Реферат: Ridley

Ridley’s Sea Turtle Essay, Research Paper

Sea Turtles

Each species of sea turtle is distinctive in appearance and behavior, all sea turtles have certain characteristics in common the shell consist of a carapace (upper part) and plastron (lower part), which are joined together by cartilage called a bridge. in most species with the exception of the leatherback scutes cover the carapace. Like all turtles sea turtles have no external ears, they hear best at low frequencies and their sense of smell is excellent. Though their vision underwater is good, on land they are nearsighted.

Sea turtles spend most of their time underwater but must come up to breath. During routine activities sea turtles can dive for about three to five minutes. Sea turtles can sleep for several hours underwater, but their ability to hold their breath is shortened by high activity and stress. This is why sea turtles drown in shrimp nets and other gear in a short time. Adult sea turtles sleep near rocks or under ledges. Hatchlings and juveniles sleep on the surface with their front flippers pulled back over the carapace.

Kemp’s ridley sea turtle (Lepidochelys kempi)

Charming Tortoise of Kemp

Ridleys are the smallest of the sea turtles. The Kemp’s ridley is slightly larger than the olive ridley, measuring 24 – 28 inches in carapace length and weighing 78 – 100 pounds when mature. An adult is olive green on top and yellowish in color on the bottom, with a large head and powerful jaws. The carapace is circular to heart shaped. Hatchlings are dark gray and about an inch and a half long.

Kemp’s ridleys were first discovered and described in 1880 by Samuel Garman. But until the 1940’s was not recognized as a species and was often confused with the olive ridley and the loggerhead. Confusion continued through the 1950’s with many biologist convinced that the ridleys sea turtle was a sterile hybrid of the green and the loggerhead turtles. No one could find nesting beaches or an egg-bearing female.

In 1963 an old film was discovered, made in 1947 by Mexican engineer Andres Herrera that showed nesting ridleys. The film showed an estimated 40,000 Kemp’s ridleys nesting on an isolated beach now called Rancho Nuevo in Tamaulipas, Mexico, 200 miles south of Texas. Ninety-five percent of the population comes to the 17 mile strip of beach. The other five percent nest at the adjacent beach in Veracruz. No other sea turtle species goes almost entirely to one nesting spot to breed.

The arribada (Spanish for “arrival”) of Kemp’s ridleys in Mexico occurs at irregular intervals between April and June. Arribadas may occur several times a season. Male and Females congregate to mate off the coast of the beaches using wind direction velocity, lunar cycles and water temperature to gather is a theory. Once mated females wait for ideal conditions to come ashore. Conditions generally are high wind and heavy surf. The high wind cools stressed females and hides traces of the nest from predators. Mass nesting is thought to be a predator “swamping” where females and hatchlings will die but many more will survive.

Herrera’s film is now being used as a base line to measure the rapid decline of Kemp’s ridleys since 1947. forty thousand turtles declined to two thousand in 1966. In 1966 Mexican officials set up its first camp to monitor and protect turtles from egg takers. In 1977, Rancho Nuevo was declared a National Reserve by Mexico. Programs were developed to help protect turtles from poachers and predators. Now eggs are moved to protective enclosures to decrease the death to predators. Every year 50,000 hatchlings are released each year. Even with these programs nest counts in 1993 showed that there were only 400 nesting females. These small numbers result in broken up arribadas into small groups and solitary nestings. The remaining females lay fewer than 1000 nest each year.

The range of Kemp’s ridleys is limited for the most part to the gulf of Mexico where adult forge for crabs. their favorite is blue crabs that share the same habitat as shrimp. So ridleys sea turtle is often caught in shrimp ne

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