The loggerhead sea turtle (Caretta caretta), named for its large head and powerful jaws, is an omnivorous marine reptile with a diet that varies throughout its life stages and geographic location. This article delves into the dietary habits of loggerheads, exploring what they eat from hatchling to adulthood, and how their diet is influenced by their environment.
Loggerhead Sea Turtle: An Introduction
The loggerhead sea turtle is a globally distributed species found in temperate and tropical regions of the Pacific, Atlantic, and Indian Oceans, as well as the Mediterranean Sea. It is the world's largest hard-shelled turtle, with adults measuring 70-110 cm in length and weighing up to 200 kg. Loggerheads are listed as Vulnerable by the International Union for Conservation of Nature (IUCN).
Diet of Loggerhead Sea Turtles
Loggerheads are opportunistic feeders, consuming a wide variety of prey. Their diet changes as they grow, reflecting their changing habitat and nutritional needs.
Hatchlings
Loggerhead hatchlings, measuring approximately 25 mm long and weighing 15-20 g, have a different diet than adults. As omnivores, hatchlings eat both plant and animal material. They often associate with mats of Sargassum algae in the open ocean, where they feed on small animals living in these mats, including barnacles, crab larvae, fish eggs, and hydrozoan colonies. They also consume prey carried by the wind to the mats, such as ants, flies, aphids, leafhoppers, and beetles.
Juveniles
Juvenile loggerheads continue to inhabit oceanic habitats until they reach 7-12 years of age, after which they migrate back to coastal waters. During their time in the open ocean, they feed on a variety of floating items, including jellyfish and other squishy invertebrates like tunicates and sea squirts. Unfortunately, they also consume trash and other debris discarded by humans, often mistaking small fragments of plastic for food.
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Adults
Adult loggerheads are primarily carnivorous, feeding mainly on bottom-dwelling invertebrates. Their powerful jaws enable them to crush hard-shelled prey such as crabs, conchs, and whelks. Other common prey items include:
- Crustaceans (crabs, shrimp, lobster)
- Mollusks (gastropods, bivalves)
- Atlantic horseshoe crabs
- Sponges
- Cnidarians (sea anemones, corals, sea pens, Portuguese men o' war)
- Echinoderms (sea urchins, sand dollars, sea cucumbers, starfish)
- Polychaete worms
- Cephalopods (squids, octopuses)
- Barnacles
- Brachiopods
- Isopods
- Insects
- Bryozoans
- Fish (eggs, juveniles, and adults)
- Hatchling turtles (including members of its own species)
- Algae
- Vascular plants
Adults forage on the bottom but sometimes eat jellyfish at the surface. Loggerheads have specialized scales on their flippers that allow them to “walk” along the sea floor.
Regional Variations in Diet
The diet of loggerhead sea turtles can vary depending on their geographic location and the availability of prey. For example, a study of stomach contents from deceased loggerheads in coastal Georgia, USA, found that the most frequently observed prey items were crustaceans, followed by bony fish, gastropod mollusks, bivalve mollusks, and Atlantic horseshoe crabs. The proportions of certain prey items differed with turtle size, with adult turtles eating proportionately more gastropods and subadults eating proportionately more fish.
Adaptations for Feeding
Loggerhead sea turtles have several adaptations that help them to feed on their diverse diet. Their large heads and powerful jaws are well-suited for crushing hard-shelled prey. Projecting scale points on the anterior margin of the forelimbs allow manipulation of the food. These points can be used as "pseudo-claws" to tear large pieces of food in the loggerhead's mouth. The loggerhead will turn its neck sideways to consume the torn food on the scale points. Inward-pointing, mucus-covered papillae found in the fore region of the loggerhead's esophagus filter out foreign bodies, such as fish hooks.
Threats to Loggerhead Sea Turtles and Their Diet
Loggerhead sea turtles face numerous threats, most of them related to human activities. These threats can also impact their diet.
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Fisheries Interactions
Bycatch, or the accidental capture, of loggerheads in fishing nets and lines is one of the greatest threats to all species of sea turtles. Discarded fishing gear, aka “ghost gear” also continues to entangle sea turtles indefinitely as it floats in the ocean, limiting their ability to forage and capture prey.
Pollution and Pathogens
Plastic pollution affects loggerheads by entangling them and impeding their movement and swimming ability. Sea turtles also eat plastic, mistaking it for food, which can cause choking, intestinal damage, and blockages. Ingestion of marine debris, including fishing line, balloons, plastic bags, plastic fragments, floating tar or oil, and other materials discarded by humans, is another threat to all species of sea turtles.
Climate Change
Changing climate impacts the loggerheads’ food sources, their migration routes, and the development of baby turtles. Rising seas and storm events can change beach morphology and cause beach erosion which may flood nests or wash them away.
Conservation Efforts
Numerous efforts are underway to conserve loggerhead sea turtles and protect their habitat and food sources. These include:
- Protecting habitat and designating critical habitat
- Reducing bycatch through gear modifications and changes to fishing practices
- Rescuing, disentangling, and rehabilitating injured turtles
- Eliminating the killing of turtles and the collection of their eggs
- Eliminating the harassment of turtles on nesting beaches through education and enforcement
- Reducing marine debris and participating in coastal clean-up events
- Responsibly disposing of fishing line
- Protecting nesting beaches by keeping them dark and safe at night
Read also: Feeding Your Box Turtle
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