Earth & Sky

Our thanks to the following individuals and institutions who assisted in the preparation of this script:

Barbara Schroeder
National Marine Fisheries Service Headquarters
Silver Spring, MD

Karen Bjorndal, Director
Archie Carr Center for Sea Turtle Research
University of Florida
Gainesville, FLA

The following books, articles and web sites were used in preparing this script:

Caribbean Conservation Corporation Webpage

Seaturtle.org

Lost Years Found (University of Florida)

Sea Stats/Florida Marine Research Institute – Sea Turtles, Nomads of the Deep

Sea Turtles and Lights (Broward County website)

Archie Carr Center for Sea Turtle Research (University of Florida)

Kemp’s Ridley Sea Turtle Research (USGS)

Other Suggested Reading (not included in References):

Sea Turtle Satellite Tracking – Tampa Bay Tracks

Sea Turtle Conservation Program, Broward County

Movement and habitat use of South Carolina post-nesting loggerhead sea turtles (South Carolina Dept of Natural Resources)

NOAA Sea Turtle Page

Southwest Fisheries Science Center Sea Turtle Page

Coastal Protection of Sea Turtles in Florida (Florida State University)

Author’s Notes:

Background Information
by Shireen Gonzaga

More about Satellite Tracking of Sea Turtles:

Several research groups are currently tracking sea turtles using satellite transmitters attached to the turtle’s carapace. Collectively, they are gathering data about the movement and behavior of different individual turtles of several species that would be otherwise be impossible to obtain.

These small transmitters are programmed to perform specific tasks, depending on what the researcher wants to know about the tagged sea turtles. According to Barbara Schroeder, of the National Marine Fisheries Service, the lifetime of a battery varies by manufacturer and battery type. The battery life itself depends on how the transmitter is programmed-it could be on a conservative cycle to transmit certain types of basic data, or programmed to transmit more often to provide additional data-it all depends on the type of study that is being conducted. The transmitters generally last between several months to 2 years, depending on how they are used, and the average lifetime is 1 year.

To learn more about the satellite tracking of sea turtles, please visit the Caribbean Conservation Corporation webpage at http://www.cccturtle.org/ . To learn more details about satellite transmitters, and to track the movements of individual sea turtles with active satellite transmitters, please go to http://www.cccturtle.org/sat1.htm .

Life History:

Sea turtles may look like they’re having a hard time lumbering on the beach, but beneath the ocean waves, they are poetry in motion. Their streamlined bodies allow them to glide gracefully in the water, propelled by powerful flippers. Being reptiles, they have to surface to breathe, several times an hour when active, less frequently when they’re at rest. But this inability to breathe underwater has not stopped them from being fully adept to life in the ocean.

At first glance, the main feature of a sea turtle is its shell. It’s made of hard scales called scutes, that covers it carapace (top of the shell) and plastron (bottom of the shell). One exception, however, is the leatherback turtle. Its shell is covered by a leathery skin. Sea turtles have no teeth, instead they have a powerful beak-like jaw that can crush, tear, and bite their food. They drink seawater, and the excess salt is secreted from tear ducts. Sea turtles possess an excellent sense of smell. Their hearing however, is more limited. There are no ears sticking out of their heads; the middle and inner ear are buried inside each side of the head and are tuned in to low frequency noises. Sea turtles have good underwater vision, and are sensitive to visible and ultraviolet colors. But outside water, they are near-sighted. And how do you tell males and females apart? Adult males have longer tails, compared to females.

Despite their life at sea, sea turtles are still tied to the land when it comes to breeding. The usually solitary adults come together during mating, meeting in the waters off the beach where they were born. After mating, the females return to their natal beach to lay their eggs. After laboriously clambering onto the beach, the female sea turtle stops at a suitable site and begins digging a hole with her powerful hind flippers. She then deposits a clutch of soft-shelled eggs, covers them with sand, and returns back to the sea. Depending on the species, most females will nest two or more times during a nesting season. After that, she may not return to nest for another 2 or more years. Sea turtle nesting seasons vary around the world, but in the Southeastern U.S., egg-laying generally occurs between April and October.

After incubating in the sand for about 60 days or so, depending on the species, the eggs hatch. The sex of the hatchlings depends on the incubation temperature: warmer temperatures produce females while cooler temperatures produce males. The hatchlings emerge from the sand, sometimes at dusk, usually at night, when the air is cooler, then make a frenzied dash to the sea. For the males, this is their last contact with dry land, whereas females that survive will return to nest at the beach they were born at in adulthood.

The lives of sea turtles from hatchling to adulthood are largely a mystery. Some scientists have theorized that young turtles spend part of their lives in large floating mats of sargassum, a type of sea algae, where they eat and grow. When they reach about 12 inches in diameter, they venture out to feed in less protected areas, perhaps feeding grounds near the shore. Sea turtles grow slowly, and depending on the species, could take 15 to 50 years to reach maturity. When it comes time to breed, the adult are drawn back to the waters off their birth beach, to begin a new generation.

Threats to Sea Turtles, and Conservation Efforts

There has been an increasing demand for turtle meat, eggs, and carapace in the past 100 years. This, along with the increasing destruction of sea turtle habitat-feeding and nesting areas-and pollution has led all sea turtle species close to extinction.

In nature, sea turtles are most vulnerable at the egg and hatchling stages. The eggs are often eaten by animals like raccoons, crabs, and ants. Hatchings that emerge from the sand have to make a fast dash to the sea or be eaten by predators like birds and crabs. In the water, they are often taken by large fish. Very few hatchlings make it to adulthood, by some estimates, one in 1,000 to 1 in 10,000. Adult sea turtles don’t have any predators, except for sharks that occasionally bite off a flipper, or worse.

The main threat to sea turtles is humans. In many countries, eggs are harvested. Although there are laws against this, enforcement is lax in many places. Sea turtles are also hunted for their meat. Their shells, especially those belonging to the Hawksbill, are still used for making jewelry. In the United States, sea turtles are protected. It is illegal to harm these animals, and illegal to import or export turtles or their products. Other countries that have signed on to the Convention of International Trade in Endangered Species (CITES) also have laws, and they are enforced at varying degrees depending on the availability of law enforcement resources.

During commercial fishing activities, especially shrimping, sea turtles are often entangled in nets and drown. U.S shrimpers are now required to have Turtle Exclusion Devices (TEDs) in their nets, a practice that has helped decrease turtle mortality during commercial fishing. But sea turtles are far ranging, and are still getting killed by commercial fishing activities in other parts of the world. Several sea turtle conservation groups are working hard to encourage governments and fishermen to use TEDs in their nets.

Trash like plastic bags, balloons, and bottles, as well as styrofoam, are mistaken as food, and eaten by sea turtles-this all too often results in their death. Pollution, like oil spills, untreated sewage, fertilizers, and urban chemical runoff, is degrading their habitat, destroying the grasses and animals that sea turtles depend on for food. Laws on dumping pollutants into the ocean need to be vigorously enforced, and educating the public about these issues can create awareness that will result in changes in how trash is treated.

Nesting sea turtles and their hatchlings also face problems on land. Coastal armoring, like the building of seawalls, and sand bags to prevent erosion, prevent female turtles from nesting on beaches. Beach nourishment, where sand from other locations are laid down on beaches to take the place of eroded sand, can also cause problems. Compact sand or sands with an unfavorable texture for sea turtles can make digging difficult for the female turtle. During the nesting season, beach renourishment can add too much sand above nests, trapping the hatchlings, or nests could get run over by machinery. Important nesting sites need to be protected. Some places have been converted to local or national refuges, such as the Archie Carr National Wildlife Refuge in Florida. But more needs to be done to buy critical parcels of beach-front land before they become developed. Beach nourishment should be more closely regulated, first making sure that such activities are not conducted during the nesting season. The sand used to replenish the beach should closely match the original sand at that location. If done properly, beach nourishment can actually benefit nesting sea turtles.

Hatchlings emerging from the sand at night immediately head towards the brightest direction. Under natural conditions, the brightest direction is towards the ocean, where the water is lit by the reflection of the stars and sometimes the moon. Bright lights from beach communities can outshine the natural brightness of ocean waters, luring hatchlings away from the water, and to their death by predation and dessication. In Florida, some beach communities have passed laws against bright beach-front lighting, to protect sea turtle hatchlings.

There are many human-induced threats facing sea turtles. And because these are far-ranging creatures, conservation steps need to be taken wherever sea turtles are found. Yet so little is known about their lives, their habits, and their ranges. Continuing research and monitoring are essential to get to know these creatures better, and to identify new ways to protect them.

Turtle Species:

Sea turtles have been around for a long time, appearing in the fossil record as long as 110 million years ago. Today, there are 7 species found in the oceans of the world. All but two species can be found off the waters of North America, particularly in the southeast U. S.. All sea turtles that occupy U.S. waters, and nest on U.S. beaches are on the Endangered Species List, except for the Loggerhead turtle that is classified as a “threatened” species.

Loggerhead Turtle (Caretta caretta)

There are two major sites for nesting Loggerhead turtles in the world; one is Masirah Island in Oman, and the other, the beaches of southeastern United States. Although these animals are quite far-ranging in their travels-turtles born in the U.S. have been found foraging in the Mediterranean!- these sea turtles always return to their birth beach to nest. Loggerheads are the most-often seen sea turtle in the U.S., and unlike other sea turtles that are classified as endangered, the Loggerhead’s status is “threatened.” This does not mean that all is well with this species, they are still very much in danger of extinction. The powerful jaws of a Loggerhead allow them to easily crush their prey, mostly clams, crabs, and horseshoe crabs. An adult Loggerhead, fully grown, can measure 32 to 41 inches long, and weigh up to 350 pounds. Their carapace is a reddish-brown color, with a dull yellow to brown plaston. During each nesting season, between May to September in Florida, a female lays 4 to 7 clutches of eggs, 14 days apart. After her nesting duties are over, she may not return for 2 or more years. A Loggerhead clutch contains about 100 to 126 eggs, and takes about 60 days to hatch.

Green Turtle (Chelonia mydas)

These sea turtles, named for their green body fat, are endangered throughout their worldwide range. They are often found during the day in shallow flats and seagrass meadows, grazing on algae and seagrasses. Although the adults are mostly vegetarian, the juveniles are carnivorous. The largest nesting site for Green turtles in the Western Hemisphere is at Tortuguero, in Costa Rica, but some also nest on Florida beaches. Nesting females are about 3 feet in length, and weigh about 300 pounds. They nest in intervals of 2 or more years. During a season, typically running from June to October in the U.S., a female Green will lay 3 to 5 clutches, each containing about 115 eggs. About 60 days later, the young emerge from the sand to make their mad dash to the sea.

Leatherback Turtle (Dermochelys coriacea)

This is the biggest of all the sea turtles. Leatherbacks can reach 4 to 8 feet in length and weigh from 650 to 1300 pounds. Despite their formidable appearance, leatherbacks primarily dine on, of all things, jellyfish! Their throat and jaws are lined with stiff spines, allowing them to swallow their slippery slimy prey. As indicated by their name, Leatherbacks do not have a hard shell. Their carapace and plastron are covered by a thin layer of leathery skin held in place by thousands of tiny bone plates. Another distinguishing field mark is the series of ridges, seven in all, that run down the carapace, which is black, peppered with many white spots. This enormous sea turtle has great stamina, capable of swimming thousands of miles in the open ocean. Unlike other turtles, Leatherbacks can tolerate colder waters, by regulating its body temperature. Leatherbacks nest on many tropical beaches throughout the year, including a few nestings on the east coast of Florida. In the U.S. nesting season occurs from March through July. Female Leatherbacks nest every 2 to 3 years, returning to their birth beach each season to lay 6 to 9 clutches, each separated by about 10 days. Each clutch contains about 110 eggs, of which 30 are unfertilized. The hatchlings emerge after 65 days of incubation.

Hawksbill Turtle (Eretmochelys imbricata)

This small agile endangered sea turtle is often hunted for its attractive shell that is used for jewelry, a product that is banned in the U.S.. Hawksbills are mostly found in tropical waters, and rarely nest on U.S. beaches. Their primary food is sponges. They measure 30 to 36 inches in length and weigh 100 to 150 pounds. These turtles nest every 2 to 3 years. During a season, females will lay 2 to 4 clutches every 15 days, each clutch containing about 160 eggs that will hatch 60 days later.

Kemp’s Ridley Turtle (Lepidochelys kempii)

Of all sea turtles, the Kemp’s Ridley is considered the rarest, and most endangered. They about 24 to 28 inches in length, making them the smallest of the sea turtle species, and weigh about 70 to 100 pounds. The adult carapace is an olive green color, while the plastron is yellow. They feed primarily on crustaceans, jellyfish, and molluscs. Kemp’s Ridleys nest every year. They lay 2 clutches every season, abut 25 days apart. Each clutch, containing around 105 eggs, takes 55 days to incubate. These turtles have only one natural nesting beach, a strip of beach at Rancho Nuevo in Mexico. (Currently, efforts are underway, by U.S. government and private organizations, to create a secondary nesting site at Padre Island National Seashore, Texas. ) Unlike other sea turtles, Kemp’s Ridleys nest in large groups, known as “arribadas,” the Spanish word for “arrival.” These arrivals occur between April and June. Sadly, these species has declined sharply. In 1995, only 1,429 Kemp’s Ridleys were documented nesting in Rancho Nuevo, compared to about 42,000 in 1942.

Flatback Turtle (Natator depressa)

This species is not encountered in U.S. waters, but found off the northern coast of Australia, and the Gulf of Papua, New Guinea. They measure about 39 inches in length and can weigh as much as 198 pounds. This sea turtle nests about 4 times per season. Its clutches are small compared to other sea turtles, about 50 eggs, but these eggs are larger than those of other sea turtle species.

Olive Ridley Turtle (Lepidochelys olivacea)

The other species not encountered in U.S. waters is the Olive Ridley, named for its olive green color. They are found in the tropical and subtropical Pacific, where large groups still nest on the Pacific side of Costa Rica (mostly at Nancite and Ostional) and Mexico (La Escobiulla, Oaxaca). This small turtle, weighing about 100 pounds, is an omnivore; besides vegetation, it also feeds on crustaceans, tunicates, molluscs. Each egg clutch has about 110 eggs, and takes 52 to 58 days to incubate.