Kemp’s Ridley Sea Turtle

Kemp’s Ridley Sea Turtles (Lepidochelys kempii) are the world’s smallest and most critically endangered sea turtles. It is one of the two extant species in the genus Lepidochelys (the other being Lepidochelys olivacea, the Olive Ridley sea turtle). These turtles are named after Richard M. Kemp, the fisherman from Key West who first submitted a specimen of this species for identification in 1906.

Once abundant in the Gulf of Mexico, thousands of these marine creatures were found thronging their nesting site in Rancho Nuevo, Mexico. However, they have eventually fallen victim to illegal harvesting, ocean pollution, oil spills, and global warming, causing an alarming decline in their population.

Description

Size: Length – 27-32 inches (68 to 82 cm)

Weight: 30 to 50 kg (66 to 110 lbs)

Body and Coloration:

The smallest of all sea turtles, they have spotted triangular heads with eyes protected by an upper eyelid, hooked beaks, and streamlined shells covering their pale bodies. These shells’ dorsal surface (carapace) is gray-green, while the ventral surface (plastron) is pale yellow. The carapace is about 50 to 70 cm long and equally wide, with five pairs of costal scutes. They have four clawed, non-retractile flippers that help them wade through the water.

Distribution

They have a strikingly unusual distribution, with the adults, juveniles, males, and females occupying different geographical regions at the same time. In the United States, the adults are found along the Gulf of Mexico, with the females ranging between the Florida Peninsula’s southern coast and the Yucatan Peninsula’s northern coast. At the same time, the males stay close to the nesting beaches of the Western Gulf waters of Texas, Tamaulipas, and Veracruz. Most females return to Rancho Nuevo, a beach in Tamaulipas, Mexico, every breeding season to lay eggs.

In contrast to the adults, the juveniles migrate to the Atlantic Ocean, occupying the coastal waters from southern Florida to Cape Cod, Massachusetts, and sometimes moving as north as Nova Scotia.

A few records suggest that Kemp’s ridleys are found near the Azores islands in Portugal, the Mediterranean Sea, and other areas around the Atlantic Basin.

Habitat

Kemp’s ridleys usually inhabit shallow coastal areas like estuaries, bays, and lagoons with muddy or sandy bottoms where prey is readily available. Though the males spend their entire lives in water, the females arrive on shore at their nesting sites during breeding season.

Diet

They primarily feed on small fishes, mollusks, coelenterates, crustaceans like floating crabs and shrimps, and benthic vegetation like algae and seaweeds.

Behavior

• The juvenile Kemp’s ridleys associate with floating Sargassum algae in offshore waters, using them as a refuge, rest, and feeding platform. This ‘developmental drifting’ lasts for about two years till the turtle reaches a length of about 8 inches.
• Depending on the breeding strategy, some male turtles migrate annually between feeding and breeding grounds. Yet, other males may not migrate at all, mating with females at their feeding grounds or close to their nesting beaches. However, female ridleys have been found migrating to and from nesting beaches in Mexico and Texas.

Lifespan

Although the exact lifespan of these turtles is unknown, like other sea turtles, they are assumed to attain sexual maturity at around the age of 10 to 16 years and are estimated to survive till 30 years. 

Reproduction and Life Cycle

Due to their long migration patterns, these turtles remain solitary throughout the year, congregating only during the time of mating and nesting. After copulation, the females in large groups swim to the shore for nesting, an event called ‘arribada’ that translates to ‘arrival’ in Spanish. The only sea turtles that nest during the day, Kemp’s ridley females return to the same beach year after year, joining large groups of nesting females called ‘arribazones,’ an astounding custom found only in Kemp’s Ridley and Olive Ridley turtles.

At the beach, the female uses her fore-flippers to dig a body pit in the ground, deep enough for her carapace to be leveled with the layer of sand. She then scoops another cavity using her hind flippers to deposit her eggs. The female lays around 50 to 200 white, leathery, and mucous-laden eggs per clutch, with one to nine clutches per nesting season from April to July. After the eggs are delivered, the female uses her hind flippers to fill the egg and nest cavities with sand. She then moves her plastron sideways on the sand to remove any markings of the nest for safety.

The eggs take about 55 days to incubate, and the embryonic development is temperature-dependent, with more males produced under low nest temperatures and more females produced under higher temperatures. The purplish hatchlings emerge independently from the eggs at night by breaking the shell using a temporary tooth called the ‘caruncle.’ They take about a week to crawl into the water, taking cues from the intensity of light reflected from it.

Predators

Due to their slow movement, these turtles are most vulnerable in their hatchling stage while crawling from the nesting sites to the shore. Dogs, raccoons, herons, and other varieties of seabirds quickly attack these slow-moving hatchlings.

The adults, however, are more prone to attack by tiger sharks and killer whales. Humans also hunt them illegally for their meat, shells, and eggs.

Adaptations

1. They have hooked beaks and powerful jaws for crushing crabs and mollusks.
2. The males use their long, curved flippers and claws to grip the females during mating.
3. If the water gets too cold, these sea turtles can adjust their metabolic rate accordingly and remain underwater for hours. They can even survive two to three months without food.

Conservation Status

The IUCN lists Kemp’s Ridley turtles under the ‘Critically Endangered’ (CR) category of the Red List, whereas they have received Federal protection under the Endangered Species Act since 1970.

In 1947, thousands of these turtles were documented nesting near Rancho Nuevo, but their population declined drastically between the late 1940s and the mid-1980s. The number of nests reached a record low of 702 in 1985, hosting less than 250 females. This continuing decline could be attributed to human interference with their nesting habitats and accidental capture (bycatch) in fishing gear like shrimp trawls, gill nets, longlines, and traps. The illegal harvesting of hatchlings and eggs, increasing ocean pollution, oil spills, and the global rise in temperatures also contribute to the cause.

However, the recent intensive conservation actions have improved their population number in the wild. Various international treaties and national laws protect Kemp’s Ridley turtles. In the United States, the National Marine Fisheries Service and the U.S. Fish & Wildlife Service regularly monitor Kemp’s Ridley populations, ensuring their numbers do not drop abruptly. 

Bycatch of these turtles is controlled by reducing fishing activities around nesting sites and introducing fishing gear modifications like turtle exclusion devices (TEDs.) These laws and control measures have improved their numbers from barely 200 nesting individuals in the 1980s to around 9,000 today.