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Kemp's ridley, Depidochelys kempi
Kemp's ridley is the smallest and most endangered of the world's seven sea turtle species. It was named after a Key West resident, Richard Kemp, who sent two ridley specimens to Harvard's Agassiz Museum for identification about 90 years ago. Adults measure 24 to 28 inches (62-70 cm) in carapace length
(shell length)
and do not exceed 30 inches shell length and weigh from 70 to 110 pounds. The carapace
circular to heart-shaped
keeled nearly
round, sometimes wider than it is long. The color is gray to olive-gray; the plastron is yellowish. The carapace of the young is gray-black. There are five pairs of costal shields, as on loggerhead turtles.
Hawksbill turtles tend to be restricted to the tropics, nesting in Florida, Mexico, the West Indies and the Caribbean coast and islands of Central and South America. Nesting is scattered throughout their range.
Kemp's ridley turtles are found mainly in the Gulf of Mexico, but may range through coastal waters along the eastern seaboard as far north as Nova Scotia. A 1931 publication noted, with some surprise, that they "are frequent summer visitors to northern harbors" and "are the species most commonly found in New York waters." Though they are sighted there on occasion, the Gulf of Mexico is truly "home" for Kemp's ridley
turtles.
The Kemp's ridley is carnivorous
mainly animal eaters, favoring crustaceans, jellyfish and mollusks
and feeds on swimming crabs and other crustaceans, clams, mussels, fish and jellyfish. Blue crabs are the preferred food in many areas. in the coastal waters of Florida on blue crabs and other crabs and shrimp.
Kemp's Ridley Turtle Estimates of age at maturity range from 7 to 15 years. In captivity a few females have become sexually mature at 5 years of age.
Range and Habitat
Kemp's ridley turtles are found mainly in the Gulf of Mexico, but may range through coastal waters along the eastern seaboard as far north as Nova Scotia. A 1931 publication noted, with some surprise, that they "are frequent summer visitors to northern harbors" and "are the species most commonly found in New York waters." Though they are sighted there on occasion, the Gulf of Mexico is truly "home" for Kemp's ridley turtles.
Adult Kemp's ridleys, are found in the Gulf of Mexico foraging in productive coastal and estuarine waters, particularly along the Louisiana coast near the mouth of the Mississippi River and the
Campeche, Mexico region. Juvenile and subadult Kemp's ridleys are widely distributed throughout the coastal waters of the U.S. from Texas to Maine. When temperatures begin to drop, the turtles in northern regions head south to Florida and the Gulf of Mexico. Cold-stunned juveniles are regularly stranded in Long Island Sound, New York and in Cape Cod Bay during the winter.
Discovery of Nesting Beach
Unlike other sea turtles, All Kemp's ridleys nest on a single stretch of beach on the Gulf coast of
Mexico Kemp’s ridleys nest annually. They lay about 2 clutches during each season, about 25 days apart. Each nest contains around 105 eggs, which incubate 55 days. The only major breeding site of the Kemp’s ridley is on a small strip of beach at Rancho Nuevo, Mexico. Kemp’s ridleys nest in mass synchronized nestings called arribadas (Spanish for “arrival”). The arribada of Kemp’s ridleys occurs at regular intervals between April and June. In 1942, a Mexican architect filmed an estimated 42,000 ridleys nesting at Rancho Nuevo in one day. During 1995, only 1,429 ridley nests were laid at Rancho Nuevo.
Kemp's ridley turtles nest from April through August at a single beach at Rancho Nuevo, in the state of
Tamaulipas, Mexico. While other turtles are solitary nesters, the ridleys come ashore in great numbers, crawling over and around each other in search of a nesting site. Such events are known as
"arribadas" (the comings/arrivals). Years ago, Rancho Nuevo hosted as many as 40,000 turtles during an
arribada. Now that the species is endangered, such events are rare and the number of nesting females arriving in an entire season rarely exceeds 500, a dim reflection of past populations.
Although Kemp's ridleys were often seen in the Gulf of Mexico and in the southeastern U.S., the location of their nesting beaches remained a mystery for many years. Turtle fishermen maintained that there were no nesting beaches because the Kemp's ridley was an infertile hybrid between a loggerhead and a hawksbill turtle. The mystery was solved with the discovery of a film made in 1947 by a Mexican engineer. The film documented the mass emergence of tens of thousands of Kemp's ridley turtles in broad daylight onto a remote beach on the Gulf coast of Mexico. The beach was near Rancho Nuevo in the state of Tamaulipas about 300 kilometers (200 miles) south of Brownsville, Texas. The film showed the feverish activity of the females as they dug their nests and covered them. So many turtles were nesting at once that they climbed over each other and dug up each other's eggs.
Kemp's Ridley Turtle Facts
Rarest and most endangered of the sea turtles
Nesting restricted to a 20-mile stretch of beach in western Gulf of Mexico
Only 300 to 350 females nest each year
Females sychronize egg laying in mass nestings
Nesting occurs during daylight
Feeds on blue crabs, clams, mussels, fish and jellyfish
A small sea turtle: Adults weigh 85 to 100 pounds and measure 24 to 30 inches in length
Hatchlings: 1 1/2 inches long
Species threatened by drowning in shrimp trawls, habitat alterations and pollution
Nesting Habits
Kemp's Ridley
Kemp's ridley turtles nest from April through August at a single beach at Rancho Nuevo, in the state of Tamaulipas, Mexico. While other turtles are solitary nesters, the ridleys come ashore in great numbers, crawling over and around each other in search of a nesting site. Such events are known as "arribadas" (the comings/arrivals). Years ago, Rancho Nuevo hosted as many as 40,000 turtles during an arribada. Now that the species is endangered, such events are rare and the number of nesting females arriving in an entire season rarely exceeds 500, a dim reflection of past populations.
The reproductive strategy of Kemp's ridley, like that of some populations of its close relative, the olive
ridley, is to synchronize the emergence of nesting females. These mass
nestings, called arribadas (Spanish for arrivals), occur at irregular intervals between April and June. Unlike the olive
ridley, however, the nesting that occurs on this one 30 kilometer (20 mile) stretch of Mexican coastline represents virtually the entire reproductive effort of the species.
Perhaps using cues such as wind direction or velocity, lunar cycles or water temperature, male and female Kemp's ridleys mass off the narrow strip of beach to mate. Scent produced by secretary pores may enable the turtles to find each other once they are in the area. Once they have mated, the females may stay offshore for days waiting for just the right conditions, which usually include heavy surf and high winds from the northeast. Wind may erase the scent of the nests and reduce predation. When conditions are finally right, the females emerge from the water to dig nests and lay their eggs, all within a few hours of each other and usually during daylight. Arribadas may be repeated several times during a season, and many females nest in successive years.
Why ridleys nest together in large groups is unknown but it may serve as a form of predator saturation or swamping. Local predators may be bewildered by the sudden abundance of prey and, although some adults and many eggs and, later, hatchlings will be taken, many will survive. Predators seem to know when an arribada is about to occur because coyotes and vultures move from inland areas to gather at the beach before the turtles arrive.
Conservation Programs
Although the location of the Kemp's ridley nesting beach eluded scientists for many years, it was well known to egg traders. Prior to the 1960s, mule trains would carry hundreds of thousands of eggs collected on the beach to market and thousands of females were caught offshore and cut open just for their eggs. From the estimated 40,000 nesting females documented in the film, the population has been reduced to 300 to 350 nesting females a year. In recent decades, population reductions have resulted in the fragmentation of the arribadas into small groups or nesting by solitary individuals. In the last few years, usually the largest arribada has been less than 200 females spread over several kilometers of beach. Less than 1,000 nests are laid each season.
Rancho Nuevo was declared a Natural Reserve by Mexico in 1977 and programs were begun to protect the nesting beach and reduce the poaching and natural mortality of eggs and turtles. Eggs are moved to protected hatcheries to decrease losses to predators, and since 1978 about 50,000 hatchlings a year have been released on the beach annually. The effort at Rancho Nuevo has been extensive and successful as very few nests now are lost. Despite this protection, however, the number of Kemp's ridleys that nest each year is declining because of the continuing loss of turtles to incidental catch by shrimp trawls.
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