Loggerhead sea turtles (Caretta caretta) migrate long distances from their nesting beaches and forage on prey in a variety of ecosystems. Their diet consists of an array of animal and plant matter including jellyfishes, squid, pteropods, molluscs, and floating egg clusters.
During their oceanic phase of life, loggerheads shift from foraging on bottom-dwelling organisms to consuming jellies, squid and surface-dwelling invertebrates such as pteropods, algae and floating egg clusters.
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Predators
Predators are a major part of the loggerhead sea turtle food web. The eggs are eaten by a wide variety of predators, including ghost crabs, raccoons, foxes, and dogs.
The hatchlings are also often preyed upon by seabirds and snakes, which can be dangerous for young turtles. Fishing gear and traps can also cause problems for loggerheads, as they can get tangled in their flippers or shells.
Goannas are another predator in the loggerhead sea turtle food chain. They are common in Australia and have been a major threat to loggerheads on the east Australian coast since their introduction.
Camera trap data indicated that large male yellow-spotted goannas (Varanus panoptes) were the most frequent predators of loggerhead nests. They also appeared more frequently than lace monitors (Varanus varius). However, goanna abundance varies between years. Their Passive Activity Index was 7 times higher than that of foxes. Moreover, goannas consumed more than half of all loggerhead nest eggs in one year.
Habitat
Loggerheads feed primarily on mollusks and crustaceans including conchs, clams, shrimp, sea urchins, horseshoe crabs, jellyfish and sponges. They also eat fish, squid and other small invertebrates.
They are a benthic predator (meaning they eat only marine organisms) and spend their lives in lagoons, estuaries, bays and coastal waters along the Atlantic Ocean. Their powerful jaws are designed to crush their prey, such as horseshoe crabs and clams.
During their early developmental years, hatchlings float in floating mats of sargassum which contain many small animals. They eat these animals and other seaweeds while they are growing.
Once they reach a certain size, juvenile loggerheads leave their land habitat and migrate offshore to the open Atlantic where they feed on large clumps of sargassum. They linger in these areas for several years before they begin their reproductive migrations, traveling thousands of miles to feed off the west coasts of Asia and Australia. These long trips, combined with a lack of suitable nesting beaches and a high rate of incidental capture in fishing gear have led to a decline in their populations.
Feeding
Loggerheads primarily feed on small animals that live in the floating mats of sargassum. They also eat jellyfish, shrimp, sponges, fish and sometimes even seaweed.
During their life span, loggerheads feed in a variety of habitats and environments including coastal lagoons, estuaries, bays, river mouths and shallow waters. They eat bottom dwelling invertebrates such as whelks, other mollusks and horseshoe crabs, and they crush their prey with their powerful jaws.
Female loggerheads lay two to five clutches of eggs per season. The average clutch size is 126 eggs. Breeding occurs year-round, but peaks in the summer months.
Breeding
Sea turtles are a keystone species in the food web, meaning they provide a source of nutrition for other animals. They consume invertebrates such as conchs, bivalves, horseshoe crabs and jellyfish.
Mature female loggerheads return to beaches where they hatched to nest each year. During breeding season, females lay two to five clutches of eggs with different mates.
During the winter, they do not migrate and feed in their usual foraging areas, such as Gulf stream currents, filled with floating sargassum weed.
The curved carapace length (CCL) of loggerhead turtles was significantly increased between 1990 and 2020, but only during the breeding/nesting season. Size followed a bimodal distribution and was most pronounced in summer, where CCLs were generally greater than 50 cm.
Climate change may lead to shifts in the migratory path of loggerhead turtles, including the selection of new nesting sites. These changes are expected to affect reproduction, incubation duration and hatchling sex ratio.
