Sea turtle#Conservation

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.{{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}}

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.{{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}} 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).{{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}} 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.{{cite web|url=http://www.turtlehospital.org/sea-turtle-species/|title=Sea Turtle Species|website=turtlehospital|access-date=29 August 2015}}

The skulls of sea turtles have cheek regions that are enclosed in bone.{{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|pages=e47852|doi=10.1371/journal.pone.0047852|pmid=23144831|pmc=3492385|bibcode=2012PLoSO...747852J|doi-access=free}}{{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}} 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.{{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}}

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}}).{{LSJ|xelw/nh|χελώνη|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.{{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}} 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 AraripemysKischlat, 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. and extinct pelomedusids.{{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 |pages=e1063 |doi=10.7717/peerj.1063 |pmc=4493680 |pmid=26157628 |doi-access=free}} 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.{{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}}{{Cite journal |title=An Introduction to Sea Turtles |url=http://seaturtlestatus.org/sites/swot/files/061810_SWOT1_p04_IntroSeaTurtles.pdf |journal=SWOT}}{{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}} 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.{{Cite journal |last1=Gable |first1=Simone M. |last2=Byars |first2=Michael I. |last3=Literman |first3=Robert |last4=Tollis |first4=Marc |date=2021-10-16 |title=A Genomic Perspective on the Evolutionary Diversification of Turtles |url=http://dx.doi.org/10.1101/2021.10.14.464421 |journal=bioRxiv|access-date=2022-11-17 |doi=10.1101/2021.10.14.464421 |s2cid=239029388 }}

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.{{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}}{{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}} 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.{{Cite journal |last1=Castillo-Visa |first1=Oscar |last2=Luján |first2=Àngel H. |last3=Galobart |first3=Àngel |last4=Sellés |first4=Albert |date=2022-11-17 |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 |pages=18322 |doi=10.1038/s41598-022-22619-w |pmid=36396968 |pmc=9671902 |bibcode=2022NatSR..1218322C |s2cid=253584457 |issn=2045-2322}}

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.{{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}}{{cite web | url=https://www.sciencedaily.com/releases/2018/03/180328083421.htm | title=Sea turtles use flippers to manipulate food}}

Below is a cladogram showing the phylogenetic relationships of living and extinct sea turtles in the Chelonioidea based on Evers et al. (2019):{{Cite journal|last1=Evers|first1=Serjoscha W.|last2=Barrett|first2=Paul M.|last3=Benson|first3=Roger B. J.|date=2019-05-01|title=Anatomy of Rhinochelys pulchriceps (Protostegidae) and marine adaptation during the early evolution of chelonioids|journal=PeerJ|volume=7|pages=e6811|doi=10.7717/peerj.6811|issn=2167-8359|pmc=6500378|pmid=31106054 |doi-access=free }}

An alternate phylogeny was proposed by Castillo-Visa et al. (2022):

{{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}}

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.{{Cite web|url=http://awsassets.panda.org/downloads/marine_turtles_factsheet2006.pdf|title=Ancient mariners threatened with extinction}}

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. Once the sea turtle has reached adulthood it moves closer to the shore. Females will come ashore to lay their eggs on sandy beaches during the nesting season.{{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}}

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.{{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}}

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.{{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}}

File:Life Cycle of a Sea Turtle.svg

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.{{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 }}{{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 }}{{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 }}{{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 }} 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, 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. She may also dig decoy nests.{{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}} The whole process takes 30 to 60 minutes. She then returns to the ocean, leaving the eggs untended.{{cite book | last =Audubon | first =Maria R. | author-link =Maria Audubon | title =Audubon and His Journals: Dover Publications Reprint | publisher =Scribner's Sons | orig-year=First published 1897 |year=1986 | location =New York | pages = 373–375| isbn = 978-0-486-25144-8}}

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.{{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 }}{{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}}{{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}}{{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}}{{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 }} Warmer temperatures produce female hatchlings, while cooler temperatures produce male hatchlings.{{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}} 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.

Image:YosriTelurPenyu6.jpg

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.{{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}} 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".{{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 }} 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.{{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}}{{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}}

Sea turtles maintain an internal environment that is hypotonic to the ocean. To maintain hypotonicity they must excrete excess salt ions.{{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 }} 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.{{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 }} 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.{{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 }}

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.{{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}}

Image:Young Honu-Kahala.png

File:Sea turtles bask in the Papahānaumokuākea Marine National Monument.png 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.

All sea turtles are poikilotherms.{{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|hdl = 1834/30782|hdl-access = free}} 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.{{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}}

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.{{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}} This behavior has only been observed in a few locations, including the Galapagos, Hawaii, Europa Island, and parts of Australia. Image:Chelonia mydas got to the surface to breath.jpg

{{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. Dive duration largely depends on activity. A foraging sea turtle may typically spend 5–40 minutes underwater{{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 }} while a sleeping sea turtle can remain underwater for 4–7 hours.{{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}}{{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}} Remarkably, sea turtle respiration remains aerobic for the vast majority of voluntary dive time. 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.

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.Spotila, J. R. (2004). Sea Turtles: A Complete Guide to Their Biology, Behavior, and Conservation. Baltimore: Johns Hopkins University Press. {{isbn|978-0801880070}}

Gruber and Sparks (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}} have observed the first fluorescence in a marine tetrapod (four-limbed vertebrates).{{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/}} 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.

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.{{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/| url-status = dead| archive-date = September 30, 2015}}{{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}}

Below the surface, the sensory cues available for navigation change dramatically.{{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 }} 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. Most sea turtle species migrate over significant distances to nesting or foraging grounds, some even crossing entire ocean basins.{{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}} 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. 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.{{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 }} 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.

File:Hatchling green sea turtle.jpg

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.{{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 }} A magnetic compass sense allows sea turtles to determine and maintain a specific magnetic heading or orientation. 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.{{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 }}

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.{{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 }} Additionally, nesting sites have been recorded to "drift" along with isoline shifts in the magnetic field.{{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 }} Magnetoreception is thought to be the primary navigation tool used by nesting sea turtles in returning to natal beaches. There are three major theories explaining natal site learning: inherited magnetic information, socially facilitated migration, and geomagnetic imprinting. 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.

File:Myrtle the Green Sea Turtle eating lettuce 02.jpg

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.{{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}}{{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}}Barbour, Roger, Ernst, Carl, & Jeffrey Lovich. (1994). Turtles of the United States and Canada. Washington, DC: Smithsonian Institution Press.{{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}} However, some species specialize on certain prey.

The diet of green sea turtles changes with age.{{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}} Juveniles are omnivorous, but as they mature they become exclusively herbivorous. This diet shift has an effect on the green sea turtle's morphology.{{Cite web|url=https://www.nwf.org/Home/Educational-Resources/Wildlife-Guide|title=Wildlife Guide|website=National Wildlife Federation}}{{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}} Green sea turtles have a serrated jaw that is used to eat sea grass and algae.{{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}}

Leatherback sea turtles feed almost exclusively on jellyfish and help control jellyfish populations.{{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}}{{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 |url-status=dead |archive-url=https://web.archive.org/web/20070928221346/http://www.cccturtle.org/leatherback.htm |archive-date=28 September 2007}}

Hawksbill sea turtles principally eat sponges, which constitute 70–95{{Thinsp}}% of their diets in the Caribbean.{{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}}

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.{{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 |pages=23 |doi=10.1186/s41610-021-00206-w |doi-access=free |issn=2288-1220}}

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.{{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 }}

Sea turtles are caught worldwide, although it is illegal to hunt most species in many countries.{{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 |url-status=dead}}{{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 |url-status=dead |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}} 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.{{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 }} Ancient Chinese texts dating to the 5th century B.C.E. describe sea turtles as exotic delicacies.{{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}} 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.{{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}}

File:Manner in which the natives of the East Coast Stirke Turtle.jpg, 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.{{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 }}{{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 |url-status=dead |archive-url=https://web.archive.org/web/20070311014928/http://archives.cnn.com/2001/TECH/science/04/10/japan.turtles/ |archive-date=11 March 2007}} 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.{{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 }} The skin of the flippers is prized for use as shoes and assorted leather goods.{{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 |url=https://www.jstor.org/stable/43882966 |journal=Earth Island Journal |volume=9 |issue=3 |pages=9 |jstor=43882966 |issn=1041-0406}} In various West African countries, sea turtles are harvested for traditional medicinal use.{{citation needed|date=July 2021}}

The Moche people of ancient Peru worshipped the sea and its animals. They often depicted sea turtles in their art.Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York: Thames and Hudson, 1997. 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.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}})Christina Scull & Wayne G. Hammond (2014), editors, The Adventures of Tom Bombadil, Harper Collins, p. 224; {{ISBN|978-0007557271}}

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.{{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}} Since the creation of a sea turtle ecotourism-based economy, Tortugero 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.{{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 }}{{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}} 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.{{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}} Thousands of people are involved in sea turtle walks, and substantial revenues accrue from the fees paid for the privilege.{{cite web |url=https://conserveturtles.org/wp-content/uploads/Tortuguero%20Green%20Turtle%20Report%201999.pdf |title=Report on the 1999 Green Turtle Program at Tortugero, 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 |url-status=dead }}

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.{{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|url-status=dead|archive-date=August 10, 2013|title=Join the turtle walk|work=New Indian Express|publisher=Newindianexpress.com|access-date=2 October 2018}} Locations in which such efforts exist include the east coast of India,{{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 |url-status=dead |archive-date=16 May 2003 |newspaper=The Hindu |title=The ebb and flow of life |date=19 May 2002 |first1=S. Theodore |last1=Baskaran}} São Tomé and Príncipe,{{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=9781841624860}} Sham Wan in Hong Kong,{{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}} and the coast of Florida.{{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=9780982694008}}

Image:Sea turtles on beach in hawaii.jpg]]

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.[http://cccturtle.org/seaturtleinformation.php?page=whycareaboutseaturtles Why Care About Sea Turtles?], Sea Turtle Conservancy.

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.{{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 |url=http://www.jstor.org/stable/27651194 |access-date=October 20, 2020 |publisher=Ecological Society of America|doi=10.1890/06-0629 |jstor=27651194 |pmid=17536720 |bibcode=2007Ecol...88.1053H |s2cid=7194642 |url-access=subscription }}

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.{{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 |url-status=dead }}

{{Main|Threats to sea turtles}}

File:Sea turtle entangled in a ghost net.jpg

The IUCN Red List classifies three species of sea turtle as either "endangered" or "critically endangered".{{cite web|title = The IUCN Red List of Threatened Species|url = http://www.iucnredlist.org/|website = www.iucnredlist.org|access-date = 2015-12-24}} An additional three species are classified as "vulnerable". The flatback sea turtle is considered as "data deficient", meaning that its conservation status is unclear due to lack of data. All species of sea turtle are listed in CITES Appendix I, restricting international trade of sea turtles and sea turtle products.{{cite web|title = Checklist of CITES species|url = http://checklist.cites.org|website = checklist.cites.org|access-date = 2015-12-24}} However, the usefulness of global assessments for sea turtles has been questioned,{{Cite journal|last1=Seminoff|first1=Jeffrey A.|last2=Shanker|first2=Kartik|title=Marine turtles and IUCN Red Listing: A review of the process, the pitfalls, and novel assessment approaches|journal=Journal of Experimental Marine Biology and Ecology|volume=356|issue=1–2|pages=52–68|doi=10.1016/j.jembe.2007.12.007|year=2008|bibcode=2008JEMBE.356...52S }} particularly due to the presence of distinct genetic stocks and spatially separated regional management units (RMUs).{{Cite journal|last1=Wallace|first1=Bryan P.|last2=DiMatteo|first2=Andrew D.|last3=Hurley|first3=Brendan J.|last4=Finkbeiner|first4=Elena M.|last5=Bolten|first5=Alan B.|last6=Chaloupka|first6=Milani Y.|last7=Hutchinson|first7=Brian J.|last8=Abreu-Grobois|first8=F. Alberto|last9=Amorocho|first9=Diego|date=2010-12-17|title=Regional Management Units for Marine Turtles: A Novel Framework for Prioritizing Conservation and Research across Multiple Scales|journal=PLOS ONE|volume=5|issue=12|pages=e15465|doi=10.1371/journal.pone.0015465|pmid=21253007|pmc=3003737|issn=1932-6203|bibcode=2010PLoSO...515465W|doi-access=free}} Each RMU is subject to a unique set of threats that generally cross jurisdictional boundaries, resulting in some sub-populations of the same species' showing recovery while others continue to decline. This has triggered the IUCN to conduct threat assessments at the sub-population level for some species recently. These new assessments have highlighted an unexpected mismatch between where conservation relevant science has been conducted on sea turtles, and where there is the greatest need for conservation.{{Cite journal|last1=Pearson|first1=Ryan M.|last2=van de Merwe|first2=Jason P.|last3=Limpus|first3=Colin J.|last4=Connolly|first4=Rod M.|date=2017|title=Realignment of sea turtle isotope studies needed to match conservation priorities|journal=Marine Ecology Progress Series|language=en|volume=583|pages=259–271|doi=10.3354/meps12353|issn=0171-8630|bibcode=2017MEPS..583..259P| hdl=10072/373398 |hdl-access=free}} For example, as at August 2017, about 69% of studies using stable isotope analysis to understand the foraging distribution of sea turtles have been conducted in RMUs listed as "least concern" by the IUCN.

Additionally, all populations of sea turtles that occur in United States waters are listed as threatened or endangered by the US Endangered Species Act (ESA).{{cite web|publisher=United States Fish & Wildlife Service|title=Endangered Species Program|url=http://www.fws.gov/endangered/|access-date=April 12, 2012}} The US listing status of the loggerhead sea turtle is under review as of 2012.

^*The ESA manages sea turtles by population and not by species.

File:Protected turtle nesting area II.jpg

In the Caribbean, researchers are having some success in assisting a comeback.{{Cite journal | last = Clarren | first = Rebecca | title = Night Life | journal = Nature Conservancy | volume = 58 | issue = 4 | pages = 32–43 | year = 2008}} In September 2007, Corpus Christi, Texas, wildlife officials found 128 Kemp's ridley sea turtle nests on Texas beaches, a record number, including 81 on North Padre Island (Padre Island National Seashore) and four on Mustang Island. Wildlife officials released 10,594 Kemp's ridley sea turtle hatchlings along the Texas coast in recent years.

The Philippines has had several initiatives dealing with the issue of sea turtle conservation. In 2007, the province of Batangas declared the catching and eating of sea turtles (locally referred to as Pawikans) illegal. However, the law seems to have had little effect as sea turtle eggs are still in demand in Batangan markets. In September 2007, several Chinese poachers were apprehended off the Turtle Islands in the country's southernmost province of Tawi-Tawi. The poachers had collected more than a hundred sea turtles, along with 10,000 sea turtle eggs.{{cite news|last=Adraneda |first=Katherine |title=WWF urges RP to pursue case vs turtle poachers |work=Headlines |publisher=The Philippine Star |date=12 September 2007 |url=http://www.philstar.com/index.php?Headlines&p=49&type=2&sec=24&aid=20070911144 |archive-url=https://archive.today/20130216153133/http://www.philstar.com/index.php?Headlines&p=49&type=2&sec=24&aid=20070911144 |url-status=dead |archive-date=16 February 2013 |access-date=12 September 2007 }}

Evaluating the progress of conservation programs is difficult, because many sea turtle populations have not been assessed adequately.{{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 }} Most information on sea turtle populations comes from counting nests on beaches, but this does not provide an accurate picture of the whole sea turtle population.{{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 }} A 2010 United States National Research Council report concluded that more detailed information on sea turtles' life cycles, such as birth rates and mortality, is needed.{{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}}

Nest relocation may not be a useful conservation technique for sea turtles. In one study on the freshwater Arrau turtle (Podocnemis expansa) researchers examined the effects of nest relocation. They discovered that clutches of this freshwater turtle that were transplanted to a new location had higher mortality rates and more morphological abnormalities compared to non-transplanted clutches.{{cite journal | last1 = Jaffé | first1 = R. | last2 = Peñaloza | first2 = C. | last3 = Barreto | first3 = G. R. | year = 2008 | title = Monitoring an endangered freshwater turtle management program: effects of nest relocation on growth and locomotive performance of the giant South American turtle (Podocnemis expansa, Podocnemididae) | journal = Chelonian Conservation and Biology | volume = 7 | issue = 2| pages = 213–222 | doi=10.2744/CCB-0696.1| s2cid = 86007443 }} However, in a study of loggerhead sea turtles (Caretta caretta), Dellert et al. found that relocating nests at risk of inundation increased the success of eggs and hatchlings and decreased the risk of inundation.{{Cite journal|last1=Dellert|first1=Lauren J.|last2=O'Neil|first2=Danielle|last3=Cassill|first3=Deby L.|date=2014-06-01|title=Effects of Beach Renourishment and Clutch Relocation on the Success of the Loggerhead Sea Turtle (Caretta caretta) Eggs and Hatchlings|journal=Journal of Herpetology|volume=48|issue=2|pages=186–187|doi=10.1670/12-135|issn=0022-1511|hdl=10806/11541|s2cid=85697630}}

Most sea turtle mortality happens early in life. Sea turtles usually lay around 100 eggs at a time, but on average only one of the eggs from the nest will survive to adulthood.Wright, Sara. [http://www.blufftontoday.com/news/2010-08-06/hilton-head-island-sees-record-sea-turtle-nesting-season "Hilton Head Island sees record sea turtle nesting season."] Bluffton Today (2010): n. pag. Web. 8 Dec 2010. Raccoons, foxes, and seabirds may raid nests or hatchlings may be eaten within minutes of hatching as they make their initial run for the ocean.[http://www.seaturtlefoundation.org/threats/natural/ "Natural."] Sea Turtle Foundation. Sea Turtle Foundation, 2010. Web. 8 Dec 2010. Once in the water, they are susceptible to seabirds, large fish and even other sea turtles.

Adult sea turtles have few predators. Large aquatic carnivores such as sharks and crocodiles are their biggest threats; however, reports of terrestrial predators attacking nesting females are not uncommon. Jaguars have been reported to smash into sea turtle shells with their paws, and scoop out the flesh.Baker, Natural History and Behavior, pp. 8–16

Fibropapillomatosis disease causes tumors in sea turtles.

While many of the things that endanger sea turtles are natural predators, increasingly many threats to the sea turtle species have arrived with the ever-growing presence of humans.{{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 }}

File:logger ted 01.jpg through a turtle excluder device (TED)]]One of the most significant and contemporary threats to sea turtles comes from bycatch due to imprecise fishing methods. Long-lining has been identified as a major cause of accidental sea turtle deaths.{{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 }}{{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 | url-status =dead | archive-date =April 30, 2007 }} There is also a black-market demand for tortoiseshell for both decoration and supposed health benefits.{{cite web |author=NYSDEC | title =Atlantic Hawksbill Sea Turtle Fact Sheet | publisher =Endangered Species Unit | url =http://www.dec.state.ny.us/website/dfwmr/wildlife/endspec/athafs.html | access-date = 7 February 2007}}

Sea turtles must surface to breathe. Caught in a fisherman's net, they are unable to surface and thus drown. In early 2007, almost a thousand sea turtles were killed inadvertently in the Bay of Bengal over the course of a few months after netting.{{cite news |author= |title=Fishermen blamed for turtle deaths in Bay of Bengal |work=Science News |publisher=Reuters |date=5 February 2007 |url=https://www.reuters.com/article/us-india-turtles-idUSDEL1456220070205 |access-date=15 November 2016 |archive-url=https://web.archive.org/web/20161115114552/https://www.reuters.com/article/us-india-turtles-idUSDEL1456220070205 |archive-date=15 November 2016}}

However, some relatively inexpensive changes to fishing techniques, such as slightly larger hooks and traps from which sea turtles can escape, can dramatically cut the mortality rate.{{Cite web|url=http://www.seaturtle.org/mtn/archives/mtn113/mtn113p13.shtml|title=MTN 113:13-14 Longline Fishery Panel Discussion at the 26th Annual Sea Turtle Symposium: Cooperative Approaches to Implement Sea Turtle Bycatch Solutions in Longline Fisheries|website=www.seaturtle.org}}{{cite news | last=O'Kelly-Lynch | first=Ruth | title=Govt: Long-line fishing won't hurt birds | url=http://www.royalgazette.com/siftology.royalgazette/Article/article.jsp?sectionId=60&articleId=7d72411300300c5 }}{{dead link|date=August 2017 |bot=InternetArchiveBot |fix-attempted=yes }} Turtle excluder devices (TEDs) have reduced sea turtle bycatch in shrimp nets by 97 percent.

File:Sea turtle nest sign (Boca raton, FL).jpg, Florida]]

Light pollution from beach development is a threat to baby sea turtles; the glow from city sources can cause them to head into traffic instead of the ocean.{{cite news|url=https://www.newsherald.com/news/20181007/disorientation-huge-problem-for-panama-city-beach-sea-turtle-hatchlings|title=Disorientation a huge problem for Panama City Beach sea turtle hatchlings|last=Landeck|first=Katie|date=7 October 2018|journal=Panama City News Herald}}{{cite episode|title=The Milky Way|series=Hijos de las Estrellas|season=1|number=8|year=2014|network=Netflix|minutes=37, 43}} There has been some movement to protect these areas. On the east coast of Florida, parts of the beach known to harbor sea turtle nests are protected by fences. Conservationists have monitored hatchings, relocating lost baby sea turtles to the beach.

Hatchlings find their way to the ocean by instinctively crawling towards the brightest horizon, which has traditionally been the ocean because of the reflection of light from the moon and the stars on the water's surface, but get disoriented due to the artificial lights along the coastline.{{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}}[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] Lighting restrictions can prevent lights from shining on the beach and confusing hatchlings. Sea turtle-safe lighting uses red or amber LED light, invisible to sea turtles, in place of white light.{{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}}

File:Turtle egg kota bharu.jpg

Another major threat to sea turtles is the black-market trade in eggs and meat. This is a problem throughout the world, but especially a concern in China, the Philippines, India, Indonesia and the coastal nations of Latin America. Estimates reach as high as 35,000 sea turtles killed a year in Mexico and the same number in Nicaragua. Conservationists in Mexico and the United States have launched "Don't Eat Sea Turtle" campaigns in order to reduce this trade in sea turtle products. These campaigns have involved figures such as Dorismar, Los Tigres del Norte and Maná. Sea turtles are often consumed during the Catholic season of Lent, even though they are reptiles, not fish. Consequently, conservation organizations have written letters to the Pope asking that he declare sea turtles meat.{{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|issn = 0458-3035|language = en-US|first = Kenneth r.|last = WEISS}}

Another danger to sea turtles comes from marine debris, especially plastics, such as in the Great Pacific Garbage Patch,{{Cite web|url=https://www.seeturtles.org/ocean-plastic|title=Ocean Plastic|website=SEE Turtles|language=en-US|access-date=2019-11-20}} which may be mistaken for jellyfish, and abandoned fishing nets in which they can become entangled.

Sea turtles in all types are being endangered by the way humans use plastic. Recycling is known of and people recycle but not everyone does. The amount of plastic in the oceans and beaches is growing every day. The littering{{Cite web|url=https://www.seeturtles.org/ocean-plastic|title=Ocean Plastic|website=SEE Turtles|language=en-US|access-date=2019-12-12}} of plastic is 80% of the amount.

When turtles hatch from their eggs on the beach, they are already endangered with plastic. Turtles have to find the ocean by themselves and on their journey from land to sea, they encounter a lot of plastic. Some even get trapped in the plastic and die from lack of resources and from the sun being too hot.

Sea turtles eat plastic bags{{Cite web|url=https://www.worldwildlife.org/stories/what-do-sea-turtles-eat-unfortunately-plastic-bags|title=What do sea turtles eat? Unfortunately, plastic bags.|website=World Wildlife Fund|language=en|access-date=2019-12-12}} because they confuse them with their actual diet, jellyfish, algae and other components. The consumption of plastic is different for every breed of sea turtle, but when they ingest the plastic, it can clog their intestines and cause internal bleeding which will eventually kill them.

In 2015, an olive ridley sea turtle was found with a plastic drinking straw lodged inside its nose.{{cite news |last1=Kirkpatrick |first1=Nick |title=Sea turtle trauma: Video shows rescuers extracting plastic straw from deep in nostril |url=https://www.washingtonpost.com/news/morning-mix/wp/2015/08/17/researchers-save-a-sea-turtle-from-a-plastic-straw-in-this-traumatic-video/ |access-date=2 February 2020 |work=Huffington Post}} The video of Nathan J. Robinson has helped raise considerable awareness about the threat posed by plastic pollution to sea turtles.

The research into turtle consumption of plastic is growing. A laboratory of Exeter{{Cite web|url=https://www.cnn.com/2018/12/05/world/microplastic-pollution-turtles-study-intl-scli/index.html|title=Microplastics found in gut of every sea turtle in new study|author=Matthew Robinson|website=CNN| date=5 December 2018 |access-date=2019-12-12}} and Plymouth Marine tested 102 turtles and found plastic in every one of their stomachs. The researchers found more than 800 pieces of plastic in those 102 turtles. That was 20 times more than what was found in the last research. Those researchers stated that the most common things found were cigarette buds, tire, plastic in many forms and fishing material.

The chemicals in the plastic that sea life eats damages their internal organs and can also clog their airway. The chemicals in the plastic that they eat is also a leading cause of the death of the turtles. If the turtles are close to laying eggs, the chemicals that they ingested from the plastic can seep into their eggs and affect their offspring. It is unlikely for the baby sea turtles to survive with those chemicals in their system.

There is a large quantity of plastic in the ocean, 80% of which comes from landfills; the ratio of plankton to plastic in the ocean is one to six. The Great Pacific Garbage Patch is a swirl of garbage in the Pacific Ocean that is {{convert|20|ft|m|0|order=flip|abbr=on}} deep and contains 3.5 million tons of garbage. This is also known as the "plastic island".

Climate change may also cause a threat to sea turtles. Since sand temperature at nesting beaches defines the sex of a sea turtle while developing in the egg, there is concern that rising temperatures may produce too many females.{{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}} However, more research is needed to understand how climate change might affect sea turtle gender distribution and what other possible threats it may pose.{{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 }}

Studies have shown that climate{{Cite web|url=https://oceanconservancy.org/blog/2018/01/25/not-cool-climate-change-turning-99-sea-turtles-female/|title=Not Cool: Climate Change Turning 99% of These Sea Turtles Female|date=2018-01-25|website=Ocean Conservancy|language=en|access-date=2019-12-12}} change in the world is making sea turtles gender change. The study that was in January 2018 Current Biology "Environmental Warning and Feminization of One of the Largest Sea Turtle Populations in the World", showed how baby sea turtles were being born female a lot more than being born male. Scientists took blood samples from many baby sea turtles near the Great Barrier Reef. Prior to this study, the ratio of male to female was pretty normal. There was a little more female than there was male but it was enough to keep reproduction and life cycle normal. The study showed that there was 99% more female sea turtles then male.

The temperature{{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=2019-12-12}} of the sand has a big impact on the sex of the sea turtle. This is not common with other animals but it is with sea turtles. Warmer or hot sand usually makes the sea turtle female and the cooler the sand usually makes male. Climate change has made the temperatures much hotter than they should be. The temperature of the sand gets hotter every time it is time for sea turtles to lay their eggs. With that, adaption to the sand should occur but it would take generations for them to adapt to that one temperature. It would be hard because the temperature of the sand is always changing.

The sand temperature is not the only thing that impacts sea turtles. The rise of the sea levels messes with their memory. They have an imprinted map in their memory that shows where they usually give birth and go after they do. With the rise in water levels, that map is getting messed up and is hard for them to get back to where they started. It is also taking away their beaches that they lay their eggs on. Climate change also has an impact on the number of storms and the severity of them. Storms can wipe out the sea turtles nesting ground and take out the eggs that already laid. The rising level of water is also a way for the nesting grounds to disappear. Sea turtles maps and their nesting grounds getting destroyed is harmful to them. That is because with their maps being messed up and not being able to lay eggs where they usually do makes it hard for them to find a new place to nest. They usually stick to a schedule and the messing up of a schedule messes them up.

The temperature of the ocean is also rising. This impacts their diet and what they can eat. Coral reefs are majorly impacted by the rising temperatures and a lot of sea turtles' diet is coral reefs or in the coral reef. Most animals that live in coral reefs need the reefs to survive. With the reefs dying, the sea life around it also does, impacting many animals.

Sea turtles are very vulnerable to oil pollution, both because of the oil's tendency to linger on the water's surface, and because oil can affect them at every stage of their life cycle.{{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}} Oil can poison the sea turtles upon entering their digestive system.

Sea turtles{{Cite web|url=https://response.restoration.noaa.gov/about/media/how-do-oil-spills-affect-sea-turtles.html|title=How Do Oil Spills Affect Sea Turtles? {{!}} response.restoration.noaa.gov|website=response.restoration.noaa.gov|access-date=2019-12-12}} have a cycle that they follow from birth. The cycle depends on the sex of the turtle, but they follow it all the way through life. They start by hatching on the beach, they reach the water then move out to find food. They then start their breeding migration and then mate with another turtle. For females, they make their way to the beach to start it all over again. With males, they go back to feeding after mating and doing that over again. Oil spills can affect this cycle majorly. If the female was to go and lay eggs and ingest oil, the chemicals from the oil can get passed on to the offspring and will be hard for them to survive. The diet of the sea turtles can also be impacted by oil. If the things that they eat has oil on it or has ingested oil, it can get into their system and start attacking the insides of the turtle.

Injured sea turtles are rescued and rehabilitated (and, if possible, released back to the ocean) by professional organizations, such as the Gumbo Limbo Nature Center in Boca Raton, Florida, the Karen Beasley Sea Turtle Rescue and Rehabilitation Center in Surf City, North Carolina, and Sea Turtles 911 in Hainan, China.

One rescued sea turtle, named Nickel for the coin that was found lodged in her throat, lives at the Shedd Aquarium in Chicago.

The goal of rehabilitation is to improve sea turtles' quality of life. Rehabilitation is often carried out using treatments intended to address any injuries or illnesses that a turtle may be suffering from. Another option is analgesia. Euthanasia frequently relieves the pain of sea turtles who are seriously ill or damaged. {{Cite journal |last1=Innis |first1=Charles |last2=Finn |first2=Sarah |last3=Kennedy |first3=Adam |last4=Burgess |first4=Elizabeth |last5=Norton |first5=Terry |last6=Manire |first6=Charles |last7=Harms |first7=Craig |date=16 April 2019 |title=A Summary of Sea Turtles Released from Rescue and Rehabilitation Programs in the United States, with Observations on Re-Encounters |url=https://bioone.org/journals/chelonian-conservation-and-biology/volume-18/issue-1/CCB-1335.1/A-Summary-of-Sea-Turtles-Released-from-Rescue-and-Rehabilitation/10.2744/CCB-1335.1.short |journal=Chelonian Conservation and Biology |volume=18 |issue=1|page=3 |doi=10.2744/CCB-1335.1 |url-access=subscription }}

Sea turtles can be returned to the wild if their rehabilitation is complete and they are in optimal health. The larger turtles are given a flipper tag and a passive integrated transponder (PIT) prior to being released. Despite having identifying tags, the turtles' living conditions often make it difficult to determine the results of rehabilitation.

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,{{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}} 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.{{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|pages=6565|doi=10.1038/s41598-019-42983-4|pmid=31024029|pmc=6483986|issn=2045-2322|bibcode=2019NatSR...9.6565P}}

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.{{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 }} 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.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.

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. 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.[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.

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}}

• Cultural depictions of turtles
• Kélonia—sea turtle observatory in Réunion
• Memorandum of Understanding concerning Conservation Measures for Marine Turtles of the Atlantic Coast of Africa
• Memorandum of Understanding on the Conservation and Management of Marine Turtles and their Habitats of the Indian Ocean and South-East Asia
• Sandwatch
• Sea Turtle Association of Japan, Kuroshima Research Station
• Sea Turtle Conservancy
• Sea turtle migration
• Sea Turtles 911
• Shrimp-Turtle Case
• Threats to sea turtles
• Use of sea turtles in West African traditional medicine

{{Reflist|30em}}

• {{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 }}

{{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]

{{Testudines}}

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Category:Endangered animals

Category:Extant Albian first appearances