Systematics: Described originally as Thalassochelys (Colpochelys) Kempii by Samuel Garman in 1880, based on two specimens from the Gulf of Mexico. Smith and Taylor (1950) restricted the type locality to Key West, Florida. It was first placed in the genus Lepidochelys by Barr (1890). In the Virginia literature this species has been included under the name Caretta kempi (Dunn, 1936) and L. olivacea kempi (Reed, 1957b; Hardy, 1962). The current spelling of kempii was established by Carr (1952). No subspecies are recognized.

Description: This is the smallest sea turtle, reaching a maximum of 76 cm (29.5 inches) carapace length (CL) and 49 kg (108.5 lb) body mass (Smith and Smith, 1979). In Virginia, the largest known Kemp's Ridley Sea Turtle was 58.7 cm curved CL (Keinath et al., 1991).

Morphology: Carapace smooth, keeled, round, and serrated along the posterior margin; carapace as wide as long; marginal scutes 12-14 on each side, pleurals 5/5, and vertebrals 5; anteriormost vertebral rhomboidal in shape, and it and 1st pleural scute on each side contact cervical scute on leading edge of carapace; 4 large inframarginal scutes on each bridge, each with a small pore near posterior margin; head, which cannot be withdrawn into shell, wide (18.2-28.2% of CL; Lutcavage, 1981) and somewhat pointed.

Coloration and Pattern: Carapace usually gray in color but sometimes greenish or blackish; bridge and hingeless plastron white; head and limbs gray or olive. Each fore-flipper bears 1 large claw and sometimes a very small 2d claw.

Sexual Dimorphism: There is no apparent sexual dimorphism in body size (Wilson and Zug, 1991). The tail in adult males extends beyond the posterior margin of the carapace; it does not in adult females.

Juveniles: Hatchlings have elongated, oval shells with 3 longitudinal keels on the 1st 3 vertebral scutes. These turtles are dark gray to black dorsally and ventrally. The flippers and carapace are edged in white (Ernst and Barbour, 1972). Hatchlings may be entirely chocolate brown (J. A. Keinath, pers. comm.). Hatchlings measured 38-46 mm CL (ave. = 42.7) and weighed 13.5-21.0 g (ave. = 16.4) (Hirth, 1980b).

Confusing Species: This species may be confused with Loggerhead Sea Turtles (Caretta caretta), which are reddish brown in color, larger, and possess 3 enlarged bridge scutes, or with Green Sea Turtles (Chelonia mydas) and Atlantic Hawksbill Sea Turtles (Eretmochelys imbricata), which have a triangular anteriormost vertebral scute and 4 pleural scutes, of which the 1st does not touch the cervical scute.

Geographic Variation: None known.

Biology:Lepidochelys kempii inhabits marine waters in Virginia. In the Chesapeake Bay, these turtles are often associated with eelgrass meadows (Lutcavage and Musick, 1985). The bay is a major developmental habitat for immature Kemp's Ridley Sea Turtles; no other location in the world harbors as many individuals in this size class each summer (Keinath et al., 1987).Kemp's Ridley Sea Turtles are found in the bay May through November when the water temperature is above 18-20°C (Musick et al., 1985; Keinath et al., 1987). During the period of 1979-1990, 53 live, 8 sick or injured, and 88 dead ridleys were recorded by Virginia Institute of Marine Science (VIMS) personnel (Keinath et al., 1991). Kemp's Ridley Sea Turtle frequent shallower water than loggerheads, particularly shoal areas close to shore (Musick et al., 1985).

Kemp's Ridley Sea Turtles use the Chesapeake Bay as a summer feeding area (Hardy, 1962) and eat primarily blue crabs (Callinectes sapidus) found in seagrass beds (Lutcavage and Musick, 1985). Other prey recorded for this species are clams, snails, and, occasionally, marine plants (Ernst and Barbour, 1989a).

Age at maturity is >8-10 years (Keinath et al., 1991). Most of the nesting of this species occurs on one beach on the coast of Tamaulipas, Mexico (Hirth, 1980b); no nesting occurs in Virginia. Mating takes place in water off the beach just before nesting (Ernst and Barbour, 1989a), which occurs at 1- or 2-year intervals (Hirth, 1980b). Females arrive on shore singly or in large groups called ar- ribadas (Spanish for "arrival"), crawling ashore during the day between April and July and laying their eggs on the beach or in the dunes. Hirth (1980b) reported that female ridleys (59.5-75.0 cm CL) laid an average of 110 eggs (54-185) per nest. Up to three clutches were laid by each female at intervals of 10-28 days. Eggs were spherical, 35.0-44.5 mm in diameter (ave. = 38.9), and weighed 24-41 g (ave. = 30.0); incubation period was 50-70 days (ave. = 54).

Eggs in nests are eaten by a variety of animals, including humans, and the hatchlings are preyed upon by birds, mammals, and crabs when they are crawling to the sea after nest emergence. In the ocean, hatchlings are eaten by sea bass, and individuals of all size classes are killed by sharks (Ernst and Barbour, 1972). Sources of mortality in Virginia are propeller wounds, entanglement in gill nets, crab pot lines, and pound net leaders (with subsequent drowning); puncture wounds from gunshot or gaff; cold stunning; and bone and other diseases (Musick et al., 1985; Keinath et al., 1991). Commensals found on Kemp's Ridley Sea Turtles in Virginia were several barnacles and unidentified bryozoans (Lutcavage, 1981; Lutcavage and Musick, 1985). High rates of mortality coincide with the spring black drum (Pogonias cromis) fishery and the fall flounder (Paralichthys dentatus) trawl fishery (Keinath et al., 1991).

Little is known of the population ecology of this species. Females migrate from foraging areas in the Gulf of Mexico to the beach in Tamaulipas. Juveniles may enter the Gulf Stream and spend several years of their lives drifting in the Sargasso Sea along with debris and biotic resources (Carr, 1986, 1987). Several Kemp's Ridley Sea Turtles have been tagged and subsequently recaptured (Musick et al., 1985; Byles, 1988) . One Kemp's Ridley Sea Turtle released at Mobjack Bay on 1 June 1988 was recaptured in the Potomac River on 25 May 1989. Another was captured in the Potomac River on 30 August 1988, released in the York River on 26 September 1988, and recaptured in the Potomac River on 26 May 1990 (Keinath et al., 1991). Of two other ridleys captured, tagged, and released in the Chesapeake Bay, one was recaptured alive on the North Carolina coast and the other was found dead on a Florida beach. The estimated annual Kemp's Ridley Sea Turtle population in the Chesapeake Bay is 311-464 (Keinath et al., 1991).

Ernst and Barbour (1972) report this turtle to be "bad-tempered," behaving violently by thrashing flippers and biting. However, VIMS personnel found juveniles to be docile (J. A. Keinath and J. A. Musick, pers. comm). Byles (1988) found that ridleys remained on the surface four times longer than loggerheads between dives and that they assumed a low profile while on the surface; the carapace was barely visible.

Remarks:Florida fishermen mistakenly believe that this species is a hybrid between the Atlantic Hawksbill Sea Turtle (Eretmochelys imbricata) and the Loggerhead Sea Turtle (Caretta caretta), and call it the bastard turtle (Carr, 1956). It has also been called the dinner plate turtle because of its resemblance to one. Chesapeake bay fishermen call this turtle "green fin".

The term arribada is used to describe the mass emergence of this species from the Gulf of Mexico on the nesting beach (and the Kemp's Ridley Sea Turtle, Lepidochelys kempii, elsewhere) (but see below). The primary nesting beach used by this species was not discovered by scientists until about 1961, when a film made in 1947 first surfaced (Phillips, 1989).

Conservation and Management:Lepidochelys kempii is the most endangered species of sea turtle in the world. It is listed as endangered under the U.S. Endangered Species Act. On one day in 1947, 40,000 females were seen coming ashore to nest on one beach, but by 1979 there were only a few hundred (Hirth, 1980b; Phillips, 1989) . There are only about 200 adult females alive today (C. H. Ernst, pers. comm.). Arribidas are a thing of the past.

The use of the Chesapeake Bay in Virginia as a developmental habitat by immature Kemp's Ridley Sea Turtles renders the bay an especially critical feature in the survival of this species. The research conducted by VIMS personnel is providing important information on this turtle. Keinath and Musick (1991d) summarized the plight of this species and provided recommendations for its conservation in the Chesapeake Bay. All standings should be reported to VIMS. Private citizens can also play a role in sea turtle conservation by supporting the restoration of the Chesapeake Bay, especially the efforts to restore the seagrass beds. A major source of mortality is drowning in shrimp nets. Therefore, if turtle excluder devices (TEDs) are not used on all North American shrimp nets, this species may become extinct.