St. Catherines Island Sea Turtle Conservation Program 2007 Gale A. Bishop Turtles Reptiles
Download 0.86 Mb.
|
1 2
- Navigate this page:
- S Loggerhead Sea Turtles commonly nest on Georgias Golden Isles. ea turtles
- A Loggerhead nest on St. Catherines Sound
- Egg chamber discontinuities allow the location of clutches averaging 113 eggs.
- Nests are protected from predators by metal or plastic screens.
- Hatchlings emerge at night after about 60 days in the sand.
St. Catherines Island Sea Turtle Conservation Program © 2007 Gale A. Bishop Turtles Reptiles are a group of vertebrates, animals with backbones, which generally are cold-blooded (body temperature is close to that of their surroundings), have scales on a dry skin, undifferentiated teeth, and reproduce sexually by laying amniote eggs (eggs which have a waterproof membrane allowing them to develop outside of water). Turtles are a group of reptiles in which the bones have become modified to encase the body in a more or less rigid, continuous armored case with only the legs, tail, and head exposed. The top shell (carapace) of turtles is formed from ribs that are expanded and fused together, the bottom shell (plastron) is formed by fusion of a group of bones not present in all vertebrates. The evolution of a rigid box-like body allows few further changes of body morphology, forcing the legs to be horizontal, causing retraction of exposed parts into the armored shell, and a unique arrangement of vertebrae, which are fused to the inner side of the carapace. 
S Loggerhead Sea Turtles commonly nest on Georgia's Golden Isles. ea turtles are turtles that live in the sea after hatching from eggs deposited on sandy beaches, such as those in Georgia. The extended life of these turtles in the oceans have led to modification of these turtle’s legs into flippers. Other significant changes were also necessary for turtles to colonize the sea including numerous physiologic adaptations to continuous life in salt water. Sea Turtles There are seven kinds (species) of sea turtles; Loggerheads, Green Turtles, Kemp’s and Olive Ridleys, Australian Flatback, Hawksbills, and Leatherbacks. All sea turtles are similar in many ways, their legs are modified into flippers, their heads, legs, and tails can not be retracted into their shell, all spend their entire life at sea except for nesting and hatching, and all take a long interval of time to mature to reproductive age. Significantly, all sea turtles are also in danger of becoming extinct. Sea turtles have been present in the Earth’s oceans since the Jurassic Period when they lived at the same time as the dinosaurs. Throughout their 150+ million year history sea turtles have adapted to changing conditions as seas rose and fell, continents drifted apart and collided, and oceans opened and closed. The one agent of change that is universally driving sea turtles toward extinction is interaction with humans. Rapidly growing human populations and an ever increasing standard of living has led to many negative impacts for sea turtles including oceanic pollution, urbanization of coasts and their encasement in seawalls and revetments, increasingly hazardous technology (such as boat propellers), and increasingly efficient fisheries. Thus, it is humans who are driving the sea turtles toward the brink of extinction, including you and me. Once an organism is extinct, it is gone forever from the face of the Earth. Although many organisms have become extinct during the past, the rate and numbers of plants and animals being driven toward extinction by humans is alarming. Because the Earth’s ecosystems are finely tuned to all plants and animals, it is important for us to minimize detrimental effects to them caused by humans. Sea turtles have become a test case to see if humans can responsibly interact with other organisms on the Earth. Ecology of Sea Turtles Sea turtles migrate annually through Georgia’s coastal waters and nest on the sandy beaches of Georgia’s Golden Isles. Leatherbacks migrate northward each spring following warming Atlantic waters and one of their favorite foods, jellyfish. Juvenile Kemps Ridleys regularly are found in Georgia’s coastal waters, apparently waifs swept out of the Gulf of Mexico by the Gulf Stream. Sea turtles nest on sandy temperate and/or tropical oceanic beaches. After depositing eggs in an urn-shaped egg chamber, the female turtle immediately returns to the ocean; never seeing her young. The eggs hatch after about 60 days of incubation and the hatchlings dig their way to the surface and emerge, scamper to the sea, and enter a swimming frenzy for about 24-72 hours. After entering the sea, we know very little about the life history of the baby turtles. We think Loggerheads live a pelagic existence for several years drifting with drift lines of Sargassum algae in oceanic currents. After approximately 20 years, the sea turtles reach maturity, breed, and the females search out sandy beaches upon which to nest and continue the life cycle. Some sea turtles are remarkable for nesting on the same beach time after time; perhaps the very beach upon which they were hatched. Other turtles show less fidelity to a single beach, but still tend to return to the same area to nest. Sea turtles crawl onto the beach to find a nesting suitable place leaving behind diagnostic crawlways. If the turtle doesn’t nest, they leave a simple non-nesting crawlway; if they do nest, they leave not only a crawlway, but an elliptical disturbed area, the nest, in which they have deposited a clutch of eggs. Between nesting seasons turtles often migrate hundreds or thousands of kilometers with seasonal water temperature changes and/or following their preferred food source. Each of the sea turtle species has its own preferences for nesting areas and food. Leatherbacks nest in the tropics and migrate great distances, even along the Georgia coast; living largely on jellyfish, diving thousands of meters to find them. Hawksbills forage on sponges from reefs or rocky areas in clear, shallow water and nest on tropical beaches. Green Turtles are found around the world in tropical and subtropical oceans and occupy high-energy beaches, convergence zones in pelagic waters, and benthic feeding grounds in shallow waters where they often eat sea grasses or algae. Loggerheads range through subtropical and temperate waters of the Atlantic, Pacific, and Indian Oceans, nesting on their sandy beaches, particularly of Oman and Florida (USA), but also in Georgia and South Carolina. Kemps Ridleys nest primarily at one beach in Mexico, Rancho Nuevo, and spend their adult life in the Gulf of Mexico except for some that are apparently carried into the Gulf Stream in the Atlantic Ocean. The distribution and ecology of sea turtles remains a major research effort because we still know so little about them. Various aspects of the ecology of sea turtles make them susceptible to different hazards during different parts of their life cycles. These hazards may be natural [like storms, parasites, or predators] or may be caused by humans [collisions with boats, drowning in gill nets or trawls, pollution, etc.]. Negative interactions that are natural [i.e. non-human] have often been overcome during the evolutionary development of each species and are of little concern to sea turtle conservationists. Negative impacts that are due to human causes are relatively new to sea turtles and are increasingly prevalent and often tend to reinforce one another. Humans rely on the environment for their very existence and must insure that negative human impacts on other species are as small as is possible. S  ea Turtles In Georgia
Loggerheads commonly nest on the sandy beaches of the Georgia barrier islands, although Green Turtles and Leatherbacks have also been documented as nesting in Georgia. Each summer from mid-May until late August, Loggerhead sea turtles crawl out of the Atlantic Ocean to find nesting sites leaving distinctive entrance crawlways across the width of the beach. Once a good site is located the female digs a depression (a body pit) in the warm sand and when she hits damp sand, excavates an urn-shaped egg chamber with her rear flippers. She then deposits a clutch of about 115 eggs, backfills the egg chamber, covers the body pit with loose surface sand forming a covering pit, and then crawls back into the ocean, leaving an exit crawlway. Such eggs are often found and eaten by raccoons and feral hogs, so that they must be protected by screening. 
When sea turtle crawlways are encountered on daily monitoring of island beaches, the trace is a A Loggerhead nest on St. Catherines Sound. ssessed by “reading the nest” and by careful excavation of the loose sand of the covering pit to locate the neck of the egg chamber which appears as a disturbed area surrounded by undisturbed layered sands of the backbeach. 
The position of the clutch of eggs is assessed in terms of probability of successful hatching and either reburied in situ or relocated to a better location and reburied. 
Egg chamber discontinuities allow the location of clutches averaging 113 eggs. The clutch of eggs is covered by a 3 x 4 foot screen held down by steel rebar to protect it from predators and marked by a numbered, wooden stake. Each nest is monitored daily and maintained by DNR sea turtle conservationists. Nests are protected from predators by metal or plastic screens. A  fter approximately 56 days the eggs hatch and the hatchling turtles emerge under the cover of darkness leaving telltale miniature crawlways and an emergence crater. Hatchlings may emerge all at once or in a series of emergences spaced over a number of days.
Hatchlings emerge at night after about 60 days in the sand. Two rare daytime emergences of Loggerhead hatchlings have been documented by St. Catherines Island conservationists since 1990. Occasional daytime emergences of hatchlings surprise us! 
After 3-5 days of emergence, the nest is excavated by sea turtle workers and the numbers of hatched and unhatched eggs counted. Eggs are counted into groups of 10 and totaled after finishing. Normal hatch success is about 60% with significantly higher success in hatcheries situations (where all nests are moved into small protected areas) and nurturies (where several nests are relocated into natural beach areas). 
Assessment of the hatch is done by excavating each nest and counting hatched and unhatched eggs. D
uring nest assessment, it is common to find stragglers or dead hatchlings within the egg chamber. Stragglers are removed from the nest during documentation and released into the ocean during the next night. Significant Nests are Trenched When Loggerhead nests fail to hatch, they are often trenched to document the conditions leading to their failure. Trenching is done by digging a trench about 50 cm in front of a nest along a wall about 1.00 m parallel to the shore and 60-70cm deep. This initial trench is then cut back into the nest by carefully shaving the back wall until the egg chamber is intersected. 
Investigations of this sort have not only led to an understanding of Loggerhead nest morphology, but also have allowed us to identify reasons for nest failure. In this instance, a rise in groundwater level inundated the nest and then the sand was fluidized by vibration from surf generated by a Nor’easter on a spring tide. This not only flooded the nest, suffocating the eggs, but caused the sand to flow and pack around the eggs eliminating any possibility of development. Trenching also developed the three dimensional visualization necessary to recognize the world’s first fossilized sea turtle nest.
Georgia Sea Turtle Nesting 
Directory: resources -> docs docs -> Efca eastern District and TouchGlobal, the crisis response ministry of efca docs -> Description docs -> The importance of Regional Jets in the future European Air Transport and the role of Alenia Aeronautica docs -> 2016 ten section Work Programme en docs -> Turkey-eu joint consultative committee docs -> Communicating turkey docs -> Final report docs -> Corridors have docs -> Payment Reform Government docs -> Payment Reform Government Download 0.86 Mb. Share with your friends:
|
1 2