Kemp’s Ridley Sea Turtles: Characteristics, Behavior, Arribadas

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Kemp's Ridley sea turtle

Kemp’s ridley sea turtles (Scientific name: Lepidochelys kempii) are the smallest sea turtle in the world. The species is named after Richard M. Kemp, a fisherman from Key West, Florida, who first submitted the species for identification in 1906. They are primarily found in the Gulf of Mexico, but juveniles are also found in the Atlantic Ocean as far north as Nova Scotia and sometimes even occur in the eastern North Atlantic. [Source: NOAA]

Kemp's ridley sea turtles are also known as ridley sea turtles and Atlantic ridley sea turtles. They stay close to shore in the in the Gulf of Mexico and the North American Atlantic. The number of female Kemp ridley turtles that nested neat Rancho Nuevo, Mexico declined from 40,000 in 1940s, to 10,000 in 1960 to a round 500 in the 1980s. There making a come back in Texas. Every few days newly hatched Kemp’s Ridley turtles are released into the surf at North Padre Island. A record 10,596 hatchling were released there in 2007.

Their main known predators of Kemp’s ridley turtles are humans and tiger sharks and maybe killer whales. Herons, seabirds and raccoons feed on eggs and hatchlings. No one knows exactly how long Kemp’s ridleys live, but like other sea turtles, they are likely long-lived, reaching maturity at about 13 years of age and have an estimated lifespan of at least 30 years, and maybe 50 years. Mortality rates are very high around the time of hatching but decreases as they et older. [Source: NOAA]

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase; Encyclopedia of Life; Smithsonian Oceans Portal ; Monterey Bay Aquarium ; MarineBio

Kemp’s Ridley Sea Turtle Habitat and Where They Are Found

range of Kemp's ridley turtles
Kemp's ridleys are distributed throughout the Gulf of Mexico and U.S. Atlantic seaboard, from Florida to New England and from Nova Scotia and Newfoundland to Bermuda. A few records exist for Kemp's ridleys near the Azores, waters off Morocco, and within the Mediterranean Sea and they are occasionally found in other areas around the Atlantic Basin. Adult Kemp's ridleys primarily occupy nearshore coastal (neritic) habitats in the Gulf of Mexico that include muddy or sandy bottoms where their preferred prey are found. [Source: NOAA]

The majority of Kemp’s ridley nesting occurs on the beaches of the western Gulf of Mexico and ninety-five percent of worldwide Kemp’s ridley nesting occurs in the state of Tamaulipas, Mexico. The three main nesting beaches in Tamaulipas are Rancho Nuevo, Tepehuajes, and Barra del Tordo. Nesting also occurs in Veracruz, Mexico, and in Texas, but on a much smaller scale. Occasional nesting has been documented in North Carolina, South Carolina, Georgia, Florida, and Alabama. [Source: NOAA]

Kemp’s ridley sea turtles mainly stays near shallow coastal regions often in bays and lagoons. They marine habitats with sandy or muddy bottoms. They occasionally may forays into the open seas and have the ability to make deep dives. They follow two major migration, routes: one heads north to the Mississippi coastline and the second extends southward to the shores of the Yucatan Peninsula at the Campeche Bank. Kemp’s ridley sea turtles are rarely seen on shore but t is not uncommon to see them floating in the water just offshore. Females come on shore to nest. [Source: Zachary Klug, Animal Diversity Web (ADW) /=]

Kemp’s Ridley Sea Turtle Physical Characteristics

Kemp’s ridley sea turtles are the smallest species of sea turtle They range in weight from 30 to 50 kilograms (66 to 110 pounds) and range in length from 55 to 75 centimeters (21.6 to 29.5 inches), with an average length is 65 centimeters (25.5 centimeters): Males and females have different shapes. [Source: Zachary Klug, Animal Diversity Web (ADW) /=]

The Kemp's ridley turtle has a triangular-shaped head with a slightly hooked beak. Hatchlings are darkly colored on both sides. Adults are generally a grayish-green color on top with a pale, yellowish bottom shell. The top shell (carapace) is often as wide as it is long. It is gray-olive in color, whereas the plastron is an off-white to light yellow. [Source: NOAA]

Kemp’s ridley sea turtles have four limbs; two foreflippers and two hindflippers. The head and limbs (flippers) can not be pulled inside the shell. The shell is streamlined, making this turtle extremely hyrdrodynamic. Each of the front flippers has one claw while the back flippers may have one or two. The foreflippers power the turtle through the water while the hindflippers are used to steer and stabilize the turtle in the water. Ridleys have an upper eyelid for eye protection. As turtles, they lack teeth. 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./=\

Kemp’s Ridley Sea Turtle Behavior, Perception and Feeding

Kemp’s ridley turtles are solitary, motile (move around as opposed to being stationary) and migratory (make seasonal movements between regions, such as between breeding and wintering grounds). Home ranges for individuals have not been reported. The activity of these animals during days versus nights has not been well studied. [Source: Zachary Klug, Animal Diversity Web (ADW) /=]

Kemp’s ridley sea turtles spend most of their life at sea in relative isolation. Social contact apparently seems to only occur during mating and nesting. Adult female sea turtles return to land to lay their eggs in the sand — they are remarkable navigators and usually return to a beach in the general area where they hatched decades earlier. [Source: NOAA]

Kemp’s ridley sea turtles sense using vision, touch, sound and magnetism and communicate with vision, touch and sound. 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.

Kemp’s ridley sea turtles are omnivores (eat a variety of things, including plants and animals. They mainly feed on animal foods such as aquatic crustaceans and cnidarians such as floating crabs, mollusks, shrimp and jellyfish.The jaws of these turtles are shaped for crushing and grinding and are suited for crushing the shells of molluscs and crustaceans.Among the plant foods they eat are algae and macroalgae (seaweed). /=\

Kemp’s Ridley Sea Turtle Mating and Reproduction

Kemp's Ridley

Kemp's Ridley sea turtles are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups, multiple times in successive annual or seasonal cycles). They engage in seasonal breeding. Females breed every two or three years, but can lay between on and nine clutches within a single breeding season. The breeding season is from April to July. The number of offspring ranges from 50 to 200, with the average number of offspring being 110. The average gestation period is 55 to 60 days. [Source: Zachary Klug, Animal Diversity Web (ADW) /=]

Females and males reach sexual maturity at 11 to 35 years. During the pre-fertilization and pre-birth stages provisioning and protecting is done by females. Females invest energy in the production of eggs and the digging of the nest and providing some protection by burying eggs. The eggs are leathery and covered in mucus which protects them from breaking as they are laid. After this females expend no further energy or effort in caring for her young. Young are independent from the time of hatching. /=\

Kemp's ridley sea turtles are polygynandrous (promiscuous), with both males and females having multiple partners. Individuals spend most of their lives in isolation, often only coming into contact with members of their own species 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. /=\

Depending on their breeding strategy, male Kemp's ridleys occupy many different areas within the Gulf of Mexico. Some males migrate annually between feeding and breeding grounds, yet others may not migrate at all, mating with females encountered at their feeding grounds or near nesting beaches. Female Kemp's ridleys have been tracked migrating to and from nesting beaches in Mexico and south Texas. Females leave breeding and nesting areas and migrate to foraging areas ranging from the Yucatán Peninsula to southern Florida to the north-central Gulf of Mexico. Some females take up residence in specific foraging grounds for months at a time and return to the same foraging grounds in subsequent years. [Source: NOAA]

Kemp’s Ridley Sea Turtle Arribada (Group Nesting)

Kemp's ridley

Nesting occurs from April to July and unlike the other species which nest at night, Kemp’s ridleys nest during daylight hours. They lay an average of 2 to 3 clutches per season, and return to the beach to nest every 1 to 3 years. The females dig an egg chamber in the sand where they lay approximately 100 eggs, which incubate for 50 to 60 days. Hatchlings orient seaward by moving away from the darkest silhouette of the landward dune or vegetation to crawl towards the brightest horizon. On undeveloped beaches, this is toward the open horizon over the ocean. [Source: NOAA]

Kemp's ridleys display one of the most unique synchronized nesting habits in the natural world. Adult female Kemp's ridleys gather off nesting beaches in northeastern Mexico and come ashore in large groups, called arribadas, which means "arrival" in Spanish. There are many theories on what triggers an arribada, including offshore winds, lunar cycles, and the release of pheromones by females. However, scientists have yet to conclusively determine what triggers an arribada. Arribada nesting is a behavior found only in the genus Lepidochelys which includes the olive ridley sea turtle (Lepidochelys olivacea) and Kemp’s ridley.

Nesting in large groups may be a defense against predators, or a result of environmental factors influencing nesting. With many turtles coming ashore together and many nests subsequently hatching at the same time, the large numbers of hatchlings entering the ocean may help to overwhelm predators and ensure that more hatchlings make it to open water to reduce predation. The other species of sea turtle that nests en masse is the olive ridley. They are the only sea turtles that routinely nest during the day.

Females may spend two or more hours nesting. Those engaging in the “arribada,” nest on beaches near the Texas-Mexico border (Tamaulipas Mexico, Padre Island National Seashore). Females use their foreflippers to dig a body pit which is deep enough for her carapace to be level with the surrounding sand. They then uses her hindflippers to dig cavities into which the eggs are deposited. After the eggs are deposited, females fill in the egg cavity and body pit with their hindflippers and uses their plastron (bottom of their shell) to erase markings of the nest. [Source: Zachary Klug, Animal Diversity Web (ADW) ]

Kemp’s Ridley Sea Turtle Hatchlings and Development

Kemp’s ridley sea turtle eggs are deposited on shore and incubate for an average of 55 days. Embryo development is temperature dependent. Generally the cooler it is the longer it take the eggs to hatch. Before they are born sex is also determined by temperature. Lower nest temperatures tend to produce more males, whereas higher temperatures tend to produce more females. [Source: Zachary Klug, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: Hatchlings uses a caruncle (temporary tooth) to break open the egg. After a hatchling escapes from the egg, it may take three to seven 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.

Kemp’s ridley sea turtles are most vulnerable when they are hatchling crawling from the nest to the shore. The slow-moving newborns are easy targets for herons, dogs, raccoons, and a variety of seabirds. 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.

Kemp's Ridley arribada

Hatchlings swim rapidly offshore. Some remain in currents within the Gulf of Mexico while others may be swept out of the Gulf, around Florida, and into the Atlantic Ocean by the Gulf Stream. Juvenile Kemp’s ridleys associate with floating Sargassum algae, using the Sargassum as an area of refuge, rest, and a place to feed on small animals and plants. This developmental drifting period lasts 1 to 2 years or until the turtle reaches a length of about 8 inches. After this oceanic phase, Kemp’s ridleys migrate to nearshore areas of the Gulf of Mexico or northwestern Atlantic Ocean. After recruiting to shallow coastal areas, crabs are their preferred food; however, they also scavenge on discarded bycatch.

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 coastal regions. Kemp’s ridley sea turtles take 11 to 35 years to reach maturity. /=\

Endangered Kemp’s Ridley Sea Turtles

The Kemp’s ridley sea turtle is listed as “endangered throughout its range”under the U.S. Endangered Species Act (ESA, U.S. Fish and Wildlife): They are designated “Critically Endangered” on the International Union for Conservation of Nature (IUCN) Red List: The Convention on International Trade in Endangered Species (CITES) lists them in Appendix I, which lists species that are the most endangered among CITES-listed animals and plants. They are also listed under Specially Protected Areas and Wildlife (SPAW) Annex II as in need of protection throughout the Wider Caribbean Region:

Prior to the mid-20th century, the Kemp's ridley was abundant in the Gulf of Mexico. An amateur video from 1947 documented tens of thousands of Kemp’s ridleys nesting near Rancho Nuevo, Mexico on a single day. This nesting population experienced a devastating decline between the late 1940s and the mid-1980s. The number of nests reached a record low of 702 in 1985, representing fewer than 250 nesting females. Due to intensive conservation actions, the Kemp's ridley began to slowly rebound during the 1990s. The number of nests increased about 15 percent each year through 2009. However, in 2010 this rapid increase abruptly ended and the number of nests has fluctuated since then. The unexpected change in Kemp’s ridley nesting highlights the importance of continued protection, monitoring, and conservation efforts. [Source: NOAA]

The Kemp's ridley sea turtle was once considered the most endangered sea turtle. Egg harvesting for the aphrodisiac market in Mexico City seems to have been a major reason why. The greatest threat to the species today is incidental capture in fishing gear, primarily in shrimp trawls, but also in gill nets, longlines, traps and pots, and dredges in the Gulf of Mexico. Other threats include change, direct harvest of turtles and eggs, loss and degradation of nesting habitat, ocean pollution and marine debris, predation of eggs and hatchlings and vessel strikes.

Almost the entire Kemp’s ridley sea turtle population nests on the beaches of the western Gulf of Mexico, primarily in Tamaulipas, Mexico, just south of the United States-Mexico border. The arribada nesting behavior concentrates females and nests at the same time and in the same place, enabling the taking of an extraordinary number of eggs for human consumption. Historically, egg collection for human consumption was a significant problem in this area, but this threat has been diminished by the protection of nests and turtles in both Mexico and the United States.

For Kemp’s ridleys, beach driving is a threat to the turtles and the nesting habitat. Driving on nesting beaches can injure or kill nesting turtles, eggs, and hatchlings. Nesting turtles can be difficult to see and they cannot move quickly on land to avoid an approaching vehicle. Beach driving also degrades the nesting habitat by causing sand compaction and creating ruts and ridges in the sand that pose obstacles to nesting turtles and hatchlings attempting to reach the ocean, resulting in an extended period of travel or entrapment.

Image Sources: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated May 2023

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