Sea turtle

{{Short description|Reptiles of the superfamily Chelonioidea}} {{pp-semi-vandalism|small=yes}} {{Automatic taxobox | name = Sea turtles | fossil_range = Early Cretaceous – Holocene,<ref name=hirTong2003>{{cite journal |author1=Hirayama R |author2=Tong H |year=2003 |doi=10.1111/1475-4983.00322 |title=''Osteopygis'' (Testudines: Cheloniidae) from the Lower Tertiary of the Ouled Abdoun phosphate basin, Morocco |journal=Palaeontology |volume=46 |issue=5 |pages=845–56|doi-access=free |bibcode=2003Palgy..46..845H }}</ref> {{fossilrange|110|0}} | image = Chelonia mydas is going for the air edit.jpg | image_caption = A green sea turtle, a species of the sea turtle superfamily | display_parents = 2 | taxon = Chelonioidea | authority = Bauer, 1893<ref name="Rhodin11" /> | subdivision_ranks = Families | subdivision = * Dermochelyidae * Cheloniidae * †Ctenochelyidae | synonyms = Chelonii - Oppel, 1811 Chlonopteria - Rafinesque, 1814 Cheloniae - Schmid, 1819 Edigitata - Haworth, 1825 Oiacopodae - Wagler, 1828 Pterodactyli - Mayer, 1849 | synonyms_ref = <ref name="Rhodin11">{{cite journal |url=http://www.iucn-tftsg.org/wp-content/uploads/file/Accounts/crm_5_000_checklist_v4_2011.pdf |title=Turtles of the world, 2011 update: Annotated checklist of taxonomy, synonymy, distribution and conservation status |journal=Chelonian Research Monographs |volume=5 |date=2011-12-31 |author1=Rhodin, Anders G.J. |author2=van Dijk, Peter Paul |author3=Inverson, John B. |author4=Shaffer, H. Bradley |author5=Roger, Bour |archive-url=https://web.archive.org/web/20120131102839/http://www.iucn-tftsg.org/wp-content/uploads/file/Accounts/crm_5_000_checklist_v4_2011.pdf |archive-date=2012-01-31 }}</ref> }}

'''Sea turtles''' (superfamily '''Chelonioidea'''), sometimes called '''marine turtles''',<ref>{{cite book|title=Conservation Genetics |url={{google books |plainurl=y |id=XHKpPwAACAAJ}}|last1=Avise |first1=J. C. |last2=Hamrick |first2=J. L. |publisher=Springer |year=1996 |isbn=978-0-412-05581-2}}</ref> are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, Kemp's ridley, and olive ridley.<ref name=":12">{{cite web|title = Sea Turtles :: NOAA Fisheries|url = http://www.nmfs.noaa.gov/pr/species/turtles/|website = www.nmfs.noaa.gov|access-date = 2015-12-20|language = en-us|first = NOAA|last = Fisheries}}</ref><ref name="auto">{{cite web|url=https://www.seaturtlestatus.org/meet-the-turtles|title=Sea Turtle Species|website=The State of the World's Sea Turtles|access-date=30 October 2023}}</ref> Five of the seven species are listed as threatened with extinction globally on the IUCN Red List of Threatened Species. The remaining two are not considered to be threatened with extinction, one of which, the flatback turtle, is found only in the waters of Australia, Papua New Guinea, and Indonesia.<ref name="flatback-article">{{cite web|url=https://www.seaturtlestatus.org/articles/2009/1/27/the-flatback-australias-own-sea-turtle|title=The Flatback: Australia's Own Sea Turtle|website=The State of the World's Sea Turtles|access-date=30 October 2023|date=2023-10-30}}</ref><ref name=":23">{{cite book |url=https://nap.nationalacademies.org/catalog/12889 |title=Assessment of Sea-Turtle Status and Trends: Integrating Demography and Abundance |date=2010 |publisher=National Academies Press |isbn=978-0-309-15255-6 |doi=10.17226/12889}}{{pn|date=November 2022}}</ref>

Sea turtles can be categorized as hard-shelled (cheloniid) or leathery-shelled (dermochelyid).<ref name=":24">Wyneken, J. 2001. The Anatomy of Sea Turtles. U.S Department of Commerce NOAA Technical Memorandum NMFS-SEFSC-470, 1-172 pp.</ref> The only dermochelyid species of sea turtle is the leatherback.<ref name=":24" />

[[File:Chelonioidea - aquarium - kanagawa - 2025 3 21.webm|thumb|A sea turtle swimming in an aquarium in Japan, 2025]] == Description ==

For each of the seven species of sea turtles, females and males are the same size. As adults, it is possible to tell male turtles from female turtles by their long tails with a cloacal opening near the tip. Adult female sea turtles have shorter tails, with a cloacal opening near the base. Hatchling and sub-adult turtles do not exhibit sexual dimorphism; it is not possible to determine their sex by looking at them.<ref name="SWOT">{{cite web|url=https://www.seaturtlestatus.org/articles/2020/2/27/how-to-tell-if-a-turtle-is-male-or-female|title=How to Tell if a Sea Turtle is Male or Female|website=The State of the World's Sea Turtles|access-date=30 October 2023|date=2023-10-23}}</ref>

In general, sea turtles have a more fusiform body plan than their terrestrial or freshwater counterparts. This tapering at both ends reduces volume and means that sea turtles cannot retract their head and limbs into their shells for protection, unlike many other turtles and tortoises.<ref name="defenders">{{cite web|url=http://www.defenders.org/sea-turtles/basic-facts|title=Sea Turtles|website=Defenders of Wildlife|access-date=15 October 2015|date=2012-03-20}}</ref> However, the streamlined body plan reduces friction and drag in the water and allows sea turtles to swim more easily and swiftly.

The leatherback sea turtle is the largest sea turtle, reaching 1.4 to more than 1.8 m (4.6 to 5.9 ft) in length and weighing between 300 and 640 kg (661 to 1,411 lbs).<ref name="Leatherback Turtle">{{cite web|url=https://www.seaturtlestatus.org/leatherback-turtle|title=Leatherback Turtle|website=The State of the World's Sea Turtles|access-date=30 October 2023|date=2023-10-30}}</ref> Other sea turtle species are smaller, ranging from as little as 60 cm (2 ft) long in the case of the Kemp's ridley, which is the smallest sea turtle species, to 120 cm (3.9 ft) long in the case of the green turtle, the second largest.<ref name="auto"/><ref>{{cite web|url=http://www.turtlehospital.org/sea-turtle-species/|title=Sea Turtle Species|website=turtlehospital|access-date=29 August 2015}}</ref>

The skulls of sea turtles have cheek regions that are enclosed in bone.<ref name="Jonesetal2012">{{Cite journal|last1=Jones|first1=MEH|last2=Werneburg|first2=I|last3=Curtis|first3=N|last4=Penrose|first4=RN|last5=O'Higgins|first5=P|last6=Fagan|first6=M|last7=Evans|first7=SE|date=2012 |title=The head and neck anatomy of sea turtles (Cryptodira: Chelonioidea) and skull shape in Testudines|journal=PLOS ONE|volume=7|issue=11|article-number=e47852|doi=10.1371/journal.pone.0047852|pmid=23144831|pmc=3492385|bibcode=2012PLoSO...747852J|doi-access=free}}</ref><ref name="Chatterjietal2020">{{Cite journal|last1=Chatterji|first1=RM|last2=Hutchinson|first2=MN|last3=Jones|first3=MEH|date=2020 |title=Redescription of the skull of the Australian flatback sea turtle, ''Natator depressus'', provides new morphological evidence for phylogenetic relationships among sea turtles(Chelonioidea) |journal=Zoological Journal of the Linnean Society|volume=191|issue=4|pages=1090–1113|doi=10.1093/zoolinnean/zlaa071}}</ref> Although this condition appears to resemble that found in the earliest known fossil reptiles (anapsids), it is possible it is a more recently evolved trait in sea turtles, placing them outside the anapsids.<ref name="Zardoyaetal1998">{{Cite journal|last1=Zardoya|first1=R|last2=Meyer|first2=A|date=1998 |title=Complete mitochondrial genome suggests diapsid affinities of turtles |journal=Proceedings of the National Academy of Sciences |volume=95|issue=24|pages=14226–14231|doi=10.1073/pnas.95.24.14226|pmid=9826682|pmc=24355|bibcode=1998PNAS...9514226Z|doi-access=free}}</ref><ref name="Jonesetal2012"/>

==Taxonomy and evolution== Sea turtles, along with other turtles and tortoises, are part of the order Testudines. All species except the leatherback sea turtle are in the family Cheloniidae. The superfamily name Chelonioidea and family name Cheloniidae are based on the Ancient Greek word for tortoise: {{lang|grc|χελώνη}} (''{{transliteration|grc|khelōnē}}'').<ref>{{LSJ|xelw/nh|χελώνη|ref}}</ref> The leatherback sea turtle is the only extant member of the family Dermochelyidae.

Fossil evidence of marine turtles goes back to the Late Jurassic (150 million years ago) with genera such as ''Plesiochelys'', from Europe. In Africa, the first marine turtle is ''Angolachelys'', from the Turonian of Angola.<ref>{{cite journal|last1=Mateus|title=The oldest African eucryptodiran turtle from the Cretaceous of Angola|journal=Acta Palaeontologica Polonica|date=2009|volume=54|issue=4|pages=581–588|display-authors=etal|doi=10.4202/app.2008.0063|s2cid=55919209|url=http://doc.rero.ch/record/203067/files/PAL_E3914.pdf|doi-access=free |bibcode=2009AcPaP..54..581M }}</ref> A lineage of unrelated marine testudines, the pleurodire (side-necked) bothremydids, also survived well into the Cenozoic. Other pleurodires are also thought to have lived at sea, such as ''Araripemys''<ref>Kischlat, E.-E & Campos, D. de 1990. Some osteological aspects of Araripemys barretoi Price, 1973 (Chelonii, Pleurodira, Araripemydidae). In Atas do I Simpósio sobre a Bacia do Araripe e Bacias Interiores do Nordeste Crato, 14 a 16 de junho de 1990, pp. 387–395.</ref> and extinct pelomedusids.<ref>{{Cite journal |last1=Ferreira |first1=Gabriel S. |last2=Rincón |first2=Ascanio D. |last3=Solórzano |first3=Andrés |last4=Langer |first4=Max C. |date=June 30, 2015 |title=The last marine pelomedusoids (Testudines: Pleurodira): a new species of Bairdemys and the paleoecology of Stereogenyina |journal=PeerJ |volume=3 |article-number=e1063 |doi=10.7717/peerj.1063 |pmc=4493680 |pmid=26157628 |doi-access=free |bibcode=2015PeerJ...3e1063F }}</ref> Modern sea turtles are not descended from more than one of the groups of sea-going turtles that have existed in the past; they instead constitute a single radiation that became distinct from all other turtles at least 110 million years ago.<ref>{{cite web |title=Meet the Turtles {{!}} SWOT |url=http://www.seaturtlestatus.org/learn/meet-the-turtles |access-date=2017-09-20 |website=www.seaturtlestatus.org}}</ref><ref>{{Cite journal |title=An Introduction to Sea Turtles |url=http://seaturtlestatus.org/sites/swot/files/061810_SWOT1_p04_IntroSeaTurtles.pdf |journal=SWOT}}</ref><ref>{{cite journal |last1=Kear |first1=Benjamin P |date=22 March 2006 |title=A primitive protostegid from Australia and early sea turtle evolution |journal=Biology Letters |volume=2 |issue=1 |pages=116–119 |doi=10.1098/rsbl.2005.0406 |pmc=1617175 |pmid=17148342}}</ref> Their closest extant relatives are in fact the snapping turtles (Chelydridae), musk turtles (Kinosternidae), and hickatee (Dermatemyidae) of the Americas, which alongside the sea turtles constitute the clade Americhelydia.<ref>{{Cite journal |last1=Gable |first1=Simone M. |last2=Byars |first2=Michael I. |last3=Literman |first3=Robert |last4=Tollis |first4=Marc |title=A Genomic Perspective on the Evolutionary Diversification of Turtles |journal=Systematic Biology |date=2022 |volume=71 |issue=6 |pages=1331–1347 |doi=10.1093/sysbio/syac019 |pmid=35253878 |biorxiv=10.1101/2021.10.14.464421 }}</ref>

The oldest possible representative of the lineage (Panchelonioidea) leading to modern sea turtles was possibly ''Desmatochelys padillai'' from the Early Cretaceous. ''Desmatochelys'' was a protostegid, a lineage that would later give rise to some very large species but went extinct at the end of the Cretaceous. Presently thought to be outside the crown group that contains modern sea turtles (Chelonioidea), the exact relationships of protostegids to modern sea turtles are still debated due to their primitive morphology; they may be the sister group to the Chelonoidea, or an unrelated turtle lineage that convergently evolved similar adaptations.<ref>{{Cite thesis |title=The Evolution of Sea Turtles |url=https://digital.library.adelaide.edu.au/dspace/handle/2440/134280 |date=2021 |degree=Thesis |language=en |first=Ray |last=Chatterji}}</ref><ref>{{Cite journal |last=Goulart |first=Isabella Vasconcellos |date=2021-01-13 |title=Evaluation of Panchelonioidea (Testudines: Cryptodira) evolution based on phylogenetic morphometrics |url=https://locus.ufv.br//handle/123456789/27977 |journal=Locus}}</ref> The earliest "true" sea turtle that is known from fossils is ''Nichollsemys'' from the Early Cretaceous (Albian) of Canada. In 2022, the giant fossil species ''Leviathanochelys'' was described from Spain. This species inhabited the oceans covering Europe in the Late Cretaceous and rivaled the concurrent giant protostegids such as ''Archelon'' and ''Protostega'' as one of the largest turtles to ever exist. Unlike the protostegids, which have an uncertain relationship to modern sea turtles, ''Leviathanochelys'' is thought to be a true sea turtle of the superfamily Chelonioidea.<ref name=":19">{{Cite journal |last1=Castillo-Visa |first1=Oscar |last2=Luján |first2=Àngel H. |last3=Galobart |first3=Àngel |last4=Sellés |first4=Albert |date=November 2022 |title=A gigantic bizarre marine turtle (Testudines: Chelonioidea) from the Middle Campanian (Late Cretaceous) of South-western Europe |journal=Scientific Reports |language=en |volume=12 |issue=1 |page=18322 |doi=10.1038/s41598-022-22619-w |pmid=36396968 |pmc=9671902 |bibcode=2022NatSR..1218322C |s2cid=253584457 |issn=2045-2322}}</ref>

Sea turtles' limbs and brains have evolved to adapt to their diets. Their limbs originally evolved for locomotion, but more recently evolved to aid them in feeding. They use their limbs to hold, swipe, and forage their food. This helps them eat more efficiently.<ref>{{cite web|url=https://www.newswise.com/articles/sea-turtles-use-flippers-to-manipulate-food |title=Sea Turtles Use Flippers to Manipulate Food |publisher=Newswise.com |access-date=2018-09-16}}</ref><ref>{{cite web | url=https://www.sciencedaily.com/releases/2018/03/180328083421.htm | title=Sea turtles use flippers to manipulate food}}</ref>

=== Phylogeny ===

The phylogenetic relationships of living and extinct sea turtles in the Chelonioidea are based on Evers et al. (2019):<ref>{{Cite journal|last1=Evers|first1=Serjoscha W.|last2=Barrett|first2=Paul M.|last3=Benson|first3=Roger B. J.|date=May 2019 |title=Anatomy of ''Rhinochelys pulchriceps'' (Protostegidae) and marine adaptation during the early evolution of chelonioids |journal=PeerJ |volume=7 |article-number=e6811 |doi=10.7717/peerj.6811 |issn=2167-8359 |pmc=6500378 |pmid=31106054 |doi-access=free |bibcode=2019PeerJ...7e6811E }}</ref>

{| style="margin:auto;" |- | {{cladogram|title=Phylogenetic relations of living and extinct chelonioid species |align=left |clades={{Clade|style=font-size:85%;line-height:85%;width:500px |label1=Panchelonioidea |1={{Clade |1=†''Toxochelys'' |2={{Clade |1=†Protostegidae 70 px |label2=Chelonioidea |2={{Clade |1=†''Corsochelys'' |2=Dermochelyidae 70 px |label3=Pancheloniidae |3={{Clade |1=†''Nichollsemys'' |2={{Clade |1=†''Allopleuron'' |2={{Clade |1=Cheloniidae 70 px |2={{Clade |1=†''Argillochelys'' |2=†''Procolpochelys'' |3={{Clade |1=†''Eochelone'' |2=†''Puppigerus'' }} |4={{Clade |1=†''Ctenochelys'' |2=†''Peritresius'' |3=†''Cabindachelys'' }} }} }} }} }} }} }} }} }} }} |}

An alternate phylogeny was proposed by Castillo-Visa et al. (2022):<ref name=":19" />

{{clade|{{clade |1=†Toxochelyidae |2={{clade |1=†Protostegidae |2=†''Corsochelys'' |label3='''Chelonioidea''' |3= {{clade |label1=Dermochelyidae |1={{clade |1=†''Eosphargis'' |2=''Dermochelys'' }} |2={{clade |1=†''Nichollsemys'' |2={{clade |1={{clade |1=†''Leviathanochelys'' |2=†''Allopleuron'' }} |2={{clade |1=†''Procolpochelys'' |2={{clade |1=†''Argillochelys'' |2={{clade |1=†''Eochelone'' |2=†''Puppigerus'' }} |label3=Ctenochelyidae |3={{clade |1=†''Cabindachelys'' |2=†''Ctenochelys'' |3=†''Peritresius'' }} |label4=Cheloniidae |4={{clade |1=''Natator'' |2=''Eretmochelys'' |3=''Chelonia'' |4={{clade |1=''Lepidochelys kempii'' |2={{clade |1=''Caretta'' |2=''Lepidochelys olivacea'' }}}}}}}}}}}}}}}}}}}}|style=font-size:85%;line-height:85%|label1=Panchelonioidea}}

== Distribution and habitat == Sea turtles can be found in all oceans except for the polar regions. The flatback sea turtle is found solely on the northern coast of Australia. The Kemp's ridley sea turtle is found solely in the Gulf of Mexico and along the East Coast of the United States.<ref>{{Cite web|url=http://awsassets.panda.org/downloads/marine_turtles_factsheet2006.pdf|title=Ancient mariners threatened with extinction}}</ref>

Sea turtles are generally found in the waters over continental shelves. During the first three to five years of life, sea turtles spend most of their time in the pelagic zone floating in seaweed mats. Green sea turtles in particular are often found in ''Sargassum'' mats, in which they find food, shelter and water.<ref name="PelagicDev" /> Once the sea turtle has reached adulthood it moves closer to the shore.<ref name="LS20070918" /> Females will come ashore to lay their eggs on sandy beaches during the nesting season.<ref name="WWFSeaturtles">{{cite web |title = WWF – Marine Turtles|work = Species Factsheets|publisher = World Wide Fund for Nature|date = 4 May 2007|url = http://www.panda.org/about_wwf/what_we_do/species/about_species/species_factsheets/marine_turtles/index.cfm|access-date = 13 September 2007}}</ref>

Sea turtles migrate to reach their spawning beaches, which are limited in numbers. Living in the ocean therefore means they usually migrate over large distances. All sea turtles have large body sizes, which is helpful for moving large distances. Large body sizes also offer good protection against the large predators (notably sharks) found in the ocean.<ref>{{cite journal | last1 = Jaffe | first1 = A. L. | last2 = Slater | first2 = G. J. | last3 = Alfaro | first3 = M. E. | year = 2011 | title = The evolution of island gigantism and body size variation in tortoises and turtles | journal =Biology Letters | volume = 7 | issue = 4| pages = 558–561 | doi=10.1098/rsbl.2010.1084 | pmid=21270022 | pmc=3130210 | bibcode = 2011BiLet...7..558J }}</ref>

In 2020, diminished human activity resulting from the COVID-19 virus caused an increase in sea turtle nesting. Some areas in Thailand saw an abnormally high number of nests, and Florida experienced a similar phenomenon. Less plastic and light pollution could explain these observations.<ref>{{Cite web|url=https://www.cnn.com/travel/article/thailand-sea-turtles-coronavirus-scli-intl-scn/index.html|title=Sea turtles thriving in Thailand after beach closures|author1=By Jack Guy |author2=Carly Walsh|website=CNN|date=20 April 2020 |language=en|access-date=2020-04-20}}</ref>

==Life cycle== thumb|300px|1) Male and female sea turtles age in the ocean and migrate to shallow coastal water. 2) Sea turtles mate in the water near offshore nesting sites. 3) The adult male sea turtles return to the feeding sites in the water. 4) Female sea turtles cycle between mating and nesting. 5) Female sea turtles lay their eggs. 6) When the season is over, female sea turtles return to feeding sites. 7) Baby sea turtles incubate for 60–80 days and hatch. 8) Newly hatched baby sea turtles emerge from nests and travel from the shore to the water. 9) Baby sea turtles mature in the ocean until they are ready to begin the cycle again. Sea turtles are thought to reach sexual maturity from about 10−20 years old depending on species and methodology. However, reliable estimates are difficult to ascertain.<ref>{{cite journal |last1=Bedolla-Ochoa |first1=C. |last2=Reyes-López |first2=M. A. |last3=Rodríguez-González |first3=H. |last4=Delgado-Trejo |first4=C. |title=Black Sea Turtle (Chelonia mydas agassizii) Life History in the Sanctuary of Colola Beach, Michoacan, Mexico |journal=Animals |date=2023 |volume=13 |issue=3 |page=406 |doi=10.3390/ani13030406|pmid=36766296 |pmc=9913439 |doi-access=free }}</ref><ref>{{cite journal |last1=Caillouet |first1=C. W. |last2=Shaver |first2=D. J. |last3=Landry |first3=A. M. |last4=Owens |first4=D. W. |last5=Pritchard |first5=P. C. H. |title=Kemp's Ridley Sea Turtle (Lepidochelys kempii) Age at First Nesting |journal=Chelonian Conservation and Biology |date=2011 |volume=10 |issue=2 |pages=288–293 |doi=10.2744/CCB-0836.1|s2cid=86092201 |doi-access=free |bibcode=2011CConB..10..288C }}</ref><ref>{{cite journal |last1=Levasseur |first1=K. E. |last2=Stapleton |first2=S. P. |last3=Quattro |first3=J. M. |title=Precise natal homing and an estimate of age at sexual maturity in hawksbill turtles |journal=Animal Conservation |date=2021 |volume=24 |issue=3 |pages=523–535 |doi=10.1111/acv.12657|bibcode=2021AnCon..24..523L |s2cid=228861161 }}</ref><ref>{{cite journal |last1=Jones |first1=T. T. |last2=Hastings |first2=M. D. |last3=Bostrom |first3=B. L. |last4=Pauly |first4=D. |last5=Jones |first5=D. R. |title=Growth of captive leatherback turtles, Dermochelys coriacea, with inferences on growth in the wild: Implications for population decline and recovery |journal=Journal of Experimental Marine Biology and Ecology |date=2011 |volume=399 |issue=1 |pages=84–92 |doi=10.1016/j.jembe.2011.01.007|bibcode=2011JEMBE.399...84J }}</ref> Mature sea turtles may migrate thousands of miles to reach breeding sites. After mating at sea, adult female sea turtles return to land to lay their eggs. Different species of sea turtles exhibit various levels of philopatry. In the extreme case, females return to the same beach where they hatched. This can take place every two to four years in maturity.

[[File:Turtle golfina escobilla Oaxaca Mexico Claudio Giovenzana 2010.jpg|thumbnail|left|An olive ridley sea turtle nesting on Escobilla Beach, Oaxaca, Mexico]]The mature nesting female hauls herself onto the beach, nearly always at night, and finds suitable sand in which to create a nest. Using her hind flippers, she digs a circular hole {{convert|40|to|50|cm|in}} deep. After the hole is dug, the female then starts filling the nest with her clutch of soft-shelled eggs. Depending on the species, a typical clutch may contain 50–350 eggs. After laying, she re-fills the nest with sand, re-sculpting and smoothing the surface, and then camouflaging the nest with vegetation until it is relatively undetectable visually.<ref name="PelagicDev" /> She may also dig decoy nests.<ref>{{cite news |last1=Waldstein |first1=David |title=Mother Sea Turtles Might Be Sneakier Than They Look |url=https://www.nytimes.com/2020/05/19/science/sea-turtles-decoy-nests.html |access-date=19 May 2020 |work=The New York Times |date=19 May 2020}}</ref> The whole process takes 30 to 60 minutes. She then returns to the ocean, leaving the eggs untended.<ref name="Audubon1897">{{cite book | last =Audubon | first =Maria R. | author-link =Maria Audubon | title =Audubon and His Journals: Dover Publications Reprint | publisher =Scribner's Sons | orig-date=First published 1897 |year=1986 | location =New York | pages = 373–375| isbn = 978-0-486-25144-8}}</ref>

Females may lay 1–8 clutches in a single season. Female sea turtles alternate between mating in the water and laying their eggs on land. Most sea turtle species nest individually. But ridley sea turtles come ashore en masse, known as an ''arribada'' (arrival). With the Kemp's ridley sea turtle this occurs during the day.

Sea turtles have temperature-dependent sex determination.<ref name=":3">{{cite journal|last=Mrosovsky|first=N.|title=Sex ratio bias in hatchling sea turtles from artificially incubated eggs|journal=Biological Conservation|date=August 1982|volume=23|issue=4|pages=309–314|doi=10.1016/0006-3207(82)90087-8|bibcode=1982BCons..23..309M }}</ref><ref name=":4">{{cite journal|last=Morreale|first=S.|author2=Ruiz, G. |author3=Spotila, J. |author4= Standora, E. |title=Temperature-dependent sex determination: current practices threaten conservation of sea turtles|journal=Science|date=11 June 1982|volume=216|issue=4551|pages=1245–1247|doi=10.1126/science.7079758 |pmid=7079758|bibcode=1982Sci...216.1245M}}</ref><ref name=":5">{{cite journal|last=Mrosovsky|first=N.|author2=Hopkins-Murphy, S. R. |author3=Richardson, J. I. |title=Sex Ratio of Sea Turtles: Seasonal Changes|journal=Science|date=17 August 1984|volume=225|issue=4663|pages=739–741|doi=10.1126/science.225.4663.739|pmid=17810293|bibcode=1984Sci...225..739M|s2cid=43726465}}</ref><ref name=":6">{{cite journal|last=Godfrey|first=Matthew H.|author2=Barreto, R. |author3=Mrosovsky, N. |title=Metabolically-Generated Heat of Developing Eggs and Its Potential Effect on Sex Ratio of Sea Turtle Hatchlings|journal=Journal of Herpetology|date=December 1997|volume=31|issue=4|pages=616–619|doi=10.2307/1565626|jstor=1565626 |bibcode=1997JHerp..31..616G }}</ref><ref name=":7">{{cite journal|last=Ewert|first=Michael A.|author2=Jackson, Dale R. |author3=Nelson, Craig E. |title=Patterns of temperature-dependent sex determination in turtles|journal=Journal of Experimental Zoology|date=15 September 1994|volume=270|issue=1|pages=3–15|doi=10.1002/jez.1402700103|bibcode=1994JEZ...270....3E }}</ref> Warmer temperatures produce female hatchlings, while cooler temperatures produce male hatchlings.<ref name=":3" /><ref name=":4" /><ref name=":5" /><ref name=":6" /><ref name=":7" /><ref>{{Cite journal|title = Temperature dependent sex determination in sea turtles|last1 = Standora |first1=Edward |last2=Spotila |first2=James|date = Aug 5, 1985|journal = Copeia|doi = 10.2307/1444765|jstor=1444765|volume=1985|issue = 3 |pages=711–722}}</ref> The eggs will incubate for 50–60 days. The eggs in one nest hatch together over a short period of time. The baby sea turtles break free of the egg shell, dig through the sand, and crawl into the sea. Most species of sea turtles hatch at night. However, the Kemp's ridley sea turtle commonly hatches during the day. Sea turtle nests that hatch during the day are more vulnerable to predators, and may encounter more human activity on the beach.

thumb|Sea turtle sex depends on sand temperature while the egg is incubating. Larger hatchlings have a higher probability of survival than smaller individuals, which can be explained by the fact that larger offspring are faster and thus less exposed to predation. Predators can only functionally intake so much; larger individuals are not targeted as often. A study conducted on this topic shows that body size is positively correlated with speed, so larger baby sea turtles are exposed to predators for a shorter amount of time.<ref>{{cite journal|last1=Janzen|first1=Fredric J.|last2=Tucker|first2=John K.|last3=Paukstis|first3=Gary L. |year=2007 |title=Experimental analysis of an early life-history stage: direct or indirect selection on body size of hatchling turtles? |journal=Functional Ecology |volume=21 |issue=1 |pages=162–170 |doi=10.1111/j.1365-2435.2006.01220.x |bibcode=2007FuEco..21..162J |url=http://www.public.iastate.edu/~fjanzen/pdf/00Ecology.pdf}}</ref> The fact that there is size dependent predation on chelonians has led to the evolutionary development of large body sizes.

In 1987, Carr discovered that the young of green and loggerhead sea turtles spent a great deal of their pelagic lives in floating sargassum mats. Within these mats, they found ample shelter and food. In the absence of sargassum, young sea turtles feed in the vicinity of upwelling "fronts".<ref name="PelagicDev">{{cite journal | last =Carr | first =Archie | author-link =Archie Carr | title =New Perspectives on the Pelagic Stage of Sea Turtle Development | journal =Conservation Biology | volume =1 | issue =2 | pages =103–121 | doi = 10.1111/j.1523-1739.1987.tb00020.x|date=August 1987 | jstor=2385827| bibcode =1987ConBi...1..103C | hdl =2027/uc1.31822031475700 | url =https://babel.hathitrust.org/cgi/imgsrv/download/pdf?id=uc1.31822031475700;orient=0;size=100;seq=1;attachment=0 | hdl-access =free | url-access =subscription }}</ref> In 2007, Reich determined that green sea turtle hatchlings spend the first three to five years of their lives in pelagic waters. In the open ocean, pre-juveniles of this particular species were found to feed on zooplankton and smaller nekton before they are recruited into inshore seagrass meadows as obligate herbivores.<ref name="LS20070918">{{cite news | last =Brynner | first =Jeanna | title =Sea Turtles' Mystery Hideout Revealed | work =LiveScience | publisher =Imaginova Corp. | date =19 September 2007 | url =http://www.livescience.com/animals/070919_sea_turtle.html | access-date =20 September 2007}}</ref><ref name="Reich2007">{{cite journal | last =Reich | first =Kimberly J. | author-link =Kimberly Reich |author2=Karen A. Bjorndal |author3= Alan B. Bolten | title =The 'lost years' of green turtles: using stable isotopes to study cryptic lifestages | journal =Biology Letters |volume= 3|issue=6 |pages=712–714 | date =18 September 2007 | doi =10.1098/rsbl.2007.0394 | pmid =17878144 | pmc =2391226}}</ref>

== Physiology ==

===Osmoregulation===

Sea turtles maintain an internal environment that is hypotonic to the ocean. To maintain hypotonicity they must excrete excess salt ions.<ref>{{cite journal |author1=Nicolson, S.W. |author2=P.L. Lutz |year=1989 |url=http://jeb.biologists.org/content/144/1/171.full.pdf |title=Salt gland function in the green sea turtle ''Chelonia mydas'' |journal=Journal of Experimental Biology |volume=144 |issue=1 |pages=171–184|doi=10.1242/jeb.144.1.171 |doi-access=free |bibcode=1989JExpB.144..171N }}</ref> Like other marine reptiles, sea turtles rely on a specialized gland to rid the body of excess salt, because reptilian kidneys cannot produce urine with a higher ion concentration than sea water.<ref name="ncbi">{{cite journal |author1=Reina RD |author2=Jones TT |author3=Spotila JR |title=Salt and water regulation by the leatherback sea turtle ''Dermochelys coriacea'' |journal=Journal of Experimental Biology |volume=205 |issue=13 |pages=1853–60 |date=July 2002 |doi=10.1242/jeb.205.13.1853 |pmid=12077161 |bibcode=2002JExpB.205.1853R |url=http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=12077161|url-access=subscription }}</ref> All species of sea turtles have a lachrymal gland in the orbital cavity, capable of producing tears with a higher salt concentration than sea water.<ref>{{cite journal |author1=Schmidt-Nielsen K |author2=Fange R |year=1958 |title=Salt glands in marine reptiles |journal=Nature |volume=182 |issue=4638 |pages=783–5 |doi=10.1038/182783a0|bibcode=1958Natur.182..783S |s2cid=4290812 }}</ref>

Leatherback sea turtles face an increased osmotic challenge compared to other species of sea turtle, since their primary prey are jellyfish and other gelatinous plankton, whose fluids have the same concentration of salts as sea water. The much larger lachrymal gland found in leatherback sea turtles may have evolved to cope with the higher intake of salts from their prey. A constant output of concentrated salty tears may be required to balance the input of salts from regular feeding, even considering leatherback sea turtle tears can have a salt ion concentration almost twice that of other species of sea turtle.<ref>{{cite journal | last1 = Hudson | first1 = D.M. | last2 = Lutz | first2 = P.L. | year = 1986 | title = Salt gland function in the leatherback sea turtle, ''Dermochelys coriacea'' | journal = Copeia | volume = 1986 | issue = 1| pages = 247–249 | jstor=1444922 | doi=10.2307/1444922}}</ref> thumb|Immature Hawaiian green sea turtle in shallow waters [[File:Sea turtles bask in the Papahānaumokuākea Marine National Monument.png|thumb|Sea turtles basking in the Papahānaumokuākea Marine National Monument in the Northwestern Hawaiian Islands.]] Hatchlings depend on drinking sea water immediately upon entering the ocean to replenish water lost during the hatching process. Salt gland functioning begins quickly after hatching, so that the young sea turtles can establish ion and water balance soon after entering the ocean. Survival and physiological performance hinge on immediate and efficient hydration following emergence from the nest.<ref name="ncbi" />

=== Thermoregulation === All sea turtles are poikilotherms.<ref name=":30">{{cite journal|title = Feasibility of Using Sea Surface Temperature Imagery to Mitigate Cheloniid Sea Turtle – Fishery Interactions off the Coast of Northeastern USA|last1 = Braun-McNeill|first1 = Joanne|date = December 2008|journal = Endangered Species Research|doi = 10.3354/esr00145|last2 = Sasso|first2 = Christopher|last3 = Epperly|first3 = Sheryan|last4 = Rivero|first4 = Carlos|volume = 5|pages = 257–266|doi-access = free| bibcode=2008ESRes...5..257B |hdl = 1834/30782|hdl-access = free}}</ref> However, leatherback sea turtles (family Dermochelyidae) are able to maintain a body temperature {{Convert|8|C-change}} warmer than the ambient water by thermoregulation through the trait of gigantothermy.<ref name=":30" /><ref>{{Cite journal|last1=Paladino|first1=Frank V.|last2=O'Connor|first2=Michael P.|last3=Spotila|first3=James R.|date=1990-04-26|title=Metabolism of leatherback turtles, gigantothermy, and thermoregulation of dinosaurs|url=https://www.nature.com/articles/344858a0|journal=Nature|language=en|volume=344|issue=6269|pages=858–860|doi=10.1038/344858a0|bibcode=1990Natur.344..858P|s2cid=4321764|issn=1476-4687|url-access=subscription}}</ref>

Green sea turtles in the relatively cooler Pacific are known to haul themselves out of the water on remote islands to bask in the sun.<ref name=":2">{{Cite journal|url = http://www.nmfs.noaa.gov/pr/pdfs/species/turtlesymposium1997.pdf#page=82|title = Basking in Galapagos Green Turtles|last = Green|first = Derek|date = March 1997|journal = Proceedings of the 17th Annual Sea Turtle Symposium}}</ref> This behavior has only been observed in a few locations, including the Galapagos, Hawaii, Europa Island, and parts of Australia.<ref name=":2" /> thumb|A green sea turtle breaks the surface to breathe.|left

=== Diving physiology === {{see also|Physiology of underwater diving#Aquatic reptiles}} Sea turtles are air-breathing reptiles that have lungs, so they regularly surface to breathe. Sea turtles spend a majority of their time underwater, so they must be able to hold their breath for long periods.<ref name=":8" /> Dive duration largely depends on activity. A foraging sea turtle may typically spend 5–40 minutes underwater<ref name=":8">{{Cite journal|title = Voluntary diving metabolism and ventilation in the loggerhead sea turtle|journal = Journal of Experimental Marine Biology and Ecology|date = 1991-05-16|pages = 287–296|volume = 147|issue = 2|doi = 10.1016/0022-0981(91)90187-2|first1 = Molly E.|last1 = Lutcavage|first2 = Peter L.|last2 = Lutz|doi-access = free| bibcode=1991JEMBE.147..287L }}</ref> while a sleeping sea turtle can remain underwater for 4–7 hours.<ref>{{cite web|title = Information About Sea Turtles: Frequently Asked Questions |url = http://www.conserveturtles.org/seaturtleinformation.php?page=seaturtle-faq#14 |publisher = Sea Turtle Conservancy|access-date = 2015-10-15}}</ref><ref name=":9">{{Cite journal|title = First records of dive durations for a hibernating sea turtle|journal = Biology Letters|date = 2005-03-22|issn = 1744-9561|pmc = 1629053|pmid = 17148134|pages = 82–86|volume = 1|issue = 1|doi = 10.1098/rsbl.2004.0250|first1 = Sandra|last1 = Hochscheid|first2 = Flegra|last2 = Bentivegna|first3 = Graeme C.|last3 = Hays}}</ref> Remarkably, sea turtle respiration remains aerobic for the vast majority of voluntary dive time.<ref name=":8" /><ref name=":9" /> When a sea turtle is forcibly submerged (e.g. entangled in a trawl net) its diving endurance is substantially reduced, so it is more susceptible to drowning.<ref name=":8" />

When surfacing to breathe, a sea turtle can quickly refill its lungs with a single explosive exhalation and rapid inhalation. Their large lungs permit rapid exchange of oxygen and avoid trapping gases during deep dives.

Cold-stunning is a phenomenon that occurs when sea turtles enter cold ocean water ({{Convert|45|–|50|F|abbr=on|order=flip}}), which causes the turtles to float to the surface and therefore makes it impossible for them to swim.<ref>Spotila, J. R. (2004). ''Sea Turtles: A Complete Guide to Their Biology, Behavior, and Conservation''. Baltimore: Johns Hopkins University Press. {{isbn|978-0801880070}}</ref>

===Fluorescence===

Gruber and Sparks (2015)<ref name=Gruber_2015>{{Cite journal| last1 = Gruber| first1 = David F.| last2 = Sparks| first2 = John S.| title = First observation of fluorescence in marine turtles| journal = American Museum Novitates| issue = 3845| pages = 1–8| doi = 10.1206/3845.1| issn = 0003-0082| date = 2015-12-01| hdl = 2246/6626| s2cid = 86196418| url = http://digitallibrary.amnh.org/bitstream/2246/6626/1/N3845.pdf}}</ref> have observed the first fluorescence in a marine tetrapod (four-limbed vertebrates).<ref>{{cite web| last = Lewis| first = Danny| title = Scientists just found a sea turtle that glows| work = Smithsonian | date = 2015 | access-date = 2017-03-19| url = http://www.smithsonianmag.com/smart-news/scientists-discover-glowing-sea-turtle-180956789/}}</ref> Sea turtles are the first biofluorescent reptile found in the wild.

According to Gruber and Sparks (2015), fluorescence is observed in an increasing number of marine creatures (cnidarians, ctenophores, annelids, arthropods, and chordates) and is now also considered to be widespread in cartilaginous and ray-finned fishes.<ref name=Gruber_2015/>

The two marine biologists accidentally made the observation in the Solomon Islands on a hawksbill sea turtle, one of the rarest and most endangered sea turtle species in the ocean, during a night dive aimed to film the biofluorescence emitted by small sharks and coral reefs. The role of biofluorescence in marine organisms is often attributed to a strategy for attracting prey or perhaps a way to communicate. It could also serve as a way of defense or camouflage for the sea turtle hiding during night amongst other fluorescent organisms like corals. Fluorescent corals and sea creatures are best observed during night dives with a blue LED light and with a camera equipped with an orange optical filter to capture only the fluorescence light.<ref>{{cite web| last = Lee| first = Jane J.| title = Exclusive video: first "glowing" sea turtle found| work = National Geographic News| access-date = 2017-03-19| date = 2015-09-28| url = http://news.nationalgeographic.com/2015/09/150928-sea-turtles-hawksbill-glowing-biofluorescence-coral-reef-ocean-animals-science150928-sea-turtles-hawksbill-glowing-biofluorescence-coral-reef-ocean-animals-science/| archive-url = https://web.archive.org/web/20150930220119/http://news.nationalgeographic.com/2015/09/150928-sea-turtles-hawksbill-glowing-biofluorescence-coral-reef-ocean-animals-science150928-sea-turtles-hawksbill-glowing-biofluorescence-coral-reef-ocean-animals-science/| archive-date = September 30, 2015}}</ref><ref>{{Cite news| last = Hanson| first = Hilary| title = Scientists discover 'glowing' sea turtle| work = Huffington Post| date = 2015-09-29| access-date = 2017-03-19| url = http://www.huffingtonpost.com/entry/sea-turtle-glowing-discovery_us_560ac2a0e4b0dd8503094fd4}}</ref>

=== Sensory modalities ===

==== Navigation ====

Below the surface, the sensory cues available for navigation change dramatically.<ref name=":16">{{Cite journal|last1=Lohmann|first1=K. J.|last2=Lohmann|first2=C. M. F.|last3=Endres|first3=C. S.|date=2008-06-01|title=The sensory ecology of ocean navigation|journal=Journal of Experimental Biology |volume=211|issue=11 |pages=1719–1728|doi=10.1242/jeb.015792 |pmid=18490387|issn=0022-0949|doi-access=free|bibcode=2008JExpB.211.1719L }}</ref> Light availability decreases quickly with depth, and is refracted by the movement of water when present, celestial cues are often obscured, and ocean currents cause continuous drift.<ref name=":16" /> Most sea turtle species migrate over significant distances to nesting or foraging grounds, some even crossing entire ocean basins.<ref name=":17">{{cite journal|last1=Lohmann|first1=Kenneth J. |last2=Putman|first2=Nathan F. |last3=Lohmann|first3=Catherine M. F.|date=2012|title=The magnetic map of hatchling loggerhead sea turtles|url=https://linkinghub.elsevier.com/retrieve/pii/S0959438811001954|journal=Current Opinion in Neurobiology |volume=22|issue=2|pages=336–342 |doi=10.1016/j.conb.2011.11.005 |pmid=22137566|s2cid=1128978|url-access=subscription}}</ref> Passive drifting within major current systems, such as those in the North Atlantic Gyre, can result in ejection well outside of the temperature tolerance range of a given species, causing heat stress, hypothermia, or death.<ref name=":17" /> In order to reliably navigate within strong gyre currents in the open ocean, migrating sea turtles possess both a bicoordinate magnetic map and magnetic compass sense, using a form of navigation termed Magnetoreception.<ref name=":17" /><ref name=":16" /><ref name=":18">{{cite journal |last1=Lohmann |first1=Kenneth J. |last2=Lohman |first2=Catherine M. F. |date=2019-02-06|title=There and back again: natal homing by magnetic navigation in sea turtles and salmon |journal=The Journal of Experimental Biology |volume=222|issue=Supplement 1 |pages=jeb184077 |doi=10.1242/jeb.184077 |pmid=30728225 |issn=0022-0949|doi-access=free|bibcode=2019JExpB.222B4077L }}</ref> Specific migratory routes have been shown to vary between individuals, making the possession of both a magnetic map and compass sense advantageous for sea turtles.<ref name=":17"/>

alt=Hatchling green sea turtle in the sand photographed by USFWS Southeast|thumb|Hatchling green sea turtle in the sand photographed by USFWS Southeast

A bicoordinate magnetic map gives sea turtles the ability to determine their position relative to a goal with both latitudinal and longitudinal information, and requires the detection and interpretation of more than one magnetic parameter going in opposite directions to generate, such as Magnetic field intensity and Inclination angle.<ref name=":18" /><ref name=":20">{{Cite journal|last1=Fuxjager|first1=M. J.|last2=Eastwood|first2=B. S.|last3=Lohmann|first3=K. J.|date=2011-08-01|title=Orientation of hatchling loggerhead sea turtles to regional magnetic fields along a transoceanic migratory pathway |journal=Journal of Experimental Biology |volume=214|issue=15|pages=2504–2508 |doi=10.1242/jeb.055921|pmid=21753042 |issn=0022-0949 |doi-access=free|bibcode=2011JExpB.214.2504F }}</ref> A magnetic compass sense allows sea turtles to determine and maintain a specific magnetic heading or orientation.<ref name=":20" /> These magnetic senses are thought to be inherited, as hatchling sea turtles swim in directions that would keep them on course when exposed to the magnetic field signatures of various locations along their species' migratory routes.<ref name=":20" /><ref>{{Cite journal |last=Lohmann|first=K. J. |date=2001-10-12 |title=Regional Magnetic Fields as Navigational Markers for Sea Turtles |url=https://www.science.org/doi/10.1126/science.1064557 |journal=Science |volume=294 |issue=5541 |pages=364–366 |doi=10.1126/science.1064557 |pmid=11598298 |bibcode=2001Sci...294..364L |s2cid=44529493|url-access=subscription }}</ref>

Natal homing behavior is well described in sea turtles, and genetic testing of turtle populations at different nesting sites has shown that magnetic field is a more reliable indicator of genetic similarity than physical distance between sites.<ref name=":21">{{Cite journal|last1=Brothers|first1=J. Roger |last2=Lohmann|first2=Kenneth J.|date=2018|title=Evidence that Magnetic Navigation and Geomagnetic Imprinting Shape Spatial Genetic Variation in Sea Turtles |journal=Current Biology |volume=28|issue=8 |pages=1325–1329.e2 |doi=10.1016/j.cub.2018.03.022 |pmid=29657117|doi-access=free|bibcode=2018CBio...28E1325B }}</ref> Additionally, nesting sites have been recorded to "drift" along with isoline shifts in the magnetic field.<ref name=":22">{{Cite journal|last1=Brothers|first1=J. Roger|last2=Lohmann |first2=Kenneth J.|date=2015|title=Evidence for Geomagnetic Imprinting and Magnetic Navigation in the Natal Homing of Sea Turtles|journal=Current Biology |volume=25|issue=3 |pages=392–396 |doi=10.1016/j.cub.2014.12.035 |pmid=25601546|doi-access=free|bibcode=2015CBio...25..392B }}</ref> Magnetoreception is thought to be the primary navigation tool used by nesting sea turtles in returning to natal beaches.<ref name=":21" /><ref name=":22" /> There are three major theories explaining natal site learning: inherited magnetic information, socially facilitated migration, and geomagnetic imprinting.<ref name=":18" /> Some support has been found for geomagnetic imprinting, including successful experiments transplanting populations of sea turtles by relocating them prior to hatching, but the exact mechanism is still not known.<ref name=":18" />

== Ecology ==

=== Diet === thumb|238x238px|A sea-turtle eating lettuce. The loggerhead, Kemp's ridley, olive ridley, and hawksbill sea turtles are omnivorous their entire life. Omnivorous turtles may eat a wide variety of plant and animal life including decapods, seagrasses, seaweed, sponges, mollusks, cnidarians, Echinoderms, worms and fish.<ref name="Burbidge">{{cite book |last = Burbidge|first = Andrew A|title = Threatened animals of Western Australia|url={{google books |plainurl=y |id=wuVEAAAAYAAJ|page=110}}|year = 2004|publisher = Department of Conservation and Land Management|isbn = 978-0-7307-5549-4|pages = 110, 114}}</ref><ref name="noaa">{{cite web |url=http://www.nmfs.noaa.gov/pr/species/turtles/loggerhead.htm |title=Loggerhead Turtle (''Caretta caretta'') |last1=Bolten |first1=A.B. |year=2003 |work=NOAA Fisheries |access-date=January 31, 2010 |archive-url=https://web.archive.org/web/20100514085206/http://www.nmfs.noaa.gov/pr/species/turtles/loggerhead.htm |archive-date=May 14, 2010 |url-status=live}}</ref><ref>Barbour, Roger, Ernst, Carl, & Jeffrey Lovich. (1994). Turtles of the United States and Canada. Washington, DC: Smithsonian Institution Press.</ref><ref name="ernst50">{{cite book|last1 = Ernst|first1 = C. H.|last2 = Lovich|first2 = J.E.|title = Turtles of the United States and Canada|url = {{google books |plainurl=y |id=nNOQghYEXZMC|page=50}}|edition = 2|publisher = JHU Press|isbn = 978-0-8018-9121-2|year = 2009|access-date = May 27, 2010|page = 50}}</ref> However, some species specialize on certain prey.

The diet of green sea turtles changes with age.<ref name=":1">{{Cite journal|url = http://researchonline.jcu.edu.au/19395/1/19395_Arthur_et_al_2008.pdf|title = Ontogenetic Changes in Diet and Habitat Use in Green Sea Turtle (''Chelonia mydas'') Life History|last1 = Arthur|first1 = Karen|date = June 30, 2008|journal = Marine Ecology Progress Series |doi = 10.3354/meps07440|access-date = Dec 20, 2015|last2 = Boyle|first2 = Michelle|last3 = Limpus|first3 = Colin|volume=362|pages=303–311|bibcode = 2008MEPS..362..303A|doi-access = free}}</ref> Juveniles are omnivorous, but as they mature they become exclusively herbivorous.<ref name="noaa" /><ref name=":1" /> This diet shift has an effect on the green sea turtle's morphology.<ref>{{Cite web|url=https://www.nwf.org/Home/Educational-Resources/Wildlife-Guide|title=Wildlife Guide|website=National Wildlife Federation}}</ref><ref>{{cite journal | last1 = Nishizawa | first1 = H. | last2 = Asahara | first2 = M. | last3 = Kamezaki | first3 = N. | last4 = Arai | first4 = N. | year = 2010 | title = Differences in the skull morphology between juvenile and adult green turtles: implications for the ontogenetic diet shift | journal = Current Herpetology | volume = 29 | issue = 2| pages = 97–101 | doi=10.3105/018.029.0205| s2cid = 86312033}}</ref> Green sea turtles have a serrated jaw that is used to eat sea grass and algae.<ref>{{cite web|url=https://seaworld.org/en/animal-info/animal-infobooks/sea-turtles/diet-and-eating-habits|title=Diet & Eating Habits|website=seaworld.org|access-date=2016-04-27}}</ref>

Leatherback sea turtles feed almost exclusively on jellyfish and help control jellyfish populations.<ref name="WWW">{{cite web | title =WWF – Leatherback turtle | work=Marine Turtles | publisher=World Wide Fund for Nature (WWF) | date =16 February 2007 | url =http://www.panda.org/about_wwf/what_we_do/species/about_species/species_factsheets/marine_turtles/leatherback_turtle/index.cfm | access-date =9 September 2007}}</ref><ref name="CCC">{{cite web|title=Species Fact Sheet: Leatherback Sea Turtle |work=Caribbean Conservation Corporation & Sea Turtle Survival League |publisher=Caribbean Conservation Corporation |date=29 December 2005 |url=http://www.cccturtle.org/leatherback.htm |access-date=6 September 2007 |archive-url=https://web.archive.org/web/20070928221346/http://www.cccturtle.org/leatherback.htm |archive-date=28 September 2007}}</ref>

Hawksbill sea turtles principally eat sponges, which constitute 70–95{{Thinsp}}% of their diets in the Caribbean.<ref>{{Cite journal |title=Spongivory in Hawksbill Turtles: A Diet of Glass |last=Meylan |first=Anne |date=1988-01-22 |journal=Science |jstor=1700236 |pmid = 17836872 |volume=239 |issue=4838 |pages=393–395 |doi=10.1126/science.239.4838.393|bibcode=1988Sci...239..393M |s2cid=22971831}}</ref>

Loggerhead turtles are regarded as flexible and predators of slow-moving animals. They eat a broad variety of things, including terrestrial insects like ants, planthoppers, and beetles, as well as sea animals and plants. This species' primary diet consists of gelatinous creatures (medusae and ctenophores) and crustaceans, particularly crabs. Sargassum, barnacles, gastropods, anemones, salps, and pelagic coelenterates have also been found in numerous studies to be loggerhead turtles' primary food sources.<ref>{{Cite journal |last1=Kim |first1=Jihee |last2=Kim |first2=Il-Hun |last3=Kim |first3=Min-Seop |last4=Lee |first4=Hae Rim |last5=Kim |first5=Young Jun |last6=Park |first6=Sangkyu |last7=Yang |first7=Dongwoo |date=2021-11-21 |title=Occurrence and diet analysis of sea turtles in Korean shore |journal=Journal of Ecology and Environment |volume=45 |issue=1 |page=23 |doi=10.1186/s41610-021-00206-w |doi-access=free |issn=2288-1220}}</ref>

=== Larynx mechanisms === There was little information regarding the sea turtle's larynx. Sea turtles, like other turtle species, lack an epiglottis to cover the larynx entrance. Key findings from an experiment reveal the following in regards to the larynx morphology: a close apposition between the linguolaryngeal cleft's smooth mucosal walls and the laryngeal folds, a dorsal part of the glottis, the glottal mucosa attached to the arytenoid cartilage, and the way the hyoid sling is arranged and the relationship between the compressor laryngis muscle and cricoid cartilage. The glottal opening and closing mechanisms have been examined. During the opening stage, two abductor artytenoideae muscles swing arytenoid cartilages and the glottis walls. As a result, the glottis profile is transformed from a slit to a triangle. In the closing stage, the tongue is drawn posteriorly due to the close apposition of the glottis walls and linguolaryngeal cleft walls and hyoglossal sling contractions.<ref>{{cite journal |last1=Fraher |first1=J |last2=Davenport |first2=J |last3=Fitzgerald |first3=E |last4=Mclaughlin |first4=P |last5=Doyle |first5=T |last6=Harman |first6=L |last7=Cuffe |first7=T |title=Opening and closing mechanisms of the leatherback sea turtle larynx: a crucial role for the tongue |journal=Journal of Experimental Biology |date=2010 |volume=213 |issue=24 |pages=4137–4145 |doi=10.1242/jeb.042218|pmid=21112993 |doi-access=free|bibcode=2010JExpB.213.4137F }}</ref>

=== Relationship with humans ===

Sea turtles are caught worldwide, although it is illegal to hunt most species in many countries.<ref name="CITES">{{cite web|author=CITES |author-link=CITES |title=Appendices |publisher=Convention on International Trade in Endangered Species of Wild Flora and Fauna |date=14 June 2006 |url=http://www.cites.org/eng/app/appendices.shtml |format=SHTML |access-date=5 February 2007 |archive-url=https://web.archive.org/web/20070203100154/http://www.cites.org/eng/app/appendices.shtml |archive-date=3 February 2007 }}</ref><ref name="CITESEI">{{cite web|author=UNEP-WCMC |author-link=UNEP-WCMC |title=Eretmochelys imbricata A-301.003.003.001 |work=UNEP-WCMC Species Database: CITES-Listed Species |publisher=United Nations Environment Programme – World Conservation Monitoring Centre |url=http://sea.unep-wcmc.org/isdb/CITES/Taxonomy/tax-species-result.cfm?displaylanguage=eng&Genus=Eretmochelys&Species=imbricata&source=animals&Country=&tabname=all |access-date=5 February 2007 |archive-url=https://web.archive.org/web/20070929132215/http://sea.unep-wcmc.org/isdb/CITES/Taxonomy/tax-species-result.cfm?displaylanguage=eng&Genus=Eretmochelys&Species=imbricata&source=animals&Country=&tabname=all |archive-date=September 29, 2007}}</ref> A great deal of intentional sea turtle harvests worldwide are for food. Many parts of the world have long considered sea turtles to be fine dining. In England during the 1700s, sea turtles were consumed as a delicacy to near extinction, often as turtle soup.<ref name=":0">{{cite book |last=Clarkson |first=Janet |title=Soup: a global history |date=2010 |publisher=Reaktion Books |isbn=978-1-86189-774-9 |location=London |pages=115–118 |oclc=642290114 }}</ref> Ancient Chinese texts dating to the 5th century B.C.E. describe sea turtles as exotic delicacies.<ref name="EatingTurtlesChina">{{cite journal | last=Schafer | first=Edward H. | author-link=Edward H. Schafer | title=Eating Turtles in Ancient China | journal=Journal of the American Oriental Society | volume=82 | issue=1 | pages=73–74 | year=1962 | doi=10.2307/595986| jstor=595986}}</ref> Many coastal communities around the world depend on sea turtles as a source of protein, often harvesting several sea turtles at once and keeping them alive on their backs until needed. Coastal peoples gather sea turtle eggs for consumption.<ref>{{cite web |url=http://www.seaturtle.org/mtn/archives/mtn68/mtn68p8.shtml |title=MTN 68:8-13 Status of Nesting Populations of Sea Turtles in Thailand and Their Conservation |publisher=Seaturtle.org}}</ref>

[[File:Manner in which the natives of the East Coast Stirke Turtle.jpg|thumb|"Manner in which Natives of the East Coast strike turtle". Near Cooktown, Australia. From Phillip Parker King's Survey. 1818.]]

To a much lesser extent, some species are targeted for their shells. Tortoiseshell, a traditional decorative ornamental material used in Japan and China, comes from the carapace scutes of the hawksbill sea turtle.<ref name="FisheriesModel">{{cite journal | last=Heppel | first=Selina S. | author-link=Selina Heppel |author2=Larry B. Crowder | title=Analysis of a Fisheries Model for Harvest of Hawksbill Sea Turtles (''Eretmochelys imbricata'') | journal=Conservation Biology | volume=10 | issue=3 | pages=874–880 | doi=10.1046/j.1523-1739.1996.10030874.x |date=June 1996 | jstor=2387111| bibcode=1996ConBi..10..874H }}</ref><ref name="CNNJapan">{{cite news|last=Strieker |first=Gary |author-link=Gark Strieker |title=Tortoiseshell ban threatens Japanese tradition |work=CNN.com/sci-tech |publisher=Cable News Network |date=10 April 2001 |url=http://archives.cnn.com/2001/TECH/science/04/10/japan.turtles/ |access-date=2 March 2007 |archive-url=https://web.archive.org/web/20070311014928/http://archives.cnn.com/2001/TECH/science/04/10/japan.turtles/ |archive-date=11 March 2007}}</ref> Ancient Greeks and ancient Romans processed sea turtle scutes (primarily from the hawksbill sea turtle) for various articles and ornaments used by their elites, such as combs and brushes.<ref name="Periplus">{{cite journal | last=Casson | first=Lionel | author-link=Lionel Casson | title=Periplus Maris Erythraei: Notes on the Text | journal=The Journal of Hellenic Studies | volume=102 | pages=204–206 | doi=10.2307/631139| year=1982 | jstor=631139| s2cid=161133205 }}</ref> The skin of the flippers is prized for use as shoes and assorted leather goods.<ref>{{Cite journal |last1=Steiner |first1=Todd |last2=Heitchue |first2=Mark |last3=Ghriskey |first3=Henry W. |date=1994 |title=Banned Sea Turtle Products Still Exported from Mexico |journal=Earth Island Journal |volume=9 |issue=3 |page=9 |jstor=43882966 |issn=1041-0406}}</ref> In various West African countries, sea turtles are harvested for traditional medicinal use.<ref>{{cite journal |last1=Fretey |first1=Jacques |last2=Segniagbeto |first2=Gabriel Hoinsoudé |last3=Soumah |first3=M'Mah |title=Presence of Sea Turtles in Traditional Pharmacopoeia and Beliefs of West Africa |journal=Marine Turtle Newsletter |year=2007 |issue=116 |pages=23–25 |url=https://renatura.org/wp-content/uploads/2019/08/Bal-G.-Br%C3%A9heret-N.-Vanleeuwe-H.-2007-An-update-on-sea-turtle-conservation-activities-in-the-Republic-of-Congo.-Marine-Turtle-Newsletter-1169-10.pdf}}</ref>

The Moche people of ancient Peru worshipped the sea and its animals. They often depicted sea turtles in their art.<ref>Berrin, Katherine & Larco Museum. ''The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera.'' New York: Thames and Hudson, 1997.</ref> J. R. R. Tolkien's poem "Fastitocalon" echoes a second-century Latin tale in the ''Physiologus'' of the ''Aspidochelone'' ("round-shielded turtle"); it is so large that sailors mistakenly land and light a fire on its back, and are drowned when it dives.<ref name="Letter 255">J. R. R. Tolkien, ''The Letters of J.R.R. Tolkien'', #255 to Mrs Eileen Elgar, 5 March 1964; Humphrey Carpenter and Christopher Tolkien, eds. (Allen & Unwin, 1981; {{ISBN|0-261-10265-6}})</ref><ref>Christina Scull & Wayne G. Hammond (2014), editors, ''The Adventures of Tom Bombadil'', Harper Collins, p. 224; {{ISBN|978-0007557271}}</ref> Beach towns, such as Tortuguero, Costa Rica, have transitioned from a tourism industry that made profits from selling sea turtle meat and shells to an ecotourism-based economy. Tortuguero is considered to be the founding location of sea turtle conservation. In the 1960s the cultural demand for sea turtle meat, shells, and eggs was quickly killing the once-abundant sea turtle populations that nested on the beach. The Caribbean Conservation Corporation began working with villagers to promote ecotourism as a permanent substitute to sea turtle hunting. Sea turtle nesting grounds became sustainable. Tourists love to come and visit the nesting grounds, although it causes a lot of stress to the sea turtles because all of the eggs can get damaged or harmed.<ref>{{cite web |url=http://www.seaturtle-world.com/sea-turtles-and-humans/ |title=Sea Turtles and Humans – Sea Turtle Facts and Information |website=www.seaturtle-world.com |date=4 January 2014 |access-date=2017-04-24}}</ref> Since the creation of a sea turtle ecotourism-based economy, Tortuguero annually houses thousands of tourists who visit the protected {{convert|22|mi|km|order=flip|adj=on}} beach that hosts sea turtle walks and nesting grounds.<ref>{{cite web |url=http://www.tortugueroinfo.com/usa/sea_turtles_tortuguero.htm |title=Sea turtles in Tortuguero Costa Rica, a turtle haven ! |work=Tortuguero Costa Rica Tours }}</ref><ref>{{cite news | url=https://www.nytimes.com/1998/10/25/travel/turtle-watch-in-costa-rica.html?scp=3&sq=costa%20rica,%20sea%20turtle&st=cse | work=The New York Times | title=Turtle Watch in Costa Rica | first=John R. | last=Alden | date=25 October 1998}}</ref> Walks to observe the nesting sea turtles require a certified guide and this controls and minimizes disturbance of the beaches. It also gives the locals a financial interest in conservation and the guides now defend the sea turtles from threats such as poaching; efforts in Costa Rica's Pacific Coast are facilitated by a nonprofit organization, Sea Turtles Forever.<ref name="Eugene">{{cite news |url=https://news.google.com/newspapers?nid=1310&dat=20060326&id=PWBWAAAAIBAJ&pg=4551,6016259 |newspaper=Eugene Register-Guard |date=March 26, 2005 |title=Seaside Couple Protect Costa Rican Turtles |access-date=November 26, 2018}}</ref> Thousands of people are involved in sea turtle walks, and substantial revenues accrue from the fees paid for the privilege.<ref>{{cite web |url=https://conserveturtles.org/wp-content/uploads/Tortuguero%20Green%20Turtle%20Report%201999.pdf |title=Report on the 1999 Green Turtle Program at Tortuguero, Costa Rica |publisher=Caribbean Conservation Corporation and the Ministry of Environment and Energy of Costa Rica |date=22 February 2000 |first1=Sebastian |last1=Troëng |first2=Jeff |last2=Mangel |first3=Sheleyla |last3=Kélez |first4=Andy |display-authors=etal |last4=Meyers |pages=11, 21–23, 29, 32 |access-date=30 November 2018 |archive-date=27 November 2018 |archive-url=https://web.archive.org/web/20181127193718/https://conserveturtles.org/wp-content/uploads/Tortuguero%20Green%20Turtle%20Report%201999.pdf }}</ref>

In other parts of the world where sea turtle breeding sites are threatened by human activity, volunteers often patrol beaches as a part of conservation activities, which may include relocating sea turtle eggs to hatcheries, or assisting hatching sea turtles in reaching the ocean.<ref name=NIE>{{cite web|url=http://newindianexpress.com/education/student/article557787.ece|archive-url=https://web.archive.org/web/20130810045119/http://newindianexpress.com/education/student/article557787.ece|archive-date=August 10, 2013|title=Join the turtle walk|work=New Indian Express|publisher=Newindianexpress.com|access-date=2 October 2018}}</ref> Locations in which such efforts exist include the east coast of India,<ref name=H>{{citation |url=https://www.thehindu.com/thehindu/mag/2002/05/19/stories/2002051900230800.htm |archive-url=https://web.archive.org/web/20030516140742/http://thehindu.com/thehindu/mag/2002/05/19/stories/2002051900230800.htm |archive-date=16 May 2003 |newspaper=The Hindu |title=The ebb and flow of life |date=19 May 2002 |first1=S. Theodore |last1=Baskaran}}</ref> São Tomé and Príncipe,<ref name=STP>{{citation |title=On Turtle Patrol: the Bradt travel guide. |work=São Tomé and Príncipe |first=Kathleen |last=Becker |location=Chalfont St. Peter |publisher=Bradt Travel Guides|year=2014 |isbn=978-1-84162-486-0}}</ref> Sham Wan in Hong Kong,<ref name=SCMP>{{citation |title=Actors and activists fight for endangered green sea turtles' nesting site in Hong Kong |newspaper=South China Morning Post|date=26 June 2018 |url=https://www.scmp.com/lifestyle/article/2152477/actors-and-activists-fight-endangered-green-sea-turtles-nesting-site-hong}}</ref> and the coast of Florida.<ref name=TITS>{{citation |title=Tracks in the Sand: Sea Turtles and Their Protectors |first1=Frank |last1=Gromling |first2=Mike |last2=Cavaliere |publisher=Ocean Publishing |location=Flagler Beach, Florida |year=2010 |isbn=978-0-9826940-0-8}}</ref>

=== Importance to ecosystems === [[Image:Sea turtles on beach in hawaii.jpg|thumb|left|Sea turtles on a beach in Hawaii]]

Sea turtles play key roles in two habitat types: oceans and beaches/dunes.

In the oceans, sea turtles, especially green sea turtles, are among the very few creatures (manatees are another) that eat sea grass. Sea grass needs to be constantly cut short to help it grow across the sea floor. Sea turtle grazing helps maintain the health of the sea grass beds. Sea grass beds provide breeding and developmental grounds for numerous marine animals. Without them, many marine species humans harvest would be lost, as would the lower levels of the food chain. The reactions could result in many more marine species eventually becoming endangered or extinct.<ref name="cccturtle.org">[http://cccturtle.org/seaturtleinformation.php?page=whycareaboutseaturtles Why Care About Sea Turtles?], Sea Turtle Conservancy.</ref>

Sea turtles use beaches and sand dunes as to lay their eggs. Such coastal environments are nutrient-poor and depend on vegetation to protect against erosion. Eggs, hatched or unhatched, and hatchlings that fail to make it into the ocean are nutrient sources for dune vegetation and therefore protecting these nesting habitats for sea turtles, forming a positive feedback loop.<ref name="cccturtle.org" /><ref>{{cite journal |last1=Hannan |first1=Laura B. |last2=Roth |first2=James D. |last3=Ehrhart |first3=Llewellyn M. |last4=Weishampel |first4=John F. |title=Dune Vegetation Fertilization by Nesting Sea Turtles |journal=Ecology |date=2007 |volume=88 |issue=4 |pages=1053–1058 |publisher=Ecological Society of America|doi=10.1890/06-0629 |jstor=27651194 |pmid=17536720 |bibcode=2007Ecol...88.1053H |s2cid=7194642 }}</ref>

Sea turtles also maintain a symbiotic relationship with yellow tang, in which the fish will eat algae growing on the shell of a sea turtle.<ref>{{Cite web |url=http://akepa.hpa.edu/~mrice/turtle/Articles%20of%20interest/symposiumpapertcs.pdf |title=CLEANING SYMBIOSIS AND DIEL BEHAVIOR OF GREEN TURTLES (''CHELONIA MYDAS'') AT PUAKO, HAWAII |last1=Catellacci |first1=Alima |first2=Alexandra |last2=Wooddell |first3=Marc R. |last3=Rice |work=Sea Turtle Research Program |publisher=Hawaii Preparatory Academy |location=USA |access-date=2019-03-23 |archive-date=2015-10-07 |archive-url=https://web.archive.org/web/20151007041618/http://akepa.hpa.edu/~mrice/turtle/Articles%20of%20interest/symposiumpapertcs.pdf }}</ref>

=== Conservation status and threats ===

thumb|upright|A sea turtle entangled in a fishing net

The IUCN Red List classifies two species of sea turtle as "critically endangered" and several others at lower levels of threat.<ref name=":13">{{cite web|title = The IUCN Red List of Threatened Species|url = http://www.iucnredlist.org/|website = www.iucnredlist.org|access-date = 2015-12-24}}</ref> An additional three species are classified as "vulnerable".<ref name=":13" /> All species of sea turtle are listed in CITES Appendix I, restricting international trade of sea turtles and sea turtle products.<ref name=":12" /><ref>{{cite web|title = Checklist of CITES species|url = http://checklist.cites.org|website = checklist.cites.org|access-date = 2015-12-24}}</ref> Conservation efforts attempt to address the multiple threats to their populations, but evaluation of the success of these efforts has been limited.<ref>{{cite journal |last1= Bjorndal |first1= Karen |last2= Bowen |first2= Brian |year= 2011 |title= Better science needed for restoration in the Gulf of Mexico |journal= Science |volume= 331 |pages= 537–538 |doi= 10.1126/science.1199935 |last3= Chaloupka |first3= M. |last4= Crowder |first4= L. B. |last5= Heppell |first5= S. S. |last6= Jones |first6= C. M. |last7= Lutcavage |first7= M. E. |last8= Policansky |first8= D. |last9= Solow |first9= A. R. |last10= Witherington |first10= B. E. |issue= 6017 |pmid= 21292956|display-authors= 8 |bibcode= 2011Sci...331..537B |s2cid= 33994573 }}</ref> Counting nests on beaches not provide an accurate picture of whole populations.<ref>{{cite journal |last1=Witherington |first1=B.E. |last2=Kubilis |first2=Anne |last3=Brost |first3=Beth |last4=Meylan |first4=Anne |year=2009 |title=Decreasing annual nest counts in a globally important loggerhead sea turtle population |journal=Ecological Applications |volume=19 |issue=1 |pages=30–54 |doi=10.1890/08-0434.1 |pmid=19323172|bibcode=2009EcoAp..19...30W }}</ref> More detailed information on birth rates and mortality is needed.<ref>{{cite web | last1=The National Research Council | title=Assessment of Sea Turtle Status and Trends: Integrating Demography and Abundance | publisher=National Academies Press | place=Washington, DC | year=2010 | url=http://dels.nas.edu/Report/Assessment-Turtle-Status/12889}}</ref> The presence of humans has increased the threats.<ref>{{cite journal|last1=Heithaus|first1=Michael R.|last2=Wirsing|first2=Aaron J.|last3=Thomson|first3=Jordan A.|last4=Burkholder|first4=Derek A. |year=2008 |title=A review of lethal and non-lethal effects of predators on adult marine turtles |journal=Journal of Experimental Marine Biology and Ecology |volume=356 |issue=1–2 |pages=43–51 |doi=10.1016/j.jembe.2007.12.013|bibcode=2008JEMBE.356...43H }}</ref> Death by bycatch due to imprecise fishing methods is a major threat; long-lining is a major cause of accidental sea turtle deaths.<ref name="RoyalGazette">{{cite news | last =Moniz | first =Jesse | title =Turtle conservation: It's now very much a political issue | work =News | publisher =The Royal Gazette Ltd. | date =3 February 2007 | url =http://www.royalgazette.com/siftology.royalgazette/Article/article.jsp?sectionId=80&articleId=7d5908e3003001d }}{{dead link|date=August 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="NationalGeographic">{{cite news | last=Scales|first = Helen | title =Glow Sticks May Lure Sea Turtles to Death | work =News | publisher =National Geographic News | date =27 April 2007 | url =http://news.nationalgeographic.com/news/2007/04/070427-glow-sticks.html | archive-url =https://web.archive.org/web/20070430043452/http://news.nationalgeographic.com/news/2007/04/070427-glow-sticks.html | archive-date =April 30, 2007 }}</ref> Light pollution from beach development is a threat to newly-hatched sea turtles.<ref>{{Cite web|last=Witherington|first=Blair E|date=|title=Understanding, Assessing, and Resolving Light Pollution Problems on Sea Turtle Nesting Beaches|url=https://www.fws.gov/caribbean/es/PDF/Library%20Items/LightingManual-Florida.pdf|access-date=2021-02-05|website=paed.org.ph}}</ref><ref>[https://hakaimagazine.com/article-short/bright-lights-and-dark-nights-the-challenge-facing-sea-turtles-in-the-city/ Bright Lights and Dark Nights: The Challenge Facing Sea Turtles in the City]</ref><ref>{{Cite web|title=Information About Sea Turtles: Threats from Artificial Lighting – Sea Turtle Conservancy|url=https://conserveturtles.org/information-sea-turtles-threats-artificial-lighting/|access-date=2021-02-05|language=en-US}}</ref> Another major threat is the black-market trade in eggs and meat.<ref>{{Cite news|title = Pope Asked to Call Sea Turtles 'Meat'|url = https://www.latimes.com/archives/la-xpm-2002-mar-14-me-turtle14-story.html|newspaper = Los Angeles Times|date = 2002-03-14|access-date = 2015-12-22|first = Kenneth r.|last = WEISS}}</ref> Another danger to sea turtles comes from marine debris, especially plastics that they can mistake for jellyfish.<ref>{{Cite web|url=https://www.seeturtles.org/ocean-plastic|title=Ocean Plastic|website=SEE Turtles|language=en-US|access-date=2019-11-20}}</ref> Climate change may pose a threat, since rising temperatures may change the sex ratio, resulting in too many females.<ref>{{Cite web|url=https://conserveturtles.org/information-sea-turtles-threats-climate-change/|title=Information About Sea Turtles: Threats from Climate Change – Sea Turtle Conservancy|language=en-US|access-date=2019-02-25}}</ref><ref>{{Cite journal | last1 = Hawkes | first1 = LA | last2 =Broderick | first2 =AC | title = Climate change and marine turtles | journal = Endangered Species Research | volume =7 | pages = 137–154| year = 2009 | doi = 10.3354/esr00198 | last3 = Godfrey | first3 = MH | last4 = Godley | first4 = BJ | doi-access = free }}</ref> Oil pollution can affect turtles at every stage of their life cycle.<ref>{{cite news|last=Hirsch|first=Masako|title=Gulf oil spill's effects on sea turtles examined|url=http://www.nola.com/news/gulf-oil-spill/index.ssf/2010/06/gulf_oil_spills_effects_on_sea.html|access-date=17 May 2012|newspaper=nola.com|date=9 June 2010}}</ref>

=== Symbiosis with barnacles === Sea turtles are believed to have a commensal relationship with some barnacles, in which the barnacles benefit from growing on sea turtles without harming them. Barnacles are small, hard-shelled crustaceans found attached to multiple different substrates below or just above the ocean. The adult barnacle is a sessile organism; however, in its larval stage it is planktonic and can move about the water column. The larval stage chooses where to settle and ultimately the habitat for its full adult life, which is typically between 5 and 10 years. However, estimates of age for a common sea turtle barnacle species, ''Chelonibia testudinaria'', suggest that this species lives for at least 21 months,<ref name=":15">{{Cite journal|last1=Doell|first1=Sophie A.|last2=Connolly|first2=Rod M.|last3=Limpus|first3=Colin J.|last4=Pearson|first4=Ryan M.|last5=van de Merwe|first5=Jason P.|date=2017|title=Using growth rates to estimate age of the sea turtle barnacle Chelonibia testudinaria|journal=Marine Biology|language=en|volume=164|issue=12|page=222|doi=10.1007/s00227-017-3251-5|bibcode=2017MarBi.164..222D |s2cid=31961046|issn=0025-3162}}</ref> with individuals older than this uncommon. ''Chelonibia'' barnacles have also been used to distinguish between the foraging areas of sea turtle hosts. By analyzing stable isotope ratios in barnacle shell material, scientist can identify differences in the water (temperature and salinity) that different hosts have been swimming through and thus differentiate between the home areas of host sea turtles.<ref>{{Cite journal|last1=Pearson|first1=Ryan M.|last2=van de Merwe|first2=Jason P.|last3=Gagan|first3=Michael K.|last4=Limpus|first4=Colin J.|last5=Connolly|first5=Rod M.|date=2019|title=Distinguishing between sea turtle foraging areas using stable isotopes from commensal barnacle shells|journal=Scientific Reports|language=en|volume=9|issue=1|page=6565|doi=10.1038/s41598-019-42983-4|pmid=31024029|pmc=6483986|issn=2045-2322|bibcode=2019NatSR...9.6565P}}</ref>

A favorite settlement for barnacle larvae is the shell or skin around the neck of sea turtles. The larvae glue themselves to the chosen spot, a thin layer of flesh is wrapped around them and a shell is secreted. Many species of barnacles can settle on any substrate; however, some species of barnacles have an obligatory commensal relationship with specific animals, which makes finding a suitable location harder.<ref name="ZardusHadfield2004">{{Cite journal | last1 = Zardus | first1 = J. D. | last2 = Hadfield | first2 = M. G. | doi = 10.1651/C-2476 | title = Larval development and complemental males in ''Chelonibia testudinaria'', a barnacle commensal with sea turtles | journal = Journal of Crustacean Biology | volume = 24 | issue = 3 | pages = 409–421 | year = 2004 | doi-access = free| bibcode = 2004JCBio..24..409H }}</ref> Around 29 species of "turtle barnacles" have been recorded. However, it is not solely on sea turtles that barnacles can be found; other organisms also serve as a barnacle's settlements. These organisms include mollusks, whales, decapod crustaceans, manatees and several other groups related to these species.<ref>Epibiont Research Cooperative. 2007. [http://www.seaturtle.org/documents/ERC-SP1.pdf A synopsis of the literature on the turtle barnacle (Cirripedia: Balanomorpha: Coronuloidea) 1758–2007]. Accessed 28 Nov 2012.</ref>

Sea turtle shells are an ideal habitat for adult barnacles for three reasons. Sea turtles tend to live long lives, greater than 70 years, so barnacles do not have to worry about host death. However, mortality in sea turtle barnacles is often driven by their host shedding the scutes on which the barnacle is attached, rather than the death of the sea turtle itself.<ref name=":15" /> Secondly, barnacles are suspension feeders. Sea turtles spend most of their lives swimming and following ocean currents and as water runs along the back of the sea turtle's shell it passes over the barnacles, providing an almost constant water flow and influx of food particles. Lastly, the long distances and inter-ocean travel these sea turtles swim throughout their lifetime offers the perfect mechanism for dispersal of barnacle larvae. Allowing the barnacle species to distribute themselves throughout global waters is a high fitness advantage of this commensalism.<ref>[http://bio390parasitology.blogspot.ca/2012/03/free-ride-under-sea-barnacles-and.html A free ride under the sea: barnacles and baleen whales]. Themes of Parasitology. 2012. Web. 28 Nov 2012.</ref>

This relationship, however, is not truly commensal. While the barnacles are not directly parasitic to their hosts, they have negative effects to the sea turtles on which they choose to reside. The barnacles add extra weight and drag to the sea turtle, increasing the energy it needs for swimming and affecting its ability to capture prey, with the effect increasing with the quantity of barnacles affixed to its back.{{Citation needed|reason=The previous reference for this paragraph does not seem to support it? http://true-wildlife.blogspot.ca/2011/01/barnacle.html|date=January 2022}}

==References== {{Reflist|30em}}

==Further reading==

* {{cite journal |last1=Brongersma |first1=L.D. |year=1972 |title=European Atlantic Turtles |url=http://www.repository.naturalis.nl/record/317577 |journal=Zoologische Verhandelingen |volume=121 |pages=1–318 |ref=none }} * {{cite book |last=Davidson |first=Osha Gray |title=Fire In The Turtle House: The Green Sea Turtle and the Fate of the Ocean |url={{google books |plainurl=y |id=meyvDAEACAAJ}} |date=14 August 2003 |publisher=PublicAffairs |isbn=978-1-58648-199-5 |ref=none }} * {{cite book |title=The Turtle Lady: Ila Fox Loetscher of South Padre |url={{google books |plainurl=y |id=NuquPQAACAAJ}} |last=Sizemore |first=Evelyn |year=2002 |page=220 |publisher=Republic of Texas Press |location=Plano, Texas |isbn= 978-1-55622-896-4 |ref=none }} * {{cite book |last=Spotila |first=James R. |title=Sea Turtles: A Complete Guide to Their Biology, Behavior, and Conservation |url={{google books |plainurl=y |id=dpsJrFxVIvUC}} |date=26 October 2004 |publisher=JHU Press |isbn=978-0-8018-8007-0 |ref=none }} * {{cite book |last=Witherington |first=Blair E. |title=Sea Turtles: An Extraordinary Natural History of Some Uncommon Turtles |url={{google books |plainurl=y |id=h-EJy0BQ_RkC}} |year=2006 |publisher=Voyageur Press |isbn=978-0-7603-2644-2 |ref=none }}

==External links== {{Commons category}} {{Wikispecies|Chelonioidea}} *[http://archive.wikiwix.com/cache/20081226000000/http://cbc.amnh.org/center/programs/reptiles-seaturtles.html Sea Turtle Research and Conservation – Center for Biodiversity and Conservation, American Museum of Natural History]

{{DEFAULTSORT:Sea turtle}} Category:Sea turtles Category:Chelonioidea Category:Endangered animals Category:Extant Albian first appearances