sea urchins, jellyfish, and algae. They can dive to considerable depths to forage for benthic invertebrates.
Specialized Feeding Adaptations
Sea turtles possess physical adaptations for their specific diets. Without teeth, their keratinous beaks are shaped for different food sources, such as the serrated beaks of green sea turtles that tear seagrasses and scrape algae from surfaces.
Loggerhead sea turtles have large heads and strong jaws. These powerful jaws crush the hard shells of prey like crabs and mollusks. Their robust mouth structure breaks down tough exoskeletons.
Hawksbill sea turtles have a sharp, narrow beak, resembling a bird’s, ideal for probing into coral reef crevices. This beak extracts sponges and other organisms from tight spaces. Their digestive systems process the glass-like spicules and toxins found in sponges.
Leatherback sea turtles have delicate, scissor-like jaws with two sharp cusps. These cusps pierce and hold soft-bodied prey like jellyfish. Their mouths and throats are lined with sharp, backward-pointing spines called papillae, which prevent slippery prey from escaping.
Kemp’s Ridley and Olive Ridley sea turtles have jaws adapted for crushing and grinding. These robust jaw structures consume hard-shelled organisms like crabs and mollusks found on the seabed. The Flatback sea turtle also has slightly serrated jaws, supporting its omnivorous diet of sea cucumbers, jellies, and various crustaceans.
Ecological Role of Sea Turtle Diets
Sea turtles play an important role in maintaining the health of marine ecosystems through their feeding habits. Their diverse diets contribute to the intricate web of life in the oceans. By consuming specific organisms, sea turtles regulate populations and facilitate nutrient cycling.
Green sea turtles, by grazing on seagrass beds, act as aquatic “lawnmowers.” This grazing prevents seagrass from becoming overgrown, promoting the growth and health of these habitats. Healthy seagrass beds serve as nurseries for many marine species and contribute to carbon sequestration.
Hawksbill sea turtles, by consuming sponges, prevent these fast-growing organisms from outcompeting slower-growing corals. Their feeding habits contribute to the biodiversity and health of coral reefs, which are habitats for countless marine organisms.
Leatherback sea turtles, as consumers of jellyfish, help control jellyfish populations. An overabundance of jellyfish can negatively impact fish populations by preying on fish eggs and larvae. Leatherbacks contribute to a balanced marine food web.
Loggerhead sea turtles, with their diet of hard-shelled crustaceans, contribute to nutrient recycling in ocean bottom ecosystems. By breaking up prey shells, they increase the rate at which these materials disintegrate, releasing nutrients back into the environment. All sea turtles also transport nutrients across vast distances through their migrations.
Threats to Their Food Supply
Sea turtles face challenges that impact their ability to find and consume their natural diets. Ocean pollution, particularly plastic, poses a significant threat. Many sea turtle species, especially leatherbacks, mistake plastic for jellyfish, leading to accidental ingestion. Ingesting plastic can cause blockages, internal injuries, and a false sense of fullness, potentially leading to starvation.
Habitat destruction also compromises their food supply. The degradation of foraging grounds, such as seagrass beds and coral reefs, due to coastal development, pollution, and climate change, reduces the availability of their food sources. Changes to coral communities from bleaching events and land-based runoff negatively affect hawksbill diets.
Climate change impacts sea turtle food availability by altering ocean temperatures and currents, which can shift prey distribution. Warming waters can affect coral reefs, a food source for some species. Overfishing depletes prey populations, particularly for carnivorous species like loggerheads and Kemp’s Ridleys, as commercial fisheries compete for similar food resources. Accidental capture in fishing gear, known as bycatch, also injures or kills turtles, preventing them from feeding.