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Loggerhead Turtle

Caretta caretta (Linnaeus 1758)

Lifespan, longevity, and ageing

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Maximum longevity: 37 years Observations: Some estimates suggest that these animals may live up to 62 years in the wild. Sexual maturity in the wild may also occur at later ages (19-24 years) than in captivity (http://www.pwrc.usgs.gov/neparc/).
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Benefits

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Caretta caretta is beneficial to humans in many ways. Sea turtles are an attraction for ecotourism and popular with people wanting to snorkel or dive with these animals, as well as for those wanting to watch the nesting process. Loggerhead sea turtles are the most common sea turtle in U.S. waters and therefore most sea turtle research is carried out on this species. Also, in many countries, especially in Central and South America, Africa, Asia, and the Mediterranean, these turtles and their eggs are exploited for food.

Positive Impacts: food ; body parts are source of valuable material; ecotourism ; research and education

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Benefits

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There are no known adverse effects of Caretta caretta on humans.

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Life Cycle

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Like many turtles, Caretta caretta has temperature-dependent sex determination (TSD). The sex of hatchlings is determined by egg temperature during the middle third of incubation. The pivotal temperature - the temperature at which an 50:50 ratio of males:females is produced - varies from location to location around the world. For example, the pivotal temperature in South Africa is 29.7 ºC , but in Australia the pivotal temperature is 28.2 ºC. Generally, the pivotal temperature is between 28 and 30 ºC. Temperatures of 24 to 26 ºC tend to produce all males and temperatures of 32 to 34 ºC tend to produce all females. Eggs are not viable outside the extremes of these ranges.

The speed of embryonic development within the egg depends on the temperature within the nest. This temperature can be affected by sun, shade, rain, heat generated within the nest, and an egg's position in the nest. At cool temperatures, around 25 ºC, development to hatching can take 65 to 70 days, but at warmer temperatures, around 35 ºC, development usually takes around 45 days.

When loggerheads are juveniles the differences between the sexes begin to emerge. Males produce increasing levels of testosterone as they approach maturity, which triggers tail growth, plastron softening, and the growth and curvature of a nail on each forelimb. Females produce estrogen and small amounts of testosterone, but externally just grow larger. Age at maturity is variable. Mature size is attained between age 10 and 30; captives are predicted to mature in 16 to 17 years. Reproductve life span (after reaching maturity) is estimated at about 32 years.

Development - Life Cycle: temperature sex determination

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Conservation Status

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Caretta caretta, like all sea turtle species, is in decline. The greatest causes of decline world-wide is probably incidental capture in fishing gear such as long lines, gill nets, shrimp trawls, and direct exploitation of adult turtles and eggs for human food. Though in sharp decline in many parts of its range, and locally along North American coasts, loggerhead sea turtles are currently the most common and least-threatened marine turtle in North American waters. They are listed as threatened under the U.S. Endangered Species Act.

Other important causes of decline include beachfront development, human disturbance of nesting females, pesticides, petroleum products (oil spills), and other ocean pollutants, human-influenced increases in nest predators such as raccoons, collisions with watercraft, and offshore and channel dredging. Artificial lighting near beaches can confuse emerging hatchlings, causing them to move away from the ocean and into hazardous urban areas. If predictions about global warming are realized, increased storms and rising sea levels could damage or destroy nesting areas and nests, and temperature changes could skew sex ratios.

The United States has taken several measures to reduce bycatch of loggerhead sea turtles. Turtle exclusion devices (TEDs) are required in commercial fishing and shrimping nets. There have been other gear modifications, changes in practice, and area closures in fishing that have reduced bycatch. Also, other countries may harvest shrimp in a way that puts loggerhead sea turtles in danger and the U.S. has put an embargo on these shrimp. Despite these measures being taken, the numbers of loggerhead sea turtles in U.S. waters is still declining.

US Federal List: threatened

CITES: appendix i

State of Michigan List: no special status

IUCN Red List of Threatened Species: endangered

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Behavior

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Communication in Caretta caretta has not been well-studied. Courtship behavior seems to largely depend on visual and tactile cues, but it has been suggested that glandular odors (especially Rathke's gland secretions) may help bring the sexes together.

Perception, however, is highly developed. As soon as hatchlings emerge from their nests (usually at night), they begin analyzing their environment to determine which direction they should go towards the ocean. It is believed that a major clue is the light on the horizon. Hatchlings orient towards the brightest light, which, historically, is the moon or star light over the ocean. They may also perceive the incline of the beach and orient towards a lower elevation. Once in the water, hatchlings use chemical and magnetic cues to orient themselves and navigate their way to the currents in which they will spend the next 10 or so years of their lives.

During the juvenile and adult years it is likely that loggerheads use chemical and magnetic cues to orient themselves during their migrations. It has been demonstrated that C. caretta uses on-site cues, not memory of past movement, in orientation and is therefore capable of map-based navigation.

Food is typically located either visually or by smell.

Communication Channels: visual ; tactile ; chemical

Other Communication Modes: pheromones

Perception Channels: visual ; polarized light ; tactile ; vibrations ; chemical ; magnetic

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Associations

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Caretta caretta has been called a "keystone species" because of its ecological impact. It feeds on large numbers of invertebrates, affecting their populations and allowing their broken shells to be used as a calcium source for other species. Also, a substantial portion of the eggs laid become food for predators. Finally, over 100 species from 13 phyla may live on the carapace of loggerheads, making it somewhat of a mobile reef.

Ecosystem Impact: creates habitat; keystone species

Commensal/Parasitic Species:

  • barnacles (Cirripedia)
  • algae
  • skeleton shrimp (Caprellidea)
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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Trophic Strategy

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Loggerhead sea turtles are primarily carnivorous, but will also eat algae - Ascophyllum, Ulothrix, Urospora, Sargassum - and vascular plants - Cymodocea, Thalassia, Zostera - making them omnivorous. Their huge heads and massive, powerful jaws make them well-adapted to eating hard-shelled prey, such as horseshoe crabs (Limulus polyphemus), bivalves, barnacles, whelks, and conchs. However, Caretta caretta is a dietary generalist and also eats many other invertebrates, such as sponges, jellyfish, cephalopods, shrimp, insects, sea urchins, and fish and fish eggs, including Brecoortia species, Ceratoscopelus species, and Diodon species. There are slight variations in the diet of each life stage, but loggerhead sea turtles are generalists throughout life.

Animal Foods: fish; eggs; insects; mollusks; aquatic or marine worms; aquatic crustaceans; echinoderms; cnidarians; other marine invertebrates

Plant Foods: leaves; algae; macroalgae

Primary Diet: omnivore

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Distribution

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Caretta caretta is found in nearly all the world's temperate and tropical oceans: the Atlantic Ocean from Newfoundland to Argentina, the Indian Ocean from southern Africa to the Arabian Gulf to western Australia, the Mediterranean Sea, and the Pacific Ocean from Alaska to Chile and Australia to Japan. During winter months loggerhead sea turtles migrate to tropical and subtropical waters.

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Habitat

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Preferred habitat of Caretta caretta individuals changes throughout the life cycle. Adult females go ashore to lay eggs and seem to prefer steeply sloped, high energy beaches. When hatchlings emerge from the nest, they head for the ocean. Young juveniles are typically found among drifting Sargassum mats in warm ocean currents. Older juveniles and adults are most often found in coastal waters and tend to prefer a rocky or muddy substrate over a sandy one. They may also be found near coral reefs and venturing into salt marshes, brackish lagoons, and the mouths of rivers.

Range depth: 0 to 61 m.

Habitat Regions: temperate ; tropical ; saltwater or marine

Aquatic Biomes: pelagic ; reef ; coastal ; brackish water

Other Habitat Features: estuarine

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Life Expectancy

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Not much is known about the lifespan of Caretta caretta. Is is estimated that they live 30 to 62 years in the wild, but data is insufficient for lifespan in captivity as well as longest known lifespans in the wild and in captivity. In Australia is has been predicted that the annual survival rate is 92% for immature individuals and 88% for adults.

Range lifespan
Status: captivity:
33 (high) years.

Typical lifespan
Status: wild:
30 to 62 years.

Average lifespan
Status: captivity:
33.0 years.

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Morphology

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Named for their huge heads and powerful jaws, loggerhead turtles are the largest hard-shelled sea turtles alive today. They have a heart-shaped carapace, which is often covered with commensal organisms such as barnacles and algae. Generally, the carapace is a reddish-brown hue with olive tones; there are five pairs of pleural scutes, the first pair touching the cervical (neck) scute. The plastron is cream to yellow, and has two longitudinal ridges that disappear with age. The skin is dull to reddish brown dorsally and medium to pale yellow around the edges and ventrally. The skin may have some orange coloration as well. The skin of males is more brown and the head more yellow than those of females. Males also have wider carapaces and a long curved claw on each forelimb. Loggerhead sea turtle hatchlings tend to be dark brown to reddish brown on the carapace and cream to reddish brown or dark brown on the plastron. The average adult Caretta caretta in the Mediterranean Sea is smaller than the average adult in the Atlantic Ocean. Two subspecies - C. caretta gigas in the Pacific and Indian Oceans and C. caretta caretta in the Atlantic - have been proposed but are not fully accepted. They differ in the number of neural bones in the carapace and marginal scutes on the edge of the carapace. Loggerhead sea turtles differ from other sea turtles in having relatively large heads and reddish coloration. Additionally, Ridley's sea turtles (Lepidochelys) have four inframarginal scutes on the bridge. Green sea turtles (Chelonia mydas) and hawksbill sea turtles (Eretmochelys imbricata imbricata) have only four pairs of pleural scutes on the carapace; the first pleurals do not touch the cervical scute.

Range mass: 77 to 545 kg.

Average mass: 135 kg.

Range length: 213 (high) cm.

Average length: 85-100 cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes colored or patterned differently; sexes shaped differently

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Associations

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Most turtles are able to withdraw into their shell as a means of escaping a predator. No sea turtle is able to do this. Loggerhead sea turtles have their hard shell, their size, and their rough, scaly skin on the head and neck to protect them from predation. These defenses are usually sufficient for adults and larger juveniles, but these turtles are sometimes preyed on by sharks and killed by humans. Hatchlings and eggs have many predators and few defenses. Females try to disguise newly laid nests as much as possible, but they still suffer high predation rates. Raccoons (Procyon lotor) in U.S. can destroy up to 80% of nests on some beaches. Red foxes (Vulpes vulpes) in Australia may destroy 90 to 95% of nests. In some areas of the world human predation on nests is substantial. Hatchlings generally emerge from the nest at night to lessen chances of predation, but many are then taken by crabs, birds (gulls, frigate birds, vultures, crows, etc.), raccoons, canids (foxes, dogs, etc.), and carnivorous fish.

Known Predators:

  • bears (Ursus)
  • red foxes (Vulpes vulpes)
  • side-striped jackals (Canis adustus)
  • raccoons (Procyon lotor)
  • honey badgers (Mellivora capensis)
  • humans (Homo sapiens)
  • dogs (Canis lupus familiaris)
  • frigatebirds (Fregata magnificens)
  • crows Corvus
  • carnivorous fish (Actinopterygii)
  • ants (Formicidae)
  • crabs (Decapoda)
  • hogs (Sus)
  • armadillos (Dasypodidae)
  • sharks (Chondrichthyes)
  • seagulls (Larus)
  • rats (Rattus)
  • small cats (Felis)
  • skunks (Mephitis)
  • opossums (Didelphis)
  • bobcats and lynxes (Lynx)
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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Reproduction

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Just before the nesting season, male loggerhead sea turtles migrate to mating grounds, which are usually located offshore from nesting beaches. They wait for females to begin courtship and mating. A male will circle a female, then approach her and bite her neck or shoulder. He will then attempt to mount her and, if she accepts him, they will mate. If a female does not accept the male she covers her cloaca and swims to the bottom, but a persistent male may wait until she needs air and make another attempt. Males use the long, curved claws on their forelimbs to hold on because mating may last for hours and other males often ram and bite the mating male, attempting to dislodge him. If a male is dislodged, another may quickly replace him.

During the nesting season a female may lay several clutches, and will re-mate each time. In some cases, she may mate several times between clutches and so a single clutch may have sperm contributed by several males.

Mating System: polygynandrous (promiscuous)

Peak mating season for Caretta caretta occurs in the early summer months. During this time, males remain in the waters offshore of the nesting beach, while females alternate between mating in the water, nesting on land, and feeding in estuaries and reefs. A female will nest every 12 to 17 days, or 2 to 5 times, during the breeding season. For each nest she must drag herself onto land, where she is in much greater danger of predation, and excavate a nest. Into this nest she lays 110 to 130 round eggs. The eggs incubate for 45 to 80 days, depending on temperature. Loggerhead sea turtles reach sexual maturity at carapace lengths longer than 90 cm, which can occur between 10 and 30 years of age.

Breeding interval: Loggerhead sea turtles breed, on average, every 12 to 17 days during the breeding season. Females will not breed again for another 2 to 4, but possibly up to 9 years.

Breeding season: Breeding may occur year-round, but it peaks between May and July.

Range number of offspring: 23 to 198.

Average number of offspring: 110-130.

Range gestation period: 46 to 80 days.

Range age at sexual or reproductive maturity (female): 12 to 35 years.

Range age at sexual or reproductive maturity (male): 12 to 35 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous

Average number of offspring: 115.

Parental energy investment in loggerhead sea turtles is largely pre-ovipositional, there is no parental care of young. Females provide nutrition in the form of yolk which is used by embryos for growth and development; residual yolk can probably support a hatchling for several days or weeks. Females also expend considerable energy when migrating to nesting beaches and in the ovipositional (nesting/ egg laying) process. Male investment is largely during courtship and mating, and in sperm production.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female)

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Duermit, L. 2007. "Caretta caretta" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Caretta_caretta.html
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Liz Duermit, Michigan State University
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James Harding, Michigan State University
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Tanya Dewey, Animal Diversity Web
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Biology

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Adults are primarily carnivorous, using their powerful jaws to crack open crustaceans such as crabs and even seemingly impenetrable molluscs such as the queen conch (Strombus gigas) and giant clam (Tridacna spp.) (7). Loggerheads may reach sexual maturity at around 35 years old, and females appear to nest an average of three to five times in one breeding season, returning to breed every couple of years (8). Nesting occurs at night throughout the summer; females drag themselves out onto beaches beyond the high-tide mark and dig nests (around 40 centimetres deep) into which around 100 eggs are laid (2). Hatchlings and small juveniles appear to spend some time in pelagic environments, often drifting amongst rafts of sargassum (brown algae) and/or flotsam in the open ocean before migrating to benthic habitats in shallower, coastal waters (6).
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Conservation

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Loggerheads are nominally protected throughout most of their range and international trade is prohibited by their listing on Appendix I of the Convention on International Trade in Endangered Species (CITES) (3). Nesting occurs on relatively few protected beaches however, and increased protection remains a conservation priority. In Oman, if locals must collect eggs, they are encouraged to only take them from below the high water mark, thus securing an income without harming the turtles' survival chances (9). Turtle Excluder Devices (TEDs) fitted to shrimp trawlers can help prevent bycatch by only allowing shrimp-sized objects to enter the nets, and these are now being adopted by many of the world's fisheries (7).
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Description

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The loggerhead is one of the most widespread of all the marine turtles and also the most highly migratory, with individuals known to cross the Atlantic and Pacific Oceans (2). This turtle's common name comes from its relatively large head, which contains powerful jaws (5). The carapace of the adult turtle is a reddish-brown colour, whilst the underneath (or plastron) is more yellow in appearance (6).
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Habitat

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Inhabit coastal waters (7), but may also be found on the open ocean where they tend to float near the water's surface (5).
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Range

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Found throughout the world in subtropical and temperate waters, loggerheads are the most common turtle in the Mediterranean Sea (7) and western North Atlantic Ocean (2). Nesting occurs in more temperate regions than for other sea turtle species and the largest breeding population is currently found in the southeastern United States from North Carolina throughout Florida (2).
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Status

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Classified as Endangered (EN) on the IUCN Red List 2007 (1). Listed on Appendix I of CITES (3), and Appendix I of the Convention of Migratory Species (CMS or Bonn Convention) (4).
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Threats

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Long-distance migration makes loggerheads particularly vulnerable to accidental capture by commercial fisheries (bycatch), and turtles can become caught in shrimp trawler nets or entangled in longlines, leading to mortal injuries or death by drowning (7). Fisheries captured 32,000 loggerhead turtles in the Atlantic and 10,500 in the Gulf of Mexico in 1987 alone (7). Loggerheads are unlikely to be deliberately hunted for their meat, which is not considered a delicacy, but eggs are collected in many parts of the world (7). Habitat loss or disturbance, particularly developments on nesting beaches, is the main threat to this species (9).
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Behaviour

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Carnivorous, feeding largely on marine invertebrates, crabs, jellyfish, sponges, and occasionally fish. Young are largely pelagic, while adults stay closer to shore. Undergoes extensive migrations from and to nest­ing beaches, feeding grounds and seasonally to escape low temperatures. Nests sometimes on fairly disturbed beaches. A nest probably belonging to this species was found on a busy public beach in Alexandria in the 1970s (Baha El Din unpub. obs.). Many nests and nesting attempts detected by Clarke et al. (2000) were in fairly dis­turbed stretches of beach. Nesting in the eastern Mediterranean takes place between June and September (Clarke et al. 2000). Sexual matu­rity reached between 10 and 15 years (Schleich et al. 1996).

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Conservation Status

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Endangered

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Description

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A large marine turtle; the largest Egyptian specimen has a carapace length of 1,240 mm. Carapace depressed, slightly elongate, smooth; scutes juxtaposed; posterior edge with moderate indentations; 5 coastal scutes; first marginal scute not in contact with first vertebral scute. Head large, with 2 pairs of prefrontals. There are 2 claws on each limb. Males smaller, with longer tails and larger claws. Color of carapace and dorsal sides of limbs and head reddish brown, some scales may be narrowly edged yellowish. All ventral sided yellowish white.

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Global Distribution

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Circum-global, within the 10°c oceanic isotherm.

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Habitat

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Warm and temperate marine waters.

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Status in Egypt

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Uncommon, declining but still widespread. Significant numbers are probably caught by commercial fishing vessels, whence they reach fish markets in Egyptian coastal cities. Loss of nesting beaches is an important problem particularly in North Sinai. However, Kasparek (1993) described the breeding pop­ulation on the western Mediterranean coast of Egypt as "negligible." The same term can be applied to the small North Sinai population. Thus, the major conservation issue facing this and other marine tur­tles in Egypt is the threat by commercial marine fisheries.

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Migration

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"In 1996, a loggerhead turtle called Adelita swam across 9,000 miles from Mexico to Japan, crossing the entire Pacific on her way. Wallace J. Nichols tracked this epic journey with a satellite tag. But Adelita herself had no such technology at her disposal. How did she steer a route across two oceans to find her destination?"

Read more at DISCOVER Blogs - Not Exactly Rocket Science: Turtles use the Earth’s magnetic field as a global GPS

Also see PBS Nature: Voyage of the Lonely Turtle

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Niger Coastal Delta Habitat

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The Niger Coastal Delta is an enormous classic distributary system located in West Africa, which stretches more than 300 kilometres wide and serves to capture most of the heavy silt load carried by the Niger River. The peak discharge at the mouth is around 21,800 cubic metres per second in mid-October. The Niger Delta coastal region is arguably the wettest place in Africa with an annual rainfall of over 4000 millimetres. Vertebrate species richness is relatively high in the Niger Delta, although vertebrate endemism is quite low. The Niger Delta swamp forests occupy the entire upper coastal delta. Historically the most important timber species of the inner delta was the Abura (Fleroya ledermannii), a Vulnerable swamp-loving West African tree, which has been reduced below populations viable for timber harvesting in the Niger Delta due to recent over-harvesting of this species as well as general habitat destruction of the delta due to the expanding human population here. Other plants prominent in the inner delta flood forest are: the Azobe tree (Lophira alata), the Okhuen tree (Ricinodendron heudelotii ), the Bitter Bark Tree (Sacoglottis gabonensis), the Rough-barked Flat-top Tree (Albizia adianthifolia), and Pycnanthus angolensis. Also present in its native range is the African Oil Palm (Elaeis guineensis)

Five threatened marine turtle species are found in the mangroves of the lower coastal delta: Leatherback Sea Turtle (Dermochelys coriacea, EN), Loggerhead Sea Turtle (Caretta caretta, EN), Olive Ridley Turtle (Lepidochelys olivacea, EN), Hawksbill Sea Turtle (Eretomychelys imbricata, CR), and Green Turtle (Chelonia mydas, EN).

There are a number of notable mammals present in the Niger Coastal Delta, including the Near Threatened Olive Colobus (Procolobus verus) that is restricted to coastal forests of West Africa and is found here in the inner coastal Niger Delta. Also found here is the restricted distribution Mona Monkey (Cercopithecus mona), a primate often associated with rivers. Also occurring here is the limited range Black Duiker (Cephalophus niger), a near-endemic to the Niger River Basin. In addition, the Endangered Chimpanzee (Pan troglodytes) is found in the Niger Delta. The near-endemic White-cheeked Guenon (Cercopithecus erythrogaster, VU) is found in the inner delta. The Critically Endangered Niger Delta Red Colubus (Procolobus pennantii ssp. epieni), which primate is endemic to the Niger Delta is also found in the inner delta.

Some of the reptiles found in the upper Niger Coastal Delta are the African Banded Snake (Chamaelycus fasciatus); the West African Dwarf Crocodile (Osteolaemus tetraspis, VU); the African Slender-snouted Crocodile (Mecistops cataphractus); the Benin Agama (Agama gracilimembris); the Owen's Chameleon (Chamaeleo oweni); the limited range Marsh Snake (Natriciteres fuliginoides); the rather widely distributed Black-line Green Snake (Hapsidophrys lineatus); Cross's Beaked Snake (Rhinotyphlops crossii), an endemic to the Niger Basin as a whole; Morquard's File Snake (Mehelya guirali); the Dull Purple-glossed Snake (Amblyodipsas unicolor); the Rhinoceros Viper (Bitis nasicornis). In addition several of the reptiles found in the outer delta are found within this inner delta area.

Other reptiles found in the outer NIger Coastal Delta are the Nile Crocodile (Crocodylus niloticus), African Softshell Turtle (Trionyx triunguis), African Rock Python (Python sebae), Boomslang Snake (Dispholidus typus), Cabinda Lidless Skink (Panaspis cabindae), Neon Blue Tailed Tree Lizard (Holaspis guentheri), Fischer's Dwarf Gecko (Lygodactylus fischeri), Richardson's Leaf-Toed Gecko (Hemidactylus richardsonii), Spotted Night Adder (Causus maculatus), Tholloni's African Water Snake (Grayia tholloni), Smith's African Water Snake (Grayia smythii), Small-eyed File Snake (Mehelya stenophthalmus), Western Forest File Snake (Mehelya poensis), Western Crowned Snake (Meizodon coronatus), Western Green Snake (Philothamnus irregularis), Variable Green Snake (Philothamnus heterodermus), Slender Burrowing Asp (Atractaspis aterrima), Forest Cobra (Naja melanoleuca), Rough-scaled Bush Viper (Atheris squamigera), and Nile Monitor (Varanus niloticus).

There are a limited number of amphibians in the inner Niger Coastal Delta including the Marble-legged Frog (Hylarana galamensis). At the extreme eastern edge of the upper coastal delta is a part of the lower Niger and Cross River watersheds that drains the Cross-Sanaka Bioko coastal forests, where the near endemic anuran Cameroon Slippery Frog (Conraua robusta) occurs.

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Threats

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Peckham et al. (2007) found that small-scale fisheries result in significant bycatch mortality of loggerheads, rivaling that of oceanwide industrial-scale fisheries. To address this serious threat, the authors advocate the localization of coastal high use areas and mitigation of bycatch in partnership with small-scale fishers.

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Benefits

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Up to several years ago (the seventies), Caretta was commonly captured in commercial operations and the meat, eggs, leather and fat were used. However, its flesh and leather is less valuable than that of the green turtle (Chelonia), and the carapace brings a lower price than that of the hawksbill turtle (Eretmochelys), which produces tortoise-shell. With few exceptions, in many countries this species has not been the major target in the sea turtle catch; but in the northern and northeastern Gulf of Mexico, Texas and Florida, it was captured as bycatch and canned together with the green sea turtle up to the early fifties. On the eastern coast of Mexico it was captured jointly with the green turtle, but while the loggerhead was consumed fresh, the green turtle was exported, principally to Tampa, Florida, up to late seventies. In Cuba, the exploitation continues, but at a restricted annual level of between 250 and 300 t. It is very Common that in places where regulations are not strictly enforced, the eggs are consumed whenever found and also widely commercialized in unknown quantities, generally through illegal markets. The most common way of Caretta harvesting has been the "turtle turning" on the beaches and the setting of entangling nets, the majority in front of nesting beaches- in Caribbean shallow waters, the nets used are made of cotton yarn with light weights on the bottom line, to avoid drowning the turtles, and similar nets are used in the Gulf of Mannar, The capture with nets is increased during the night time- Several kinds of harpoons with detachable iron points have been widely used. Harpooning generally was performed by two fishermen on small wooden boats, one of them paddling and the other "hunting" at the bow of the boat. In the transparent Caribbean waters it is possible to observe the turtles on the bottom, so the turtlers can follow the prey until it comes up to breathe. This moment is used for harpooning it; this method is called "correteada", -rove or boat-chase - on the Western Caribbean coast of Mexico. The FAO Yearbook of Fishery Statistics reports loggerhead catches only from Fishing Area 31 (Western Central Atlantic, Cuba only). The registered world catch was 273 t in 1983, 277 t in 1984, 322 t in 1985, 309 t in 1986 and 238 t in 1987. Because of their feeding behaviour and their habit of overwintering in shallow waters, this species, together with Lepidochelys, is more prone to capture by shrimp trawlersand gillnets (mainly shark-nets). In recent years, in Atlantic waters of the USA, around 32 000 loggerheads were caught annually and nearly 21% of them died by drowning; in addition, more than 10 500 turtles were trapped annually in the Gulf of Mexico by the same types of gear, and approximately 29.8% of them were killed during trawling. The majority were late juveniles and subadults, while adults were relatively few. Also the records of the "Sea Turtle Stranding and Salvage Network" from the east coast of the USA show that loggerhead turtles were the most frequently stranded (73%) of the five Atlantic species, with a total of 2 373 individuals registered during 1987. The blasting of old petroleum platforms is another cause of high sea-turtle mortality, especially of loggerheads. This kind of mortality is also reported for Mexico, Australia, South Africa, Japan, China, and wherever the loggerhead lives. The extent of the mortality needs to be evaluated in all these and other areas such as the Mediterranean Sea and the southern coast of the Arabian Peninsula. The FAO Yearbook of Fishery Statistics reported for 1996 a total catched of 10 t. in Western Central Atlantic, Cuba only. The total catch reported for this species to FAO for 1999 was 5 t. The countries with the largest catches were Cuba (5 t).
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FAO species catalogue. Vol.11: Sea turtles of the world. An annotated and illustrated catalogue of sea turtlespecies known to date.Márquez M., R. FAO Fisheries Synopsis.  No. 125, Vol. 11. Rome, 1990 FAO. 81 p.
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Diagnostic Description

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In adults, the carapace in dorsal view is heart-shaped, its width about 76 to 86% of its length. Head large, broad and subtriangular, 23 to 28% of carapace length, with 2 pairs of prefrontal scales, and commonly one inter-prefrontal; horny beak very strong, comparatively thicker than in other sea turtles. Carapacial scutes thin, but hard and very rough, commonly covered with barnacles. They include 5 pairs of laterals, the anterior touching the precentral scute, 5 centrals (neurals), and commonly 12 or 13 pairs of marginals, including the postcentral or pygal scute. Underneath the bridge of the plastron, there are 3 pairs of inframarginal scutes which rarely have pores. Fore flippers relatively short and thick, each with 2 visible claws on anterior margin; rear flippers with 2 or 3 claws. Hatchlings and juvenile turtles have blunt spines on the carapace scutes, forming 3 longitudinal keels that disappear during the juvenile stage. Colour: The adults of Caretta generally have a constant dorsal pattern, easily recognisable by the reddishbrown coloration, sometimes with dark streaks (South African turtles), that become orange-creamy on the flanks and yellow-creamy underneath. The hatchlings are darkbrown dorsally, with the flippers pale brown marginally and underneath, and the plastron usually is much paler.

References

  • Achaval , 1965
  • Alfaro, Blain & Munoz, 1987
  • Argano & Baldani , 1983
  • Balazs, 1981
  • Berry, 1983
  • Bjorndal & Meylan , 1983
  • Bleakney, 1965
  • Brongersma, 1972, 198
  • Bruno, 1973
  • Bustard & Limpus , 1971
  • Caldwell , 1959, 1962, 1969
  • Caldwell, Carr & Hellier , (1955);
  • Caldwell & Carr , (1957)
  • Capocaccia , 1966
  • Carr , (1952, 1986a,b, 1987)
  • Carr, Ogren & Mc Vea, 1980
  • Carranza, (1956)
  • Deraniyagala , (1939)
  • de Silva, 1969
  • de Silva, 1981
  • Discovery Center, 1987
  • Dood, 1988, pers com.
  • Dupuy , 1986
  • Ehrhart & Witherington, 1986
  • Fletemeyer, 1984
  • Frazer & Erhart , 1985
  • Frazier , 1979, 1984, 1985a,b
  • Frazier & Salas, 1983, 1984
  • Fretey , 1987
  • Geldiay, Koray & Balik, 1981
  • GilHernandez, 1988
  • Gramentz, 1988
  • Grassman & Owens, 1982
  • Hoffman & Conley, 1987
  • Hoffman & Fritts, 1982
  • Hopkins, Murphy, Stansell & Wilkinson, 1979
  • Hughes , 1974, 1975, 1977, 1981
  • Hughes, Bass & Mentis, 1967
  • Hughes & Mentis, 1967
  • Kamezaki, 1986
  • Kauffman, 1966, 1971, 1972, 1975
  • Kondo, 1968
  • Kuriyan, (1950)
  • Kushlan , 1986
  • Lazell, 1979
  • Limpus & Reed , 1985
  • Maigret , 1983, 1986
  • Margaritoulis , 1983 , 1985
  • Marquez & Bauchot , 1987
  • Marquez & Fritts , 1988
  • Martinez , 1984
  • Mc Allister, Bass & van Schoor , 1965
  • Mc Cann, 1966
  • Mc Gehee, 1974
  • Mendonca & Erhart , 1982
  • Moreira & Benitez , 1986
  • Musick et al., 1983
  • Nishimura, 1967
  • Ogren , 1983
  • Ogren, Watson Jr- & Wickman, 1977
  • Orgen & Mc Vea , 1981
  • Pascual , 1985
  • Pope, 1935
  • Pritchard, 1981
  • Rebel , 1974
  • Rodin, Springer & Pritchard , 1980
  • Ross , 1972, 1981
  • Routa, 1968
  • Schaiefer , 1962
  • Schleich , 1987a,b
  • Schroeder & Warner, 1988
  • Schwartz , 1974
  • Senaris, 1988
  • Shoop & Ruckdeschel, 1982
  • Spring, 1981
  • Sutherland , 1985
  • Suvvelo, Sumertha & Soetrisno, 1981
  • Uchicia, 1977
  • Uchida & Teruya, 1988
  • Veniselos, 1986
  • Wickramsinge, 1982
  • Witham , 1974
  • Zug, Hynn & Ruckdeschel, 1986

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FAO species catalogue. Vol.11: Sea turtles of the world. An annotated and illustrated catalogue of sea turtlespecies known to date.Márquez M., R. FAO Fisheries Synopsis.  No. 125, Vol. 11. Rome, 1990 FAO. 81 p.
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Distribution

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Caretta caretta is widely distributed in coastal tropical and subtropical waters (16-20°C) around the world . Commonly this species wanders into temperate waters and to the boundaries of warm currents.It is suspected that some loggerhead turtles undertake long migrations using warm currents (e.g., the Gulf Stream in the North Atlantic ; the North Equatorial and Kuroshio Currents and the California Current (12-20°C) in the North Pacific and other currents in the southern hemisphere), that bring them far from the nesting and feeding grounds. [more...] Apparently, the limit of distribution is waters of about 10°C; if they encounter colder waters, they may become stunned, drift helplessly and strand on nearby shores. Records are quoted from New England and eastern Canada, Labrador and Nova Scotia, especially between July and October of warm years. The northern limit of distribution is a summer capture of a live young turtle entangled in a fishing line off Murmansk, Barents Sea (68° SS'N). Brongersma (1972) quotes this and many other records for European waters. Occasionally, the species is sighted in southern Australia and New Zealand. In South America it is absent from west Colombia, Ecuador and Peru, but there are some records from Arica and Coquimbo, in Chile; on the eastern coast, the southernmost record is Rio de la Plata, Argentina.
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bibliographic citation
FAO species catalogue. Vol.11: Sea turtles of the world. An annotated and illustrated catalogue of sea turtlespecies known to date.Márquez M., R. FAO Fisheries Synopsis.  No. 125, Vol. 11. Rome, 1990 FAO. 81 p.
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Size

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In general, the mean straight carapace length (SCL) of the mature females is between 81.5 and 105.3 cm (n a; 3502), with a mean weight near to 75; kg (65.7 to 101.4 kg, n a 153). The carapace length (SCL) in nesting females varies within a limited size range, but is always over 70 cm. [more...]
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FAO species catalogue. Vol.11: Sea turtles of the world. An annotated and illustrated catalogue of sea turtlespecies known to date.Márquez M., R. FAO Fisheries Synopsis.  No. 125, Vol. 11. Rome, 1990 FAO. 81 p.
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Brief Summary

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This turtle primarily is an inhabitant of continental shores of warm seas, common in shallow waters, but it also lives around some islands as: Masirah in Oman, Zakinthos in Greece, and the Ryukyu and Japan Archipelago.This turtle primarily is an inhabitant of continental shores of warm seas, common in shallow waters, but it also lives around some islands as: Masirah in Oman, Zakinthos in Greece, and the Ryukyu and Japan Archipelago. This is the only sea turtle that can nest successfully outside of the tropics, but the summer surface temperature must be over 20°C. During, or soon after the breeding season ends, some females disperse to distant feeding grounds. Migratory routes are not clearly delineated, but hatchlings theoretically follow warm currents such as the Gulf Stream, or may enter the big gyre of the North Pacific Ocean, along the Kuroshio, the California and the North Equatorial currents. It is possible that if they are "trapped" by these enormous warm currents and complete the intercontinental circuit (gyre) they may be near maturity when they are carried back to their natal beaches. Loggerhead hatchlings and juveniles are frequently associated with sea fronts (oceanic current convergences), downwellings and eddies, where floating epipelagic animals and floatsam are gathered. The elapsed time, usually more than a year - during which the small turtles remain in those places feeding and growing - is called the "lost year". During this first period of life there is evidence that these turtles lead a pelagic-nectonic existence, feeding on organisms usually associated with sargassum mats. There are several major nesting grounds, and some of them are located in northern latitudes. In general, the loggerhead does not form "arribazones" but nests on large beaches. The major nesting grounds are located in the southeastern USA, principally in Florida and South Carolina with a mean annual production (in 1986) of about 24 000 and 4 000 nests respectively; in Florida, the nesting is much more important on the Atlantic than on the Gulf coast: Georgia with 1 250, and North Carolina with 280 nests per year. In the eastern USA, minor and solitary nesting occurs as far north as New Jersey. Along the Gulf of Mexico coasts, only minor and solitary nesting is recorded. In Mexico, on the northeastern coasts of the Yucatan peninsula and in Quintana Roo State, small groups of turtles occur from Cape Catoche and Contoy Island to Ascencion Bay, with a relatively greater abundance between Carmen Port and Ascencion Bay, including Cozumel Island and Boca Paila Beach as the more important nesting places in this region. Minor nesting beaches are located on some islands of the Caribbean region, principally on the south-central coasts, islands and cays of Cuba. Going south in this region, other nesting is negligible, except for Colombia, where the remains of an important nesting aggregation is reported, especially to the east side of Santa Marta, between the rivers Piedras and Riohacha (which includes the Buritaca Reserve). It was calculated that about 2 000 nests were laid every season in this area, but they have recently declined to a few hundred. East of Colombia, the presence and nesting of loggerheads are negligible. In Brazil, e.g., Maranhao and Ceara, an annual production of over a thousand nests is reported; nesting is consistently reported from Sergipe and also occurs in the states of Bahia, Espirito Santo and Rio de Janeiro. Subadult and few adult loggerhead turtles have been reported as far south as Uruguay, especially between Rocha and Malclonado, including the area of Rio de la Plata. Nesting does not occur this far south. In the Mediterranean Sea, Caretta is the most common turtle, and it is regularly captured either directly or incidentally. Nesting is reported principally from the coasts of Greece, Turkey to Israel, Tunisia, both coasts of Italy, Sicily and historically from Sardinia and Corsica; in Cyprus and Algeria, nesting was formerly more widely and consistently observed, but nowadays occurs only from time-to-time. The annual production of nests, in all of the Mediterranean continental rookeries was believed not to exceed 1 000 nests, but recently the Zakinthos Island, in Greece, was indicated as an important nesting place, with over 2 000 nests per year. In the southern Mediterranean, the northeast coast of Libya is known as a minor nesting beach.Caretta is also reported from the Iberian peninsula, but no nesting has been observed there up to now. The western and the southwestern coasts of the Black Sea probably also have sporadic nesting. On the Bahamas, Bermuda and the oceanic North Atlantic islands nesting does not occur, but juvenile loggerheads are commonly observed (reported from around Madeira, the Canary Islands and especially the Azores). These turtles apparently originate in the Western Atlantic rookeries, from which hatchlings enter the Gulf Stream and are carried to these islands. These oceanic gyres and eddies are considered as feeding grounds and developing habitats, where the loggerheads reach the last juvenile stages. In the Eastern Atlantic, minor nesting takes place in Morocco, the Cape Verde Archipelago and on the coast of Senegal (Dakar). In the Gulf of Guinea, loggerheads may nest, but no reports are as yet available from this area. Minor nesting is reported for southern Angola and northern Namibia, known in the region as the "Skeleton coast". Major Indian Ocean nesting grounds occur in South Africa, especially in the northeastern part of Tongaland on the Natal coast, where the nesting population comprises several hundred females. Other important nesting grounds are those in southern Madagascar, but no mention is made of the Comores Archipelago in the compilation prepared by Frazier (1985). Further north, the largest known breeding aggregation occurs on the Arabian peninsula, described in 1979 as the most important rookery for loggerheads in the world, with an annual rough estimate of 30 000 nesting females on Masirah Island, Sultanate of Oman alone; other nesting may occur in the area but it is negligible and there is apparently no nesting in the Red Sea or the Persian (Arabian) Gulf. Around the islands of the Indian Ocean, this species is nearly unknown. There is minor turtle nesting in Kosgoda, southwestern Sri Lanka, where ridleys and green turtles are common, but loggerheads are rare. In China, nesting occurs along the coasts of the South China Sea, principally in Hainan Island. Caretta is frequently observed from Kuangsi (south) to Hopei (north) in Taiwanese waters, but without nesting records. Going northeast, nesting occurs just up to Japanese waters, especially on the southern islands, from the Ryukyu Archipelago to Kyushu and Shikoku Islands. The northernmost point of nesting in the Western Pacific is about 37°N, on the east coast of Honshu Island, where Caretta is the most abundant of all sea turtles. In the western Pacific, nesting is mentioned, but not quantified for waters of Sumatra, Borneo, Sabah, Philippines, Indochina, Malaysia and Thailand; from the Arafura Sea to Australia, the loggerhead not only nests, but is recognized as being very common. For the coasts of western Australia (Shark Bay and Barrow Island) and Queensland, south of the Great Barrier Reef (Mon Repos-Bundaberg, Crab Islands and Swain Reefs Islands) there are estimates of annual numbers of over 3 000 females. Records are also available from around Papua New Guinea and New Caledonia, but they become less frequent in New Zealand waters and nearly absent in the western and central Pacific Oceanic Islands, except Tokelau, Fiji, New Caledonia and Solomon, where they are reported as rare. Those records have been apparently confused with the olive ridley (L. olivacea). In the Hawaiian Archipelago, Caretta is not common, and nesting does not occur. In the Eastern Pacific Ocean, nesting of Caretta was reported from the Gulf of Panama and El Salvador, but it is unclear whether the identification of the species was accurate. It was very probably confused with the olive ridley (L. olivacea) Loggerheads are absent on the coasts of Colombia, Ecuador and Peru. There are also several non-nesting reports from Chile. Thousands of loggerheads appear during spring and summer in Baja California and the Gulf of California waters, but apparently all these turtles are non-reproductive, measuring between 25 and 92 cm of CCL. Until now, no turtle in this area has been reported bearing mature eggs. Nesting of Caretta usually occurs in spring and summer, with variations according to the latitude and geographical characteristics of the coast. Data available in the literature show that the nesting season also varies in extent: In the Caribbean area it extends from April to July or the first week of August, with the peak in May or June (principally southern Cuba and Quintana Roo, Mexico). In the northwest Atlantic Ocean, from April to September, with the peak in June-July (Florida). In the southwestern Atlantic, from April to August, with the peak in June (Colombia). In the Eastern Atlantic, from June to September (eastern Mediterranean, Turkey, Libya, and Zakinthos Island, Greece), and from July to October (Senegal). In the southwestern Indian Ocean from October to February, with the peak in NovemberDecember (South Africa: Natal -Tongaland) in the northwestern Indian Ocean, from May to June, but there are also reports for the winter from November to March, with the peak in December-January (Masirah Island, Oman). In the east up to Sri Lanka, questionable reports that may correspond to Lepidochelys olivacea, state that the season runs in the winter, starting from September and lasting seven months up to the next year. In the Northwest Pacific Ocean there are no big nesting grounds; in China, the season goes from April to August with a peak in June or July; in Japan (Honshu, Kiushu and the Ryukyu Archipelago), the situation is similar, but the season starts earlier in the southern beaches and also has the peak in June or July. In Australia, the season runs from October to April, with the peak between November to January. No nesting is reported from New Zealand. Caretta shows renesting frequency intervals of nearly two weeks; females usually lay between two and five times per season, depositing on each occasion from 40 to 190 eggs (mean: 110 eggs). Hence, a single female could lay a maximum of 560 eggs per season. The major pattern of the reproductive cycle is two or three years, but some parts of the population may shift from one cycle to another, including to a yearly cycle. The size of the egg clutch varies from place to place, from a minimum of 23 to a maximum of 190 eggs per clutch. [more...] In general, the egg size in diameter and mass usually varies proportionally to the size of the turtle, hence small turtles lay smaller eggs. The egg diameter ranges from 34.7 to 55.2 mm. [more...] The nests of these turtles sometimes contain undersized eggs, laid together with the normal ones, but never in such large quantities as in the leatherback turtle; oversized and abnormal-shaped eggs are also present, but not frequent. Egg weight measurements are less frequent than those of diameter size, and available data range from 26.2 to 46.8 gr. [more...] The incubation period varies among populations and with beach latitude; e.g. USA, South Carolina, 55 to 62 days; Hutchinson Island, Florida, mean duration 68 days; Mexico, Quintana Roo, mean duration 56 days; Turkey, 50 to 64 days, mean duration 57 days; Greece, Zakinthos Islands 49 to 69 days, mean duration 57 days; South Africa, Tongaland, 55 to 65 days, mean duration 68 days; Japan, Hiwasa, usually 58 days. In general, the warmest places and times result in the shortest periods of incubation, so there are differences on the same beaches depending on location of the nest and time of oviposition; even in the same localities, the incubation length changes from season to season. Size and weight of hatchlings are considered to be correlated directly with the size of the eggs; the more frequent measurements are straight carapace length (SCL) which ranges from 33.5 to 55 mm, and total weight (range of mean values from 18.8 to 21.1 g). [more...] Age at first maturity has not been clearly determined yet. Data derivated from research in captivity indicate ages from 6 to 20 years; the back calculation from capture - recapture data of tagged nesting females, analyzed through logistic and von Bertalanffy growth curves, produce ranges from 12 to 30 or more years, for minimum (74 cm) and maximum (92 cm) straight carapace lengths; these data apply to the southeastern coast of the United States, but differences must be expected for nesting beaches located on different latitudes, as Colombia, Oman, Australia or Japan. Unlike other sea turtles, courtship and mating are usually not performed near or in front of the nesting beaches, but along the migration routes between feeding and breeding grounds. Courtship and mating are not commonly observed, but some photographs have been taken, e.g. the photograph by Mr Larry Bearse (Anon., 1985) south of Cape Hatteras in North Carolina, USA, on 28 March 1985, in waters of the western side of the Gulf Stream. Mating apparently is accomplished while floating on the water surface, but in Australia near Sandy Cape, Limpus (1985) has reported underwater copulation. In captivity, it is common for one female to be covered several times by different males before the nesting time, but other females are covered by only one male before nesting, apparently without any effect on the fertility of the eggs. It is also possible that through storage of the sperm of one or several males in the reproductive tract (oviducts) of the female, all clutches of the current nesting season can be fertilized without repeated matings. Mating usually is performed several weeks before the nesting season. Optimal incubation occurs within a limited range of temperatures, usually between a minimum of 26°C and a maximum of 32°C; there is evidence that sex determination is male-biased in cool temperatures and that survival rate decreases at the extreme temperatures of this range. The "pivotal temperature", defined as the temperature where a 1: 1 sex ratio occurs, seems to be about 30°C for this species, but it may show small variations among populations and with geographical latitude- As in all the other sea turtles, hatching occurs in the course of several days (2 to 3); it takes several hours for the hatchlings to reach the surface of the sand and only a few minutes to emerge from the nests. Emergence occurs mostly at night; the peak time usually lies between 21:00 and 02:00 hours, but during cloudy days it may continue late in the morning. After the majority of hatchlings appear at the surface of the nest, they start a frenzied race to the surf and disappear in the waves. Highest predation occurs in the incubation period and during the race of the hatchlings to the sea. Small turtles swim straight out from the coastal shallow waters, since fish predation decreases strongly in deep waters. Massive destruction of eggs and embryos is also caused by natural phenomena such as erosion or sea overwash. Eggs, embryos and hatchlings are devoured by a great variety of predators and primarily or secondarily affected by bacterial and fungal diseases. It is common that clutches of eggs or hatchlings, while remaining in the nests, are eaten by ghost crabs, ants and fly larvae; predation by monitor lizards (Varanus) in South Africa and Northern Australia, and by raccoons in some beaches of Florida and South Carolina is responsible for over 40 and 56% of egg losses respectively; skunks, feral dogs, genets, pigs, foxes, jackals (in Cape Verde and Libya) also destroy nests. During the synchronous nocturnal travel from the nest to the surf, hatchlings are devoured by many of the abovementioned predators. Land and shore birds also take their quota if hatchlings emerge in day time. After reaching the waves, predation continues by marine birds and neritic and pelagic fishes (e.g., Centropristes, Coryphaena). Little is known about predation on juveniles and adults, but they are usually too large for many predators except the big carnivorous fishes such as groupers, snappers and jacks. Sharks are the principal enemies for all size classes of turtles. Turtles above medium size are able to avoid shark attacks, by presenting the flat side of the plastron or carapace to prevent biting. The worst predator of loggerhead turtles is man who is able to take the entire egg production of any beach or capture any size and quantity of turtles. The loggerhead turtle is the most prone to bear epibiontic organisms, including leeches, crabs, green filamentous algae, etc. Leeches could be the cause of skin damage and secondary infection and also propiciate the tissue degeneration known as papillomae. Feeding behaviour may change somewhat with age, but this species is carnivorous throughout its life. There is evidence that hatchlings obtain their food from the fauna living in seagrass mats, frequently distributed along the drift lines and eddies. Hatchling gut contents have shown jellyfishes, pieces of Sargassum, gastropods (Diacria, Litiopa), crustacean appendages and materials as grit, feathers, bark and plastic pieces. Juveniles, subadults and adults have been more extensively studied and show a very wide variety of prey, principally benthic fauna like, conchs (Strombus, Cypraea, Conus, Kelletia, Cassis, Janthina, Harpa, etc), clams (Cardium, Pecten, Mactra, Pinna, Venus, etc.), horse shoe crab (Limulus), crabs (Calappa,Callinectes, Portunus, Cancer, Hepatus, etc.), occasionally shrimps (Pennaeus, Sicyonia), sea urchins, sponges, fishes (Brevoortia, Sardinops, Scomber, Diodon, etc.), squids, octopuses, and also man-caught fauna (shrimp-trawl bycatch). Because of their carnivorous diet (molluscs-crustaceans), loggerheads compete for food with ridley sea turtles (Lepidochelys). During their migration through the open sea they eat jellyfishes, pteropods, floating molluscs (Janthina), floating egg clusters, flying fishes, squids, lobsterets (Galatheids). In western Baja California, many of the dissected loggerheads had full stomachs containing only Pleuroncodes planipes (the pelagic small red lobsteret). Sometimes the diet includes sea turtle hatchlings, floating algae (Sargassum) and other plants, but it is suspected that plant ingestion is involuntary during feeding activities. In a loggerhead from Trinidad and Tobago, the only species found in the stomach was Conus ermius. Experiments show that although this species has food preferences, it clearly is a facultative feeder over a wide range of food items.
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bibliographic citation
FAO species catalogue. Vol.11: Sea turtles of the world. An annotated and illustrated catalogue of sea turtlespecies known to date.Márquez M., R. FAO Fisheries Synopsis.  No. 125, Vol. 11. Rome, 1990 FAO. 81 p.
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Food and Agriculture Organization of the UN
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Distribution

provided by ReptileDB
Continent: Africa Oceania Near-East Middle-America Asia Caribbean South-America North-America Australia Europe
Distribution: Pacific, Indian and Atlantic oceans, Japan, Gulf of Thailand, India, Pakistan, Sri Lanka, Maldives, Solomon Islands [McCoy 2000], Chile, Argentina, Kenya, the British Isles, United Kingdom, and Newfoundland Tunisia, Libya, Egypt, Israel, Eritrea, Tanzania (?), United Arab Emirates (UAE), Somalia, Mauritania, South Africa, tropical western Africa, Cameroon, Madagascar Caribbean and Mediterranean seas (Adriatic Sea: Croatia), Italy [E. RAZZETTI, pers. comm.], Greece (Corfu), France Turkey [Basoglu 1973],Portugal, Australia (North Territory, Queensland, Tasmania, West Australia) SE Mexico (Yucatan, Baja California), Belize, Guatemala, Honduras, Nicaragua, Costa Rica, Panama Colombia [Castro,F. (pers. comm.)] caretta: Atlantic Ocean gigas: Indian and Pacific Ocean acording to the 1994 IUCN Red List of Threatened Animals: EC/NE/NW/SE/SW/WC Atlantic, E/W Indian Ocean, Mediterranean and Black Sea, EC/NE/NW/SE/SW/WC Pacific, Angola, Australia, Bahamas, Bangladesh, Belize, Brazil, Cape Verde, Cayman Islands, China, Colombia, Costa Rica, Cuba, Cyprus, Dominican Republic, Egypt, Greece, Grenada, Guadeloupe, Guatemala, Haiti, Honduras, India, Indonesia, Israel, Italy, Jamaica, Japan, Libya, Madagascar, Mexico, Montserrat, Morocco, Mozambique, Myanmar (= Burma), Namibia, New Caledonia, Nicaragua, Oman, Panama, Papua New Guinea, Philippines, Puerto Rico, Senegal, South Africa, Sri Lanka, St Lucia, Turkey, Turks and Caicos Islands, USA (Alaska, Washington, Western Atlantic: Maine, New Hampshire, Massachusetts, Connecticut, New Jersey, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, Florida), Venezuela, Virgin Islands (British) Two finds in waters of Russia are known: in the Barents Sea's Kolsky Bay and in the Sea of Japan's Peter the Great Bay (fide KHALIKOV, pers. comm.)
Type locality: œAmericanas
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Comprehensive Description

provided by Smithsonian Contributions to Zoology
Thalassochelys corticata Girard, 1858

[= Caretta caretta (Linnaeus, 1758); fide, Boulenger, 1889:185; Stejneger, 1904:716, Dodd, 1990:483.1]

Girard, 1858. Herpetology, U.S. Explor. Exped., 20:431, pl. 29: figs. 1–4.

Holotype: USNM 7778 (dry stuffed juvenile, CL 230 mm), collector unknown, 16–25 Sept 1838.

Type Locality: “Madeira” [Funchal, Canary Islands] (see “Remarks”).

Etymology: The name corticata is from the Latin corticatus, covered with bark, and refers to the appearance of the carapace scutes.

Remarks: The specimen was “collected at Madeira, in 1838, on the passage out of the Expedition” (Girard, 1858:434). The Exploring Expedition operated in Madeira during 16–25 Sept 1838 (Viola and Margolis, 1985:257).

FAMILY CHELYDRIDAE
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Reynolds, Robert P., Gotte, Steve W., and Ernst, Carl H. 2007. "Catalogue of Type Specimens of Recent Crocodilia and Testudines in the National Museum of Natural History, Smithsonian Institution." Smithsonian Contributions to Zoology. 1-49. https://doi.org/10.5479/si.00810282.626

Loggerhead sea turtle

provided by wikipedia EN

The loggerhead sea turtle (Caretta caretta) is a species of oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around 90 cm (35 in) in carapace length when fully grown. The adult loggerhead sea turtle weighs approximately 135 kg (298 lb), with the largest specimens weighing in at more than 450 kg (1,000 lb). The skin ranges from yellow to brown in color, and the shell is typically reddish brown. No external differences in sex are seen until the turtle becomes an adult, the most obvious difference being the adult males have thicker tails and shorter plastrons (lower shells) 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 invertebrates. Its large and powerful jaws serve as an effective tool for 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 animals, such as large sharks.

The loggerhead sea turtle is considered a vulnerable species by the International Union for Conservation of Nature. In total, 9 distinct population segments are under the protection of the Endangered Species Act of 1973, with 4 population segments classified as "threatened" and 5 classified as "endangered"[6] Commercial international trade of loggerheads or derived products is prohibited by CITES Appendix I. Untended fishing gear is responsible for many loggerhead deaths. The greatest threat is loss of nesting habitat due to coastal development, predation of nests, and human disturbances (such as coastal lighting and housing developments) that cause disorientations during the emergence of hatchlings.[7] Turtles may also suffocate if they are trapped in fishing trawls. Turtle excluder devices have been implemented in efforts to reduce mortality by providing an escape route for the turtles. Loss of suitable nesting beaches and the introduction of exotic predators have 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 across several countries.

Taxonomy

Carl Linnaeus gave the loggerhead its first binomial name, Testudo caretta, in 1758.[4][8] Thirty-five other names emerged over the following two centuries, with the combination Caretta caretta first introduced in 1873 by Leonhard Stejneger.[5] The English common name "loggerhead" refers to the animal's large head.[9][10] The loggerhead sea turtle belongs to the family Cheloniidae, which includes all extant sea turtles except the leatherback sea turtle.[11] The subspecific classification of the loggerhead sea turtle is debated, but most authors consider it a single polymorphic species.[12] Molecular genetics has confirmed hybridization of the loggerhead sea turtle with the Kemp's ridley sea turtle, hawksbill sea turtle, and green sea turtles. The extent of natural hybridization is not yet determined; however, second-generation hybrids have been reported, suggesting some hybrids are fertile.[13]

Evolution

Although evidence is lacking,[14] modern sea turtles probably descended from a single common ancestor during the Cretaceous period. Like all other sea turtles except the leatherback, loggerheads are members of the ancient family Cheloniidae, and appeared about 40 million years ago.[1] 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 led 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 coldwater barriers to migrating turtles. The result was a complete isolation of the Atlantic and Pacific populations of loggerheads.[15] 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.[15]

The distinct populations of loggerheads have unique characteristics and genetic differences. For example, Mediterranean loggerheads are smaller, on average, than Atlantic Ocean loggerheads.[16] 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.[15]

Description

Photo of the carapace of a loggerhead sea turtle.
The carapace of this loggerhead is reddish brown; five vertebral scutes run down the turtle's midline bordered by five pairs of costal scutes.

The loggerhead sea turtle is the world's largest hard-shelled turtle, slightly larger at average and maximum mature weights than the green sea turtle and the Galapagos tortoise. It is also the world's second largest extant turtle after the leatherback sea turtle.[17][18][19] Adults have an approximate weight range of 80 to 200 kg (180 to 440 lb), averaging around 135 kg (298 lb), and a straight-line carapace length range of 70 to 95 cm (28 to 37 in).[17] The maximum reported weight is 545 kg (1,202 lb) and the maximum (presumed total) length is 213 cm (84 in).[17] The head and carapace (upper shell) range from a yellow-orange to a reddish brown, while the plastron (underside) is typically pale yellow.[20] The turtle's neck and sides are brown on the tops and yellow on the sides and bottom.[9]

The turtle's shell is divided into two sections: carapace and plastron. The carapace is further divided into large plates, or scutes.[20] Typically, 11 or 12 pairs of marginal scutes rim the carapace.[8] Five vertebral scutes run down the carapace's midline, while five pairs of costal scutes border them.[21] The nuchal scute is located at the base of the head.[21] The carapace connects to the plastron by three pairs of inframarginal scutes forming the bridge of the shell.[21] The plastron features paired gular, humeral, pectoral, abdominal, femoral, and anal scutes.[8] The shell serves as external armor, although loggerhead sea turtles cannot retract their heads or flippers into their shells.[22]

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 carapaces of males are wider and less domed than the females', and males typically have wider heads than females.[23] 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).[23]

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.[24] The urea content is high in Caretta caretta tears.[25]

The skull is most easily distinguished from other sea turtles by having maxillae that meet in the mid-line of the palate.[26][27] The portion of skull behind the eyes is also relatively large and bulbous due to the extensive jaw muscles.[27]

Distribution

A map of the range of a loggerhead sea turtle covering the Atlantic, Pacific, and Indian Oceans, and the Mediterranean Sea
Range of the loggerhead sea turtle according to the National Oceanic and Atmospheric Administration

The loggerhead sea turtle has a cosmopolitan distribution, nesting over the broadest geographical range of any sea turtle. It inhabits the Atlantic, Indian, and Pacific Oceans and the Mediterranean Sea.[28]

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.[29] Florida is the most popular nesting site, with more than 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.[28]

In the Indian Ocean, loggerheads feed along the coastlines of Africa, the Arabian Peninsula, and in the Arabian Sea.[16] Along the African coastline, loggerheads nest from Mozambique's Bazaruto Archipelago to South Africa's St Lucia estuary.[30] 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.[16]

Pacific loggerheads live in temperate to tropical regions.[30] 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.[31] 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.[16] After nesting, females often find homes in the East China Sea, while the Kuroshio Current Extension's Bifurcation region provides important juvenile foraging areas.[30] Eastern Pacific populations are concentrated off the coast of Baja California, where upwelling provides rich feeding grounds for juvenile turtles and subadults. 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.[32] 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.[32] 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.[33] Evidence of a return journey came from an adult female loggerhead named Adelita, which in 1996, equipped with a satellite tracking device, made the 14,500 km (9,000 mi) trip from Mexico across the Pacific. Adelita was the first animal of any kind ever tracked across an ocean basin.[34]

The Mediterranean Sea is a nursery for juveniles, as well as a common place for adults in the spring and summer months.[29][35] Almost 45% of the Mediterranean juvenile population has migrated from the Atlantic.[29] Loggerheads feed in the Alboran Sea and the Adriatic Sea,[29] with tens of thousands of specimens (mainly sub-adult) seasonally present in the North-Eastern portion of the latter, above all in the area of the Po Delta.[36] Greece is the most popular nesting site along the Mediterranean, with more than 3,000 nests per year.[16] Zakynthos hosts the largest Mediterranean nesting with the second one being in Kyparissia Bay.[37] Because of this, Greek authorities do not allow planes to take off or land at night in Zakynthos due to the nesting turtles.[38] In addition to the Greek coast, the coastlines of Cyprus and Turkey are also common nesting sites.[16]

One record of this turtle was made in Ireland when a specimen washed ashore on Ballyhealy Beach in County Wexford.[39] Another records one specimen being washed up on a beach in County Donegal, Ireland.[40]

Habitat

Loggerhead sea turtles spend most of their lives in the open ocean and in shallow coastal waters. They rarely come ashore besides the females' brief visits to construct nests and deposit eggs. Hatchling loggerhead turtles live in floating mats of Sargassum algae.[41] Adults and juveniles live along the continental shelf as well as in shallow coastal estuaries.[42] 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.[43] Loggerheads occupy waters with surface tempheratures ranging from 13.3–28 °C (56–82 °F) during non-nesting season. Temperatures from 27–28 °C (81–82 °F) are most suitable for nesting females.[44]

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. Prey found in Sargassum mats may include barnacles, crab larvae, fish eggs, and hydrozoan colonies. Some prey, such as ants, flies, aphids, leafhoppers, and beetles, are carried by the wind to the mats.[41] Marine mammals and commercial fishes, including tuna and mahi-mahi, also inhabit the Sargassum mats.[45]

Behavior

A loggerhead sea turtle resting under a rock with its eyes open
A resting loggerhead sea turtle

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, they spread their forelimbs to about midstroke swimming position. They remain motionless with eyes open or half-shut and are easily alerted during this state. At night, captives sleep in the same position with their eyes tightly shut, and are slow to react.[44] 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 min, but they can stay submerged for up to four hours.[46] Juvenile loggerheads and adults differ in their swimming methods. A juvenile keeps its forelimbs pressed to the side of its carapace, and propels itself by kicking with its hind limbs. As the juvenile matures, its swimming method is progressively replaced with the adult's alternating-limb method. They depend entirely on this method of swimming by one year old.[47]

Water temperature affects the sea turtle's metabolic rate.[44] Lethargy is induced at temperatures between 13 and 15 °C (55 and 59 °F). The loggerhead takes on a floating, cold-stunned posture when temperatures drop to around 10 °C (50 °F).[44] However, younger loggerheads are more resistant to cold and do not become stunned until temperatures drop below 9 °C (48 °F). The loggerheads' migration helps to prevent instances of cold-stunning.[48] 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; their critical thermal maximum is currently unknown.[48] In February 2015, a live loggerhead turtle was found floating in British Columbian waters of 10.5 °C (50.9 °F) with extensive algal growth on its carapace.[49]

Female-female aggression, which is fairly rare in other 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.[50] 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.[50] 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.[50] 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.[46]

Feeding

Translucent moon jelly on black blackground: The jelly contains a solid white mass extending through about two-thirds of its body
An adult Aurelia jellyfish which loggerheads eat during migration through the open sea

The loggerhead sea turtle is omnivorous, feeding mainly on bottom-dwelling invertebrates, such as gastropods, bivalves, decapods, and horseshoe crabs.[51] It has a greater list of known prey than any other sea turtle. Other food items include sponges, corals, sea pens, polychaete worms, tube worms, sea anemones, cephalopods, barnacles, brachiopods, amphipods, isopods, Portuguese men o' war, insects, bryozoans, hydrozoans, sea urchins, sand dollars, sea cucumbers, starfish, tunicates, fish (eggs, juveniles, and adults), hatchling turtles (including members of its own species), algae, and vascular plants.[52][53] During migration through the open sea, loggerheads eat jellyfish, floating molluscs, floating egg clusters, squid, and flying fish.[9]

Loggerheads crush prey with their large and powerful jaws.[9][54] 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.[54] Inward-pointing, mucus-covered papillae found in the fore region of the loggerhead's esophagus filter out foreign bodies, such as fish hooks. The next region of the esophagus is not papillated, with numerous mucosal folds. The digestion rate in loggerheads is temperature-dependent; it increases as temperature increases.[54]

Predators

A horned ghost crab (Ocypode ceratophthalma) preying on a loggerhead hatchling in Gnaraloo, Western Australia. Ghost crabs are one of the chief causes of egg and hatchling mortality in sea turtles.[55][56][57]
A red fox walking along a fallen tree
The red fox is a predator of loggerhead nests in Australia.

Loggerheads have numerous predators, especially early in their lives. Egg and nestling predators include ghost crabs, oligochaete worms, beetles, fly larvae, ants, flesh flies, snakes, gulls, corvids, opossums, bears, rats, armadillos, mustelids, skunks, canids, procyonids, cats, pigs, and humans. During their migration from their nests to the sea, hatchlings are preyed on by dipteran larvae, crabs, toads, lizards, snakes, seabirds such as frigatebirds, and other assorted birds and mammals. In the ocean, predators of the loggerhead juveniles include portunid crabs and various fishes, such as parrotfishes and moray eels. Adults are more rarely attacked due to their large size, but may be preyed on by large sharks, seals, and killer whales. Nesting females are attacked by flesh flies, feral dogs, and humans. Salt marsh mosquitos can also pester nesting females.[54][58]

In Australia, the introduction of the red fox (Vulpes vulpes) by British 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.[59] 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.[60]

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.[59] 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.[60]

Up to 40% of nesting females around the world have wounds believed to come from shark attacks.[58]

Disease and parasites

Infectious bacteria such as Pseudomonas and Salmonella attack loggerhead hatchlings and eggs. Fungi such as Penicillium infect loggerhead sea turtle nests and cloacae.[58]

Fibropapillomatosis disease caused by a form of the herpes-type virus threatens loggerheads with internal and external tumors. These tumors disrupt essential behaviors and, if on the eyes, cause permanent blindness.[61] Trematodes of the family Spirorchiidae inhabit tissues throughout the body of the loggerhead, including vital organs, such as the heart and the brain.[62] Trematode infection can be highly debilitating. For example, inflammatory trematode lesions can cause endocarditis and neurological disease.[62] A nematode, Angiostoma carettae, also infects loggerheads,[63] causing histologic lesions in the respiratory tract.[63]

More than 100 species of animals from 13 phyla, as well as 37 kinds of algae, live on loggerheads' backs.[64] These parasitic organisms, which increase drag, offer no known benefit to the turtle, although the dulling effect of organisms on shell color may improve camouflage.[64]

In 2018, researchers from Florida State University examined 24 individual turtle carapaces and found an average of 33,000 meiofauna with one turtle having 150,000 organisms living on the shell. A collection of 7,000 nematodes from 111 genera were found on the turtles studied.[65]

Life history

Early life

Hatchling running to sea
A pair of hatchlings to scale with a human hand

Hatchlings range in color from light brown to almost black, lacking the adult's distinct yellows and reds.[20] Upon hatching, they measure about 4.6 cm (1.8 in) and weigh about 20 g (0.7 oz).[9] The eggs are typically laid on the beach in an area above the high-tide line. The eggs are laid near the water so the hatchlings can return to the sea.[66] The loggerhead's sex is dictated by the temperature of the underground nest. Incubation temperatures generally range from 26–32 °C (79–90 °F). Sea turtle eggs kept at a constant incubating temperature of 32 °C become females. Eggs incubating at 28 °C become males. An incubation temperature of 30 °C results in an equal ratio of male to female hatchlings.[67] 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.[59]

After incubating for around 80 days, hatchlings dig through the sand to the surface, usually at night, when darkness increases the chance of escaping predation and damage from extreme sand surface temperatures is reduced.[66] Hatchlings enter the ocean by navigating toward the brighter horizon created by the reflection of the moon and starlight off the water's surface.[68]

Hatchlings can lose up to 20% of their body mass due to evaporation of water as they journey from nest to ocean.[69] They initially use the undertow to push them five to 10 m away from the shore.[69] Once in the ocean, they swim for about 20 hours, taking them far offshore.[20] An iron compound, magnetite, in their brains allows the turtles to perceive the Earth's magnetic field,[70] for navigation. Many hatchlings use Sargassum in the open ocean as protection until they reach 45 cm (18 in).[20] Hatchling loggerheads live in this pelagic environment until they reach juvenile age, and then they migrate to nearshore waters.[20]

Maturation

Photo of a loggerhead swimming above a reef
A mature loggerhead sea turtle

When ocean waters cool, loggerheads must migrate to warmer areas or hibernate to some degree. In the coldest months, they 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.[71] During their seasonal migration, juvenile loggerheads have the ability to use both magnetic and visual cues.[72] When both aids are available, they are used in conjunction; if one aid is not available, the other suffices.[72] The turtles swim at about 1.6 km/h (0.9 kn; 0.4 m/s) during migration.[73]

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.[74] 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.[75] Nesting loggerheads have a straight carapace length of 70–109 cm (28–43 in). Because of the large range, carapace length is not a reliable indicator of sexual maturity.[76] Their estimated maximum lifespan is 47–67 years in the wild.[52]

Reproduction

Loggerhead turtle track on a beach
A female loggerhead sea turtle from the back, laying eggs into the hole it has dug
A loggerhead sea turtle laying eggs

Female loggerheads first reproduce between the ages of 17 and 33,[75] and their mating period may last more than six weeks.[74] They court their mates, but these behaviors have not been thoroughly examined.[77] Male forms of courtship behavior include nuzzling, biting, and head and flipper movements.[77] Studies suggest females produce cloacal pheromones to indicate reproductive ability.[77] 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.[77] While nesting, females produce an average of 3.9 egg clutches, and then become quiescent, producing no eggs for two to three years.[74][78] 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.[77] Recent evidence indicates ovulation in loggerheads is mating-induced.[79] 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.[79] In the Northern Hemisphere, loggerheads mate from late March to early June. The nesting season is short, between May and August in the Northern Hemisphere and between October and March in the Southern Hemisphere.[76]

Loggerheads may display multiple paternity.[80] Multiple paternity is possible due to sperm storage. The female can store sperm from multiple males in her oviducts until ovulation.[81] A single clutch may have as many as seven fathers, each contributing sperm to a portion of the clutch.[82] Multiple paternity and female size are positively correlated.[80][82] Two hypotheses explain this correlation. One posits that males favor large females because of their perceived higher fecundity (ability to reproduce).[80] The other states, because larger females are able to swim more quickly to mating grounds, they have longer mating periods.[80]

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.[77][78] 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.[83] This process takes one to two hours, and occurs in open sand areas or on top of sand dunes, preferably near dune grasses that the females can use to camouflage the nest.[78] The nesting area must be selected carefully because it affects characteristics such as fitness, emergence ratio, and vulnerability to nest predators.[66] Loggerheads have an average clutch size of 112.4 eggs.[84]

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.[85]

Threats

An orange diamond sign with the words
Loggerhead sea turtle nest roped off as part of the Sea Turtle Protection Project on Hilton Head Island

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.[86] In Mexico, turtle eggs are a common meal; locals claim the egg is an aphrodisiac.[87] 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.[86][88]

The US 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.[89] 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.[89] Many juvenile loggerheads aggregate off the coast of Baja California Sur, Mexico, where small coastal fisheries increase these turtles' mortality risk; fishers have reported catching dozens of loggerheads with bottom-set gear per day per boat.[89] The most common commercial fishery that accidentally takes loggerheads are bottom trawls used for shrimp vessels in the Gulf of California.[90] In 2000, between 2,600 and 6,000 loggerheads were estimated to have been killed by pelagic longlining in the Pacific.[89]

Fishing gear is the biggest threat to loggerheads in the open ocean. They often become entangled in longlines or gillnets. 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.[90] They also become stuck in traps, pots, trawls, and dredges.[9] 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 11 million metric tons of plastic are released into the ocean annually. A number that is projected to increase to 29 million metric tons by 2040.[91] Turtles ingest a wide array of this floating debris, including bags, sheets, pellets, balloons and abandoned fishing line.[92] 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 and malnutrition, suffocation, ulcerations, 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.[93]

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.[66] 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.[68] Artificial lighting causes tens of thousands of hatchling deaths per year.[94]

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.[78] Urbanization often leads to the siltation of sandy beaches, decreasing their viability.[78] 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.[61]

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. Nesting sites exposed to unseasonably warm temperatures over a three-year period produced 87–99% females.[95] This raises concern over the connection between rapid global temperature changes and the possibility of population extinction.[96] A more localized effect on gender skewing comes from the construction of tall buildings, which reduce sun exposure, lowering the average sand temperature, which results in a shift in gender ratios to favor the emergence of male turtles.[78] Construction of new thermal power stations can raise local water temperature, which is also said to be a threat.[97]

The increase of temperature and food availability will increase reproduction output of loggerhead turtles. Many researchers agree that temperature increases due to climate change has a complicated impact on turtles. At breeding sites when a loggerhead turtle lays multiple clutches in a season, a higher temperature will cause the duration of time between laying two different nests to become shorter. The amount of food availability makes a difference in reproductive output because when there is a greater amount of food available, the turtles will grow to a larger size. The larger a turtle is, the more likely they will have a greater reproductive output. The amount of food also has a relationship to temperature. Researchers have found that an increase of temperature causes feeding grounds to produce more food.[98]

Tropical Cyclones have a significant impact on hatchling loss. The associated storm surges push water higher up the beach, flooding nest and drowning the embryos. Strong wave action may eroded away sand, exposing the eggs to drying and predation. The current trend of rising sea surface temperatures and the increase in both numbers and intensities of tropical cyclones as a result of climate change pose a growing threat to turtle populations.[99]

Conservation efforts

A loggerhead sea turtle escapes a circular fisherman's net via a TED
Loggerhead sea turtle escapes from fishing net through a turtle excluder device

Since the loggerhead occupies such a broad range, successful conservation requires efforts from multiple countries.[9]

Loggerhead sea turtles are classified as vulnerable by the International Union for Conservation of Nature and are listed under Appendix I of the Convention on International Trade in Endangered Species, making commercial international trade prohibited.[9] In the United States, the Fish and Wildlife Service and National Marine Fisheries Service classify them as a threatened species under the Endangered Species Act.[9] 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.[100][101] Throughout Japan, the Sea Turtle Association of Japan aids in the conservation of loggerhead sea turtles.[102] Greece's ARCHELON works for their conservation.[103] The Marine Research Foundation works for loggerhead conservation in Oman.[104] Annex 2 of the Specially Protected Areas and Wildlife Protocol of the Cartagena Convention, which deals with pollution that could harm marine ecosystems, also protects them.[9][105] Conservation organizations worldwide have worked with the shrimp trawling industry to develop turtle exclusion devices (TEDs) to exclude even the largest turtles. TEDs are mandatory for all shrimp trawlers.[9]

In many places during the nesting season, workers and volunteers search the coastline for nests,[106] and researchers may also go out during the evening to look for nesting females for tagging studies and 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.[107]

Symbols

The loggerhead sea turtle appears on the $1000 Colombian peso coin. In the United States, the loggerhead sea turtle is the official state reptile of South Carolina and also the state saltwater reptile of Florida.[108][109]

See also

References

Footnotes

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Bibliography

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Loggerhead sea turtle: Brief Summary

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The loggerhead sea turtle (Caretta caretta) is a species of oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around 90 cm (35 in) in carapace length when fully grown. The adult loggerhead sea turtle weighs approximately 135 kg (298 lb), with the largest specimens weighing in at more than 450 kg (1,000 lb). The skin ranges from yellow to brown in color, and the shell is typically reddish brown. No external differences in sex are seen until the turtle becomes an adult, the most obvious difference being the adult males have thicker tails and shorter plastrons (lower shells) 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 invertebrates. Its large and powerful jaws serve as an effective tool for 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 animals, such as large sharks.

The loggerhead sea turtle is considered a vulnerable species by the International Union for Conservation of Nature. In total, 9 distinct population segments are under the protection of the Endangered Species Act of 1973, with 4 population segments classified as "threatened" and 5 classified as "endangered" Commercial international trade of loggerheads or derived products is prohibited by CITES Appendix I. Untended fishing gear is responsible for many loggerhead deaths. The greatest threat is loss of nesting habitat due to coastal development, predation of nests, and human disturbances (such as coastal lighting and housing developments) that cause disorientations during the emergence of hatchlings. Turtles may also suffocate if they are trapped in fishing trawls. Turtle excluder devices have been implemented in efforts to reduce mortality by providing an escape route for the turtles. Loss of suitable nesting beaches and the introduction of exotic predators have 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 across several countries.

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Distribution

provided by World Register of Marine Species
cosmopolitan warm to temperate waters

Reference

van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO).

license
cc-by-4.0
copyright
WoRMS Editorial Board
contributor
Jacob van der Land [email]

Distribution

provided by World Register of Marine Species
Scotian Shelf to the Gulf of Maine and to Cape Hatteras

Reference

North-West Atlantic Ocean species (NWARMS)

license
cc-by-4.0
copyright
WoRMS Editorial Board
contributor
Kennedy, Mary [email]