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Loggerhead sea turtle

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The Loggerhead Sea Turtle
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Reptilia
Subclass:
Anapsida
Order:
Testudines
Family:
Cheloniidae
Genus:
Caretta

Species:
C. caretta
Binomial name
Caretta caretta
Linnaeus, 1758
Range of Caretta caretta

The Loggerhead Sea Turtle (Caretta caretta) is a sea turtle and the only member of the genus Caretta. It has become the world's most-studied and best known sea-turtle.[1] The genus name "Caretta" is a latinization of the French "caret", meaning turtle, tortoise, or sea turtle.[2] A loggerhead sea turtle reportedly grows up to 315 pounds.[3] Their shell color is a reddish brown color, and the color of their skin is brown yellow. They are named for their disproportionately large head. They are also the state reptile of South Carolina.[4]

Anatomy and Morphology

The adult loggerhead sea turtle typically has a carapace, shell length of approximately 36 inches (92 cm) and weighs about 250 pounds (113 kg).[5] The coloration of the flippers and carapace range from a dull brown to a reddish-brown, and the plastron, underside, is typically a pale yellow.[5] The carapace is thick and bony and covered by non-overlapping scutes at the seam lines. Typically, there are 11 or 12 pairs of marginal scutes, 5 pairs of both vertebral and costal scutes, and a nuchal scute that comes into to contact with the costals. The carapace is connected to the plastron by 3 pairs of inframarginal scutes that lack pores. On the plastron itself features paired gular, humeral, pectoral, abdominal, femoral, and anal scutes. [6]

Hatchlings vary in color from grays to browns, and lack the distinct yellows and reds that the adult may have. They measure approximately 1.8 inches at birth, and weigh about .04 pounds.[5] The hatchlings' carapaces have 3 keels while the plastrons have 2.[6]

Distribution

Loggerheads are distributed throughout the world; They live in the Atlantic Ocean, Indian Ocean, Pacific Ocean, and the Mediterranean Sea.[1]

Atlantic Ocean

The greatest concentration of loggerheads is along the southeastern coast of North America and in the Gulf of Mexico.[1] Very few loggerheads are found along the European and African coastline.[1] Florida is the most popular nesting site with over 67,000 nests per year, however nesting extends as far north as Virginia, as far south as Brazil, and as far east as the Cape Verde Islands.[1] The Cape Verde Islands are the only significant nesting site on the eastern side of the Atlantic.

Indian Ocean

Indian Ocean loggerheads feed along the coastlines of Africa, the Arabian Peninsula, and in the Arabian Gulf.[1] The largest population is located near the coast of western Australia.[1] The largest nesting site, Oman, is located on the Arabian Peninsula and receives around 15,000 nests annually.[1] Western Australia and Southern Africa are other notable nesting areas.

Pacific Ocean

Loggerheads live in the temperate to tropical regions of the Pacific Ocean.[6] Pacific loggerheads forage in the East China Sea, southwestern Pacific, and along the Baja Peninsula.[1] Eastern Australia and Japan are the major nesting areas.[1] Very little nesting occurs on the eastern Pacific coastline however thousands of loggerheads live there during the summers.[1] There are also few breeding grounds in the northern and southern Pacific Ocean. In fact, loggerheads have been found to nest in Japan in the northern Pacific Ocean. Eastern Australia, New Caledonia, and rarely Vanuatu and Tokelau. Yakushima Island, Miyazaki, Minabe, and Atsumi beaches on the mainland provide important nesting areas for loggerheads. Yakushima Island is the most important of these, having three nesting grounds that 40% of all loggerheads near Japan attend. Post-nesting females often find homes in the East China Sea, while the Kuroshio Extension Bifurcation Region and the Coast of Baja California Sur, Mexico provide important juvenile foraging areas.[6] Hatchlings migrate from the east Pacific to Mexico only to return later as sub-adults.[1]

Mediterranean Sea

The Mediterranean is a nursery for juvenile loggerheads. Almost 45 percent of the juvenile population migrates from the Atlantic.[1] Loggerheads feed in the western and eastern basins of the Mediterranean, Alboran Sea and Adriatic Sea areas respectively.[1] Greece is the most popular nesting site with more than 3,000 nests per year.[1] The coastlines of Cyprus and Turkey are also common nesting sites.[1]

Ecology and life history

Habitat

During its lifetime, the loggerhead sea turtle is known to live in terrestrial, oceanic, and neritic ecosystems.[5] Upon birth, hatchlings enter the ocean and continue to swim away from land for several days. When the loggerhead returns from its brief swim, it will find a home in a local downwellings.[5] Downwellings are created when surface waters converge and feature floating material such as seaweed. The post-hatchlings may stay in this environment for months, feeding on floating material and occasionally swimming to keep from getting too cold. Eventually, they will be picked up by ocean currents farther from shore and will move into the oceanic zone.[5] The post-hatchlings will stay in the oceanic zone until they become juveniles (between ages 7 and 12). They will then move into the neritic zone and remain there until adulthood.[5] The neritic zone is an important area for not only the juveniles, but also the adults for foraging and inter-nesting habitats.[5]

Feeding ecology

The species feeds on molluscs, crustaceans, fish, jellyfish, crabs, shrimp and Portuguese Man o' War and other small to medium-sized marine animals, which they crush with their large and powerful jaws. As with other sea turtles, females return to lay their eggs on or near the same beach where they hatched. Unlike other sea turtles, courtship and mating usually do not take place near the nesting beach but rather along the migration routes between feeding and breeding grounds.

Scientists in Hawaii use satellite transponders to track loggerhead sea turtles in the Northern Pacific Ocean.[7].

Adult loggerhead turtles feature a somewhat reddish-brown, heart-shaped carapace and a pale yellow plastron. The turtle's neck and sides are brown on the tops and yellow on the sides and bottom. Upon birth, hatchlings lack the reddish-brown color of the adults and are light to dark brown or gray. Hatchlings average about 1.8 inches in length and weigh around 20 grams at birth.[5] Nesting loggerhead turtles have a straight caraprace length of about 70-109 cm, 70 being the minimum breeding size. However, this number is not universal because not all loggerhead sea turtles begin nesting at the minimum size, therefore the minimum is not a good indicator of sexual maturity.[8]

The loggerhead mainly feeds on bottom dwelling invertebrates. It eats horseshoe crabs, clams, mussels, and other sea species. Their powerful jaw muscles allow them to easily crush shellfish.[5] During migration through the open sea, loggerheads eat jellyfishes, floating mollusks, floating egg clusters, squids, and flying fishes.[citation needed]

Life history

A baby loggerhead is crawling across the sand.
Baby Loggerhead Sea Turtle.

The loggerhead sea turtle becomes sexually mature at around age 35.[5] Like all marine turtles, the loggerhead will prepare for reproduction in its foraging area. This takes place several years before the loggerhead will migrate to a mating area. The loggerhead first creates a nest and then enters a mating period that can last up to six weeks. Over several months, the females will produce several clutches of eggs and then become quiescent, not producing eggs for several years.[8]

In the Mediterranean, Loggerheads mate from late March to early June. The female nesting season is at its peak in June and July, but this depends on the nesting beach. The clutch may vary from 70 to 150 eggs. Each egg is roughly the size and shape of a ping-pong ball. The average interval between nesting seasons is two to three years.

A female loggerhead sea turtle from the back, laying eggs into the hole it has dug.
Loggerhead Sea Turtle laying eggs.

Loggerhead turtles are the most common sea turtle to nest in the United States. Loggerheads nest from Texas to North Carolina, requiring soft sandy beaches, where there is little light pollution; with the largest concentration of nests in southFlorida. Statistics collected in Florida since 1998 however indicate the lowest nesting levels Florida has seen in 17 years, where nesting rates have declined from 85,988 nests in 1998 to approximately 45,084 in 2007.[9]

After approximately 80 days, the hatchlings emerge usually at night when protection from predation is greater. Because they usually follow the brightest light to the ocean's edge, artificial lights from human activity can lead them astray. Once in the ocean, Atlantic turtles use ocean currents to travel to the Sargasso Sea using the Sargassum as protection until they mature.[10]

An alternative to migration for many loggerheads is hibernation to varying degrees as the water cools. By February they are submerged for up to seven hours at a time, emerging for only seven minutes to recover. Although outdone by freshwater turtles, these are the longest recorded dives for any air-breathing marine vertebrate[11]

Most loggerheads that reach adulthood live for longer than 30 years, and can often live past 50 years. They are immune to the toxins of a Portuguese Man o' War as the turtles have often been seen feeding on them.[citation needed]

Behavior

It is known that loggerhead sea turtles engage in courtship behavior, but these behaviors are poorly described and have not been thoroughly examined. Observations that have been made indicate that nuzzling, biting, head movements, and flipper movements may be forms of courtship behavior by males. It is unknown whether or not females produce cloacal pheromones to suggest reproductive ability. However, observations show that females may do this. When mating, males will approach females and attempt to mount them, and the females will try to stop the male from mounting them. The male and female may circle each other. If the female has other competitors for her, she may leave the males so that they may react with each other. Once a mate is chosen, the male will mount the female. The other courting males will bite the male, damaging his flippers and tail sometimes to the point of causing bones to protrude. This damage can cause the male to dismount and requires several weeks to heal. The male's curved claws damage the shoulders of the female's shell when he mounts her. He also injures her by biting her neck during mating.[8]

All sea turtles have similar basic nesting behaviors. The loggerhead sea turtle will emerge from the surf, rise to the beach, excavate a body pit, lay eggs, fill the egg chamber, fill the body pit, and finally return to sea.[8]

Taxonomy

Two subspecies are recognized: Caretta caretta gigas, is found in the Indian and Pacific Oceans, and C. caretta caretta, the Atlantic loggerhead, also found in south Italy and the Greek islands ofZakynthos,Kefalonia, Crete, and the Peloponese and in Dalyan in southwestern Turkey. (see article; June Haimoff). The Caretta caretta gets its name from its considerably large head that supports the jaws necessary for crushing protected prey such as conch. [5]

Linnaeus was the first person to name the loggerhead, calling it Testudo caretta. There were 35 other names suggested for the species for two centuries after Linnaeus named the species, but there is now agreement that Caretta caretta is an acceptable name.[6]

Importance to humans

Loggerhead Sea Turtles were once intensively hunted for their meat and eggs, along with their fat which was used in cosmetics and medication. The Loggerhead Sea Turtles were also killed for their shells, which are used to make items such as combs. As a result, both subspecies are now internationally protected.

Conservation

A Loggerhead sea turtle escapes a circular fisherman's net via a TED.
Loggerhead Sea Turtle escapes from fishing net through a TED (Turtle Excluder Device).

Loggerhead turtles are classified as endangered by the International Union for the Conservation of Nature and are listed under Appendix I of the Convention on International Trade in Endangered Species. In the United States, the U.S. Fish and Wildlife Services and National Marine Fisheries Service classify them as a threatened species under theEndangered Species Act.

Today the main threat to the adult loggerheads lies in shrimp trawls and crab fishing nets, to which many loggerheads annually fall victim[12]. Furthermore, adults are often injured by speedboat propellers and by swallowing fishing hooks or getting caught in nets. Internationally, animal protection organizations take pains to monitor and protect the turtles' nesting grounds in Turkey,[13] Greece[14], Bonaire, and Costa Rica. The turtles can also be found around the Italian islands of Lampedusa andLinosa, off the coast of Sicily, and in Calabria, where it is particularly endangered. Furthermore, the turtles are known to nest on the beaches of Cyprus, especially Akamas and Alagadi Beach.[15]

An orange diamond sign with the words "Loggerhead Turtle Nesting Area" is blocking off a roped-off area on the beach where a loggerhead has laid eggs.
Loggerhead Sea Turtle nest roped off as part of the Sea Turtle Protection Project on Hilton Head Island

In many places during the nesting season, workers search the coastline to find evidence of nests. Once found, a nest will be uncovered and the eggs carefully counted, if the nest is dangerously located the eggs will be moved to a better spot. Plastic fencing will be placed at or near the surface to protect the eggs from large predators such as raccoons or even dogs. The barrier used is large enough to allow the hatchlings to emerge without difficulty. The nests are checked daily for disturbances; several days after there is indication that the eggs have hatched the nest will be uncovered and the tally of hatched eggs, undeveloped eggs, and dead hatchlings will be recorded. If any hatchlings are found, they are either taken to be raised and released, or taken to research facilities. Ones that appear strong and healthy may instead be released to the ocean. Typically, those that lacked the strength to hatch and climb to the surface by that point would have died otherwise.

Hatchlings require the travel from their nest to the ocean in order to build up strength for the journey ahead, so interfering by helping it to the ocean actually lowers their chances of survival.[citation needed] The Fripp Island, SC Turtle Patrol each year sets pieces of drift wood from the nests toward the sea as guides so the hatchlings get to start out in the right direction. Loggerheads are listed as Endangered under both Australia's Environment Protection and Biodiversity Conservation Act 1999 and Queensland's Nature Conservation Act 1992.

Threats

The threat of being caught in fishing gear is currently the biggest concern for loggerhead turtles. They are most commonly caught in longlines and gillnets but have also been accidentally captured in traps and pots, trawls, and dredges.[5] When caught in these traps, loggerheads can receive serious damage from the ropes of traps and can even drown. Risk of drowning is high when a loggerhead is caught in a trawl that does not have turtle excluder devices. Since loggerheads spend a significant portion of their lives in open ocean environments, floating debris such as plastic pellets and ghost fishing gear can be ingested and harm the loggerheads.[16]

A disease by the name of fibropapillomatosis has been a problem for loggerheads. It is a condition that causes internal and external tumors that can lead to disruption of essential behaviors and, if tumors are on the the eyes, permanent blindness.


See also

References

  1. ^ a b c d e f g h i j k l m n o p q Spotila, James R. (2004). Sea Turtles: A Complete Guide to their Biology, Behavior, and Conservation. Baltimore, Maryland: The Johns Hopkins University Press and Oakwood Arts. pp. 163–179. ISBN 0-8018-8007-6.
  2. ^ http:www.widecast.org/sea/definitions.cfm[dead link]
  3. ^ a b My Scribe (May 8, 2009). "Loggerhead Facts". Loggerhead preservation. KiawahTurtles. Retrieved February 4, 2010. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  4. ^ <http://www.enchantedlearning.com/usa/states/southcarolina/>
  5. ^ a b c d e f g h i j k l m Bolten, A.B. (2003). "Loggerhead Turtle (Caretta caretta)". NOAA Fisheries. NOAA Fisheries. Retrieved January 31, 2010.
  6. ^ a b c d e f Terese, Conant (August 2009). LOGGERHEAD SEA TURTLE (CARETTA CARETTA) 2009 STATUS REVIEW UNDER THE U.S. ENDANGERED SPECIES ACT (PDF). Loggerhead Biological Review Team. p. 222. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); line feed character in |coauthors= at position 54 (help); line feed character in |title= at position 40 (help)
  7. ^ Dennis Hollier (August/September 2008). "Mapping the Void". Hana Hou!, Vol. 11, No. 4. {{cite web}}: Check date values in: |date= (help)
  8. ^ a b c d e Miller, Jeffrey D.; Limpus, Colin J.; Godfrey, Matthew H. (in press), "Nest Site Selection, Oviposition, Eggs, Development, Hatching and Emergence of Loggerhead Turtles", in Bolten, Alan; Witherington, Blair (eds.), Biology and Conservation of Loggerhead Sea Turtle (PDF), University of Florida Press, retrieved February 2, 2010 {{citation}}: Check date values in: |year= (help)CS1 maint: year (link)
  9. ^ [1][dead link]
  10. ^ BBC NEWS | Science/Nature | Turtles return home after UK stay
  11. ^ Hochscheid, S. (2005). "First records of dive durations for a hibernating sea turtle". Biol. Lett. 1 (1): 82–6. doi:10.1098/rsbl.2004.0250. PMC 1629053. PMID 17148134. Retrieved 2 December 2009. These represent the longest dives ever reported for a diving marine vertebrate. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  12. ^ http://community.oceana.org/creatures/loggerhead-turtle
  13. ^ "Loggerhead Turtles in the Dalyan River, Mulğa Province, Turkey, 2004". seaturtle.org. Retrieved 2007-06-27.
  14. ^ Skoufas, George (July 2005). "Nesting and hatching success of the sea turtle Caretta caretta on Marathonissi island" (PDF). Belgian Journal of Zoology. 135 (2): 243–246. Retrieved 2009-01-02. {{cite journal}}: Cite has empty unknown parameter: |coauthors= (help)
  15. ^ "Conservation of the Akamas Peninsula (Cyprus)" (PDF), CONVENTION ON THE CONSERVATION OF EUROPEAN WILDLIFE AND NATURAL HABITATS, Strasbourg: Council of Europe, 29 November - 3 December-2004, retrieved 2009-01-02 {{citation}}: |format= requires |url= (help); Check date values in: |date= (help); Cite has empty unknown parameters: |coeditors= and |coauthors= (help)
  16. ^ a b NOAA Fisheries (2010). "Threats to Marine Turtles". Endangered marine animal preservation. NOAA Fisheries Office of Protected Resources. Retrieved February 7, 2010. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
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