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Lepidochelys kempiiAtlantic Ridley, Kemp’s Ridley Seaturtle

By Zachary Klug

Geographic Range

Kemp’s Ridleys (Lepidochelys kempii) can be found from Nova Scotia and Newfoundland to Bermuda. Nesting Ridleys are found mainly in the Gulf of Mexico. In migration, they follow two major routes: one heads north to the Mississippi coastline and the second extends southward to the shores of the Yucatan Peninsula at the Campeche Bank. (U.S. National Park Service, 2003; ; Ernst and Barbour, 1972; Wilkinson, 2003)

Habitat

Lepidochelys kempii mainly stays near shallow coastal regions characterized by bays and lagoons. These turtles prefer waters that have sandy or muddy bottoms, but also may take to the open seas. At sea, this species has the ability to dive to great depths.

This species is rarely seen on shore, but it is not uncommon to see L. kempii floating in the water just offshore. Females come on shore to nest. (; Ernst and Barbour, 1972)

Physical Description

Lepidochelys kempii is the smallest species of sea turtle, measuring from 55 to 75 cm in length. Average length is 65 cm. Individuals weigh between 30 and 50 kg. The head and limbs (flippers) are non-retractile. The shell is streamlined, making this turtle extremely hyrdrodynamic. The carapace is a gray-olive color, whereas the plastron is an off-white to light yellow color.

Lepidochelys kempii has four limbs; two foreflippers and two hindflippers. The foreflippers power the turtle through the water while the hindflippers are used to steer and stabilize the turtle in the water. One to two claws are present on each foreflipper.

Ridleys have an upper eyelid for eye protection. As turtles, they lack teeth, and the jaw has a broad-beak shape. The external features of males and females do not differ until they reach maturity. Males are characterized by longer, thicker tails, and may have larger curved foreflippers. (; Ernst and Barbour, 1972)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range mass
    30 to 50 kg
    66.08 to 110.13 lb
  • Range length
    55 to 75 cm
    21.65 to 29.53 in

Development

Eggs are deposited on shore and incubate for an average of 55 days. Embryo development is temperature dependent. Lower nest temperatures tend to produce more males, whereas higher temperatures tend to produce more females.

Hatchlings uses a caruncle (temporary tooth) to break open the egg. After a hatchling escapes from the egg, it may take 3 to 7 days to crawl to the surface of the beach. Hatchlings emerge from the sand at night and immediately crawl towards the water. To locate the sea, hatchlings apparently orient themselves toward the greater light intensity reflected off the water. There may also be an internal magnetic compass that directs them to the water. After an individual hatchling enters the water, it goes into a “swim frenzy” for 24 to 48 hours. The hatchling swims into deeper water that protects it from predators.

The first year of life is spent away from shore. This year is dubbed the “lost year” because individuals in this age class are rarely seen near costal regions.

Lepidochelys kempii takes 11 to 35 years to reach maturity. (U.S. National Park Service, 2003; ; Wilkinson, 2003)

  • Development - Life Cycle
  • temperature sex determination

Reproduction

Individuals of this species spend most of their lives in isolation, generally coming into contact with conspecifics only to mate and to nest.

Mating takes place in the water. Males use their long curved flippers and claws to grip a female during mating.

Females swim to shore in a congregation called a “arribada,” then nest on beaches near the Texas-Mexico border (Tamaulipas Mexico, Padre Island National Seashore). A female uses her foreflippers to dig a body pit which is deep enough for her carapace to be level with the surrounding sand. She then uses her hindflippers to dig the cavity into which the eggs will be deposited. After the eggs are deposited, the female fills in the egg cavity and body pit with her hindflippers and uses her plastron to erase markings of the nest.

The eggs are leathery and covered in mucus which protects them from breaking as they are laid. Females may spend two or more hours nesting.

Females nest every two to three years, and may lay between one and nine clutches per nesting season. Females lay between 50 and 200 eggs per clutch. The nesting season extends from April to July.

Both males and females are reported to reach sexual maturity between the ages of 11 and 35 years. (U.S. National Park Service, 2003; )

  • Breeding interval
    Females breed every two or three years, but can lay multiple clutches within a single breeding season.
  • Breeding season
    The breeding season is from April to July.
  • Range number of offspring
    50 to 200
  • Average number of offspring
    110
    AnAge
  • Average gestation period
    55 days
  • Average gestation period
    60 days
    AnAge
  • Range age at sexual or reproductive maturity (female)
    11 to 35 years
  • Range age at sexual or reproductive maturity (male)
    11 to 35 years

Females invest energy in the production of eggs and the digging of the nest. However, after providing their eggs with some protection by burying them, females expend no further energy or effort in caring for their young. Young are independent from the time of hatching. (U.S. National Park Service, 2003; ; Wilkinson, 2003)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Mortality for L. kempii is very high around the time of hatching. For individuals reaching adulthood, lifespan generally ranges from 30 to 50 years. ()

  • Typical lifespan
    Status: wild
    30 to 50 years

Behavior

This species is strongly adapted for swimming, spending nearly all of its life in the water. These turtles are migratory. Lepidochelys kempii spends most of its life in relative isolation. Social contact apparently occurs only during mating and nesting. The activity of these animals during days versus nights has not been well studied.

Home Range

Home ranges for individuals of this species have not been reported. ()

Communication and Perception

It is not known to what extent sea turtles communicate with one another. They make grunting noises which can be heard by other turtles, and apparently use these vocalizations to locate each other. Visual cues are probably important in identifying other members of their species, and some tactile communication undoubtedly occurs during mating. However, the bulk of communication in this species remains undescribed. (Scholastic, Inc., 2001; Scholastic, Inc., 1998; Scholastic, Inc., 2001; Scholastic, Inc., 1998; Scholastic, Inc., 2001; Scholastic, Inc., 1998)

Food Habits

Lepidochelys kempii feeds on floating crabs, mollusks, shrimp, jellyfish and some vegetation. The jaws of these turtles are shaped for crushing and grinding. (; Ernst and Barbour, 1972)

  • Animal Foods
  • mollusks
  • aquatic crustaceans
  • cnidarians

Predation

Lepidochelys kempii is most vulnerable as a hatchling crawling from the nest to the shore. The slow-moving hatchlings make easy targets for herons, dogs, raccoons, and a variety of seabirds. The primary predatory threat to adults comes from sharks, especially the tiger sharks. Killer whales have also been known to consume sea turtles.

Human interference with nesting behavior may facilitate predation, and act as a barrier to this species. Lights around nesting areas confuses hatchlings about which way to crawl, sometimes causing them to crawl away from the water. Trash and noise can cause females to turn around from the nesting beach and back into the water, preventing deposition of eggs. The turtles are also hunted illegally to harvest meat. The shells can be made into combs and eyeglass frames. Eggs are also illegally collected because it is believed they have an aphrodisiac effect. (; Ernst and Barbour, 1972)

Ecosystem Roles

Sea turtles have no significant economic role. Eggs and turtles were harvested in the past for reasons outlined under "Predation", but the harvesting of turtles or their eggs is now illegal. ()

Economic Importance for Humans: Positive

As a result of illegal harvesting, sea turtle meat may be eaten, and shells be made into combs or eyeglass frames. The eggs of L. kempii are believed to have an aphrodisiac effect. ()

Economic Importance for Humans: Negative

There is no known direct economic importance for humans. ()

Conservation Status

Lepidochelys kempii is currently listed as endangered by the United States Fish and Wildlife Service and IUCN.

Contributors

Zachary Klug (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College, Nancy Shefferly (editor), Animal Diversity Web.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

coastal

the nearshore aquatic habitats near a coast, or shoreline.

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

macroalgae

seaweed. Algae that are large and photosynthetic.

magnetic

(as perception channel keyword). This animal has a special ability to detect the Earth's magnetic fields.

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

Ernst, C., R. Barbour. 1972. Turtles of the United States. Lexington, Kentucky: The University Press of Kentucky.

Scholastic, Inc., 2001. "Meet Dr. Frank Paladino" (On-line). Ocean Life. Accessed November 13, 2005 at http://teacher.scholastic.com/activities/explorer/oceanlife/main.asp?template=meet_explorer&article=interview_frank.

Scholastic, Inc., 1998. "Meet Dr. Richard Reina" (On-line). Ocean Life. Accessed November 13, 2005 at http://teacher.scholastic.com/activities/explorer/oceanlife/main.asp?template=meet_explorer&article=interview_reina.

U.S. National Park Service, 2003. "Kemp's ridley nesting." (On-line). National Parks (Padre Island National Seashore). Accessed August 04, 2006 at http://www.nps.gov/pais/website/kemp's_ridley.htm.

Wilkinson, T. 2003. The riddle of ridley's.. National Parks, 77: 26-29.

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