Jump to content

Loggerhead sea turtle

From Wikipedia, the free encyclopedia
This is an old revision of this page, as edited by Michaelduly (talk | contribs) at 01:28, 29 March 2010 (→Mediterranean Sea). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

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 the world's most-studied and well-known sea-turtle.[1] It is the only member of the genus Caretta. The genus name "Caretta" is a latinization of the French "caret", meaning turtle, tortoise, or sea turtle.[2] Adult loggerhead sea turtles weigh from Template:Lb to kg to Template:Lb to kg and measure Template:In to cm to Template:In to cm.[2] Their shell is a reddish brown color, and their skin ranges from yellow to brown. The name loggerhead comes from their disproportionately large head.[3] The loggerhead sea turtle also holds the title of the world's largest hard-shelled turtle.[4]

Taxonomy

Two subspecies are recognized: C. caretta gigas which inhabits the Indian and Pacific Oceans, and C. caretta caretta which inhabits the Atlantic as well as the Mediterranean sea.

C. caretta gets its name from its large head that supports the jaws necessary for crushing exoskeletons or shells of its prey such as conches.[3] Linnaeus first named the loggerhead, calling it Testudo caretta.[5] Thirty-five other names emerged over the following two centuries, but Caretta caretta has prevailed.[5]

Range and distribution

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 coastlines.[1] Florida is the most popular nesting site with over 67,000 nests per year.[1] 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 Sea.[1] In Africa, the loggerhead nests from Mozambique's Bazaruto Archipelago south to South Africa's St Lucia estuary.[5] The largest population is located near the coast of western Australia.[1] The largest nesting site is in Oman, on the Arabian Peninsula, and hosts around 15,000 nests annually.[1] Western Australia and Southern Africa are other notable nesting areas.

Pacific Ocean

Loggerheads live in temperate to tropical regions of the Pacific Ocean.[5] 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] Pacific loggerheads have been found to nest in Japan, eastern Australia, New Caledonia, and rarely Vanuatu and Tokelau. Yakushima Island is the most important Pacific nesting site with three nesting grounds that 40% of all loggerheads near Japan visit.

Little nesting occurs on the eastern Pacific coastline however thousands of loggerheads live there during the summers.[1].

Post-nesting females often find homes in the East China Sea, while the Kuroshio Extension Bifurcation Region as well as the Coast of Baja California provide important juvenile foraging areas.[5] 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 in the Mediterranean has migrated 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 Greek authorities do not allow planes to take off or land at night at Zakynthos due to the turtles nesting on the beaches. The coastlines of Cyprus and Turkey are also common nesting sites.[1]

Anatomy and Morphology

Average adult loggerhead sea turtles have a weight range from Template:Lb to kg to Template:Lb to kg.[2] On average, they measure Template:In to cm to Template:In to cm.[2] The adult has a carapace (upper side of the shell) length of approximately Template:In to cm.[3] The flippers and carapace range from a dull brown to a reddish-brown, and the plastron (underside) is typically pale yellow.[3] The turtle's neck and sides are brown on the tops and yellow on the sides and bottom.[3] Hatchlings vary in color from gray to brown, and lack the adults' distinct yellows and reds. They measure approximately Template:In to cm at birth, and weigh about .04 pounds (18 g).[3]

The heart-shaped 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 contacts the costals. The carapace is connected to the plastron by 3 pairs of inframarginal scutes that lack pores. The plastron itself features paired gular, humeral, pectoral, abdominal, femoral, and anal scutes.[5] Hatchlings' carapaces have 3 keels while the plastrons have 2.[5]

Ecology

Habitat

During its lifetime, the loggerhead sea turtle inhabits terrestrial, oceanic, and neritic ecosystems.[3] Upon birth, hatchlings enter the ocean and swim away from land for several days. The "post-hatchlings" then return to find a home in a local downwelling.[3] They may stay there for months, feeding on floating material and occasionally swimming to keep from getting too cold. Conditions become life threatening if water temperatures dip below 50 °F (10 °C).[6] Eventually, they enter ocean currents farther from shore and move into the oceanic zone[3] where they remain until they reach the juvenile stage (between ages 7 and 12). They then move into the neritic zone and remain there until reaching adulthood.[3] The neritic zone is also an important area for adult foraging and inter-nesting habitats.[3]

Feeding

The loggerhead mainly feeds on bottom dwelling invertebrates, including horseshoe crabs, clams, mussels, molluscs, crustaceans, fish, jellyfish, crabs, shrimp, Portuguese Man o' War and other small to medium-sized marine animals, which they crush with their large and powerful jaws. Their powerful jaw muscles allow them to easily crush shellfish.[3] During migration through the open sea, loggerheads eat jellyfishes, floating mollusks, floating egg clusters, squids, and flying fishes.[3]

Life history

Breeding

The loggerhead mating period may last up to six weeks.[7] It appears that these turtles court their mates, however these behaviors have not been thoroughly examined.[7] Nuzzling, biting, head movements, and flipper movements are forms of male courtship behavior.[7] Females may produce cloacal pheromones to suggest reproductive ability.[7] Males approach females and attempt to mount them, while females resist. The male and female may circle each other. If the male has competitors, the female may leave the males to struggle with each other. The winner then mounts the female. Other courting males bite the male during mating, damaging his flippers and tail, sometimes to the point of exposing bones. Such damage can cause the male to dismount, requiring weeks to heal.[7] The male's curved claws damage the shoulders of the female's shell when he mounts her. He may injure her by biting her neck during mating.[7]

Photo of a baby loggerhead crawling across the sand.
Baby Loggerhead Sea Turtle.

Over several months, females produces many egg clutches and then become quiescent, producing no eggs for an average two to three years.[7] 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.[7] In the Mediterranean, Loggerheads mate from late March to early June. The nesting season peaks in June and July, but varies by nesting beach.[7]

All sea turtles have similar basic nesting behaviors. Females return to lay their eggs on or near the beach where they hatched.[7] They haul out of the water, climb the beach, excavate a body pit, lay eggs, fill the egg chamber, fill the body pit, and finally return to sea.[7] The nesting area must be selected carefully because it will have an affect on characteristics of the turtle such as fitness, emergence ratio, and vulnerability to nest predators.[7] Clutch size ranges from 7–15 centimetres (70–150 mm). Each egg is roughly the size and shape of a ping-pong ball.

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 or no light pollution. The largest concentration of nesting is in south Florida.

Early life

The loggerhead's sex is determined during incubation. Temperatures range from 79–90 °F (26–32 °C). Lower temperatures produce males while higher temperatures result in females.[4] After incubating for approximately 80 days, hatchlings emerge, usually at night when predation is reduced. Hatchlings average about 1.8 inches (4.6 cm) in length and weigh around 20 grams (0.71 oz) at birth.[3]

Maturation

Once in the ocean, Atlantic turtles use ocean currents to travel to the Sargasso Sea and use the Sargassum as protection until they mature.[8]

An alternative to migration is hibernation to varying degrees as the water cools. By February loggerheads submerge for up to seven hours at a time, emerging for only seven minutes to breathe. Although outdone by freshwater turtles, these are among the longest recorded dives for any air-breathing marine vertebrate.[9]

Loggerheads mature sexually at around age 35.[3] Nesting loggerheads have a straight caraprace length of 70–109 centimetres (28–43 in). Seventy is the minimum size for breeding. However, not all loggerheads begin nesting after reaching minimum size. Therefore carapace length is not a good indicator of sexual maturity.[7] Most loggerheads that reach adulthood live more than 30 years, and often live past 50 years.

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.[7]

Importance to humans

Loggerhead Sea Turtles were once intensively hunted for their meat and eggs. Turtle meat and eggs in general are still widely used today for food sources despite international regulations.[10] In Mexico, eating turtle eggs is a very common tradition and the eggs can be easily bought in the markets.[11] The locals claim that the turtle egg acts as an aphrodisiac.[11] However, eating loggerhead meat or eggs can lead to serious illness. This can be attributed to high levels of toxic metals that build up in the turtles through bioaccumulation and harmful bacteria that can be found in the loggerheads such as Pseudomonas aeruginosa and Serratia marcescens.[10][12] Their fat has been in cosmetics and medication and the shells are used to make items such as combs. As a result, loggerhead sea turtles are now internationally protected.

Conservation

Threats

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.

Fishing gear is currently the biggest threat to loggerheads. They are most commonly caught in longlines and gillnets but have also been accidentally captured in traps, pots, trawls, and dredges.[3] Caught in this gear, loggerheads risk serious injury or drowning. Turtle excluder devices for nets and other gear help protect them. Due to the fishing traps, the loggerheads are now on the endangered list.

Because hatchlings usually follow the brightest light to the ocean's edge, artificial lights can lead them astray.

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, causing harm. [13]

Fibropapillomatosis disease has been a problem for loggerheads. It causes internal and external tumors that disrupt essential behaviors and, if on the eyes, permanent blindness.[13]

Human activities are often threatening to many marine animals. Loggerhead turtles are no exception. The creation of docks and marinas can destroy near shore habitats and risk harming the loggerheads even more through gasoline and oil discharge at the marina fueling stations. Boat traffic and dredging can degrade the loggerheads' habitats and can also potentially injure or kill loggerheads by hitting them. [13]

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 (TED).

Since the loggerhead occupies such a broad range, successful conservation requires efforts from multiple countries.[3]

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, making international trade of the loggerhead sea turtle illegal.[3] In the United States, the U.S. Fish and Wildlife Service and National Marine Fisheries Service classify them as a threatened species under the Endangered Species Act.[14] Loggerheads are listed as Endangered under both Australia's Environment Protection and Biodiversity Conservation Act 1999 and Queensland's Nature Conservation Act 1992. Annex 2 of the Specially Protected Areas and Wildlife (SPAW) Protocol of the Cartagena Convention also protects the loggerheads. The National Marine Fisheries Service and the U.S. Fish and Wildlife services hold joint jurisdiction over the loggerhead sea turtles in the United States[3]

In many places during the nesting season, workers search the coastline for nests. They uncover the nest and count its eggs. If necessary they relocate it to protect it from humans and other threats. Plastic fencing can protect eggs from large predators such as raccoons or even dogs. The fence's gauge must be large enough to allow the hatchlings to pass through without difficulty. The nests are checked daily for disturbances. Several days after eggs hatch, the workers examine the nest, tallying hatched eggs, undeveloped eggs, and dead hatchlings. Any remaining live hatchlings are either raised and released or taken to research facilities. Typically, those that lacked the strength to hatch and climb to the surface would have died by this point[5] those which appear strong and healthy may be immediately released to the ocean.

Hatchlings use the journey from nest to ocean to build strength for the coming swim. Therefore, helping them to reach the ocean lowers their chances of survival.[5] The Fripp Island, South Carolina Turtle Patrol each year arranges driftwood to guide the hatchlings towards the closest shoreline.

Footnotes

  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. {{cite book}}: line feed character in |publisher= at position 47 (help); line feed character in |title= at position 33 (help)
  2. ^ a b c d e "Loggerhead Sea Turtle (Caretta caretta)". Virginia: Virginia Herpetological Society. Retrieved 2/15/10. {{cite web}}: Check date values in: |accessdate= (help)
  3. ^ a b c d e f g h i j k l m n o p q r s t Bolten, A.B. (2003). "Loggerhead Turtle (Caretta caretta)". NOAA Fisheries. NOAA Fisheries. Retrieved January 31, 2010.
  4. ^ a b c MarineBio (March). "Caretta caretta Loggerhead Sea Turtle". Retrieved March 2, 2010. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help)
  5. ^ a b c d e f g h i j 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)
  6. ^ a b Basu, Rebecca (1 March 2010). "Winter is culprit in manatee death toll". Melbourne, Florida: Florida Today. pp. 3A.
  7. ^ a b c d e f g h i j k l m n o 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. {{cite book}}: Check date values in: |year= (help); line feed character in |contribution= at position 5 (help); line feed character in |title= at position 43 (help)CS1 maint: year (link)
  8. ^ a b Lever, Anna-Marie (6/30/08). "Turtles return home after UK stay". BBC News. {{cite news}}: Check date values in: |date= (help)
  9. ^ a b 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. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  10. ^ a b c Aguirre, A.; Gardner, S. (July 12). "Hazards Associated with the Consumption of Sea Turtle Meat and Eggs: A Review for Health Care Workers and the General Public". Retrieved March 2, 2010. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help)
  11. ^ a b c Dellios, Hugh (September 18). "Mexico Cracks Open Myth of Sea Turtle Eggs". Retrieved March 2, 2010. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help)
  12. ^ a b Craven, Kathryn; Taylor, Judy (September 11). "Identification of Bacterial Isolates from Unhatched Loggerhead (Caretta caretta) Sea Turtle Eggs in Georgia, USA". Retrieved March 16, 2010. {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help)
  13. ^ a b c d 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)
  14. ^ [1]
  15. ^ My Scribe (May 8, 2009). "Loggerhead Facts". Loggerhead preservation. KiawahTurtles. Retrieved February 4, 2010. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)

References

  • Bolten, Alan B.; Witherington, Blair E., eds. (2003). Loggerhead Sea Turtles. Washington, D.C.: Smithsonian Books.
  • Lutz, Peter L.; Musick, John A.; Wyneken, Jeanette (1997). The Biology of Sea Turtles. Vol. 1. Boca Raton, Florida: CRC Press.
  • Lutz, Peter L.; Musick, John A.; Wyneken, Jeanette (2003). The Biology of Sea Turtles. Vol. 2. Boca Raton, Florida: CRC Press.
  • Gulko, D.; Eckert, K.L. (2004). Sea Turtles: An Ecological Guide. Honolulu, Hawai’i: Mutual Publishing.
Wikispecies has information related to Caretta caretta.
Wikimedia Commons has media related to Loggerhead Sea Turtle.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Loggerhead_sea_turtle&oldid=352653329"