Caretta caretta

See Dodd (1988) for a discussion of taxonomy. Dodd (1988, 1990) recommended that subspecies not be recognized. Accordingly, Crother (2012, 2017) and Turtle Taxonomy Working Group (2012, 2021) recognized no subspecies.

MtDNA data from major nesting populations in the Atlantic, Indian, and Pacific oceans and the Mediterranean Sea indicate that most breeding colonies have diagnostic genetic characteristics, indicating strong natal homing by nesting females (Bowen et al. 1994). Two major matrilines were identified, and each occurred in both Atlantic-Mediterranean and Indian-Pacific samples. This was attributed to recent interoceanic gene flow, probably mediated by the ability of this turtle to utilize habitats around southern Africa.

Crother et al. (2008) has returned to the use of "sea turtles" (rather than "seaturtles") as part of the standard English name for marine turtles. The combined name has not been used recently in the literature.

Wide distribution and not uncommon in warm oceans and seas; a few subpopulations declining significantly in recent years, but others stable or increasing. Many nesting sites are protected, though perhaps not adequately; subject to many threats that land conservation alone cannot solve.

Warmer parts of Atlantic, Pacific, and Indian oceans, and Mediterranean and Caribbean seas (Bolten et al. 1992, Conant et al. 2009, COSEWIC 2010, Casale and Tucker 2017, Environment and Climate Change Canada 2020). Ranges into temperate zones in summer; rare or absent far from mainland shores. Major nesting areas are in warm temperate and subtropical areas in Oman, the southeastern U.S., Mexico, Australia, South Africa, the Mediterranean, and Japan (Dodd 1992). Conant et al. (2009) divided the global population into nine Distinct Population Segments (DPS), but subsequently the IUCN Red List assessment divides the North Indian Ocean DPS into two and thus defines 10 subpopulations. Separate Red List assessments are available for each IUCN subpopulation: North Pacific (Casale and Matsuzawa 2015), South Pacific (Limpus and Casale 2015), North West Indian Ocean (Casale 2015a), North East Indian Ocean (Casale 2015b), South East Indian Ocean (Casale et al. 2015), South West Indian Ocean (Nel and Casale 2015), North West Atlantic (Ceriani and Meylan 2017), North East Atlantic (Casale and Marco 2015), Mediterranean (Casale 2015c), and South West Atlantic (Casale and Marcovaldi 2015).

The world's largest nesting aggregation was on Masirah Island, Oman, although this has declined over the past few decades to 10,223-11,500 females (Willson et al. 2020).

The North West Atlantic subpopulation breeds mostly along the southeast coast of the United States (Shoop 1985, Dodd 1988, NMFS and USFWS 2011) and on the Yucatan Peninsula of Mexico (Ceriani and Meylan 2017), and its marine habitats extend throughout all the north and central Atlantic Ocean (northwest, northeast, central west and central east). This subpopulation hosts one of the two most significant nesting assemblages in the world, and over 85% of the nesting effort within the subpopulation is on beaches in peninsular Florida (NMFS and USFWS 2011). About 90% of the population nests in Brevard, Indian River, St. Lucie, Martin, Palm Beach, and Broward counties, Florida (CSTC 1990). Large numbers occur off primary nesting beaches in Florida during spring and summer (CSTC 1990). Nests regularly in small numbers in Virginia and sometimes north to New Jersey. In recent years a few have nested on barrier islands along the Texas coast. Chesapeake Bay is an important habitat for subadults in summer. Occurs in summer in waters off the northeastern U.S., mainly between Long Island and Cape Hatteras, usually in water less than 60 m deep (Shopp and Kenney 1992). See Seminoff et al. (2004) for information on occurrence in the Gulf of California. See Dodd (1988, 1990) for further details.

Represented by many occurrences throughout much of the range. Exact number not known, depends somewhat on partly subjective determination of EO-boundaries. There are at least two dozen major nesting areas worldwide (Dodd 1990).

Threats are summarized by Wallace et al. (2011) and National Marine Fisheries Service (2020), presented in order of importance here.

1. Fisheries bycatch: capture in fishing gear targeting other species. Bycatch occurs in numerous types of fishing, including pelagic and demersal longlines; drift and set nets; bottom and mid-water trawling; fishing dredges; pound nets and weirs; haul and purse seines; pots and traps; and hook and line gear. Illegal, unreported, and unregulated fishing is likely the single greatest source of bycatch.
2. Direct hunting/fishing of turtles or eggs
3. Coastal development of nesting habitat: alteration of coastal environments by construction, dredging, beach modification, etc. Erosion, shoreline structures, and coastal development reduce the availability of suitable nesting habitat. Artificial lighting, beach use, beach debris, and shoreline structures and coastal developments deter nesting females and prevent hatchlings from reaching the sea.
4. Pollution and Pathogens: marine pollution and debris that affect marine turtles (i.e., through ingestion or entanglement, disorientation caused by artificial lights), as well as impacts of pervasive pathogens (for example fibropapilloma virus).
5. Climate change: increasing nesting beach temperatures affecting hatchling sex ratios, sea level rise, storm frequency and intensity affecting nesting habitats, etc.).

Threatened through direct exploitation for food (including eggs) and curio materials, incidental take (chiefly by drowning in shrimp trawls), and by habitat degradation, including beach development, beachfront lighting (Peters and Verhoeven 1994, Salmon and Witherington 1995), ocean pollution (including marine debris, which may be ingested), and dredging (direct kills and injuries). Beach armoring, including sea walls, rock revetments, riprap, sandbag installation, groins, and jetties, can result in loss of nesting beaches due to accelerated erosion, prevention of natural beach and dune accretion, and interference with females attempting to reach suitable nesting sites. Beach cleaning operations can destroy nests or produce tire ruts that inhibit movement of hatchlings to sea. The effect of beach restoration may depend on sand type used and subsequent management. Additional threats include predation and/or trampling of eggs and young by raccoons and feral mammals, trampling/crushing of eggs or young by vehicles or human pedestrians, deaths caused by collisions with boats (e.g., in southeastern and southern Florida and shallow coastal bays of the Gulf of Mexico) and intentional attacks by humans (fishermen) (Mitchell 1991). Long-term threats include sea level rise which, coupled with inland urbanization, may reduce available nesting beaches. Since sexual differentiation depends on incubation temperature, there is concern that global warming may result in an imbalance in the sex ratio (Mrosovsky and Provancha 1989). Annual mortality due to drowning in shrimp nets has been estimated at 5000-50,000 in the southeastern U.S.; an additional 550-5500 may die each year from other human activities (CSTC 1990). The fall bottom fishery and black drum fishery may be having adverse effects on loggerheads that use Chesapeake Bay (Mitchell 1991). Susceptible to entanglement and drowning in pound net hedging in Chesapeake Bay (Lutcavage and Musick 1985). In Georgia, predation by the imported fire ant may be a serious threat to eggs and hatchlings (Moulis 1997). See USFWS (1998) for detailed information on certain threats, including beach erosion, beach armoring, beach nourishment, artificial lighting, beach cleaning, increased human presence, recreational beach equipment, exotic dune and beach vegetation, nest loss to abiotic factors, predation, and poaching.