Sea Turtles: Final Paper
Spring has started! The Swans are Courting in Western Pond one day late in March! (Quicktime movie)
The biology of the sea turtle and facors affecting its population
Upon first sight of the great sea turtle it might just think that it is like any other turtle. The truth is that marine turtles are beautiful creatures spending a majority of their lives wandering endlessly through our massive ocean. These reptiles have the ability to do amazing things. Some of these things include evolving to a range of purely innate responses to the demands of a changing suite of environments and having remarkable navigations skills for their excursions that may last up to several years. Sea turtles have been in existence for more than 100 million years and researchers have been studying them for great deal of time. During the past 20 years however, the natural history of marine turtles has received growing attention and much has been learned (Bjorndal 19). Instantly you will fall in love with their beauty and majestic way of life.
The biology behind these amazing animals causes them stand out from much of the ocean life. There are seven different species of sea turtles. These species include Kemp�s Ridley, Flatback, Loggerhead, Olive Ridley, Leatherback, Hawksbill, and the Hawaiian Green Turtle (Gardner 2004). Unlike many animals the female sea turtle is generally larger than the males. The main distinction between the two is that the male tends to have a longer tail. The core part of the sea turtle and the part that helps protect them from predators is the shell. The shell grows around the body protecting the organs of the animal. There are different sections that cover the shell, which are called scutes. The skin that covers their body is a leathery material. Marine turtles also have a beneficial shape that allows them to glide through the water with their paddle-like flippers. These flippers provide the main movement and mobility of the turtles and contain a claw and in some cases two claws.
Courtship between among sea turtles begins when the male turtle first approaches the female it swims round to face the female and nuzzles her head. Continued nuzzling on the neck and shoulder accompanied by nonaggressive �bites� leads to �biting actions at one of the rear flippers.� If the female accepts she will turn toward him and assume a vertical position in the water (Bjorndal 30). The male will the attempt to mount the female and reproduction occurs between the male and female through sperm that is passed to the female though the males tail. The beginning of mating takes place in the water and then concludes on land (Ching 21). A sea turtle lives most of its life in the water, however the female will return to land to lay her eggs. �Biologist believe that nesting female turtles return to the same beach where they were born. This beach is referred to as the natal beach: (Gardner 2004). The female sea turtle will lay her eggs at nighttime, making her way up on to the land to find a good place to construct a pit for her offspring. The process of laying eggs is as follows: �she dug a pit for her body with her flippers. She nested in it and used her back flippers, like shovels, to scoop out a bottle-shaped hole. Now she drops about one hundred white, leathery eggs that look like ping pong balls into this hole. When she finishes she will cover the nest with sand and slowly go back to sea, leaving a trail behind her� (Jacobs 13).
Heat from the sun helps the growth and development of the unhatched sea turtles. Usually two months are needed for the eggs to hatch. When they have reached maturity they have a sharp snout that they uses to cut open and escape from the shells. A nest of sea turtles will hatch at about the same time. This is beneficial because the movement as a group helps each egg. When the baby sea turtles are out of the shells they start scraping away the sand when they feel the cool sand and then they know that it is night. The little hatchlings will spend a couple of days digging its way to the surface. Once they have reached the surface they make their way towards the ocean. Only a few make it to adulthood. They have many predators like birds and lizards on the beach and even the fish will eat them in the ocean. If they do make it to the ocean they have a chance to live a long adventurous life.
Sea turtles are not generally considered social animals, however some species do congregate offshore. Even hatchlings, once they reach the water, generally remain solitary until they mate. In the ocean turtles may spend hours at the surface floating, apparently asleep or basking in the sun while seabirds perch on their backs. Sea turtles tend to dive in a cycle that follows the daily rising and sinking of the dense layer of plankton and jellyfish. As dawn approaches, their dives become deeper as the plankton and jellyfish retreat to deeper water and away from the light of day. The turtles bask at the surface at midday when the layer sinks beyond their typical diving range. As dusk approaches, the turtles' dives become more shallow as the layer rises.
Migration habitats are different among species and different populations of the same species as well. Some sea turtle populations feed in the same general areas and other will travel great distances. The Green sea turtle population migrates primarily along the coasts from nesting to feeding grounds. However, some populations will travel across the Atlantic Ocean from the Ascension Island nesting grounds to the Brazilian coast feeding grounds. Researchers have documented nonmigratory and short-distance migratory populations among sea turtles. Leatherbacks have the longest migration of all sea turtles. They have been found more than 4,831 km (3,000 miles) from their nesting beaches.
A sea turtle�s diet also varies with species. Some maybe be carnivorous, others herbivorous, or both plant and meat eating. The jaw structure of the species can indicate their diet. Marine turtles with finely serrated jaws are more adapted for a vegetarian diet of sea grasses and algae. The Loggerheads and Ridleys have jaws that are tailored for crushing and grinding crabs, mollusks, shrimps, jellyfish, and vegetation. The hawksbill has a narrow head with jaws meeting at an small angle, adapted for getting food from crevices in coral reefs. They eat things like sponges, tunicates, shrimps, and squids. As sea turtles age they sometimes change their eating habits from carnivorous at hatching and to a herbivore as an adult.
Sea turtles can be spotted around the globe. Adults of most species are found in shallow, coastal waters, bays, lagoons, and estuaries. Some also venture into the open sea. Younger sea turtles of some species may be found in bays and estuaries, as well as at sea.
Despite the abundance of interest and love of sea turtles they are still endangered. There are many factors that contribute to the threatened lives of sea turtles. One main cause of the death of sea turtles is from hunters. Marine turtles are hunted for their meat, eggs and their shell, which is usually used for tools and ornaments (Olafsson and Daly 2). Their skin is often used to make leather goods. �The Hawksbill is prized for its shell to make tortoise shell combs, brush handles, eyeglass frames, buttons, hair clips and jewelry� (Jacobs 21). Sea turtles are even killed and then stuffed to be hung on peoples walls. Once dead fat is taken from these reptiles to make makeup. Now the sea turtles are under the Endangered Species Act. This has helped them make a slow recovery and the population is slowly increasing.
Another great cause of the death of sea turtles is within the fishing industry. �Shrimp trawling, one of the world�s most destructive fishing practices, had been documented as the greatest threat to the continued survival of sea turtle populations� (Fugazzotto and Steiner 1). When people are fishing for shrimp they drag a big net behind a boat. This results in sea turtles getting caught in the net and then dragged for many hours. They die from the exhaustion from attempting to escape. A simple and inexpensive technology, known as TED (Turtle Excluder Device), can be attached to shrimp nets to prevent the needless decimation of the remaining sea turtles. New ideas to help preserve the last of our precious sea turtles are happening are being made every day.
Recently they have discovered tumors developing on the skin of the sea turtles. Scientists have identified the tumors as fibropapillomas because it is a tumor that grows and develops on fibrous tissue. Fibropapillomas develops and appears as lobe-shaped tumors. They can appear and can infect all soft portions on the turtle�s body, which is mainly its skin (Gardner 2004). The tumors start out small at first but can grow to 10 centimeters or more in diameter. The causes of the tumors are yet to be discovered. Researchers have not been able to determine and pinpoint the major factor leading to the cause of death of these turtles. The size and location of the tumors implied that much of the turtles died because they were unable to breathe normally or eat. The impact that this disease has on the population of sea turtles is tragic and unfortunate. Most of the turtles contract these tumors and die in just a few years.
Human are a sea turtle�s largest predator aside from the birds, lizards, and large fish that eat them when they are newly hatched. Humans need to get rid of waste causes things like plastic bags and other harmful things to be put into the ocean. Often times the turtles will mistake plastic bags as jellyfish. The plastic is very hard for them to digest and ends up staying in their bodies for a long period of time. This can also clog the turtle�s digestive system (Gardner 2004). Marine turtles are also sensitive to all kinds of oils and chemicals that are often spilled into the ocean. Humans and their needs for a beachfront property sometimes take up the breeding grounds for turtles leaving them no place to lay their eggs.
There are many conservations programs that are set up to help protect these wonderful creatures. As mentioned before shrimping nets are often equipped with the TED to prevent sea turtles from being trapped in the net and killed. Each of the eight species of sea turtles are listed as threatened or endangered on the U.S. Endangered and Threatened Wildlife and Plants List. Which makes it illegal to harm, or in any way interfere with, a sea turtle or its eggs. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) is an international treaty developed in 1973 to regulate trade in certain wildlife species. CITES protects all species of sea turtles. The U.S. and 115 other countries have banned the import or export of sea turtle products. Other things that can be done are protecting the nests by covering them with a screen, maintaining wildlife refugees, managing sex ratios, and zoos like Sea World with an Animal Rescue and Rehabilitation Program.
Sea turtles are amazing animals for their beauty and intelligence. They have roamed our oceans for millions of years and hopefully with our help we can keep it going. Now that you have learned more knowledge about sea turtles here are a few interesting facts: Scientists believe that sea turtles navigate by using their own innate global positioning system. Hatchlings are born with the ability to navigate using the earth's magnetic field. The leatherback is the most ancient species of living sea turtle, as well as the largest and heaviest turtle in the world. Studies have shown that loggerhead eggs incubated at about 90 degrees F (32 degrees C) or higher develop into females. Eggs incubated at 82 degrees F (28 degrees C) or below produce males. Incubation temperatures between the two result in both males and females.
Ancona, George. (1987). Turtle Watch. New York: Macmillan Publishing Company.
Bjorndal, Karen A. (Ed.). (1979). Biology and Conservation of Sea Turtles. Washington & London: Smithsonian Institution Press.
Bolton, Alan B., & Blair E. Witherington. (2003). Loggerhead Sea Turtles. Washington: Smithsonian Books.
Bush Entertainment Corporation. (2002). Sea Turtles. Retrieved March 31, 2004, from http://seaworld.org
Ching, Patrick. (2001). Sea Turtles of Hawaii. University of Hawaii Press.
Committee on Sea Turtle Conservation. (1990). Decline of the Sea Turtles: Causes and Prevention. Washington, D.C.: National Academy Press.
Florida Marine Research Institute. (2004). Sea Turtles. Retrieved March 31, 2004, from http://flordiamarine.org
Fugazzotto, Peter, Todd Steiner. (1998). Slain by Trade. Sea Turtle Restoration Project.
Garder, Emily M.S. (2004) Hawaii�s Marine Wildlife: Whales, Dolphins, Turtles, and Seals: A course study. Retrieved April 19, 2004, from http://www.earthtrust.org/wlcurrie/index.html
Jacobs, Francine. (1995). Sea Turtles. Hawaiian Island Humpback Whale National Sanctuary and the U.S. Fish and Wildlife Service.
Klemens, Michael W. (Ed.). (2000). Turtle Conservation. Washington & London: Smithsonian Institution.
Olafsson, Hugi, Trevor Daly (1990). Sea Turtles: Endangered and Exploited. Spachee Environmental News Alert no. 2.
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Sea turtles are large, air-breathing reptiles that inhabit tropical and 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 come in many different sizes, shapes and colors. The olive ridley is usually less than 100 pounds, while the leatherback typically ranges from 650 to 1,300 pounds! The upper shell, or carapace, of each sea turtle species ranges in length, color, shape and arrangement of scales.
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. Research on marine turtles has uncovered many facts about these ancient creatures. Most of this research has been focused on nesting females and hatchlings emerging from the nest, largely because they are the easiest to find and study.
Thousands of sea turtles around the world have been tagged to help collect information about their growth rates, reproductive cycles and migration routes. After decades of studying sea turtles, much has been learned. However, many mysteries still remain.
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.
Why Care About Sea Turtles?
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.
Nesting, Incubation and Emergence
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.
Migration and Navigation Abilities
Status of the Species
The earliest known sea turtle fossils are about 150 million years old. In groups too numerous to count, they once navigated throughout the
world’s oceans. But in just the past 100 years, demand for turtle meat, eggs, skin and colorful shells has dwindled their populations. Destruction
of feeding and nesting habitats and pollution of the world’s oceans are all taking a serious toll on remaining sea turtle populations. Many breeding
populations have already become extinct, and entire species are being wiped out. There could be a time in the near future when sea turtles are just
an oddity found only in aquariums and natural history museums – unless action is taken today.
Green, leatherback and hawksbill sea turtles are classified as Endangered in the United States under the Endangered Species Act, while the loggerhead and olive ridley sea turtles are listed as Threatened. Internationally, green and loggerhead sea turtles are listed as Endangered (facing a very high risk of extinction in the wild in the near future) by the International Union for Conservation of Nature and Natural Resources (IUCN), while hawksbill and Kemp’s ridley sea turtles are listed as Critically Endangered (facing an extremely high risk of extinction in the wild in the immediate future), olive ridley seaz turtles are listed as Endangered (facing a very high risk of extinction in the wild in the near future), and leatherback sea turtles are listed as Vulnerable (facing a high risk of extinction in the wild in the immediate future).
What is Extinction?
Sea Turtle Classification
KINGDOM – Animalia
PHYLUM – Chordata
CLASS – Reptilia
Class Reptilia includes snakes, lizards, crocodiles, and turtles. Reptiles are ectothermic (cold-blooded) and are vertebrates (have a spine). All
reptiles have scaly skin, breathe air with lungs, and have a three-chambered heart. Most reptiles lay eggs.
ORDER – Testudines
Order Testudines includes all turtles and tortoises. It is divided into three suborders. Pleurodira includes side-necked turtles, Cryptodira includes
all other living species of turtles and tortoises, and Amphichelydia includes all extinct species.
SUBORDER – Cryptodira
Suborder Cryptodira includes freshwater turtles, snapping turtles, tortoises, soft-shelled turtles, and sea turtles.
FAMILY – Cheloniidae or Dermochelyidae
Sea turtles fall into one of two families. Family Cheloniidae includes sea turtles which have shells covered with scutes (horny plates). Family
Dermochelyidae includes only one modern species of sea turtle, the leatherback turtle. Rather than a shell covered with scutes, leatherbacks have leathery skin.
GENUS and SPECIES
Most scientists currently recognize seven living species of sea turtles grouped into six genera.
How You Can Help
There are many things each of us can do to help sea turtles survive. First, we must remember that we share the oceans and the beaches with many other species. Second, become informed about the things that are killing sea turtles or destroying their habitat. Elected officials and other leaders are making decisions on issues that affect sea turtles almost every day. As an informed citizen, you have the power to influence the outcome of
these issues by making your voice heard. One way to keep informed about important issues is to join and support groups like the Sea Turtle Conservancy, which monitor issues and encourage their members to get involved.