Brief Overview 
Sea turtles are large, air-breathing reptiles that inhabit tropicaland subtropical seas throughout the world. Their shells consist of an upper part (carapace) and a lower section (plastron). Hard scales (or scutes) cover all but the leatherback, and the number and arrangement of these scutes can be used to determine the species. 

Sea turtles do not have teeth, but their jaws have modified "beaks" suited to their particular diet. They do not have visible ears but have eardrums covered by skin. They hear best at low frequencies, and their sense of smell is excellent. Their vision underwater is good, but they are nearsighted out of water. Their streamlined bodies and large flippers make them remarkably adapted to life at sea. However, sea turtles maintain close ties to land. 

Females must come ashore to lay their eggs in the sand; therefore, all sea turtles begin their lives as tiny hatchlings on land. R

Sea Turtles and Humans
Sea turtles have long fascinated people and have figured prominently in the mythology and folklore of many cultures. In the Miskito Cays off the eastern coast of Nicaragua, the story of a kind “Turtle Mother,” still lingers. Unfortunately, the spiritual significance of sea turtles has not saved them from being exploited for both food and for profit. Millions of sea turtles once roamed the earth’s oceans, but now only a fraction remain.
Reproduction
Only females come ashore to nest; males rarely return to land after crawling into the sea as hatchlings. Most females return to nest on the beach where they were born (natal beach). Nesting seasons occur at different times around the world. In the U.S., nesting occurs from April through October. Most females nest at least twice during each mating season; some may nest up to ten times in a season. A female will not nest in consecutive years, typically skipping one or two years before returning. 
Growth & Development 
Researchers do not yet know how long baby turtles spend in the open sea, or exactly where they go. It is theorized that they spend their earliest, most vulnerable years floating around the sea in giant beds of sargasso weeds, where they do little more than eat and grow. Once turtles reach dinner-plate size, they appear at feeding grounds in nearshore waters. They grow slowly and take between 15 and 50 years to reach reproductive maturity, depending on the species. There is no way to determine the age of a sea turtle from its physical appearance. It is theorized that some species can live over 100 years. 
Status of the Species 
 

 Sea turtles sleep at the surface in the open ocean or on the bottom or under ledges in inshore waters. Fishermen in the Caribbean catch green turtles by setting nets over the rocks where the turtles sleep. Hatchlings sleep floating at the surface with their flippers tucked over their backs.  Turtles can rest or sleep underwater for several hours at a time but submergence time is much shorter while diving for food or to escape predators. 
Hearing, Sense of Smell and Vision

Sea turtles hear well, particularly at lower frequencies, and their sense of smell is well developed. They can see well underwater but are nearsighted when looking through air. Research with hatchling loggerhead and green turtles has shown that they can see light at wavelengths invisible to humans. These hatchings were attracted to light in the ultraviolet, violet and blue-green part of the spectrum and moved away from light in the yellow-orange range. The response to light is complex and may differ among species or between hatchlings and adults.

Courtship & Mating
Courtship and mating for most sea turtles is believed to occur during a limited “receptive” period prior to the female's first nesting emergence. Afterwards, only females come ashore to nest; males almost never return to land once they leave the sand of their natal beach. During mating season, males may court a female by nuzzling her head or by gently biting the back of her neck and rear flippers. If the female does not flee, the male attaches himself to the back of the female's shell by gripping her top shell with claws in his front flippers. He then folds his long tail under her shell to copulate. 

Females observed on the nesting beach after recently mating often have scratched shells and may be bleeding from where the males' were hooked to their shells. Copulation can take place either on the surface or under water. Sometimes several males will compete for females and may even fight each other. Observers of sea turtle mating have reported very aggressive behavior by both the males and females. Females may mate with several males just prior to nesting season and store the sperm for several months. When she finally lays her eggs, they will have been fertilized by a variety of males. This behavior may help keep genetic diversity high in the population. 
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Nesting, Incubation and Emergence

Very little in known about why sea turtles nest on some beaches and not on others. In Florida, loggerheads nest by the thousands on the central east coast, while identical looking beaches to the north see far fewer loggerheads. This nesting distribution may reflect conditions that existed centuries ago, when temperature, beach profiles or the lack of predation made some areas preferable to sea turtles. Today, humans are affecting the places where sea turtles nest. Beach erosion caused by coastal armoring and navigational inlets, artificial lighting and beach renourishment are all impacting once pristine beaches. These changes will likely have lasting effects on future nesting patterns. The more we understand about how, where and when sea turtles nest, the better we will be able to protect their nesting habitat. 

Beach Selection 
Most females return faithfully to the same beach each time they are ready to nest. Not only do they appear on the same beach, they often emerge within a few hundred yards of where they last nested. 

Nesting Behavior 
Only the females nest, and it occurs most often at night. The female crawls out of the ocean, pausing frequently as if carefully scoping out her spot. Sometimes she will crawl out of the ocean, but for unknown reasons decide not to nest. This is a "false crawl," and it can happen naturally or be caused by artificial lighting or the presence of people on the beach. Most females nest at least twice during the nesting season, although individuals of some species may nest only once and others more than ten times. Sea turtles are generally slow and awkward on land, and nesting is exhausting work. 

Constructing the Nest
The female turtle crawls to a dry part of the beach and begins to flings away loose sand with her flippers. She then constructs a "body pit" by digging with her flippers and rotating her body. After the body pit is complete, she digs an egg cavity using her cupped rear flippers as shovels. The egg cavity is shaped roughly like a tear drop and is usually tilted slightly. 

Laying and Burying the Eggs 
When the turtle has finished digging the egg chamber, she begins to lay eggs. Two or three eggs drop out at a time, with mucus being secreted throughout egg-laying. The average size of a clutch ranges from about 80 to 120 eggs, depending on the species. Because the eggs are flexible, they do not break as they fall into the chamber. This flexibility also allows both the female and the nest to hold more eggs. Nesting sea turtles appear to shed tears, but the turtle is just secreting salt that accumulates in her body. Many people believe that while laying her eggs a sea turtles goes into a trance from which she can not be disturbed. This is not entirely true. A sea turtle is least likely to abandon nesting when she is laying her eggs, but some turtles will abort the process if they are harassed or feel they are in danger. For this reason, it is important that sea turtles are never disturbed during nesting. Once all the eggs are in the chamber, the mother turtle uses her rear flippers to push sand over the top of the egg cavity. Gradually, she packs the sand down over the top and then begins using her front flippers to refill the body pit and disguise the nest. By throwing sand in all directions, it is much harder for predators to find the eggs. After the nest is thoroughly concealed, the female crawls back to the sea to rest before nesting again later that season or before beginning her migration back to her feeding ground. Once a female has left her nest, she never returns to tend it. 

Incubation
Incubation takes about 60 days, but since the temperature of the sand governs the speed at which the embryos develop, the hatching period can cover a broad range. Essentially, the hotter the sand surrounding the nest, the faster the embryos will develop. Cooler sand has a tendency to produce more males, with warmer sand producing a higher ratio of females. 

Emerging from the Nest 
Unlike baby alligators, which are liberated from their nest by their mother, sea turtle hatchlings must do it all themselves. To break open their shells, hatchlings use a temporary, sharp egg-tooth, called a "caruncle." The caruncle is an extension of the upper jaw that falls off soon after birth. Digging out of the nest is a group effort that can take several days. Hatchlings usually emerge from their nest at night or during a rainstorm when temperatures are cooler. Once they decide to burst out, they erupt from the nest cavity as a group. The little turtles orient themselves to the brightest horizon, and then dash toward the sea. If they don't make it to the ocean quickly, many hatchlings will die of dehydration in the sun or be caught by predators like birds and crabs. Once in the water, they typically swim several miles off shore, where they are caught in currents and seaweed that may carry them for years before returning to nearshore waters. There are many obstacles for hatchlings in the open ocean. Sharks, big fish and circling birds all eat baby turtles, and they die after accidentally eating tar balls and plastic garbage. The obstacles are so numerous for baby turtles that only about one in 1,000 survives to adulthood.
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Sea Turtle Journey : The Story of a Loggerhead Turtle     by Lorraine A. Jay, Katie Lee (Illustrator), Peter Thomas (Narrator), Lorraine A. Joy

Distribution and Habitat

Sea turtles, obviously, make their homes in the world oceans. Rarely do they go ashore. Female turtles, however, must return to beaches for the ancient ritual of egg laying.


Green turtles are a more tropical species. Although they may be found in the Atlantic from New England to Argentina, they frequent Gulf of Mexico and Caribbean waters.

Hawksbill turtles are even more restricted to the tropics than green sea turtles, but they occasionally range from Massachusetts to Brazil. Kemp's ridley turtles are found in the Gulf of Mexico and along the eastern coast of the United States as far north as Nova Scotia. Juvenile Kemp's found in European waters appear to be waifs. Leatherbacks range throughout the Atlantic, from Newfoundland to Argentina, and occasionally the Mediterranean Sea.

In general, sea turtles found in Florida may range throughout the waters of northeastern United States in warmer months. Loggerheads and leatherbacks are frequently seen off the northeast coast of the United States. Juvenile Kemp's ridleys are regularly sighted in the Chesapeake Bay, Long Island Sound and in the vicinity of Cape Cod, Massachusetts. Greens and hawksbills are rarely seen outside of tropical or subtropical areas.

In some places, green sea turtles are known to bask, crawling onto beaches or rocks to rest in the sun. Off the coast of Australia, green turtles were observed "piled up like rocks," basking; northwest of the Hawaiian Islands, basking green turtles are often seen during the breeding season. The activity is thought to have been more common in the past, when humans were less likely to disturb them.

As air-breathing reptiles with lungs, sea turtles must surface periodically. They are, however, capable of remaining submerged for extended periods. A leatherback fitted with a time-depth recorder made a dive of more than 3,300 feet off the Virgin Islands. In other studies over a ten-day period, the average depth of all dives of a leatherback was 222 feet and in some cases the animal was submerged as long as 27.8 minutes. The tagged female leatherback averaged 2.7 dives per hour during daylight and 3.6 dives each hour (average) at night.

Life History

Sea turtles nest on beaches, depositing eggs in a pit dug with the hind flippers. In approximately two months, hatchlings emerge from the nest and scramble to the sea. Little is known of the first year or so of growth and development. Biologists often refer to this interval as "the lost year." Evidence is growing, however, that many hatchlings get caught up in "rafts" of floating sargassum weeds. The young turtles are thought to spend quite a while in these habitats, moved about the ocean currents.

Sea turtles appear to lead rather solitary lives at sea, except when they congregate off nesting beaches, where they mate in the near shore waters. The female goes ashore to lay her eggs and the cycle begins again. The scenario is similar for each species, with minor variations.

In the United States, loggerhead turtles nest from April through August from Virginia to Florida. They are the most common nesting turtle in the U.S.; the U.S. nesting population is the second largest in the world. Florida has the largest percentage of loggerhead nesting with approximately 30,000 nests each year. Between 300 to 700 green turtle nests and 50 to 80 leatherback nests are also recorded annually on the state's east coast; hawksbills rarely nest there.

Loggerhead nesting occurs on sandy beaches above the high tide line. If the nest is flooded by the tide, the eggs will "drown" in salt water. The female crawls ashore at night, digs a shallow pit and then makes a nest cavity where she deposits the eggs. The eggs are white, soft and round, measuring about 1-3/4 inches. A clutch averages about 100 eggs. Once the eggs are deposited, the rear flippers fill and cover the nest with sand and the turtle returns to the sea. The female may nest two or more times a season, about 14 days apart. The age of sexual maturity is not known with certainty. Loggerheads are thought to be mature when the carapace length is greater than 30 inches, which may be 13 to 15 years of age. Some people, however, believe that sexual maturity in nature may be as much as 20 to 30 years of age. In captivity, a well-fed loggerhead may reach maturity at seven years, but growth in the wild is much slower.

When hatchlings scramble from the nest, they instinctively head for the water, where they swim seaward. They are thought to become entrained in oceanic currents and disbursed. There is evidence that young turtles drift with rafts of sargassum weed where they find food and shelter. The duration of this oceanic phase is unknown, but it appears to be longer for loggerheads than for green and hawksbill turtles.

As loggerheads mature, they travel and forage through near shore waters until the breeding season, when they return to the nesting beach areas. The majority of mature loggerheads appear to nest on a two or three year cycle.

Green turtle life histories are basically similar. They nest mainly from July through September in the West Indies, Mexico, South and Central America, and on the east coast of Florida.

Green turtles nest on Ascension Island in the south central Atlantic Ocean from January through April. They then head westward to Brazilian waters, traveling more than 1500 miles to favored feeding grounds.

The temperature at which green turtle eggs are incubated is a factor in determining the sex of the hatchlings. In the laboratory, "cool" nests incubated at a constant 82.5 F (28 C) or less produce almost no females (0-10%) , while "warm" nests at 85 F (29.5 C) produce almost all females (95-100%).

Sexual maturity of green turtles in nature is estimated variably at 15 to 30 years of age.
Leatherbacks nest from February through July in the West Indies, Central and South America and Florida.
Leatherback Turtle

The endangered leatherback turtle is the largest and most active of the sea turtles. They travel thousands of miles, dive thousands of feet deep, and venture into much colder water than any other kind of sea turtle. Up to eight feet in length, these huge turtles have a rubbery dark shell marked by seven narrow ridges that extend the length of the back. Remarkable, leatherbacks feed on jellyfish and soft-bodied animals that would appear to provide very little nutrition for such huge animals. Ingestion of plastic bags and egg collecting are reasons for mortality and population declines. About 100 to 200 leatherback nests are recorded in Florida each year.

Leatherback (Dermochelys coriacea) 

Leatherbacks are also endangered, but a few nest on the east coast of Florida each year. The leatherback is the champion of sea turtles. It grows the largest, dives the deepest, and travels the farthest of all sea turtles. Mature leatherbacks typically reach about 4 to 8 feet in length and weigh from 650 to 1,300 pounds. The largest leatherback ever recorded was almost 10 feet (3 m) from the tip of its beak to the tip of its tail and weighed in at 2,019 pounds (916 kg). The leatherback is the only sea turtle that lacks a hard shell. It is named for its large, elongate shell which is composed of a layer of thin, tough, rubbery skin, strengthened by thousands of tiny bone plates. Seven narrow ridges run down the length of the carapace, which is typically black with many white spots. The lower shell is whitish to black and marked by 5 ridges. The body of a leatherback is barrel shaped, tapering at the rear to a blunt point. With this streamlined body shape and the powerful front flippers, a leatherback can swim thousands of miles over open ocean and against fast currents.

Leatherbacks feed almost exclusively on jellyfish. It is remarkable that this large, active animal can survive on a diet of jellyfish, which are composed mostly of water and appear to be a poor source of nutrients. Young leatherbacks in captivity can eat twice their weight in jellyfish each day. Leatherbacks approach coastal waters only during breeding season. Nesting occurs throughout the Caribbean, on the northern coast of South America, the Pacific Coast of Central America, and on the east coast of Florida. Nesting season runs from March through July. Leatherbacks nest every 2 to 3 years, laying 6 to 9 egg clutches in a nesting season. Each clutch contains approximately 80 fertilized eggs the size of billiard balls and 30 smaller, unfertilized eggs. There is an average of 10 days between nestings. The eggs incubate for approximately 65 days.

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