(Garman, 1880)
Kemp's ridley turtle
Recognition
This small (to 74.9 cm) sea turtle has only five pleurals on each side of the heart-shaped, keeled, yellowish to gray carapace. The carapace is wider than long in adults, highest anterior to the bridge, and serrated behind. Vertebrals 1 and 5 are broader than long, but vertebrals 2-4 are often longer than broad. An additional small vertebral may occur between the 4th and 5th. The 1st pair of pleurals touches the cervical, and there are 12 to 14 marginals on each side. The bridge and plastron are immaculate white. The formula for the six large plastral scutes is: gul > an >< fem > abd > pect > hum; however, a small interanal scute may also be present, as well as one or two small intergulars. The head and limbs are gray. The head is wide and somewhat pointed anteriorly; the snout is short and broad. The bony alveolar surface of the upper jaw has a conspicuous ridge running parallel to the cutting edge.
The karyotype has not been described, but presumably involves 56 chromosomes as in other members of the Cheloniidae (Bickham, 1981).
Males have concave plastra, long tails, which extend beyond the posterior carapacial margin, and a recurved claw on each forelimb.
Distribution
Lepidochelys kempii ranges in the western Atlantic Ocean from Nova Scotia and, possibly, Newfoundland south to Bermuda and west through the Gulf of Mexico to Mexico. It also crosses the Gulf Stream to England, Ireland, the Scilly Isles, France, and the Azores, and occasionally enters the Mediterranean Sea.
Almost 100% of the nests are dug on or near the beach at Rancho Nuevo, Tamaulipas, Mexico, but scattered nesting has also been reported from beaches in Veracruz, Tabasco, and Campeche, Mexico, Colombia, Padre Island, Texas, Pinellas and Palm Beach counties, Florida, Georgetown County, South Carolina, and Brunswick County, North Carolina (Palmatier, 1993; Ernst et al., 1994).
Habitat
Kemp's ridley prefers shallow water. In the Florida Keys it is closely associated with the subtropical shoreline of red mangrove.
Natural History
Mature females are at least 52.5-60.0 cm in carapace length (Chávez, 1967; Pritchard and Márquez, 1973; Márquez, 1990); The average carapace length of nesting females is 64.6 cm (Van Buskirk and Crowder, 1994). Captives of both sexes have gained maturity in 5-7 years (Wood and Wood, 1988), but wild individuals may need 11-12 years to mature (Márquez, 1990; Zug, 1991). The size at which male L. kempii mature is unknown, as are also the gametic cycle of both sexes.
Courtship and mating occur shortly before nesting, at the surface of the water just off the beaches. The males become quite active at this time; Carr (1967) reported that one even followed a nesting female onto the beach and attempted to mount her on the way. Matings have been observed in April and June. Courtships were observed by Wood and Wood (1984, 1988) and Shaver (1992). Typically, the male pursued the female, circled to approach her head, and then bit her neck and shoulders. Next he swung his body to bring his tail near that of the female while continuing to bite her. Using the claws in his front flippers, the male secured a hold on the anterior rim of the female's carapace, while his rear flippers were placed over her posterior carapacial rim. Insertion soon followed.
Nesting occurs sporadically from April through mid-July, with a peak period in May and June (Hirth, 1980c), and is usually diurnal and is on a 1-3 year cycle (average, 1.50; Van Buskirk and Crowder, 1994). Although some females come up to nest individually, most do so in large groups (arribadas)—formerly in the thousands, but now only a few hundred. Nests are flask-shaped, and dug to a depth of 37-49 cm beneath a body pit 10-15 cm deep.
Up to four clutches (Márquez, 1990) are laid each year, with an average of 1.8 (Van Buskirk and Crowder, 1994). Intervals between nestings are 10-49 days, but usually 20-28 days. Eggs are spherical with soft white shells; the diameter is 34.6-45.5 mm; 51-185 eggs (average, 110; Van Buskirk and Crowder, 1994) make up a clutch. The numbers of eggs laid decreases with each successive clutch after the first. Incubation takes 50-70 days.
Hatchlings have a relatively elongated (38-46 mm; average 42 mm, Van Buskirk and Crowder, 1994), oval carapace with three tuberculate keels and a plastron with four longitudinal ridges. They are dark gray to black, with a white border on both flippers and carapace.
Lepidochelys kempii is predominantly carnivorous, feeding on crabs (particularly Callinectes and Ovalipes, but at least nine other genera), shrimp (Penaeus, Sicyonia), barnacles, insects, sea urchins, snails (mostly Nassurius, but other genera as well), bivalves (Corbula, Mulinia, Nuculana, Polinices, and other genera), cephalopods (including egg cases of squid), hydrozoans, jellyfish (Physalia), fish (Hippocampus, Leiostomus, Lutjanus, Stellifer), turtles (Malaclemys), and marine plants and algae (Cymodacea, Gracilaria, Halodule, Sargassum, Thalassia, Ulva, Zostera, and several other genera) (Carr, 1952; Pritchard and Márquez, 1973; Zwinenberg, 1977; Ernst et al., 1994; Burke et al., 1993a, 1993b; Dobie, 1996; Frick, 1997). It seems to be largely a bottom feeder. Captives readily eat fish.
IUCN Red List Status (1996)
Critically endangered (A1ab). This ridley's chances of survival are more precarious than those of other sea turtles. Its numbers have been decimated by fishing, nest robbing, oil spills, and the slaughter of nesting females. Fortunately, the Mexican government, in an effort to save this turtle, now protects nesting females on the beaches of Tamaulipas. A group of concerned American conservationists is transplanting eggs and hatchlings from Tamaulipas to Padre Island, Texas, a known natural nesting site, in an attempt to re-establish the breeding colony.