Systematics: Originally described by Carolus Linnaeus in 1758 as Testudo Mydas, based on three shells from "insulas Pelagi: insulum Adscensionis" (= Ascension Island). Mertens and Muller (1928) restricted the type locality to "Insel Ascension." Although the shells are actually those of Caretta caretta, Linnaeus's formal description of C. mydas is considered to be valid (Wallin, 1985; comments in Iverson, 1992). The genus Chelonia was first used for this species by Brongniart (1800).

The Black Turtle of the Pacific Ocean has been considered a separate species (Chelonia agassizii) by some authors (e.g., Pritchard and Trebbau, 1984, SSAR Contrib. Herpetol. 2: 1–403), a subspecies of Chelonia mydas by others (Kamezaki and Matsui, 1995, J. Herpetol. 29: 51–60), and synonymous with Chelonia mydas by others (e.g., Bowen et al., 1992, Evolution 46: 865–881). We follow Parham and Zug (1996, Marine Turtle Newsl. 72: 2–5) and Karl and Bowen (1999, Cons. Biol. 13: 990–999) in not recognizing it taxonomically until more work is done.

Description: A moderate- to large-sized marine turtle reaching a maximum carapace length (CL) of 153 cm (60.2 inches; Ernst and Barbour, 1989a) and a body mass of 340 kg (750lb: Carr, 1952). In Virginia, CL was 28-42 cm and body mass was <20 kg (Barnard et al., 1989).

Morphology: Carapace oval to heart-shaped, smooth, and weakly serrated posteriorly; middorsal keel lacking; marginal scutes 12/12, pleural scutes 4/4, and vertebrals scutes 5; 1st vertebral scute triangular in shape, cervical scute on leading edge of carapace separated from 1st pleural scutes on each side by 1st vertebral; bridge with 4 enlarged inframarginal scutes lacking pores; 2 prefrontal scutes on dorsum of head located between eyes.

Coloration and Pattern: Carapace olive to brown, gray, or black in color; a variable number of yellow, green, brown, copper, or black streaks or blotches on carapace, or a mottled pattern may be present; bridge and hingeless plastron cream to yellowish in color and patternless; head and limbs brown, olive, gray, or black; scales often edged in yellow.

Sexual Dimorphism: The tail of males is strongly prehensile, extends beyond the posterior margin of the carapace, and is tipped with a claw-like appendage. In females, the tail rarely extends beyond the carapace. Males possess 1 or 2 elongated, curved claws on each of the forelimbs; they are short and straight in females.

Juveniles: The carapace of hatchlings and juveniles is brown to dark green and keeled. The undersurface is white, and the head and flippers are black. The limbs and all scutes on the shell are edged in white. This color pattern is an example of countershading, a means of being cryptic to potential predators from above and below in the open water. Hatchlings had a CL of 41-59 mm (ave. = 50.2) and weighed 18-35 g (ave. = 24.9) (Hirth, 1980b).

Confusing Species: Loggerheads (Caretta caretta) have a reddish-brown carapace; Kemp's Ridley Sea Turtle (Lepidochelys kempii) also have 5 pleural scutes, the anteriormost of which contact the cervical scute, and a rectangular 1st vertebral. Atlantic Hawksbill Sea Turtle (Eretmochelys imbricata imbricata) have 2 sets of prefrontal scutes.

Geographic Variation: None in Virginia.

Biology: While more common in North Carolina and in states further south, Green Sea Turtles are relatively rare in Virginia. All verified observations are of juveniles. Seven stranded (dead) individuals and two live turtles were recorded by Virginia Institute of Marine Science (VIMS) personnel between 1979 and 1988 (Barnard et al., 1989). Dead Green Sea Turtles have been found in Virginia waters August through December and live ones between June and September. Adults and immatures occupy shallow waters with an abundance of submerged aquatic vegetation (Carr, 1952). For several years after hatching, the juvenile habitat is the Sargasso Sea and the open-ocean pelagic drift of debris, with their associated flora and fauna (Carr, 1987). These turtles drift with the ocean currents between the Americas and the islands off western Africa.

Juvenile Green Sea Turtles are more carnivorous than adults, feeding on mollusks, crustaceans, sponges, and jellyfish (Ernst and Barbour, 1989a). Adults in the Caribbean and the Gulf of Mexico feed almost exclusively on submerged seagrasses (Hirth, 1971). Unlike other sea turtles, Green Sea Turtles can digestplant material (Bjorndal, 1979). Numerous animals, including humans, rob eggs from the nests. Hatchlings on the beach are prey of various mammals and birds (Ernst and Barbour, 1972). In the ocean, sharks, dolphins, and some fish are known to prey on juveniles and immatures (Hirth, 1971; Witham, 1974). Adults are eaten by humans and sometimes attacked in the ocean by sharks (Carr, 1967).

All nesting grounds of this sea turtle are tropical (Hirth, 1980b). Females nest on the same beach every 2 years (Carr and Carr, 1972). Females crawl ashore at night and lay 3-238 eggs (ave. = 111.0) in nest cavities dug in the sand at or behind the dune line (Ernst and Barbour, 1972; Hirth, 1980b). Hirth reported that a single female may nest six to eight times per season at an interval of 2-21 days (Hirth, 1980b) but may follow a 2- to 3-year nesting cycle. The round eggs were 37-58 mm in diameter and weighed 29-60 g; incubation was usually 42-90 days (Hirth, 1980b). Warm nest temperatures produce females and cool nest temperatures produce males (Morreale et al., 1982).

The navigational abilities of this turtle have been studied extensively. Migrations from feed ing areas in Brazil to nesting beaches on Ascension Island of up to 2,000 km have been recorded (e.g., Carr, 1967; Carr and Coleman, 1974). The mechanisms (visual, olfaction, celestial navigation, magnetic orientation) by which these turtles migrate long distances have been examined by several authors (see lists in Carr, 1980, 1987; Pritchard and Trebbau, 1984). Juvenile Green Sea Turtle sometimes migrate long distances northward from southern locations, such as one captive released in Florida and recaptured 16.5 months later on a New Jersey beach (Witham, 1980). Immature turtles breaking away from the Gulf Stream current (see Carr, 1986, 1987) may be a source of immigrants into Virginia waters, in addition to those migrating north along the coast.

Remarks: The common name, Green Sea Turtle, is based on the greenish color of its body fat (called calipee), the primary ingredient in clear turtle soup (Keinath and Musick, 1991b). This turtle and its eggs have been and are eaten the world over by numerous human cultures (see Bjorndal, 1981). Fishermen in the Chesapeake Bay call them "green fins" but are unable to distinguish green sea turtles from ridleys (J. A. Keinath, pers. comm.).

Considerable research has been conducted on the ecology and conservation of this species since Archie Carr (1909-1987) began his work in the early 1950s. Much of what is known about Green Sea Turtles worldwide is based on his research and that of his students.

Conservation and Management: Humans continue to have a devastating effect on the Green Sea Turtle throughout the world. Populations from some nesting beaches have been completely extirpated, and several countries continue to harvest adults (Bjorndal, 1981). This species has been the most economically important reptile in the world (Carr, 1956). It is listed as threatened under the U.S. Endangered Species Act. Florida populations are listed as endangered. VIMS maintains records of all strandings and observations in Virginia's waters. Keinath and Musick (1991b) listed the threats to this species and discussed conservation recommendations. More public education is needed to heighten awareness of this and other sea turtles, and of the importance of the Chesapeake Bay in their survival.