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New Jersey Endangered and Threatened Species Field Guide
Kemp's ridley turtle
Species Group: Reptile
This is the smallest of all sea turtles. From above, the short, chunky shell appears broadly heart-shaped to nearly round, with high vertebral projections and serrated edges. The turtle has a moderate-sized triangular head and a somewhat hooked beak with large crushing surfaces. The plastron has several small pores on each side, which lead to Rathke's glands (secretory structures that release an odiferous substance that may play a pheromonal role when females mass together off their nesting beaches). Each foreflipper has one visible claw, with one or two claws on the rear clippers.
The color of the adult skin and shell is plain olive-gray above, and white or yellowish underneath. When wet, hatchlings are jet black on both sides, with two visible flipper claws. As the turtle matures, the plastron changes to white, then yellow while the carapace changes to gray, then olive green.
Adults weigh on average around 100 pounds with a carapace length of 24-28 inches.
Distribution and Habitat
Unlike land turtles from which they evolved more than 150 million years ago, sea turtles spend almost their entire lives in the sea. When active, they often come to the surface to breathe, but can remain underwater for several hours at a time while resting.
Though most sea turtles inhabit warm, tropical and subtropical waters, they migrate northward as water temperatures increase in the late spring and summer and remain in northern waters until late fall. From late May until November, New Jersey coastal waters provide important seasonal foraging habitat.
Kemp’s ridley turtles are found only within the Gulf of Mexico and the U.S. Atlantic coast from Florida in the south to Maine and Nova Scotia in Canada. They are typically found in nearshore shallow waters. They have been observed within Barnegat Bay in New Jersey.
Nearly 95% of nesting activity occurs within the state of Tamaulipas, Mexico. Nesting also occurs in Veracruz, Mexico and southern Texas within the U.S., but on a much smaller scale. An occasional nest has also been documented in Florida and the Carolinas. They do not nest as far north as New Jersey.
After emerging from the nest, hatchlings make their way to the relative safety of the ocean. They then swim to offshore areas, where they are believed to live for several years feeding near the surface on a variety of small plants and animals. Once their shells are 8-10 inches in length (around 2-3 years of age), they’ll travel to foraging grounds in coastal areas for larger prey.
Hatchlings will feed on small crabs, plants, and snails. Adults feed on bottom-dwelling animals such as mollusks and crustaceans, but crabs comprise the bulk of their diet.
Kemp’s ridley turtles begin mating in March. Nesting occurs between April and August. Females return to the beaches where they were born in order to lay their eggs. When female Kemp's ridleys come ashore to nest, they do so at the same time and at the same nesting beach. Wave upon wave of females come ashore together and nest in what is known as an "arribada," which means "arrival" in Spanish.
Females lay an average of 3 clutches of about 110 eggs at intervals of about 3 weeks, every 1.5 years. Kemp’s ridleys are the only sea turtle species which nests primarily during daylight hours. Eggs hatch in about 2 months. Egg mortality may result from predation, beach erosion, invasion of clutches by plant roots, crushing by off-road vehicles, or flooding by sea water or excessive rainfall. The gender of hatchlings is affected by incubation temperature, with warmer temperatures resulting in a higher number of females and cooler temperatures producing mainly males. Hatchlings emerge from the nest typically during darkness, each weighing about half an ounce and measuring 1.5 inches. Of every thousand hatchlings, only a few are believed to survive to adulthood. Once they reach water, male hatchlings will never return to land while females will only do so to nest.
Kemp’s ridleys are found in New Jersey waters typically between summer and fall, when water temperatures are warmer. When water temperatures begin to drop, they must migrate south or risk dying or becoming “cold-stunned”. “Cold-stunning” occurs when sea turtles become immobile due to the dramatic decrease in water temperature (usually below 50°F) making it impossible for them to escape the cold water and migrate to warmer water. A cold-stunned sea turtle may appear to be dead, but may actually be alive. Without proper intervention a cold-stunned sea turtle will inevitably die.
Aside from humans, the only predator of adult green turtles is large sharks. Hatchlings may be preyed upon as soon as they leave their nest by raccoons, crabs, and birds. Once in the ocean, hatchlings may also be preyed upon by large fish and seabirds.
Current Threats, Status, and Conservation
Kemp’s ridley populations have been decimated by overharvesting of adults and eggs, loss of nesting habitat, interactions with fisheries, and entanglement or ingestion of marine debris. Their populations are currently a small fraction of their historical size. The number of Kemp's ridley females at the species' primary nesting site, a beach on the Gulf of Mexico near Ranch Nuevo, Mexico, plummeted from 40,000 in 1947 to just 200 by 1978. As a result of such declines, the Kemp’s ridley was listed as federally endangered in 1970 and was listed as endangered by the state of New Jersey in 1979. Since being better protected, the number of nests has been increasing with almost 7,000 nests counted in 2003.
Kemp’s ridley turtles are currently faced with many threats such as the direct exploitation for food (including eggs), entanglement in fishing gear, oil spills, habitat degradation (such as beach development), beachfront lighting, ocean pollution (including marine debris, which may be ingested), and dredging (direct kills and injuries). Beach cleaning operations can destroy nests or produce tire ruts that inhibit movement of hatchlings to sea. Additional threats include predation and trampling of eggs and young by raccoons and feral mammals, crushing of eggs or young by vehicles or humans, collisions with boats and intentional attacks by fishermen. 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.
Habitat use of sea turtles within New Jersey waters is poorly understood. The degree to which New Jersey plays a critical function in providing foraging habitat and migration corridors is unknown. Surveys are currently being conducted off the New Jersey coastline in order to determine where sea turtles are located, how many individuals are there, and during what time of year. Based on these findings, further knowledge regarding their habitat use in New Jersey waters may be gained and attention may then focus on protecting important habitats.
Text derived from the book, Endangered and Threatened Wildlife of New Jersey. 2003. Originally edited by Bruce E. Beans and Larry Niles. Edited and updated Michael J. Davenport in 2010.
Species: L. kempii
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