Sea turtles, majestic reptiles gliding through the world's oceans, exhibit a fascinating range of dietary habits. What a sea turtle eats depends upon the species. Their diets are as diverse as the marine environments they inhabit, playing crucial roles in maintaining the health and balance of these ecosystems. From the specialized diets of the hawksbill and leatherback to the omnivorous tendencies of the olive ridley, each species has adapted to thrive on a unique menu.
Dietary Specializations Among Sea Turtle Species
The seven existing species of sea turtles display remarkable dietary differences:
- Green Turtle: Adults are referred to as herbivores although as hatchlings they are omnivores. Their diet consists primarily of algae, seagrasses, and seaweed. Greens have a finely serrated (sawlike) beak that allows them to scrape algae off rocks and tear grasses and seaweeds. The seagrass Thalassia testudinum is commonly known as "turtle grass" because in some areas like the Caribbean, green sea turtles eat it almost exclusively. Herbivores like the green sea turtle are important for maintaining the health of coral reefs. Without them eating algae, corals can be overgrown and die from the algae which out-competes them.
- Leatherback: Sometimes referred to as gelatinivores (eating gelatinous prey) because their diet consists exclusively of jellies and other soft-bodied invertebrates like tunicates and sea squirts. They have 2 sharply pointed cusps, one on the upper and one on the lower jaw that allows them to pierce jellies and other soft-bodied organisms. They also have sharp, downward curving spines called papillae in their mouth and throat which help move prey to their stomach. Because leatherbacks primarily eat jellyfish, they are attracted to plastic bags which resemble jellies when floating in the water. Eating them often leads to death.
- Loggerhead: Adults are carnivores, eating crabs, conchs, whelks, and horseshoe crabs. Hatchlings are omnivores, eating both plant and animal material. Loggerheads have a massive head and strong jaws which enable them to crush hard-shelled prey.
- Hawksbill: Often referred to as spongivores because of their specialized diet which consists almost exclusively of sponges. The hawksbill has a sharp, narrow "bird-like" beak that allows them to reach within crevices on the reef. Sponges contain spicules (glass-like spines) and toxins which the hawksbills immune to, making less competition for this food source. They are also particular about the types of sponges they eat which gives rare sponges an opportunity to grow creating greater diversity on the reef. Hawksbills for example, are mainly found on and around coral reefs where their main prey sponges are found.
- Olive Ridley: An omnivore, these turtles eat a variety of animals and plants including crabs, shrimp, lobster, urchins, jellies, algae, and fish.
- Kemp's Ridley: A carnivore that eats crabs, fish, jellies, shrimp, and a variety of molluscs.
- Flatback: Flatbacks are mainly carnivorous, feeding in shallow waters on soft bottoms. Nudibranches, or sea slugs, are a favourite of flatbacks.
The Role of Diet in Sea Turtle Habitats and Ecosystems
Sea turtles are adapted to live in the ocean, with some unique features that help them to survive in the marine environment. What a sea turtle eats depends upon the species. The diet of each sea turtle species is closely linked to its habitat and plays a vital role in maintaining the health and balance of marine ecosystems. Each sea turtle species has uniquely evolved to different environments and available food depending. Sea turtles therefore play a vital role in ocean ecosystems, affecting the diversity and function of ocean habitats by what they eat.
- Coral Reefs: Hawksbills, with their specialized diet of sponges, help maintain the diversity of coral reefs. By selectively feeding on certain sponge species, they prevent any single species from dominating, creating opportunities for rare sponges to grow and fostering greater biodiversity.
- Seagrass Beds: Green turtles, as herbivores, graze on seagrass, preventing it from overgrowing and shading out other species. This grazing promotes healthy seagrass beds, which serve as important nurseries for many marine species. Greens forage among seagrass beds and nearshore habitats.
- Open Ocean: Leatherbacks, as deep divers, are found in pelagic (open ocean) environments where they feed exclusively on jellyfish and other soft-bodied invertebrates that float in the water column. Some sea turtles undertake impressive migrations to find food. The leatherback has been tracked crossing the entire Pacific Ocean from Asia to the US West coast to forage on swarms of jellyfish off the coasts.
Mouths and Jaws: Adaptations for Diverse Diets
Sea turtle mouths and jaws are also shaped differently depending on their particular diet. The physical characteristics of sea turtles, particularly their mouths and jaws, are perfectly adapted to their specific diets. Sea turtles do not have teeth to help them eat; instead, they have keratinous beaks with varying structures to accommodate their diets.
- Green Turtles: Greens sea turtles have a beak with finely serrated edges, like the teeth of a saw, which enable them to tear seagrasses and scrape algae off of hard surfaces. Green sea turtles have finely serrated beaks that enable them to scrape algae off rocks and tear grasses and seaweeds.
- Loggerheads: Loggerheads have strong, massive jaws which enable them to crush hard-shelled prey like conchs and whelks. Loggerhead sea turtles have large heads and incredibly strong jaws that allow them to crush hard-shelled prey.
- Hawksbills: The hawksbill has a sharp, narrow "bird-like" beak that allows them to reach within crevices on the reef. Hawksbill sea turtles have sharp, narrow beaks that enable them to reach inside crevices on a reef.
- Kemp’s ridley and olive ridley: Kemp’s ridley and olive ridley sea turtles both have well-adapted jaws for crushing and grinding, allowing them to eat hard-shelled organisms.
- Flatback: Flatback sea turtles have slightly serrated jaws that allow them to eat a wide variety of marine organisms.
- Leatherbacks: Leatherbacks have sharp, pointed cusps on their jaws which enable them to pierce and hold onto jellyfish. Leatherback sea turtles have delicate, scissor-like jaws, with two sharp cusps on both parts of their jaw that allow them to pierce soft-bodied organisms, like jellyfish. They also have sharp, downward curving spines called papillae in their mouth and throat which help move prey to their stomach. Leatherbacks, along with a few other species, have an interesting - and slightly terrifying - adaptation called papillae that line the inside of the esophagus. These backward-pointing spines make it certain that once a jellyfish is caught in the turtle’s jaws, it will not be able to escape.
Dietary Shifts During Development
The diet of hatchlings varies from that of adults. The diet of sea turtles can change as they grow. For example, green sea turtles tend to transition their diets as they grow older. When they are juveniles, they are omnivores and eat a mix of fish, invertebrates, and leafy greens. As they grow, they typically become herbivores, eating almost entirely plants, such as seagrass and algae. Kemp’s ridleys are omnivores at the beginning of their lives, feeding on seaweed and small creatures like crabs and snails.
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Threats to Sea Turtle Diets
Unfortunately, sea turtles may also accidentally consume plastic marine debris and other items that they confuse for their food in the ocean. There have even been cases of rescued sea turtles found with ingested balloons. One of the most significant threats to sea turtles is the increasing amount of plastic pollution in the ocean. Because leatherbacks primarily eat jellyfish, they are attracted to plastic bags which resemble jellies when floating in the water. Eating them often leads to death. For leatherback sea turtles in particular, plastic waste is incredibly dangerous. When floating in the water, plastic debris looks extremely similar to jellyfish, and leatherbacks often eat plastic by mistake.
Conservation Efforts and the Future of Sea Turtle Diets
NOAA Fisheries and our partners are dedicated to protecting and recovering green turtle populations worldwide. We use a variety of innovative techniques to study, protect, and recover these threatened and endangered populations. Given the threats facing sea turtles, conservation efforts are crucial to protect these animals and their diets. These efforts include:
- Protecting Habitat and Designating Critical Habitat: Once a species is listed under the ESA, NOAA Fisheries evaluates and identifies whether any marine areas meet the definition of critical habitat. Those areas may be designated as critical habitat through a rulemaking process. A critical habitat designation does not set up a marine preserve or refuge.
- Reducing Bycatch: NOAA Fisheries is working to reduce the bycatch of sea turtles in commercial and artisanal fisheries. Our efforts are focused on documenting bycatch, understanding how, why, and where sea turtles are bycaught, and how to reduce that bycatch. We work with partners and industry to develop modifications to fishing gear and practices to reduce bycatch and/or to reduce bycatch injuries.
- Responding to Strandings and Entanglements: A stranded sea turtle is one that is found on land or in the water and is either dead or is alive but unable to undergo normal activities and behaviors due to an injury, illness, or other problem. Most strandings are of individual turtles, and thousands are documented annually along the coasts of the United States and its territories. Organized networks of trained stranding responders are authorized to recover dead turtles or assist live turtles and document important information about the causes of strandings. These networks include federal, state, and private organizations. The actions taken by stranding network participants improve the survival of sick, injured, and entangled turtles while also helping scientists and managers expand their knowledge about threats to sea turtles and causes of mortality.
- Reducing Marine Debris: Reduce marine debris and participate in coastal clean-up events. Responsibly dispose of fishing line - lost or discarded fish line kills hundreds of sea turtles and other animals every year.
- Responsible Boating: Boat strikes are a serious threat to sea turtles. When boating, watch for sea turtles in the water, slow down, and steer around them. If you encounter them closer than 50 yards, put your engine in neutral to avoid injury.
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