LOGGERHEAD SEA TURTLES
Named for their relatively large heads,loggerhead sea turtles (Scientific name: Caretta caretta) are the largest hard-shelled sea turtles. They can weigh up to 230 kilograms (500 pounds). They generally live in depths of 9 to 22 meters (30 to 72 feet) but sometimes dive over 230 meters (755 feet) to regulate their body temperatures.
The loggerhead turtle head supports powerful jaw muscles that enable them to feed on hard-shelled prey, such as whelks and conch.A typical adult weighs 90 to 160 kilograms (200 to 350 pounds) and is 0.75 to 1.1 meters (2.5 to 3.5 feet) in length. Their lifespan is unknown, but estimated to be 70 years or more. Some loggerhead sea turtles may be over 100 years old. In Australia it has been predicted that the annual survival rate is 92 percent for juveniles and 88 percent for adults.
Loggerhead sea turtles are generally not aggressive but the powerful beak can inflict a crushing bite. A fisherman in the Caribbean was crippled when one bit him in the knee. Loggerheads are also sometimes attracted to blonds with bikinis and feed on Portuguese man-o-war jellyfish. A critter cam was hooked up to a one in 1987 by National Geographic researchers.
Loggerhead sea turtles have been called a "keystone species" because of their ecological impact. They feed on large numbers of invertebrates, keeping their populations in check and allowing their broken shells to be used as a calcium source for other species. More than 100 species from 13 phyla live on their shells making them sort of like moving reefs. Humans utilize loggerhead sea turtles for food, ecotourism, research and education. People like viewing them while snorkeling or diving and watch the nesting process. Loggerhead sea turtles are the most common sea turtle in U.S. waters. Most sea turtle research in the U.S. is carried out on this species. In some places in Central and South America, Africa, Asia, and the Mediterranean, these turtles and their eggs are still exploited for food. [Source: Liz Duermit, Animal Diversity Web (ADW) /=]
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures
Loggerhead Sea Turtle Habitat and Where They Are Found
Loggerhead turtles are found worldwide primarily in subtropical and temperate regions of the Atlantic, Pacific, and Indian Oceans, and in the Mediterranean Sea. In the western Atlantic, the loggerhead turtle's range extends from Newfoundland to Argentina. In the Pacific, loggerheads have been reported from Alaska to Chile in the east and Australia to Japan in the west. In the Indian Ocean the are found from southern Africa to the Arabian Gulf to western Australia. [Source: NOAA]
Loggerhead sea turtles live in saltwater and marine environments and are found in the open ocean, around coral reefs and in coastal areas at depths of zero to 61 meters (200 feet).. They are sometimes seen in brackish water in estuaries, salt marshes, brackish lagoons and the mouths of rivers. The preferred habitat of loggerhead sea turtles changes throughout their life cycle. In the Atlantic Ocean young juveniles have usually been observed among drifting Sargassum mats in warm ocean currents. Older juveniles and adults are most often seen in coastal waters and tend to prefer rocky or muddy substrates over sandy ones. During winter months loggerhead sea turtles migrate to tropical and subtropical waters. [Source: Liz Duermit, Animal Diversity Web (ADW) /=]
Loggerhead turtles are found worldwide with nine distinct population segments (DPS) listed under the U.S. Endangered Species Act. They are the most abundant species of sea turtle that nests in the United States. Juvenile and adult loggerheads live in U.S. coastal waters, but many adults that nest on U.S. beaches migrate from neighboring nations like the Bahamas, Cuba, and Mexico.
Loggerhead Sea Turtle Physical Characteristics
Loggerhead sea turtle reach lengths of 2.13 meters (seven feet), with their average length being 0.87 to one meters (2.8 to 3.3 feet). They range in weight from 77 to 545 kilograms (169.60 to 1200.44 pounds), with their average weight being 135 kilograms (297.36 pounds). Sexual Dimorphism (differences between males and females) is minor but exists: sexes are colored and patterned differently Males and females have different shapes. [Source: Liz Duermit, Animal Diversity Web (ADW) /=]
Loggerhead sea turtle Loggerhead turtles have large heads with powerful jaws. The top shell (carapace) is slightly heart-shaped and reddish-brown, with olive tones, in adults and sub-adults, while the bottom shell (plastron) is generally a cream to pale yellowish color. The neck and flippers are usually dull brown to reddish brown on top and medium to pale yellow on the sides and bottom.Unlike freshwater turtles and tortoises, sea turtles cannot withdraw their head or flippers into their shells. Hatchlings are mostly dark brown, their flippers have white to white-gray margins, and the bottom shell is generally yellowish to tan. They are often covered with commensal organisms such as barnacles and algae. [Source: NOAA]
According to Animal Diversity Web: There are five pairs of pleural scutes (thickened bony plate on a turtle's shell): the first pair touching the cervical (neck) scute. The plastron has two longitudinal ridges that disappear with age. The skin is dull to reddish brown on the back and medium to pale yellow around the edges and on the bottom. The skin may have some orange coloration as well. The skin of males is more brown and the head more yellow than those of females. Males also have wider carapaces and a long curved claw on each forelimb. /=\
Loggerhead sea turtles differ from other sea turtles in having relatively large heads and reddish coloration. Additionally, Ridley's sea turtles have four inframarginal scutes on the bridge. Green sea turtles and hawksbill sea turtles have only four pairs of pleural scutes on the carapace; the first pleurals do not touch the cervical scute. The average adult loggerhead sea turtles in the Mediterranean Sea is smaller than the average adult in the Atlantic Ocean. Two subspecies — C. caretta gigas in the Pacific and Indian Oceans and C. loggerhead sea turtles in the Atlantic — have been proposed but are not fully accepted. They differ in the number of neural bones in the carapace and marginal scutes on the edge of the carapace. /=\
Loggerhead Sea Turtle Behavior and Perception
Loggerhead sea turtles are motile (move around as opposed to being stationary), migratory (make seasonal movements between regions, such as between breeding and wintering grounds) and solitary. Loggerhead turtles, like all sea turtles, are marine reptiles and must come to the surface to breathe air. They can hold their breath for long periods of time. Though a typical dive lasts only 4 to five minutes, loggerheads are capable of diving for up to 20 minutes and can rest for hours without breathing. As a general rule, males are more active swimmers than females. As a special adaptation, these marine reptiles have salt glands near their eyes, which allow them to drink sea water and excrete salt in high concentrations. Many people have seen nesting females supposedly "crying" for their young, but they are simply excreting excess salt. [Source: NOAA; Liz Duermit, Animal Diversity Web (ADW) /=]
Adult female sea turtles return to land to lay their eggs in the sand — they are remarkable navigators and usually return to a beach in the general area where they hatched decades earlier. The home range of juveniles is their feeding grounds. There have been some indications that feeding grounds are chosen near natal nest sites. Juveniles removed from their feeding grounds quickly make their way back to it.
Loggerhead sea turtles sense using vision, polarized light, touch, vibrations, magnetism and chemicals usually detected with smelling or smelling-like senses. Food is typically located either visually or by smell. They communicate with vision, touch and chemicals usually detected by smelling. They also employ pheromones (chemicals released into air or water that are detected by and responded to by other animals of the same species)./=\
Perception in loggerhead sea turtles is highly developed. Juveniles and adults appear to be able to employ chemical and magnetic cues to orient themselves during their migrations. It has been demonstrated that they also use on-site cues, not memory of past movement, in orientation and this means they are capable of map-based navigation. /=\
Loggerhead Sea Turtle Food and Predators
Loggerheads are technically omnivores (eat a variety of things, including plants and animals) but are primarily carnivores, only occasionally do they consume plant material. Animal foods include fish eggs, mollusks, aquatic or marine worms, crustaceans, echinoderms, cnidarians and other marine invertebrates. Among the plant foods they eat are leaves,algae and macroalgae.
During their open ocean phase, loggerhead sea turtles feed on a wide variety of floating items. Unfortunately, trash and other debris discarded by humans also tends to accumulate in their habitat. Small fragments of plastic are often mistaken for food and eaten by turtles. Juveniles and adults in coastal waters eat mostly bottom dwelling invertebrates such as whelks, other mollusks, horseshoe crabs, and other crabs. Their powerful jaws are designed to crush their prey. [Source: NOAA]
The huge heads and massive, powerful jaws of loggerhead sea turtles are ideal for cracking open hard-shelled prey, such as horseshoe crabs, bivalves, barnacles, whelks, and conchs. As dietary generalist they also eat sponges, jellyfish, cephalopods, shrimp, insects, sea urchins, fish eggs, and fish such as menhaden, lantern fish and porcupine fish. Loggerheads also eat Ascophyllum, Ulothrix, Urospora and Sargassum algae and Cymodocea, Thalassia and Zostera vascular plants. There are some variations of their diet at different stages of their life stage, but as a rule loggerhead sea turtles are generalists throughout their life.[Source: Liz Duermit, Animal Diversity Web (ADW) /=]
The main predators of loggerhead sea turtle adults are humans, sharks and large carnivorous fish. Among the animals that have been observed feeding on loggerhead eggs and hatchlings have been bears, red foxes, side-striped jackals, raccoons, honey badgers, dogs, frigatebirds, crows, ants, crabs, hogs, armadillos, seagulls, rats, small cats, skunks, opossums, bobcats and lynxes. /=\
Loggerhead sea turtles rely on their hard shell, their size, and their rough, scaly skin on their head and neck to protect them from predation. These defenses are usually sufficient for adults and larger juveniles. Hatchlings and eggs have many predators and few defenses. Females try to disguise newly laid nests as much as possible, but they still suffer high predation rates. Raccoons in U.S. have destroyed up to 80 percent of nests on some beaches. Red foxes in Australia have destroyed 90 to 95 percent of nests there. In some areas of the world human predation on nests is substantial. Hatchlings are killed and eaten by crabs, carnivorous fish, raccoons, foxes, dogs and birds such as gulls, frigate birds, vultures and crows. /=\
Loggerhead Sea Turtle Migrations
Loggerhead sea turtles are known for their migratory behavior. They make seasonal movements between between breeding and feeding grounds and have uncanny homing and navigation abilities. Using satellite tracking, researchers have discovered that loggerheads in the Pacific undertake a trans-Pacific migration.
Hatchlings from nesting beaches in Japan and Australia migrate across the Pacific to feed off the coast of Baja California, Mexico, Peru and Chile — nearly 12,975 kilometers (8,000 miles)! They spend many years (possibly up to 20 years) growing to maturity and then migrate back to the beaches where they hatched in the Western Pacific Ocean to mate and nest and live out the remainder of their lives. [Source: NOAA]
Turtles born on Yakushima Island in southern Japan have been tagged and tracked making their way across the Pacific to Baja California in a two to six month period following the "plankton trail" between cold and warm water, feeding on jellyfish. Some of the Japan-born turtles spend most of the life off the west coast of Mexico and California. When they reach sexual maturity between 14 and 20 years of age they swim the 12,000 kilometers distance across the Pacific back to Japan to nest, and repeat the journey every other year..
Adults and juveniles in temperate waters migrate towards the equator during the winter to avoid cold stunning in waters under 10 ºC (50̊F). Cold stunning occurs in sea turtles that find themselves in waters under 10 ºC (50̊F), they become lethargic and float on the surface. If the water temperature drops below 5ºC (41̊F), the turtles could die. [Source: Liz Duermit, Animal Diversity Web (ADW) /=]
Loggerhead Sea Turtle Mating and Reproduction
are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). They engage in seasonal breeding and take 12 to 35 years to reach reproductive maturity. Generally, every two to three years they mate in coastal waters and return to nest on a beach in the general area where they hatched decades earlier. In the northern hemisphere, mating occurs in late March to early June and females lay eggs between late April and early September. [Source: NOAA]
Loggerhead sea turtles breed, on average, every 12 to 17 days during the breeding season. After that females do not breed again for another two to four, but possibly up to nine years. The breeding may occur year-round, but it peaks between May and July. The number of offspring ranges from 23 to 198, with the average number of offspring being 110-130, with the average number of offspring being 115. The gestation period ranges from 46 to 80 days. Pre-birth provisioning is done by females. There is no parental care of young after the eggs are laid. [Source: Liz Duermit, Animal Diversity Web (ADW) /=]
Loggerhead sea turtles are polygynandrous (promiscuous), with both males and females having multiple partners. Peak mating season for Loggerhead sea turtles occurs in the early summer months. During this time, males remain in the waters offshore of the nesting beach, while females alternate between mating in the water, nesting on land, and feeding in estuaries and reefs. Courtship behavior seems to largely depend on visual and tactile cues. It has been been suggested that glandular odors (especially Rathke's gland secretions) may help the two sexes locate each other. /=\
During the nesting seasons females generally lay several clutches, and re-mate afterwards each time. In some cases, they mate several times between clutches and so a single clutch may have sperm contributed by several males. According to Animal Diversity Web: Just before the nesting season, male loggerhead sea turtles migrate to mating grounds, which are usually located offshore from nesting beaches. They wait for females to begin courtship and mating. A male will circle a female, then approach her and bite her neck or shoulder. He will then attempt to mount her and, if she accepts him, they will mate. If a female does not accept the male she covers her cloaca and swims to the bottom, but a persistent male may wait until she needs air and make another attempt. Males use the long, curved claws on their forelimbs to hold on because mating may last for hours and other males often ram and bite the mating male, attempting to dislodge him. If a male is dislodged, another may quickly replace him. /=\
Nesting Loggerhead Sea Turtles
Loggerheads are solitary, night-time nesters, and they generally prefer relatively narrow, steeply sloped, coarse-grained beaches with a fair amount of surf for nesting. Egg-laying females get easily spooked and confused by lights when they are searching for nesting sites. [Source: NOAA]
Adult females lay three to five nests, sometimes more, two weeks apart during a single nesting season. Each nest contains about 100 to 130 eggs. At nesting sites loggerhead females dig 60-centimeter (two-foot) -deep holes, deposit their eggs and cover them and head back to the sea. . Females provide nutrition in the form of yolk which is used by embryos for growth and development. Females expend considerable energy migrating to nesting beaches and nesting and egg laying.
A female nests every 12 to 17 days, or two to five times, during the breeding season. For each nest she drags herself onto land, where she is in much greater danger to predation than in the sea,, and excavate a nest. The eggs incubate for 45 to 80 days, depending on temperature. The sex of hatchlings is determined by the temperature of the sand — cooler temperatures produce males and warmer temperatures produce females.
Loggerhead Sea Turtle Nesting Sites
Loggerheads nest sparsely throughout the Caribbean, on both sides of the Atlantic Ocean (Cape Verde Islands and Brazil), in the eastern Mediterranean Sea, throughout the Indian Ocean in small numbers (with the exception of Oman), and in the North and South Pacific Ocean. [Source: NOAA]
The most recent reviews show that only two loggerhead nesting beaches have greater than 10,000 females nesting per year: South Florida and Oman. Oman hosts the second largest nesting assemblage of loggerheads in the world, but recent trends analyses indicate this important nesting population is declining. In the United States, the Northwest Atlantic Ocean DPS of loggerhead turtles nests primarily along the Atlantic coast of Florida, South Carolina, Georgia, and North Carolina and along the Florida and Alabama coasts in the Gulf of Mexico. Total estimated nesting in the United States is more than 100,000 nests per year.
In the Pacific, there are two distinct population segments of loggerheads. The North Pacific Ocean DPS nests only on the coasts of Japan. This population has declined 50 to 90 percent during the last 60 years, however the overall nesting trend in Japan has been stable or slightly increasing over the last decade. The South Pacific Ocean DPS nests primarily in Australia with some nesting in New Caledonia. In 1977, about 3,500 females may have nested in the South Pacific — today there are only around 500 per year.
Loggerhead Sea Turtle Hatchlings
Like many turtles, loggerhead sea turtles experience temperature-dependent sex determination (TSD). This means that the sex of hatchlings is determined by egg temperature during the middle third of incubation. The pivotal temperature — the temperature at which an 50:50 ratio of males:females is produced — varies from place to place. In South Africa, the pivotal temperature is 29.7ºC (85.5̊ F) , but in Australia it is 28.2 ºC (82.8̊F) . As a rule, the pivotal temperature is between 28 º and 30ºC (82.4̊ and 86̊F) . Temperatures of 24º to 26ºC (75.2º to 79 º F) generally produce all males and temperatures of 32º to 34 ºC (89.6º to 93.2 ºF) generally produce all females. Eggs outside these temperature ranges don’t survive.[Source: Liz Duermit, Animal Diversity Web (ADW) /=]
Temperature also effect the speed of embryonic development within the egg. Temperature within the nest can be affected by sun, shade, rain, heat generated within the nest, and an egg's position in the nest. At cool temperatures, around 25 ºC, development to hatching can take 65 to 70 days, but at warmer temperatures, around 35 ºC, development usually takes around 45 days. /=\
Generally, after about two months incubating in the warm sand, the eggs hatch and the hatchlings emerge from the soft shells. The hatchlings hatch at night often during the full moon and climb up through the sand out of the pit where the eggs were layed make their way to the sea. When hatchlings emerge from their nests they scope out their their environment to determine which direction they should go towards the ocean. It is believed that the light on the horizon is their primary cue. Hatchlings orient towards the brightest light, which, historically, is the moon or star light over the ocean. They may also perceive the incline of the beach and orient towards a lower elevation./=\
Newly hatched loggerhead turtles are susceptible to predation from a host of animals including crabs, gulls, frigate birds, vultures, crows, raccoons, foxes, dogs, and carnivorous fish. Hatchlings and eggs have few defenses. Females try to disguise newly laid nests as much as possible, but they still suffer high predation rates. Raccoons in U.S. have destroyed up to 80 percent of nests on some beaches. Red foxes in Australia have destroyed 90 to 95 percent of nests there. In some areas of the world human consumption of eggs is significant.
Newly hatched loggerhead turtles are particularly threatened by artificial beachfront lighting, which can disorient them and prevent them from finding the sea. Hatchlings orient by moving away from the darkest silhouette of the landward dune or vegetation to crawl towards the brightest horizon. On undeveloped beaches, this is toward the open horizon over the ocean. However, in areas with artificial lighting hatchlings are disoriented and often crawl landward instead of toward the ocean. Artificial light can similarly disorient nesting female turtles. [Source: NOAA]
Loggerhead Sea Turtle Juveniles and Development
Loggerhead sea turtle hatchlings tend to have a dark brown to reddish brown carapace (upper part of their shell) and cream to reddish brown or dark brown plastron (lower, bottom part of the shell. Only one in every 5,000 loggerhead eggs produces a turtle that reaches reproductive age. Many are taken by predators waiting for them to hatch on the beach. Those that make it to the sea are often taken by aquatic predators and fishing nets.
The hatchlings that survive swim out to the open sea less than 20 hours after hatching. Once in the water, they use chemical and magnetic cues to orient themselves and navigate their way to the open ocean currents in which they will spend the next 10 or so years of their lives. Some scientist believe they sense the earth's magnetism when the move across the sand and develop an instinct for direction that helps them later to find their way back to their birthplace later on. [Source: Liz Duermit, Animal Diversity Web (ADW) /=]
Loggerhead sea turtles reach sexual maturity at carapace lengths longer than 90 centimeters, which can occur between 10 and 30 years of age. The life of these turtles involves a series of stages of development from hatchling to adult. Hatchlings and juveniles spend the first 7 to 15 years of their lives in the open ocean. Then they migrate to nearshore coastal areas where they forage and continue to grow for several more years. Adult loggerhead turtles migrate hundreds to thousands of kilometers from their foraging grounds to their nesting beaches. Juvenile turtles rely on their hard shell, their size, and their rough, scaly skin on their head and neck to protect them from predation. [Source: NOAA]
According to Animal Diversity Web: When loggerheads are juveniles the differences between the sexes begin to emerge. Males produce increasing levels of testosterone as they approach maturity, which triggers tail growth, plastron softening, and the growth and curvature of a nail on each forelimb. Females produce estrogen and small amounts of testosterone, but externally just grow larger. Age at maturity is variable. Mature size is attained between age 10 and 30; captives are predicted to mature in 16 to 17 years. Reproductive life span (after reaching maturity) is estimated at about 32 years. /=\
Endangered Loggerhead Sea Turtles
Loggerhead sea turtle numbers, like those of all sea turtle species, are in decline. There are listed as Endangered on the International Union for Conservation of Nature (IUCN) Red List: and Threatened on the U.S. Endangered Species Act (ESA). The Convention on International Trade in Endangered Species (CITES) lists them in Appendix I, which lists species that are the most endangered among CITES-listed animals and plants. There are listed in Specially Protected Areas and Wildlife (SPAW) Annex II throughout the Wider Caribbean Region: Despite this loggerhead sea turtles are currently the most common and least-threatened marine turtle in North American waters. /=\
Threats to loggerhead sea turtle include bycatch in fishing gear, climate change, direct harvest of turtles and eggs, loss and degradation of nesting habitat, ocean pollution/marine debris, predation of eggs and hatchlings and vessel strikes. Artificial lighting near beaches can confuse emerging hatchlings, causing them to move away from the ocean and into hazardous urban areas. The biggest source of decline world-wide is probably incidental capture in fishing gear such as long lines, gill nets, shrimp trawls, and direct exploitation of adult turtles and eggs for human food. The use of turtle excluder devices (TEDs) in shrimp trawls, gillnet bans, and other gear modification have reduced sea turtle bycatch in some fisheries, but bycatch in fishing gear remains the biggest threat facing loggerheads. [Source: NOAA]
There are nine distinct loggerhead turtles population segments (DPS) worldwide listed under the U.S. Endangered Species Act (ESA) .Those in which loggerheads are listed as “Endangered” are 1) the North Pacific Ocean, 2) the Mediterranean Sea, 3) the Northeast Atlantic Ocean, 4) the North Indian Ocean and 5) the South Pacific Ocean. Those in which loggerheads are listed as “Threatened” are 6) the Northwest Atlantic Ocean, 7) the South Atlantic Ocean, 8) the Southeast Indo-Pacific Ocean and 9) the Southwest Indian Ocean. Based on counts of turtles at nesting sites, loggerhead populations dropped by half between 1990 and 2000. In Mexico tens of thousands of loggerheads were illegally caught for food at that time. The practice probably still endures but is less common now. .
Image Sources: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last Updated May 2023