Loggerhead sea turtle
Encyclopedia
The loggerhead sea turtle (Caretta caretta), or loggerhead, is an oceanic turtle
distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around 90 centimetres (35.4 in) long when fully grown, although larger specimens of up to 270 centimetres (106.3 in) have been discovered. The adult loggerhead sea turtle weighs approximately 135 kilograms (297.6 lb), with the largest specimens weighing in at more than 454 kilograms (1,000.9 lb). The skin ranges from yellow to brown in color, and the shell is typically reddish-brown. There are no external differences in gender until the turtle becomes an adult, the most obvious difference being that adult males have thicker tails and shorter plastrons than the females.
The loggerhead sea turtle is found in the Atlantic
, Pacific
, and Indian
oceans as well as the Mediterranean Sea
. It spends most of its life in saltwater and estuarine habitats, with females briefly coming ashore to lay eggs. The loggerhead sea turtle has a low reproductive rate; females lay an average of four egg clutches
and then become quiescent, producing no eggs for two to three years. The loggerhead reaches sexual maturity within 17–33 years and has a lifespan of 47–67 years.
The loggerhead sea turtle is omnivorous
, feeding mainly on bottom dwelling invertebrate
s. Its large and powerful jaws serve as an effective tool in dismantling its prey. Young loggerheads are exploited by numerous predators; the eggs are especially vulnerable to terrestrial organisms. Once the turtles reach adulthood, their formidable size limits predation to large marine organisms such as sharks.
Loggerheads are considered an endangered species
and are protected by the International Union for the Conservation of Nature. Untended fishing gear is responsible for many loggerhead deaths. Turtles may also suffocate if they are trapped in fishing trawls
. Turtle excluder device
s (TEDs) have been implemented in efforts to reduce mortality by providing the turtle an escape route. Loss of suitable nesting beaches and the introduction of exotic predators has also taken a toll on loggerhead populations. Efforts to restore their numbers will require international cooperation since the turtles roam vast areas of ocean and critical nesting beaches are scattered among several countries.
gave the loggerhead its first binomial name, Testudo caretta, in 1758. Thirty-five other names emerged over the following two centuries, with the combination Caretta caretta first introduced in 1902 by Leonhard Stejneger. The English common name
"loggerhead" refers to the animal's large head. The loggerhead sea turtle belongs to the family
Cheloniidae, which includes all sea turtles except the leatherback sea turtle
. The subspecific classification of the loggerhead sea turtle is debated, but most authors consider it a single polymorphic
species. Molecular genetics has confirmed hybridization of the loggerhead sea turtle with the Kemp's ridley sea turtle, hawksbill sea turtle, and green sea turtle
s. The extent of natural hybridization is not yet determined; however, second generation hybrids have been reported, suggesting some hybrids are fertile.
algae. Adults and juveniles live along the continental shelf, as well as in shallow coastal estuaries. In the northwestern Atlantic Ocean, age plays a factor in habitat preference. Juveniles are more frequently found in shallow estuarine habitats with limited ocean access compared to non-nesting adults. Loggerheads occupy waters with surface temperatures ranging from 13.3–28 °C (55.9–82.4 F) during non-nesting season. Temperatures from 27–28 °C (80.6–82.4 F) are most suitable for nesting females.
Juvenile loggerheads share the Sargassum habitat with a variety of other organisms. The mats of Sargassum contain as many as 100 different species of animals on which the juveniles feed. Some of the prey, such as ant
s, flies
, aphid
s, leafhopper
s, and beetle
s, are carried by the wind to these areas. Endemic prey of the Sargassum mats include barnacle
s, small crab larvae, fish eggs, and hydrozoa
n colonies. Marine mammals and commercial fish, such as tuna
, dolphin fish, and amberjack
s, also inhabit the Sargassum mats.
, nesting over the broadest geographical range of any sea turtle. The loggerhead inhabits the Atlantic, Indian, and Pacific Oceans and the Mediterranean Sea.
In the Atlantic Ocean, the greatest concentration of loggerheads is along the southeastern coast of North America and in the Gulf of Mexico. Very few loggerheads are found along the European and African coastlines. Florida
is the most popular nesting site, with over 67,000 nests built per year. Nesting extends as far north as Virginia
, as far south as Brazil, and as far east as the Cape Verde Islands. The Cape Verde Islands are the only significant nesting site on the eastern side of the Atlantic. Loggerheads found in the Atlantic Ocean feed from Canada to Brazil.
In the Indian Ocean, loggerheads feed along the coastlines of Africa, the Arabian Peninsula
, and in the Arabian Sea
. Along the African coastline, loggerheads nest from Mozambique
's Bazaruto Archipelago
to South Africa's St Lucia estuary. The largest Indian Ocean nesting site is Oman
, on the Arabian Peninsula, which hosts around 15,000 nests, giving it the second largest nesting population of loggerheads in the world. Western Australia
is another notable nesting area, with 1,000-2,000 nests per year.
Pacific loggerheads live in temperate
to tropical regions. They forage in the East China Sea
, the southwestern Pacific, and along the Baja California peninsula
. Eastern Australia and Japan are the major nesting areas, with the Great Barrier Reef
deemed an important nesting area. Pacific loggerheads occasionally nest in Vanuatu
and Tokelau
. Yakushima Island is the most important site, with three nesting grounds visited by 40% of all nearby loggerheads. After nesting, females often find homes in the East China Sea, while the Kuroshio Extension Bifurcation region provides important juvenile foraging areas. Eastern Pacific populations are concentrated off the coast of Baja California, where upwelling provides rich feeding grounds for juvenile turtles and subadults (individuals past the juvenile stage that lack adult characteristics). Nesting sites along the eastern Pacific Basin are rare. mtDNA sequence polymorphism analysis and tracking studies suggest 95% of the population along the coast of the Americas hatch on the Japanese Islands in the western Pacific. The turtles are transported by the prevailing currents across the full length of the northern Pacific, one of the longest migration routes of any marine animal. The return journey to the natal beaches in Japan has been long suspected, although the trip would cross unproductive clear water with few feeding opportunities. Evidence of a return journey came from an adult female loggerhead named Adelita, who in 1996, equipped with a satellite tracking device, made the 9000 miles (14,484.1 km) trip from Mexico across the Pacific. Adelita was the first animal of any kind ever tracked across an ocean basin.
The Mediterranean Sea is a nursery for juveniles, as well as a common place for adults in the spring and summer months. Almost 45% of the Mediterranean juvenile population has migrated from the Atlantic. Loggerheads feed in the Alboran Sea
and the Adriatic Sea
.
Greece is the most popular nesting site along the Mediterranean, with more than 3,000 nests per year. Because of this, Greek authorities do not allow planes to take off or land at night in Zakynthos
due to the nesting turtles. In addition to the Greek coast, the coastlines of Cyprus and Turkey are also common nesting sites.
Cheloniidae
. About 40 million years ago, a branch of the Cheloniidae gave rise to loggerhead sea turtle. Of the six species of living Cheloniidae, loggerheads are more closely related to the Kemp's ridley sea turtle
, olive ridley sea turtle, and the hawksbill turtle
than they are to the flatback turtle
and the green turtle.
Around three million years ago, during the Pliocene
epoch, Central America emerged from the sea, effectively cutting off currents between the Atlantic and Indo-Pacific
Oceans. The rerouting of ocean currents lead to climatic changes as the Earth entered a glacial cycle. Cold water upwelling around the Cape of Good Hope
and reduction in water temperature at Cape Horn
formed cold water barriers to migrating turtles. The result was a complete isolation of the Atlantic and Pacific populations of loggerheads. During the most recent ice age
, the beaches of southeastern North America were too cold for sea turtle eggs. As the Earth began to warm, loggerheads moved farther north, colonizing the northern beaches. Because of this, turtles nesting between North Carolina and northern Florida represent a different genetic population from those in southern Florida.
The distinct populations of loggerheads have unique characteristics and genetic differences. For example, Mediterranean loggerheads are smaller, on average, than Atlantic Ocean loggerheads. North Atlantic and Mediterranean loggerhead sea turtles are descendants of colonizing loggerheads from Tongaland
, South Africa. South African loggerhead genes are still present in these populations today.
The loggerhead sea turtle is the world's largest hard-shelled turtle. Adult loggerheads have an average weight range of 80 to 200 kg (176.4 to 440.9 lb) and a length range of 70 to 95 cm (27.6 to 37.4 in). The maximum reported weight is 545 kilograms (1,201.5 lb) and the maximum carapace length is 213 centimetres (83.9 in). The head and carapace
(upper shell) range from a yellow-orange to a reddish-brown, while the plastron (underside) is typically pale yellow. The turtle's neck and sides are brown on the tops and yellow on the sides and bottom.
The turtle's shell is divided into two sections: carapace and plastron. The carapace is further divided into large plates, or scute
s. Typically, there are 11 or 12 pairs of marginal scutes which rim the carapace. Five vertebral scutes run down the carapace's midline, while five pairs of costal scutes border them. The nuchal scute is located at the base of the head. The carapace connects to the plastron by 3 pairs of inframarginal scutes forming the bridge of the shell. The plastron features paired gular, humeral, pectoral, abdominal, femoral, and anal scutes. The shell serves as external armor, although loggerhead sea turtles cannot retract their head or flippers into their shells.
Sexual dimorphism
of the loggerhead sea turtle is only apparent in adults. Adult males have longer tails and claws than females. The males' plastrons are shorter than the females', presumably to accommodate the males' larger tails. The carapace of males are wider and less domed than the females, and males typically have wider heads than females. The sex of juveniles and subadults cannot be determined through external anatomy, but can be observed through dissection, laparoscopy
(an operation performed on the abdomen), histological
examination (cell anatomy), and radioimmunological assays (immune study dealing with radiolabeling
).
Lachrymal glands located behind each eye allow the loggerhead to maintain osmotic balance by eliminating the excess salt obtained from ingesting ocean water. On land, the excretion of excess salt gives the false impression that the turtle is crying.
Water temperature affects the sea turtle's metabolic rate. Lethargy is induced at temperatures between 13 and 15 °C (55.4 and 59 F). The loggerhead takes on a floating, cold-stunned posture when temperatures drop to approximately 10 °C (50 °F). However, younger loggerheads are more resistant to cold and do not become stunned until temperatures drop below 9 °C (48.2 °F). The loggerheads' migration
help prevent instances of cold-stunning. Higher water temperatures cause an increase in metabolism and heart rate. A loggerhead's body temperature increases in warmer waters more quickly than it decreases in colder water. The loggerhead sea turtle's critical thermal maximum
is currently unknown.
Female-female aggression, which is especially uncommon in marine vertebrates), is common among loggerheads. Ritualized aggression escalates from passive threat displays to combat. This conflict primarily occurs over access to feeding grounds. Escalation typically follows four steps. First, initial contact is stimulated by visual or tactile cues. Second, confrontation occurs, beginning with passive confrontations characterized by wide head-tail circling. They begin aggressive confrontation when one turtle ceases to circle and directly faces the other. Third, sparring
occurs with turtles snapping at each other’s jaws. The final stage, separation, is either mutual, with both turtles swimming away in opposite directions, or involves chasing one out of the immediate vicinity. Escalation is determined by several factors, including: hormone
levels, energy expenditure, expected outcome, and importance of location. At all stages, an upright tail shows willingness to escalate, while a curled tail shows willingness to submit. Because higher aggression is metabolically costly and potentially debilitating, contact is much more likely to escalate when the conflict is over access to good foraging grounds. Further aggression has also been reported in captive loggerheads. The turtles are seemingly territorial
and will fight with other loggerheads and sea turtles of different species.
s, cats, hogs, and humans. During their migration from their nest to the sea, hatchlings are preyed on by dipteran larvae, crabs, toads, lizards, snakes, birds, and mammals. In the ocean, predators of the loggerhead juveniles and adults include sharks, other fish, such as parrotfish
, moray eel
s, portunid crabs, gulls, monk seals, and killer whales. Nesting females are attacked by flesh flies, feral
dogs, and humans. Salt marsh mosquitoes can also pester nesting females.
In Australia, the introduction of the red fox (Vulpes vulpes) by English settlers in the 19th century led to significant reductions in loggerhead sea turtle populations. In one coastal section in eastern Australia during the 1970s, predation of turtle eggs destroyed up to 95% of all clutches laid. Aggressive efforts to destroy foxes in the 1980s and 1990s has reduced this impact; however, it is estimated that it will be the year 2020 before populations will experience complete recovery from such dramatic losses.
Along the southeastern coast of the United States, the raccoon (Procyon lotor) is the most destructive predator of nesting sites. Mortality rates of nearly 100% of all clutches laid in a season have been recorded on some Florida beaches. This is attributed to an increase in raccoon populations, which have flourished in urban environments. Aggressive efforts to protect nesting sites by covering them with wire mesh has significantly reduced the impact of raccoon predation on loggerhead sea turtle eggs. On Bald Head Island, in North Carolina, wire mesh screens are used on every confirmed nest to prevent excavation by resident red foxes (http://www.bhic.org/). A new concern with the steel cage technique is interference with the normal development of the nestlings' magnetic sense due to the use of ferrous wire (http://www.unc.edu/depts/geomag/), which may disrupt the turtles' ability to navigate properly. Efforts are underway to find a nonmagnetic material that will prevent predator's gnawing through the barrier.
Up to 40% of nesting females around the world have wounds believed to come from shark attacks.
and Salmonella
attack loggerhead hatchlings and eggs. Fungi such as Penicillium
infect loggerhead sea turtle nests and cloaca.
Fibropapillomatosis
disease threatens loggerheads in the form of the herpes-type
virus which causes internal and external tumors. These tumors disrupt essential behaviors and, if on the eyes, cause permanent blindness. Trematodes of the family Spirorchiidae
inhabit tissues throughout the body of the loggerhead, including vital organs such as the heart and the brain. Trematode infection can be highly debilitating. For example, inflammatory
trematode lesion
s can cause endocarditis
and neurological disease
. A nematode
, Angiostoma carettae
, also infects loggerheads. The nematodes cause histologic
lesions in the respiratory tract
.
More than 100 species of animals from 13 phyla
as well as 37 kinds of algae live on loggerheads' backs. These parasitic organisms, which increase drag, offer no known benefit to the turtle, although it has been suggested that the dulling effect of organisms on shell color improves camouflaging
ability.
.jpg)
The loggerhead sea turtle is omnivorous, feeding mainly on bottom dwelling invertebrate
s, such as gastropods, bivalves
, and decapods
. The loggerhead has a greater list of known prey than any other sea turtle. Other food items include sponges, coral
s, sea pen
s, polychaete worms
, sea anemone
s, cephalopod
s, barnacles, brachiopod
s, isopods
, insects, bryozoa
ns, sea urchin
s, sand dollar
s, sea cucumber
s, starfish, fish (eggs, juveniles, and adults), wrasses, hatchling turtles (including members of its own species), algae, and vascular plant
s. During migration through the open sea, loggerheads eat jellyfish
, floating molluscs, floating egg clusters, squid
, and flying fish.
Loggerheads crush prey with their large and powerful jaws. 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, mucosal (mucus
-covered) papillae found in the foreregion of the loggerhead's esophagus
filter out foreign bodies, such as fish hooks. The next region of the esophagus is nonpapillated, with numerous mucosal folds. The rate of digestion in loggerheads is temperature dependent; digestion rate increases as temperature increases.
. The eggs are laid near the water so the hatchlings can return to the sea. The loggerhead's sex is dictated by the temperature of the underground nest. Incubation temperatures generally range from 26–32 °C (78.8–89.6 F). Studies show loggerhead sea turtle eggs kept at a constant incubating temperature of 32 °C (89.6 °F) become females. Eggs incubating at 28 °C (82.4 °F) become males. An incubation temperature of 30 °C (86 °F) results in an equal ratio of male to female hatchlings. Hatchlings from eggs in the middle of the clutch tend to be the largest, grow the fastest, and be the most active during the first few days of sea life.
After incubating for approximately 80 days, hatchlings dig through the sand to the surface. This usually occurs at night, when darkness increases the chance of escaping predation and damage from extreme sand surface temperatures is reduced. Hatchlings enter the ocean by navigating toward the brighter horizon created by the reflection of the moon and star light off the water's surface.
Hatchlings can lose up to 20% of their body mass due to evaporation of water as they journey from nest to ocean. Hatchlings initially use the undertow
to push them five to ten yards away from the shore. Once in the ocean, hatchlings swim for about 20 hours, bringing them far offshore. An iron compound, magnetite
, in their brains allows the turtles to perceive the Earth's magnetic field
, for navigation.
Many hatchlings use Sargassum in the open ocean as protection until they reach 45 centimetres (17.7 in). Hatchling loggerheads live in this pelagic environment
until they reach juvenile age, and then they migrate to nearshore waters.
When ocean waters cool, loggerheads must migrate to warmer areas or hibernate
to some degree. In the coldest months, loggerheads submerge for up to seven hours at a time, emerging for only seven minutes to breathe. Although outdone by freshwater turtles
, these are among the longest recorded dives for any air-breathing marine vertebrate. During their seasonal migration, juvenile loggerheads have the ability to use both magnetic and visual cues. When both aids are available, they are used in conjunction; if one aid is not available, the other suffices. The turtles swim at about 1.6 kph during migration.
Like all marine turtles, the loggerhead prepares for reproduction in its foraging area. This takes place several years before the loggerhead migrates to a mating area. Female loggerheads first reproduce at ages 28–33 in Southeastern United States and Australia, and at ages 17–30 in South Africa. Age at first reproduction in the Mediterranean, Oman, Japan, and Brazil are unknown. Nesting loggerheads have a straight carapace length of 70–109 cm (27.6–42.9 in). Because of the large range, carapace length is not a reliable indicator of sexual maturity. Loggerheads have an estimated maximum lifespan of 47–67 years in the wild.
Female loggerheads first reproduce between the ages of 17 and 33, and their mating period lasts up to six weeks. They court their mates, however these behaviors have not been thoroughly examined. Male forms of courtship behavior include nuzzling, biting, and head and flipper movements. Studies suggest females produce cloaca
l pheromone
s to indicate reproductive ability. Before mating, the male approaches a female and attempts to mount her, while she resists. Next, the male and female begin to circle each other. If the male has competitors, the female may let the males struggle with each other. The winner then mounts the female; the male's curved claws usually damage the shoulders of the female's shell during this process. Other courting males bite the male while he is attempting to copulate, damaging his flippers and tail, possibly exposing bones. Such damage can cause the male to dismount and may require weeks to heal.
While nesting, females produce an average of 3.9 egg clutches, and then become quiescent, producing no eggs for an average of two to three years. Unlike other sea turtles, courtship and mating usually do not take place near the nesting beach, but rather along migration routes between feeding and breeding grounds. Recent evidence indicates ovulation
in loggerheads is mating-induced. Through the act of mating, the female ovulates eggs which are fertilized by the male. This is unique, as mating-induced ovulation is rare outside of mammals. In the Mediterranean, loggerheads mate from late March to early June. The nesting season
peaks in June and July, but varies by nesting beach.
Loggerheads may display multiple paternity. Multiple paternity is possible due to sperm storage. The female can store sperm from multiple males in her oviducts until ovulation. A single clutch may have as many as five fathers, each contributing sperm to a portion of the clutch. Multiple paternity and female size are positively correlated. Two hypotheses explain this correlation. One states that males favor large females due to perceived higher fecundity
(ability to reproduce). The other states that because larger females are able to swim more quickly to mating grounds, they have a longer mating period.
All sea turtles have similar basic nesting behaviors. Females return to lay eggs at intervals of 12–17 days during the nesting season, on or near the beach where they hatched. They exit the water, climb the beach, and scrape away the surface sand to form a body pit. With their hind limbs, they excavate an egg chamber in which the eggs are deposited. The females then cover the egg chamber and body pit with sand, and finally return to the sea. This process takes one to two hours, and occurs in open sand areas or on top of sand dunes. The nesting area must be selected carefully because it affects characteristics such as fitness, emergence ratio, and vulnerability to nest predators. Loggerheads have an average clutch
size of 4 eggs.
Loggerhead sea turtles were once intensively hunted for their meat and eggs
; consumption has decreased, however, due to worldwide legislation. Despite this, turtle meat and eggs are still consumed in countries where regulations are not strictly enforced. In Mexico, turtle eggs are a common meal; locals claim the egg is an aphrodisiac
. Eating turtle eggs or meat can cause serious illness due to harmful bacteria, such as Pseudomonas aeruginosa
and Serratia marcescens
, and high levels of toxic metals that build up through bioaccumulation
.
The U.S. West Coast is a critical migratory corridor for the Pacific loggerheads, in which these turtles swim across the Pacific to California’s coast from breeding grounds in Japan. Important foraging habitats for juveniles in the central North Pacific have been revealed through telemetry
studies. Along with these foraging habitats, high levels of bycatch from industrial-scale fisheries have been found to overlap; with drift gillnets in the past and longline fisheries presently. Many juvenile loggerheads aggregate off the coast of Baja California Sur, Mexico, where small coastal fisheries (6-8m) increase these turtle’s mortality risk; fishers have reported catching dozens of loggerheads with bottom-set gear per day per boat. The most common commercial fishery that accidentally take loggerheads are bottom trawls used for shrimp vessels in the Gulf of California; as well as gillnets, longlines, etc. In 2000, between 2,600 and 6,000 loggerheads were estimated to have been killed by pelagic longlining in the Pacific.
Fishing gear is the biggest threat to loggerheads in the open ocean. They often become entangled in longlines or gillnet
s. According to the 2009 status review of loggerheads by the Fisheries Service, drowning from entanglement in longline and gillnet fishing gear is the turtles’ primary threat in the North Pacific. They also become stuck in traps, pots, trawls, and dredge
s. Caught in this unattended equipment, loggerheads risk serious injury or drowning. Turtle excluder devices for nets and other traps reduce the number being accidentally caught.
Nearly 24,000 metric tons of plastic is dumped into the ocean each year. Turtles ingest a wide array of this floating debris, including plastic bags, plastic sheets, plastic pellets, balloons and abandoned fishing line. Loggerheads may mistake the floating plastic for jellyfish, a common food item. The ingested plastic causes numerous health concerns, including: intestinal blockage, reduced nutrient absorption, suffocation, ulcerations, malnutrition or starvation. Ingested plastics release toxic compounds, including polychlorinated biphenyls, which may accumulate in internal tissues. Such toxins may lead to a thinning of eggshells, tissue damage or deviation from natural behaviors.
Artificial lighting
discourages nesting and interferes with the hatchlings' ability to navigate to the water's edge. Females prefer nesting on beaches free of artificial lighting. On developed beaches, nests are often clustered around tall buildings, perhaps because they block out the man-made light sources. Loggerhead hatchlings are drawn toward the brighter area over the water which is the consequence of the reflection of moon and star light. Confused by the brighter artificial light, they navigate inland, away from the protective waters, which exposes them to dehydration and predation as the sun rises. Artificial lighting causes tens of thousands of hatchling deaths per year.
Destruction and encroachment of habitat by humans is another threat to loggerhead sea turtles. Optimum nesting beaches are open sand beaches above the high tide line. However, beach development deprives them of suitable nesting areas, forcing them to nest closer to the surf. Urbanization often leads to the siltation
of sandy beaches, decreasing their viability. Construction of docks and marinas can destroy near-shore habitats. Boat traffic and dredging degrades habitat and can also injure or kill turtles when boats collide with turtles at or near the surface.
Annual variations in climatic temperatures can affect sex ratios, since loggerheads have temperature-dependent sex determination. High sand temperatures may skew gender ratios in favor of females. In one study (Mrosovsky, N. & Provancha, J. 1992), nesting sites exposed to unseasonably warm temperatures over a three-year period produced 87-99% females. This raises concerns over the connection between rapid global temperature changes and the possibility of population extinction. A more localized effect on gender skewing comes from the construction of tall buildings, which reduce sun exposure, lowering the average sand temperature. This results in a shift in gender ratios that favor the emergence of male turtles.
Since the loggerhead occupies such a broad range, successful conservation requires efforts from multiple countries.
Loggerhead sea turtles are classified as endangered by the International Union for the Conservation of Nature and are listed under Appendix I of the Convention on International Trade in Endangered Species, making international trade illegal. In the United States, the U.S. Fish and Wildlife Service
(FWS) and National Marine Fisheries Service
(NMFS) classify them as a threatened species under the Endangered Species Act
. Loggerheads are listed as endangered under both Australia's Environment Protection and Biodiversity Conservation Act 1999
and Queensland's Nature Conservation Act 1992
. The Convention on Migratory Species works for the conservation of loggerhead sea turtles on the Atlantic coast of Africa, as well as in the Indian Ocean and southeast Asia. Throughout Japan, the Sea Turtle Association of Japan aids in the conservation of loggerhead sea turtles. Greece's ARCHELON
works for their conservation. The Marine Research Foundation works for loggerhead conservation in Oman. Annex 2 of the Specially Protected Areas and Wildlife (SPAW) Protocol of the Cartagena Convention, which deals with pollution that could harm marine ecosystems, also protects them. Conservation organizations worldwide have worked with the shrimp trawling industry to develop TEDs to exclude even the largest turtles. These devices are mandatory for all shrimp trawlers.
In many places during the nesting season, workers and volunteers search the coastline for nests, and researchers may also go out during the evening to look for nesting females for tagging studies, gather barnacles, and tissues samples. Volunteers may, if necessary, relocate the nests for protection from threats, such as high spring tides and predators, and monitor the nests daily for disturbances. After the eggs hatch, volunteers uncover and tally hatched eggs, undeveloped eggs, and dead hatchlings. Any remaining live hatchlings are released or taken to research facilities. Typically, those that lack the vitality to hatch and climb to the surface die. Hatchlings use the journey from nest to ocean to build strength for the coming swim. Helping them to reach the ocean bypasses this strength building exercise and lowers their chances of survival.
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...
distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around 90 centimetres (35.4 in) long when fully grown, although larger specimens of up to 270 centimetres (106.3 in) have been discovered. The adult loggerhead sea turtle weighs approximately 135 kilograms (297.6 lb), with the largest specimens weighing in at more than 454 kilograms (1,000.9 lb). The skin ranges from yellow to brown in color, and the shell is typically reddish-brown. There are no external differences in gender until the turtle becomes an adult, the most obvious difference being that adult males have thicker tails and shorter plastrons than the females.
The loggerhead sea turtle is found in the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, and Indian
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
oceans as well as the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
. It spends most of its life in saltwater and estuarine habitats, with females briefly coming ashore to lay eggs. The loggerhead sea turtle has a low reproductive rate; females lay an average of four egg clutches
Clutch (eggs)
A clutch of eggs refers to all the eggs produced by birds or reptiles, often at a single time, particularly those laid in a nest.In birds, destruction of a clutch by predators, , results in double-clutching...
and then become quiescent, producing no eggs for two to three years. The loggerhead reaches sexual maturity within 17–33 years and has a lifespan of 47–67 years.
The loggerhead sea turtle is omnivorous
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
, feeding mainly on bottom dwelling invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s. Its large and powerful jaws serve as an effective tool in dismantling its prey. Young loggerheads are exploited by numerous predators; the eggs are especially vulnerable to terrestrial organisms. Once the turtles reach adulthood, their formidable size limits predation to large marine organisms such as sharks.
Loggerheads are considered an endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
and are protected by the International Union for the Conservation of Nature. Untended fishing gear is responsible for many loggerhead deaths. Turtles may also suffocate if they are trapped in fishing trawls
Trawling
Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net that is used for trawling is called a trawl....
. Turtle excluder device
Turtle excluder device
A turtle excluder device or TED is a specialized device that allows a captured sea turtle to escape when caught in a fisherman's net.In particular, sea turtles can be caught when bottom trawling is used by the commercial shrimp fishing industry. In order to catch shrimp, a fine meshed trawl net is...
s (TEDs) have been implemented in efforts to reduce mortality by providing the turtle an escape route. Loss of suitable nesting beaches and the introduction of exotic predators has also taken a toll on loggerhead populations. Efforts to restore their numbers will require international cooperation since the turtles roam vast areas of ocean and critical nesting beaches are scattered among several countries.
Taxonomy
Carolus LinnaeusCarolus Linnaeus
Carl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...
gave the loggerhead its first binomial name, Testudo caretta, in 1758. Thirty-five other names emerged over the following two centuries, with the combination Caretta caretta first introduced in 1902 by Leonhard Stejneger. The English common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
"loggerhead" refers to the animal's large head. The loggerhead sea turtle belongs to the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Cheloniidae, which includes all sea turtles except the leatherback sea turtle
Leatherback Sea Turtle
The leatherback sea turtle is the largest of all living sea turtles and the fourth largest modern reptile behind three crocodilians. It is the only living species in the genus Dermochelys. It can easily be differentiated from other modern sea turtles by its lack of a bony shell. Instead, its...
. The subspecific classification of the loggerhead sea turtle is debated, but most authors consider it a single polymorphic
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
species. Molecular genetics has confirmed hybridization of the loggerhead sea turtle with the Kemp's ridley sea turtle, hawksbill sea turtle, and green sea turtle
Green Sea Turtle
The Green sea turtle or green turtle is a large sea turtle of the family Cheloniidae. It is the only species in the genus Chelonia. Its range extends throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Oceans...
s. The extent of natural hybridization is not yet determined; however, second generation hybrids have been reported, suggesting some hybrids are fertile.
Habitat
Loggerhead sea turtles spend most of their lives in the open ocean and in shallow coastal waters. They rarely come ashore, with the exception of the females' brief visits to construct nests and deposit eggs. Hatchling loggerhead turtles live in floating mats of SargassumSargassum
Sargassum is a genus of brown macroalga in the order Fucales. Numerous species are distributed throughout the temperate and tropical oceans of the world, where they generally inhabit shallow water and coral reefs. However, the genus may be best known for its planktonic species...
algae. Adults and juveniles live along the continental shelf, as well as in shallow coastal estuaries. In the northwestern Atlantic Ocean, age plays a factor in habitat preference. Juveniles are more frequently found in shallow estuarine habitats with limited ocean access compared to non-nesting adults. Loggerheads occupy waters with surface temperatures ranging from 13.3–28 °C (55.9–82.4 F) during non-nesting season. Temperatures from 27–28 °C (80.6–82.4 F) are most suitable for nesting females.
Juvenile loggerheads share the Sargassum habitat with a variety of other organisms. The mats of Sargassum contain as many as 100 different species of animals on which the juveniles feed. Some of the prey, such as ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s, flies
Fly
True flies are insects of the order Diptera . They possess a pair of wings on the mesothorax and a pair of halteres, derived from the hind wings, on the metathorax...
, aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s, leafhopper
Leafhopper
Leafhopper is a common name applied to any species from the family Cicadellidae. Leafhoppers, colloquially known as hoppers, are minute plant-feeding insects in the superfamily Membracoidea in the order Hemiptera...
s, and beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, are carried by the wind to these areas. Endemic prey of the Sargassum mats include barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s, small crab larvae, fish eggs, and hydrozoa
Hydrozoa
Hydrozoa are a taxonomic class of very small, predatory animals which can be solitary or colonial and which mostly live in saltwater. A few genera within this class live in freshwater...
n colonies. Marine mammals and commercial fish, such as tuna
Tuna
Tuna is a salt water fish from the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers, and some species are capable of speeds of . Unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red coloration derives from myoglobin, an...
, dolphin fish, and amberjack
Amberjack
Amberjack refers to 3 species of Atlantic fish of the Carangidae family , which includes the jacks and the pompanos.Greater amberjacks, Seriola dumerili, are the largest of the jacks. They usually have dark stripes extending from nose to in front of their dorsal fins...
s, also inhabit the Sargassum mats.
Distribution
The loggerhead sea turtle has a cosmopolitan distributionCosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
, nesting over the broadest geographical range of any sea turtle. The loggerhead inhabits the Atlantic, Indian, and Pacific Oceans and the Mediterranean Sea.
In the Atlantic Ocean, the greatest concentration of loggerheads is along the southeastern coast of North America and in the Gulf of Mexico. Very few loggerheads are found along the European and African coastlines. Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
is the most popular nesting site, with over 67,000 nests built per year. Nesting extends as far north as Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
, as far south as Brazil, and as far east as the Cape Verde Islands. The Cape Verde Islands are the only significant nesting site on the eastern side of the Atlantic. Loggerheads found in the Atlantic Ocean feed from Canada to Brazil.
In the Indian Ocean, loggerheads feed along the coastlines of Africa, the Arabian Peninsula
Arabian Peninsula
The Arabian Peninsula is a land mass situated north-east of Africa. Also known as Arabia or the Arabian subcontinent, it is the world's largest peninsula and covers 3,237,500 km2...
, and in the Arabian Sea
Arabian Sea
The Arabian Sea is a region of the Indian Ocean bounded on the east by India, on the north by Pakistan and Iran, on the west by the Arabian Peninsula, on the south, approximately, by a line between Cape Guardafui in northeastern Somalia and Kanyakumari in India...
. Along the African coastline, loggerheads nest from Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
's Bazaruto Archipelago
Bazaruto Archipelago
The Bazaruto Archipelago is a group of six islands in Mozambique, near the mainland city of Vilankulo. It comprises the islands of Bazaruto, Benguerra, Magaruque, Banque, Santa Carolina and Shell....
to South Africa's St Lucia estuary. The largest Indian Ocean nesting site is Oman
Oman
Oman , officially called the Sultanate of Oman , is an Arab state in southwest Asia on the southeast coast of the Arabian Peninsula. It is bordered by the United Arab Emirates to the northwest, Saudi Arabia to the west, and Yemen to the southwest. The coast is formed by the Arabian Sea on the...
, on the Arabian Peninsula, which hosts around 15,000 nests, giving it the second largest nesting population of loggerheads in the world. Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
is another notable nesting area, with 1,000-2,000 nests per year.
Pacific loggerheads live in temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
to tropical regions. They forage in the East China Sea
East China Sea
The East China Sea is a marginal sea east of China. It is a part of the Pacific Ocean and covers an area of 1,249,000 km² or 750,000 square miles.-Geography:...
, the southwestern Pacific, and along the Baja California peninsula
Baja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...
. Eastern Australia and Japan are the major nesting areas, with the Great Barrier Reef
Great Barrier Reef
The Great Barrier Reef is the world'slargest reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometres over an area of approximately...
deemed an important nesting area. Pacific loggerheads occasionally nest in Vanuatu
Vanuatu
Vanuatu , officially the Republic of Vanuatu , is an island nation located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is some east of northern Australia, northeast of New Caledonia, west of Fiji, and southeast of the Solomon Islands, near New Guinea.Vanuatu was...
and Tokelau
Tokelau
Tokelau is a territory of New Zealand in the South Pacific Ocean that consists of three tropical coral atolls with a combined land area of 10 km2 and a population of approximately 1,400...
. Yakushima Island is the most important site, with three nesting grounds visited by 40% of all nearby loggerheads. After nesting, females often find homes in the East China Sea, while the Kuroshio Extension Bifurcation region provides important juvenile foraging areas. Eastern Pacific populations are concentrated off the coast of Baja California, where upwelling provides rich feeding grounds for juvenile turtles and subadults (individuals past the juvenile stage that lack adult characteristics). Nesting sites along the eastern Pacific Basin are rare. mtDNA sequence polymorphism analysis and tracking studies suggest 95% of the population along the coast of the Americas hatch on the Japanese Islands in the western Pacific. The turtles are transported by the prevailing currents across the full length of the northern Pacific, one of the longest migration routes of any marine animal. The return journey to the natal beaches in Japan has been long suspected, although the trip would cross unproductive clear water with few feeding opportunities. Evidence of a return journey came from an adult female loggerhead named Adelita, who in 1996, equipped with a satellite tracking device, made the 9000 miles (14,484.1 km) trip from Mexico across the Pacific. Adelita was the first animal of any kind ever tracked across an ocean basin.
The Mediterranean Sea is a nursery for juveniles, as well as a common place for adults in the spring and summer months. Almost 45% of the Mediterranean juvenile population has migrated from the Atlantic. Loggerheads feed in the Alboran Sea
Alboran Sea
|300px|thumb|]]The Alboran Sea is the westernmost portion of the Mediterranean Sea, lying between Spain on the north and Morocco and Algeria on the south...
and the Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...
.
Greece is the most popular nesting site along the Mediterranean, with more than 3,000 nests per year. Because of this, Greek authorities do not allow planes to take off or land at night in Zakynthos
Zakynthos
Zakynthos , also Zante, the other form often used in English and in Italian , is a Greek island in the Ionian Sea. It is the third largest of the Ionian Islands. It is also a separate regional unit of the Ionian Islands region, and the only municipality of the regional unit. It covers an area of ...
due to the nesting turtles. In addition to the Greek coast, the coastlines of Cyprus and Turkey are also common nesting sites.
Evolutionary history
All modern sea turtles probably descended from a single common ancestor during the Cretaceous period; however, evidence of a specific ancestor is lacking. Loggerheads, like all other sea turtles excluding the leatherback sea turtle, are members of the ancient familyFamily (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Cheloniidae
Cheloniidae
Cheloniidae is a family of turtles belonging to the sea turtle superfamily Chelonioidea.-Extant genera:*Genus Caretta**Loggerhead sea turtle *Genus Chelonia**Green sea turtle *Genus Eretmochelys...
. About 40 million years ago, a branch of the Cheloniidae gave rise to loggerhead sea turtle. Of the six species of living Cheloniidae, loggerheads are more closely related to the Kemp's ridley sea turtle
Kemp's Ridley
Kemp's ridley sea turtle , or Atlantic ridley sea turtle is the rarest sea turtle and is critically endangered. It is one of two living species in the genus Lepidochelys Kemp's ridley sea turtle (Lepidochelys kempii), or Atlantic ridley sea turtle is the rarest sea turtle and is critically...
, olive ridley sea turtle, and the hawksbill turtle
Hawksbill turtle
The hawksbill sea turtle is a critically endangered sea turtle belonging to the family Cheloniidae. It is the only extant species in its genus. The species has a worldwide distribution, with Atlantic and Pacific subspecies. E. imbricata imbricata is the Atlantic subspecies, while E...
than they are to the flatback turtle
Flatback Turtle
The flatback sea turtle is a sea turtle that is endemic to the continental shelf of Australia. Flatback turtles belong to the Cheloniidae, or sea turtle, superfamily and are the only species found in the genus Natator....
and the green turtle.
Around three million years ago, during the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
epoch, Central America emerged from the sea, effectively cutting off currents between the Atlantic and Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
Oceans. The rerouting of ocean currents lead to climatic changes as the Earth entered a glacial cycle. Cold water upwelling around the Cape of Good Hope
Cape of Good Hope
The Cape of Good Hope is a rocky headland on the Atlantic coast of the Cape Peninsula, South Africa.There is a misconception that the Cape of Good Hope is the southern tip of Africa, because it was once believed to be the dividing point between the Atlantic and Indian Oceans. In fact, the...
and reduction in water temperature at Cape Horn
Cape Horn
Cape Horn is the southernmost headland of the Tierra del Fuego archipelago of southern Chile, and is located on the small Hornos Island...
formed cold water barriers to migrating turtles. The result was a complete isolation of the Atlantic and Pacific populations of loggerheads. During the most recent ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
, the beaches of southeastern North America were too cold for sea turtle eggs. As the Earth began to warm, loggerheads moved farther north, colonizing the northern beaches. Because of this, turtles nesting between North Carolina and northern Florida represent a different genetic population from those in southern Florida.
The distinct populations of loggerheads have unique characteristics and genetic differences. For example, Mediterranean loggerheads are smaller, on average, than Atlantic Ocean loggerheads. North Atlantic and Mediterranean loggerhead sea turtles are descendants of colonizing loggerheads from Tongaland
Tongaland
Tongaland is a region in the north-east of Zululand. It shares its northern border with Mozambique. Its western border is marked by the Lebombo Mountains, and the Indian Ocean is its eastern border.-Geography:...
, South Africa. South African loggerhead genes are still present in these populations today.
Anatomy and morphology
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
(upper shell) range from a yellow-orange to a reddish-brown, while the plastron (underside) is typically pale yellow. The turtle's neck and sides are brown on the tops and yellow on the sides and bottom.
The turtle's shell is divided into two sections: carapace and plastron. The carapace is further divided into large plates, or scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...
s. Typically, there are 11 or 12 pairs of marginal scutes which rim the carapace. Five vertebral scutes run down the carapace's midline, while five pairs of costal scutes border them. The nuchal scute is located at the base of the head. The carapace connects to the plastron by 3 pairs of inframarginal scutes forming the bridge of the shell. The plastron features paired gular, humeral, pectoral, abdominal, femoral, and anal scutes. The shell serves as external armor, although loggerhead sea turtles cannot retract their head or flippers into their shells.
Sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
of the loggerhead sea turtle is only apparent in adults. Adult males have longer tails and claws than females. The males' plastrons are shorter than the females', presumably to accommodate the males' larger tails. The carapace of males are wider and less domed than the females, and males typically have wider heads than females. The sex of juveniles and subadults cannot be determined through external anatomy, but can be observed through dissection, laparoscopy
Laparoscopy
Laparoscopy is an operation performed in the abdomen or pelvis through small incisions with the aid of a camera...
(an operation performed on the abdomen), histological
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
examination (cell anatomy), and radioimmunological assays (immune study dealing with radiolabeling
Isotopic labeling
Isotopic labeling is a technique for tracking the passage of a sample of substance through a system. The substance is 'labeled' by including unusual isotopes in its chemical composition...
).
Lachrymal glands located behind each eye allow the loggerhead to maintain osmotic balance by eliminating the excess salt obtained from ingesting ocean water. On land, the excretion of excess salt gives the false impression that the turtle is crying.
Ecology and behavior
Loggerhead sea turtles observed in captivity and in the wild are most active during the day. In captivity, the loggerheads' daily activities are divided between swimming and resting on the bottom. While resting, loggerheads spread their forelimbs to about mid-stroke swimming position. They remain motionless with eyes open or half-shut and are easily alerted during this state. At night, captive loggerheads sleep in the same position with their eyes tightly shut and are slow to react. Loggerheads spend up to 85% of their day submerged, with males being the more active divers than females. The average duration of dives is 15–30 minutes, but they can stay submerged for up to four hours. Juvenile loggerheads and adults differ in their swimming methods. Juveniles keep their forelimbs pressed to the side of their carapace and propel themselves by kicking with their hind limbs. As the juveniles mature, their swimming method is progressively replaced with the adults' alternating-limb method. The loggerheads depend entirely on this method of swimming by the time they are one year old.Water temperature affects the sea turtle's metabolic rate. Lethargy is induced at temperatures between 13 and 15 °C (55.4 and 59 F). The loggerhead takes on a floating, cold-stunned posture when temperatures drop to approximately 10 °C (50 °F). However, younger loggerheads are more resistant to cold and do not become stunned until temperatures drop below 9 °C (48.2 °F). The loggerheads' migration
Animal migration
Animal migration is the relatively long-distance movement of individuals, usually on a seasonal basis. It is a ubiquitous phenomenon, found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. The trigger for the migration may be local...
help prevent instances of cold-stunning. Higher water temperatures cause an increase in metabolism and heart rate. A loggerhead's body temperature increases in warmer waters more quickly than it decreases in colder water. The loggerhead sea turtle's critical thermal maximum
Critical thermal maximum
Critical thermal maximum, in zoology, is that temperature for a given species above which most individuals respond with unorganized locomotion, subjecting the animal to likely death...
is currently unknown.
Female-female aggression, which is especially uncommon in marine vertebrates), is common among loggerheads. Ritualized aggression escalates from passive threat displays to combat. This conflict primarily occurs over access to feeding grounds. Escalation typically follows four steps. First, initial contact is stimulated by visual or tactile cues. Second, confrontation occurs, beginning with passive confrontations characterized by wide head-tail circling. They begin aggressive confrontation when one turtle ceases to circle and directly faces the other. Third, sparring
Sparring
Sparring is a form of training common to many martial arts. Although the precise form varies, it is essentially relatively 'free-form' fighting, with enough rules, customs, or agreements to make injuries unlikely...
occurs with turtles snapping at each other’s jaws. The final stage, separation, is either mutual, with both turtles swimming away in opposite directions, or involves chasing one out of the immediate vicinity. Escalation is determined by several factors, including: hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
levels, energy expenditure, expected outcome, and importance of location. At all stages, an upright tail shows willingness to escalate, while a curled tail shows willingness to submit. Because higher aggression is metabolically costly and potentially debilitating, contact is much more likely to escalate when the conflict is over access to good foraging grounds. Further aggression has also been reported in captive loggerheads. The turtles are seemingly territorial
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
and will fight with other loggerheads and sea turtles of different species.
Predators
Loggerheads have numerous predators. Egg and nestling predators include oligochaete worms, beetles, fly larvae, ants, parasitoid wasp larvae, flesh flies, crabs, snakes, gulls, crows, opossums, bears, rats, armadillos, honey badgers, skunks, canids, raccoonRaccoon
Procyon is a genus of nocturnal mammals, comprising three species commonly known as raccoons, in the family Procyonidae. The most familiar species, the common raccoon , is often known simply as "the" raccoon, as the two other raccoon species in the genus are native only to the tropics and are...
s, cats, hogs, and humans. During their migration from their nest to the sea, hatchlings are preyed on by dipteran larvae, crabs, toads, lizards, snakes, birds, and mammals. In the ocean, predators of the loggerhead juveniles and adults include sharks, other fish, such as parrotfish
Parrotfish
Parrotfishes are a group of fishes that traditionally had been considered a family , but now often are considered a subfamily of the wrasses. They are found in relatively shallow tropical and subtropical oceans throughout the world, but with the largest species richness in the Indo-Pacific...
, moray eel
Moray eel
Moray eels are cosmopolitan eels of the family Muraenidae. The approximately 200 species in 15 genera are almost exclusively marine, but several species are regularly seen in brackish water and a few, for example the freshwater moray can sometimes be found in freshwater...
s, portunid crabs, gulls, monk seals, and killer whales. Nesting females are attacked by flesh flies, feral
Feral
A feral organism is one that has changed from being domesticated to being wild or untamed. In the case of plants it is a movement from cultivated to uncultivated or controlled to volunteer. The introduction of feral animals or plants to their non-native regions, like any introduced species, may...
dogs, and humans. Salt marsh mosquitoes can also pester nesting females.
In Australia, the introduction of the red fox (Vulpes vulpes) by English settlers in the 19th century led to significant reductions in loggerhead sea turtle populations. In one coastal section in eastern Australia during the 1970s, predation of turtle eggs destroyed up to 95% of all clutches laid. Aggressive efforts to destroy foxes in the 1980s and 1990s has reduced this impact; however, it is estimated that it will be the year 2020 before populations will experience complete recovery from such dramatic losses.
Along the southeastern coast of the United States, the raccoon (Procyon lotor) is the most destructive predator of nesting sites. Mortality rates of nearly 100% of all clutches laid in a season have been recorded on some Florida beaches. This is attributed to an increase in raccoon populations, which have flourished in urban environments. Aggressive efforts to protect nesting sites by covering them with wire mesh has significantly reduced the impact of raccoon predation on loggerhead sea turtle eggs. On Bald Head Island, in North Carolina, wire mesh screens are used on every confirmed nest to prevent excavation by resident red foxes (http://www.bhic.org/). A new concern with the steel cage technique is interference with the normal development of the nestlings' magnetic sense due to the use of ferrous wire (http://www.unc.edu/depts/geomag/), which may disrupt the turtles' ability to navigate properly. Efforts are underway to find a nonmagnetic material that will prevent predator's gnawing through the barrier.
Up to 40% of nesting females around the world have wounds believed to come from shark attacks.
Disease and parasites
Infectious bacteria such as PseudomonasPseudomonas
Pseudomonas is a genus of gammaproteobacteria, belonging to the family Pseudomonadaceae containing 191 validly described species.Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the...
and Salmonella
Salmonella
Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...
attack loggerhead hatchlings and eggs. Fungi such as Penicillium
Penicillium
Penicillium is a genus of ascomycetous fungi of major importance in the natural environment as well as food and drug production. Members of the genus produce penicillin, a molecule that is used as an antibiotic, which kills or stops the growth of certain kinds of bacteria inside the body...
infect loggerhead sea turtle nests and cloaca.
Fibropapillomatosis
Fibropapillomatosis
Fibropapillomatosis is a condition characterized by the presence of fibropapillomas, neoplasms consisting of both the epidermal and dermal skin layers.-In sea turtles:...
disease threatens loggerheads in the form of the herpes-type
Herpesviridae
The Herpesviridae are a large family of DNA viruses that cause diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word herpein , referring to the latent, recurring infections typical of this group of viruses...
virus which causes internal and external tumors. These tumors disrupt essential behaviors and, if on the eyes, cause permanent blindness. Trematodes of the family Spirorchiidae
Spirorchiidae
Spirorchiidae is a family of digenetic trematodes. They are parasites of turtles. Disease caused by them is commonly called spirorchiidiosis.- Genera :Genera in the family Spirorchiidae include:* Amphiorchis** Amphiorchis solus* Hapalotrema...
inhabit tissues throughout the body of the loggerhead, including vital organs such as the heart and the brain. Trematode infection can be highly debilitating. For example, inflammatory
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
trematode lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s can cause endocarditis
Endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...
and neurological disease
Neurological disorder
A neurological disorder is a disorder of the body's nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord, or in the nerves leading to or from them, can result in symptoms such as paralysis, muscle weakness, poor coordination, loss of sensation, seizures,...
. A nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
, Angiostoma carettae
Angiostoma carettae
Angiostoma carettae is the first nematode known to inhabit turtles. Its specific name comes from its presence in Loggerhead Sea Turtles ....
, also infects loggerheads. The nematodes cause histologic
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
lesions in the respiratory tract
Respiratory tract
In humans the respiratory tract is the part of the anatomy involved with the process of respiration.The respiratory tract is divided into 3 segments:*Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx...
.
More than 100 species of animals from 13 phyla
Phylum
In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....
as well as 37 kinds of algae live on loggerheads' backs. These parasitic organisms, which increase drag, offer no known benefit to the turtle, although it has been suggested that the dulling effect of organisms on shell color improves camouflaging
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
ability.
Feeding
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, such as gastropods, bivalves
Bivalvia
Bivalvia is a taxonomic class of marine and freshwater molluscs. This class includes clams, oysters, mussels, scallops, and many other families of molluscs that have two hinged shells...
, and decapods
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
. The loggerhead has a greater list of known prey than any other sea turtle. Other food items include sponges, coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
s, sea pen
Sea pen
Sea pens are colonial marine cnidarians belonging to the order Pennatulacea. There are 14 families within the order; they are thought to have a cosmopolitan distribution in tropical and temperate waters worldwide...
s, polychaete worms
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
, sea anemone
Sea anemone
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...
s, cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s, barnacles, brachiopod
Brachiopod
Brachiopods are a phylum of marine animals that have hard "valves" on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection...
s, isopods
Isopoda
Isopods are an order of peracarid crustaceans, including familiar animals such as woodlice and pill bugs. The name Isopoda derives from the Greek roots and...
, insects, bryozoa
Bryozoa
The Bryozoa, also known as Ectoprocta or commonly as moss animals, are a phylum of aquatic invertebrate animals. Typically about long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia...
ns, sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...
s, sand dollar
Sand dollar
The term Sand dollar refers to species of extremely flattened, burrowing echinoids belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are known as sea biscuits...
s, sea cucumber
Sea cucumber
Sea cucumbers are echinoderms from the class Holothuroidea.They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. There are a number of holothurian species and genera, many of which are targeted...
s, starfish, fish (eggs, juveniles, and adults), wrasses, hatchling turtles (including members of its own species), algae, and vascular plant
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
s. During migration through the open sea, loggerheads eat jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
, floating molluscs, floating egg clusters, squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
, and flying fish.
Loggerheads crush prey with their large and powerful jaws. 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, mucosal (mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
-covered) papillae found in the foreregion of the loggerhead's esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
filter out foreign bodies, such as fish hooks. The next region of the esophagus is nonpapillated, with numerous mucosal folds. The rate of digestion in loggerheads is temperature dependent; digestion rate increases as temperature increases.
Early life
Hatchlings range in color from light brown to almost black, lacking the adult's distinct yellows and reds. Upon hatching, they measure approximately 4.6 centimetres (1.8 in) and weigh about 20 gram (0.705479242102239 oz). The eggs are typically laid on the beach in an area above the high-tide lineStrandline
The strandline, or high water mark, is the area at the top of a beach where debris is deposited. Where there are tides, this line is formed by the highest position of the tide, and moves up and down the beach on a fortnightly cycle...
. The eggs are laid near the water so the hatchlings can return to the sea. The loggerhead's sex is dictated by the temperature of the underground nest. Incubation temperatures generally range from 26–32 °C (78.8–89.6 F). Studies show loggerhead sea turtle eggs kept at a constant incubating temperature of 32 °C (89.6 °F) become females. Eggs incubating at 28 °C (82.4 °F) become males. An incubation temperature of 30 °C (86 °F) results in an equal ratio of male to female hatchlings. Hatchlings from eggs in the middle of the clutch tend to be the largest, grow the fastest, and be the most active during the first few days of sea life.
After incubating for approximately 80 days, hatchlings dig through the sand to the surface. This usually occurs at night, when darkness increases the chance of escaping predation and damage from extreme sand surface temperatures is reduced. Hatchlings enter the ocean by navigating toward the brighter horizon created by the reflection of the moon and star light off the water's surface.
Hatchlings can lose up to 20% of their body mass due to evaporation of water as they journey from nest to ocean. Hatchlings initially use the undertow
Undertow (wave action)
Undertow is a subsurface flow of water returning seaward from shore as result of wave action. This type of shore current can play a role in material deposition such as creating sand bars....
to push them five to ten yards away from the shore. Once in the ocean, hatchlings swim for about 20 hours, bringing them far offshore. An iron compound, magnetite
Magnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
, in their brains allows the turtles to perceive the Earth's magnetic field
Earth's magnetic field
Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
, for navigation.
Many hatchlings use Sargassum in the open ocean as protection until they reach 45 centimetres (17.7 in). Hatchling loggerheads live in this pelagic environment
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
until they reach juvenile age, and then they migrate to nearshore waters.
Maturation
Hibernation
Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...
to some degree. In the coldest months, loggerheads submerge for up to seven hours at a time, emerging for only seven minutes to breathe. Although outdone by freshwater turtles
Terrapin
A terrapin is a turtle living in fresh or brackish water.Terrapin may also refer to:* Terrapin , a transport vehicle used for amphibious assault by the Allies during the Second World War...
, these are among the longest recorded dives for any air-breathing marine vertebrate. During their seasonal migration, juvenile loggerheads have the ability to use both magnetic and visual cues. When both aids are available, they are used in conjunction; if one aid is not available, the other suffices. The turtles swim at about 1.6 kph during migration.
Like all marine turtles, the loggerhead prepares for reproduction in its foraging area. This takes place several years before the loggerhead migrates to a mating area. Female loggerheads first reproduce at ages 28–33 in Southeastern United States and Australia, and at ages 17–30 in South Africa. Age at first reproduction in the Mediterranean, Oman, Japan, and Brazil are unknown. Nesting loggerheads have a straight carapace length of 70–109 cm (27.6–42.9 in). Because of the large range, carapace length is not a reliable indicator of sexual maturity. Loggerheads have an estimated maximum lifespan of 47–67 years in the wild.
Reproduction
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
l pheromone
Pheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
s to indicate reproductive ability. Before mating, the male approaches a female and attempts to mount her, while she resists. Next, the male and female begin to circle each other. If the male has competitors, the female may let the males struggle with each other. The winner then mounts the female; the male's curved claws usually damage the shoulders of the female's shell during this process. Other courting males bite the male while he is attempting to copulate, damaging his flippers and tail, possibly exposing bones. Such damage can cause the male to dismount and may require weeks to heal.
While nesting, females produce an average of 3.9 egg clutches, and then become quiescent, producing no eggs for an average of two to three years. Unlike other sea turtles, courtship and mating usually do not take place near the nesting beach, but rather along migration routes between feeding and breeding grounds. Recent evidence indicates ovulation
Ovulation
Ovulation is the process in a female's menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum . Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle...
in loggerheads is mating-induced. Through the act of mating, the female ovulates eggs which are fertilized by the male. This is unique, as mating-induced ovulation is rare outside of mammals. In the Mediterranean, loggerheads mate from late March to early June. The nesting season
Nesting season
The nesting season is the time of year during which birds and some other animals, particularly some reptiles, build nests, lay eggs in them, and in most cases bring up their young. It is usually in the spring....
peaks in June and July, but varies by nesting beach.
Loggerheads may display multiple paternity. Multiple paternity is possible due to sperm storage. The female can store sperm from multiple males in her oviducts until ovulation. A single clutch may have as many as five fathers, each contributing sperm to a portion of the clutch. Multiple paternity and female size are positively correlated. Two hypotheses explain this correlation. One states that males favor large females due to perceived higher fecundity
Fecundity
Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...
(ability to reproduce). The other states that because larger females are able to swim more quickly to mating grounds, they have a longer mating period.
All sea turtles have similar basic nesting behaviors. Females return to lay eggs at intervals of 12–17 days during the nesting season, on or near the beach where they hatched. They exit the water, climb the beach, and scrape away the surface sand to form a body pit. With their hind limbs, they excavate an egg chamber in which the eggs are deposited. The females then cover the egg chamber and body pit with sand, and finally return to the sea. This process takes one to two hours, and occurs in open sand areas or on top of sand dunes. The nesting area must be selected carefully because it affects characteristics such as fitness, emergence ratio, and vulnerability to nest predators. Loggerheads have an average clutch
Clutch (eggs)
A clutch of eggs refers to all the eggs produced by birds or reptiles, often at a single time, particularly those laid in a nest.In birds, destruction of a clutch by predators, , results in double-clutching...
size of 4 eggs.
Conservation
Many human activities have negative effects on loggerhead sea turtle populations. The prolonged time required for loggerheads to reach sexual maturity and the high mortality rates of eggs and young turtles from natural phenomena compound the problems of population reduction as a consequence of human activities.Threats
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
; consumption has decreased, however, due to worldwide legislation. Despite this, turtle meat and eggs are still consumed in countries where regulations are not strictly enforced. In Mexico, turtle eggs are a common meal; locals claim the egg is an aphrodisiac
Aphrodisiac
An aphrodisiac is a substance that increases sexual desire. The name comes from Aphrodite, the Greek goddess of sexuality and love. Throughout history, many foods, drinks, and behaviors have had a reputation for making sex more attainable and/or pleasurable...
. Eating turtle eggs or meat can cause serious illness due to harmful bacteria, such as Pseudomonas aeruginosa
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...
and Serratia marcescens
Serratia marcescens
Serratia marcescens is a species of Gram-negative, rod-shaped bacterium in the family Enterobacteriaceae. A human pathogen, S. marcescens is involved in nosocomial infections, particularly catheter-associated bacteremia, urinary tract infections and wound infections, and is responsible for 1.4% of...
, and high levels of toxic metals that build up through bioaccumulation
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
.
The U.S. West Coast is a critical migratory corridor for the Pacific loggerheads, in which these turtles swim across the Pacific to California’s coast from breeding grounds in Japan. Important foraging habitats for juveniles in the central North Pacific have been revealed through telemetry
Telemetry
Telemetry is a technology that allows measurements to be made at a distance, usually via radio wave transmission and reception of the information. The word is derived from Greek roots: tele = remote, and metron = measure...
studies. Along with these foraging habitats, high levels of bycatch from industrial-scale fisheries have been found to overlap; with drift gillnets in the past and longline fisheries presently. Many juvenile loggerheads aggregate off the coast of Baja California Sur, Mexico, where small coastal fisheries (6-8m) increase these turtle’s mortality risk; fishers have reported catching dozens of loggerheads with bottom-set gear per day per boat. The most common commercial fishery that accidentally take loggerheads are bottom trawls used for shrimp vessels in the Gulf of California; as well as gillnets, longlines, etc. In 2000, between 2,600 and 6,000 loggerheads were estimated to have been killed by pelagic longlining in the Pacific.
Fishing gear is the biggest threat to loggerheads in the open ocean. They often become entangled in longlines or gillnet
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...
s. According to the 2009 status review of loggerheads by the Fisheries Service, drowning from entanglement in longline and gillnet fishing gear is the turtles’ primary threat in the North Pacific. They also become stuck in traps, pots, trawls, and dredge
Dredge
Dredging is an excavation activity or operation usually carried out at least partly underwater, in shallow seas or fresh water areas with the purpose of gathering up bottom sediments and disposing of them at a different location...
s. Caught in this unattended equipment, loggerheads risk serious injury or drowning. Turtle excluder devices for nets and other traps reduce the number being accidentally caught.
Nearly 24,000 metric tons of plastic is dumped into the ocean each year. Turtles ingest a wide array of this floating debris, including plastic bags, plastic sheets, plastic pellets, balloons and abandoned fishing line. Loggerheads may mistake the floating plastic for jellyfish, a common food item. The ingested plastic causes numerous health concerns, including: intestinal blockage, reduced nutrient absorption, suffocation, ulcerations, malnutrition or starvation. Ingested plastics release toxic compounds, including polychlorinated biphenyls, which may accumulate in internal tissues. Such toxins may lead to a thinning of eggshells, tissue damage or deviation from natural behaviors.
Artificial lighting
Electric light
Electric lights are a convenient and economic form of artificial lighting which provide increased comfort, safety and efficiency. Most electric lighting is powered by centrally-generated electric power, but lighting may also be powered by mobile or standby electric generators or battery systems...
discourages nesting and interferes with the hatchlings' ability to navigate to the water's edge. Females prefer nesting on beaches free of artificial lighting. On developed beaches, nests are often clustered around tall buildings, perhaps because they block out the man-made light sources. Loggerhead hatchlings are drawn toward the brighter area over the water which is the consequence of the reflection of moon and star light. Confused by the brighter artificial light, they navigate inland, away from the protective waters, which exposes them to dehydration and predation as the sun rises. Artificial lighting causes tens of thousands of hatchling deaths per year.
Destruction and encroachment of habitat by humans is another threat to loggerhead sea turtles. Optimum nesting beaches are open sand beaches above the high tide line. However, beach development deprives them of suitable nesting areas, forcing them to nest closer to the surf. Urbanization often leads to the siltation
Siltation
Siltation is the pollution of water by fine particulate terrestrial clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments, and to the increased accumulation of fine sediments on bottoms where they are undesirable...
of sandy beaches, decreasing their viability. Construction of docks and marinas can destroy near-shore habitats. Boat traffic and dredging degrades habitat and can also injure or kill turtles when boats collide with turtles at or near the surface.
Annual variations in climatic temperatures can affect sex ratios, since loggerheads have temperature-dependent sex determination. High sand temperatures may skew gender ratios in favor of females. In one study (Mrosovsky, N. & Provancha, J. 1992), nesting sites exposed to unseasonably warm temperatures over a three-year period produced 87-99% females. This raises concerns over the connection between rapid global temperature changes and the possibility of population extinction. A more localized effect on gender skewing comes from the construction of tall buildings, which reduce sun exposure, lowering the average sand temperature. This results in a shift in gender ratios that favor the emergence of male turtles.
Conservation efforts
Loggerhead sea turtles are classified as endangered by the International Union for the Conservation of Nature and are listed under Appendix I of the Convention on International Trade in Endangered Species, making international trade illegal. In the United States, the U.S. Fish and Wildlife Service
United States Fish and Wildlife Service
The United States Fish and Wildlife Service is a federal government agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats...
(FWS) and National Marine Fisheries Service
National Marine Fisheries Service
The National Marine Fisheries Service is a United States federal agency. A division of the National Oceanic and Atmospheric Administration and the Department of Commerce, NMFS is responsible for the stewardship and management of the nation's living marine resources and their habitat within the...
(NMFS) classify them as a threatened species under the Endangered Species Act
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...
. Loggerheads are listed as endangered under both Australia's Environment Protection and Biodiversity Conservation Act 1999
Environment Protection and Biodiversity Conservation Act 1999
The Environment Protection and Biodiversity Conservation Act 1999 is an Act of the Parliament of Australia that provides a framework for protection of the Australian environment, including its biodiversity and its natural and culturally significant places...
and Queensland's Nature Conservation Act 1992
Nature Conservation Act 1992
The Nature Conservation Act 1992 is an act of the Parliament of Queensland that provides for the legislative protection of Queensland's threatened biota. As originally published, it provided for biota to be declared presumed extinct, endangered, vulnerable, rare or common...
. The Convention on Migratory Species works for the conservation of loggerhead sea turtles on the Atlantic coast of Africa, as well as in the Indian Ocean and southeast Asia. Throughout Japan, the Sea Turtle Association of Japan aids in the conservation of loggerhead sea turtles. Greece's ARCHELON
ARCHELON, the Sea Turtle Protection Society of Greece
ARCHELON, the Sea Turtle Protection Society of Greece was founded in 1983. It aims to protect sea turtles and their habitats in Greece through research, public awareness campaigns, restoring habitats, and through its rescue centre, built in 1994....
works for their conservation. The Marine Research Foundation works for loggerhead conservation in Oman. Annex 2 of the Specially Protected Areas and Wildlife (SPAW) Protocol of the Cartagena Convention, which deals with pollution that could harm marine ecosystems, also protects them. Conservation organizations worldwide have worked with the shrimp trawling industry to develop TEDs to exclude even the largest turtles. These devices are mandatory for all shrimp trawlers.
In many places during the nesting season, workers and volunteers search the coastline for nests, and researchers may also go out during the evening to look for nesting females for tagging studies, gather barnacles, and tissues samples. Volunteers may, if necessary, relocate the nests for protection from threats, such as high spring tides and predators, and monitor the nests daily for disturbances. After the eggs hatch, volunteers uncover and tally hatched eggs, undeveloped eggs, and dead hatchlings. Any remaining live hatchlings are released or taken to research facilities. Typically, those that lack the vitality to hatch and climb to the surface die. Hatchlings use the journey from nest to ocean to build strength for the coming swim. Helping them to reach the ocean bypasses this strength building exercise and lowers their chances of survival.
Symbol
The loggerhead sea turtle is the official state reptile of South Carolina and also the state saltwater reptile of Florida.See also
- Sea turtle threats
- AdelitaAdelita (turtle)Adelita was the name of the first sea turtle tracked across an ocean basin, the northern Pacific Ocean. A satellite tag was placed on Adelita, a loggerhead sea turtle , in 1996 by Wallace "J" Nichols, as part of a research project....
the first sea turtle tracked across an ocean basin.
External links
- International: ARKive – images and movies of the loggerhead turtle (Caretta caretta)
- Greece: Go Zakynthos about Caretta Turtle