UNEP-WCMC - Kemp's Ridley Turtle

HABITAT Adult Kemp's Ridley are normally bottom-feeders, foraging in the same crab-rich shallow inshore waters that are swept by shrimp trawls. They remain nearshore and spend most of their time beneath the surface. Juvenile Turtles inhabit shallow waters characterised by eelgrass beds and shoal areas of sand, gravel and mud.

GEOGRAPHICAL SPREAD The single major nesting ground is a 20km stretch of beach on the Gulf of Mexico near Rancho Nuevo in the southern part of the State of Tamaulipas, north-east Mexico. A few individuals have nested sporadically to the north and south of the primary nesting site, on Padre Island (Texas), in the States of Veracruz and Tabasco (Mexico). This highly localised nesting range is in marked contrast to the scattered circumglobal distributions of most other sea turtles. Major known feeding grounds for adult Kemp's Ridley are also in the Gulf of Mexico, including the crab-rich shallow waters off Louisiana, notably around the Mississippi Delta, and the Tabasco-Campeche area of Mexico.

CURRENT POPULATION The total population of this species is thought to number no more than 900 adult females and an unknown number of males and subadults. This population has been drastically depleted since the late 1940s when over 42,000 females were recorded nesting together in a single day.

SIZE A small sea turtle, carapace length 66 to 70 cm.

WEIGHT 27 to 40kg.

AVERAGE LIFE EXPECTANCY Potentially long-lived.

NORMAL DIET Kemp's Ridley is carnivorous in adult feeding habits, mainly a bottom-feeding species. Fish, jellyfish, echinoderms, crustaceans, gastropod and cephalopod molluscs, are among recorded prey items, but crabs appear to be the favoured diet of non-hatchling Kemp's Ridley.

NORMAL LIFESTYLE Sexual maturity may be attained after about six years. Female Kemp's Ridley, emerge to nest in synchronised aggregations, termed arribadas (Spanish for arrival). The arribada nesting strategy, with the sudden mass arrival of adults and subsequent mass emergence of hatchlings, may serve as a predator swamping device. Most remigrant females of both Lepidochelys species nest on a one or two year cycle; this is in contrast to most other sea turtles, where annual nesting is rare and a three year cycle is most typical. Kemp's Ridley is unusual among sea turtles in that nesting is largely diurnal. The clutch averages 110 eggs (range 54 to 185).

PREVIOUS GEOGRAPHICAL SPREAD Before its recent drastic depletion, Kemp's Ridley was a regular and abundant species along the Florida east coast and in North Carolina, and similarly occurred regularly in New England waters, notably in Massachusetts where it is reportedly still seasonally common. It is probable that the Atlantic coast, at least as far as North Carolina or northward to the New England region, is a natural part of the developmental and foraging range of the species.

REASONS FOR DECLINE The dramatic decline of Kemp's Ridley in the 1950s and 1960s is attributed to several factors; intensive predation on eggs by local people and by coyotes, fishing for juveniles and adults, slaughter of nesting adults for meat, and incidental catch by trawlers.

CURRENT THREATS Exploitation for eggs and meat is now illegal. However, the major current direct threat to the vestigial Kemp's Ridley population is accidental catch in shrimp trawls and shark nets. Turtles not drowned in the nets may be killed once hauled aboard, partly to avoid furtherdamage to the net. Adult Kemp's Ridley Turtles are normally bottom-feeders, foraging in the same crab-rich shallow inshore waters that are swept by shrimp trawls; the species is thus particularly vulnerable to this activity .

CONSERVATION PROJECTS The Mexican Government has conducted a tagging programme at the nesting beach since 1966, and has protected the area with armed patrols. Regulations requiring the use of Turtle Excluder Devices (TED's) by shrimpers have also been introduced to reduce accidental drowning of marine turtles. A head start programme was initiated in 1978 to establish a nesting colony at the Padre Island National Seashore, Texas, as a back up to the primary nesting beach near Rancho Nuevo, Tamaulipas, Mexico. The National Mexican Turtle Centre, based in Oaxaca, hopes to educate people about the threats to marine turtles, also promoting research contributing to their conservation. Recently a increase in the numbers of nesting female Kemp's Ridleys has occurred. This has been attributed to the international effort to protect turtle nesting sites, and to the use of devices (TEDs) that prevent turtles from being trapped and drowned in shrimp nets. It has been suggested that the Kemp's Ridley might reach a population goal of 10,000 nesting turtles by 2010 if protection of nest sites, and the reduction of mortality by shrimp nets continues. Captive breeding has not yet been attempted. Adult and half-grown juveniles adapt well to captivity and have survived in public aquaria for many years.

SPECIAL FEATURES The most endangered species of marine turtle.

REFERENCES

Groombridge, B. 1982. The IUCN Amphibia Reptilia Red Data Book: Testudines, Crocodylia, Rhynchocephalia. IUCN, Switzerland.

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