|Hawksbill Sea Turtle
Green Sea Turtle
|Olive Ridley Sea Turtle
Loggerhead Sea Turtle
Kemp’s Ridley Sea Turtle
Sea Turtles are ancient creatures. Some scientists say they are over 110 million years old, while others claim their lineage goes back 140 million years. They were here before the dinosaurs roamed the planet; and yet today, all species are on the IUCN (World Conservation Union) Red List meaning they are facing a high risk of global extinction. The United States Endangered Species Act (ESA) also places sea turtles species as endangered. In addition and unfortunately, scientists believe that leatherback sea turtles could be facing extinction in as little as ten years. Save the Turtles, Inc, stands humbled by these gentle creatures and works towards their survival.
About Sea Turtles
- Air breathing reptiles, but can spend hours submerged in the ocean.
- Adult females must return to land in order to lay their eggs. Many species return to the same beach where they were born to lay their eggs.
- Are found in oceans all over the world, except the Arctic Ocean.
- May migrate hundreds or thousands of miles. It is believed that they use the earth’s magnetic forces to navigate throughout the oceans.
- Most prefer open water, but they are also encountered in coastal waters near reefs and estuaries.
- Are sensitive to smells and sound. They hear through eardrums below their skin.
- The adult green turtles are unique among sea turtles in that they are herbivorous, feeding primarily on seagrasses and algae. Most sea turtles are mainly carnivores and feed on jellyfish, tunicates (ascidians, sea squirts), sponges (one of a few animals that eat them), soft corals, crabs, squids and fishes.
- All 7 species of marine turtles are listed under the Endangered Species Act (ESA).
Sea Turtles & Taxonomy: the scientific classification system
Class: Reptilia (includes turtles, snakes, lizards, and crocodiles)
Order: Testudines (includes turtles, tortoises and terrapins). See additional notes below that explain the difference between these categories.
Family: Dermochelyidae: The Leatherback is the only non-extinct species remaining in this family and is distinguished from all other turtles by the semi-flexible “leathery” skin on its outer shell
Cheloniidae: Most scientists group remaining sea turtle species under the family Cheloniidae. These species have shells covered with hard bony plates or scutes
How to Distinguish the Seven Different Species
The outer shell or carapace is the primary feature used in the identification of sea turtle species. The number of scutes on the carapace, their shape, coloring and patterning is specific to each species. Another anatomical feature utilized to distinguish between sea turtles are the prefrontal scales located on the turtle’s head.
There are seven living species of sea turtles (the first name listed is based on their physical characteristics and this common name varies in different counties). The name in parenthesis refers to their scientific taxonomy of species and genus:
Leatherback (Dermochelys coriacea)Leatherbacks are the largest of all sea turtles, the only sea turtle with a leathery soft shell, and unfortunately are the specie that is most in danger of extinction.
Hawksbill (Eretmochelys imbricata)The beak-like mouth gives the Hawksbill turtle its name. Unfortunately for the hawksbill, their shell is so beautiful that this turtle is often hunted for its shell.
Loggerhead (Caretta caretta) Named for their large heads. Known to migrate from Japan to Mexico.
Green Sea Turtle (Chelonia mydas)Largest of all the hard-shelled sea turtles and as an adult, are the only species that are herbivorous.
Kemp’s Ridley (Lepidochelys kempii)This species is the smallest of the sea turtles. The name Kemp is used because of the man, Richard M. Kemp, who first described these turtles.
Olive Ridley (Lepidochelys olivacea)Most abundant sea turtle and derives its name from the olive coloration of its heart-shaped shell.
Flatback (Natator depressa)Only sea turtle that exclusively nests in just one country, Australia. They are so named because of their flat shell.
Sea Turtles are Global:
Although each species has their own preference for nesting grounds, migration patterns and diet, they also have similar characteristics and unfortunately share the same threats.
Migration & Navigation
There has been extensive research conducted regarding the sea turtles’ abilities to return to their nesting regions. They may migrate hundreds or even thousands of miles. In the water, their path is greatly affected by powerful currents. Despite their limited vision, and lack of landmarks in the open water, turtles are able to retrace their migratory paths. One explanation of this phenomenon is that sea turtles use the earth’s magnetic fields to navigate.
Sea turtles are generally solitary and usually interact with one another only for courting and mating. Sexual maturity varies with species, ranging early with the hawksbill at three years and age twenty to fifty for the leatherback. During mating season, two or more males may court a female and the male attaches himself to the back of the female’s shell and then folds his long tail under her shell to copulate. Fertilization is internal and copulation takes place on the surface or underwater, often close to shore. 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.
Nesting & Reproduction
Sea turtles usually nest in intervals of two to three years although some nest yearly. Depending on the species, females may nest from one to ten times during a nesting season. Only the females come ashore to the beach to lay their eggs a few weeks after mating.
When the female Leatherback is ready to nest, she will choose a beach without a coral reef, one close to the deep water, such as ’s Beach. Crawling up from the ocean, she will locate a dry area and begin the arduous task of nest excavation. Using her flippers and the rotation of her body, she will dig an egg cavity that is approximately 70 centimeters deep. She will then lay 80 to 100 eggs, a process that can take over two hours. Eggs are often referred to as the size of billiard balls: she lays an average of 80 fertilized eggs and 30 smaller, unfertilized eggs in each nest. After she is finished, she will carefully cover and camouflage the clutch, and may even construct false nests to fool predators. Her role now complete, she will depart to the ocean, leaving her eggs to their fate.
Remarkably, most female turtles share a nesting instinct that drives them to return to the beach of their birth, or natal beach, in order to lay eggs. In fact, her ability to successfully reproduce depends on the ecological health of this original habitat. However, recent satellite tracking data indicates that the Leatherback, unique among turtles in many ways, may return to a range area or region, rather than a natal beach. The Caribbean coastline of Costa Rica is an example of one of the most important Leatherback nesting regions in the world.
When the female turtle comes ashore at night to lay her eggs, she will first dig a body cavity with her front flippers, and then use her back flippers to dig out the nest. Depending upon the species, 80-120 eggs will be deposited in the cavity. Afterwards the female will laboriously cover the nest with sand and often even create another false nest to confuse predators, before she finally crawls back to the sea. Incubation varies with species, clutch size (number of eggs) and temperature, but averages from 45-70 days.
Hatchlings use a caruncle, a temporary egg tooth to break open their shells. It may take several days for a group of hatchlings to dig their way up out of the nest cavity. Although they usually emerge at night, coolness of sand temperature and other factors influence their emergence. The hatchlings crawl towards the ocean in small groups. They must make it to the ocean quickly so they don’t die from dehydration or predators. When a hatchling reaches the surf, it swims continuously for 24-48 hours to get to deeper water away from predators. The turtles must survive several years in a relatively protected area away from predators and one with ample food supply. Juveniles will spend time eating and growing in habitats near the shore. Once they reach adulthood, they migrate to find a primary feeding ground. During mating season, the sea turtles will migrate closer to their nesting beach.
Why Sea Turtles Are Endangered
Unfortunately, there are many reasons why sea turtles are now at risk
- Human harvesting of turtles and their eggs.
- Destruction of nesting habitats.
- Commercial fisheries who use longline fishing practices or gill nets and do not use Turtle Excluder Devices (TEDS),
- Pollution affecting nesting habitats and/or species: such as entanglement in marine debris; plastic debris, and commercial and industrial ocean water pollution from oil spills and chemical waste.
- Global Warming.
Vital to the Eco-system
Sea turtles contribute to the delicate balance of ecosystems in our oceans and on the beaches where they nest. Their presence helps replenish both sea and beach nutrients and helps maintain the equilibrium of marine vegetation. For example, without Green turtles to feed on sea grass, the grasses would become overgrown and diseased which would have a negative impact on the many species that rely on this vegetation for sustenance. Sea turtles also play a significant role in balancing the oceans’ food chain. Leatherbacks for instance, consume large quantities of jellyfish, which feed on fish larvae. Some scientists are now looking at the possibility that the severe decline of Leatherback turtles over recent decades may have allowed for a proliferation of jellyfish, thus contributing to the drop in fish populations in the world’s oceans.
Sea turtles also support the health of our terrestrial ecosystem. The nutrients from their eggs bring food energy to species on beaches and sand dunes, which has an out-rippling effect to species in surrounding areas. The truth is that our planetary ecosystems are so intricately intertwined that it is difficult to predict just how far ranging the implications are when a global species such as the sea turtle, declines or is lost forever.
Scott Eckert’s (PhD) testimony to the Ocean Commission provides many examples of the interconnectedness of sea turtles and the eco-system:
Eckert also quotes another scientist, Dr. Nat Frazer, who eloquently describes their importance:
“Envision this with me . . . millions of sea turtles pulsing ashore onto the beaches . . . fertilizing the rims of thousands of islands and two continents. And after this wave of nutrients enters the rims, it is pulsed on up and into the interior lands in successive waves of biological transport. Year after year – tons of nutrients and billions of kilojoules of energy in a predictable, regular cycle – for tens of millions of years.
Envision this with me . . . millions of turtles grazing on seagrass beds, stimulating primary productivity at the base of the ocean’s food chain. And this surge of increased productivity works its way up the food chain, nourishing shrimp, mollusks, lobsters, and fish – as well as eventually pulsing onto the shore in the annual ballet of nesting activity.
Envision this with me . . . millions of sea turtles nibbling on sponges – trimming back the invading poriferans that otherwise would overgrow and shut down the coral reef machine. A constant system of checks and balances that also contributes to the gift of energy that sea turtles offer to the land each year in the form of nests and eggs. Year after year, for tens of million of years, the ecosystem engineers, these hawksbill and green and loggerhead and ridley and leatherback turtles, shape and improve and fine-tune the complex and mysterious and marvelous cybernetic machines of the oceans.”
We are a non-profit organization dedicated to sea turtle conservation, and we are proud to be a vital link to the international efforts of protecting marine life.
We appreciate gathering some of our data from the resources below. Many of these websites have additional pages with links that will provide more detailed information about sea turtles. In addition, we gratefully acknowledge the photographers who have given us permission to use their turtle photos.
Sea Turtle Resources
IUCN – The World Conservation Union: For information on Taxonomy and endangered species
Article by P.Tyson, Impact on Animals involving the Magnetic Field on animals
Amazing turtle information including satellite tracking
Also, see drawings of turtles and taxonomy
Taxonomy of the leatherback sea turtle
Endangered Species Act home page
Information on the difference between turtles, tortoises and terrapins