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Sea Turtles differ from other reptiles mainly in that the body of a Sea Turtle is protected by a carapace. The oldest known Sea Turtle fossils are about 150 million years old. It has been determined that they lived on Earth more than 220 million years ago.
Differences between Sea Turtles and Terrestrial Turtles Unlike their terrestrial relatives, who are also known as Land Turtles or Tortoises, Sea Turtles cannot pull their heads and fins into their carapaces. They are thus more vulnerable to predators and fishing nets.
A group of Sea Turtles split from Freshwater Turtles about 100 million years ago. Sea Turtles differ from Terrestrial and Freshwater Turtles by the presence of salt glands in the skull, limbs transformed into fins and a more reduced carapace.
Role of Sea Turtles in the Oceans Sea Turtles have a crucial role in the functioning of coral ecosystems. They directly affect the composition, structure and species diversity of these ecosystems.
Sea Turtle Species All Tortoises are Turtles, but not all Turtles are Tortoises. There are two families of Sea Turtles: Dermochelyiidae with only one representative in the great Leatherback (Dermochelys coriacea) and Cheloniidae which comprise 6 species.
Cheloniidae are characterized by keratin plates covering a well-developed bony carapace. In contrast, the Leatherback has a carapace formed by a thin solid layer of elastic skin, reinforced with thousands of small bone tufts.
Amazing Orientation Sea Turtles have a built-in GPS system. They can detect the angle and intensity of the Earth's magnetic field and use it to navigate thousands of miles, e.g. they can find an island in the middle of the ocean. Turtles can see well underwater, but are short-sighted on the ground. Turtles also have tears, but not because they are sad. They have glands that help them empty excess salt from their eyes, making them appear to be crying.
Habitat of Sea Turtles The Leatherback species inhabits the entire world's oceans. Leatherbacks lay eggs in the tropics and subtropics, and their food habitats can be observed even in northern areas above 50 °N. Their habitats and main nesting sites are shown in the map below.
Some species change eating habits as they age. For example, Green Sea Turtles are mainly carnivorous from hatching until juvenile size; then progressively shift to a herbivorous diet.
Their food includes: jellyfish, fungi, small crustaceans and small fish.
Did you know … 6 of the 7 species of Sea Turtles are endangered, mainly through human neglect and greed?
Seven Species of Sea Turtles, all listed under the Endangered Species Act, are:
These turtles have a beautiful tortoiseshell pattern on their carapace and live in the tropical and subtropical waters of the Atlantic, Pacific and Indian Oceans. They are found among reefs, rocky areas, mangrove swamps, lagoons and estuaries. About 20 000 - 23 000 Hawksbill Turtles nest per year. IUCN Red List satus: Critically endangered.
Life Cycle Sea Turtles, during their slow growth, undergo dramatic ontogenetic changes. When they reach a certain size, after the initial juvenile ocean phase, they usually inhabit coastal areas. They mature after a few more years and then travel to hatcheries to reproduce. Little is known about the biology of Sea Turtles in the period between their first entry into the sea and reaching sexual maturity.
Did you know… only 1 in 1 000 turtles will survive into adulthood?
Sea Turtles, after reaching sexual maturity, may migrate thousands of miles to reach breeding sites, usually in the open sea. Female Sea Turtles return to land to lay their eggs. Due to their difficult migration with many associated threats, Sea Turtles do not reproduce regularly every year.
During one reproductive season lasting less than 3 months, females can lay 7 clutches, each containing 80 - 100 eggs. The young hatch after about 60 days. After hatching, turtles can take from 3 - 7 days to dig themselves out on to the surface.
Sea Turtle eggs are vital for healthy beaches. Eggshells and unhatched eggs provide important nutrients that aid dune vegetation, preventing coastal erosion.
The sex of the young is determined by the temperature during incubation. Higher temperatures produce females and lower temperatures, males. As a result of global warming, more females are produced.
Hundreds of years ago, millions of Sea Turtles were found in the oceans. Now their population is declining sharply. Turtles, by eating jellyfish help keep jellyfish populations under control. Unfortunately, plastic bags often look like jellyfish, and as a result, many turtles die though suffocatiion by plastics. Autopsies of turtles have found that some of them had an entire digestive tract full of pieces of plastic bags.
6 of the 7 species of Sea Turtles are endangered. Mainly through human neglect and greed. Their lives are endangered by being entangled in fishing nets, the illegal trade in meat, eggs and tortoiseshell, the development of human coastal settlements, plastic and other ocean pollution and global warming.
During the terrestrial phase, which forms only a small part of the life of Sea Turtles, the females, eggs and young are exposed to a large number of threats. Some dangers are natural, but man is responsible for the intensity of many others e.g. due to fishing nets, development of coastal settlements, shrinking beaches, tourism and ocean pollution. Due to global climate change, sea levels are rising and there is a risk of more frequent flooding of eggs. The most common predators are dogs and rats.
However, the biggest problem in many places remains the direct collection of turtle eggs and the killing of females for meat. Adult Sea Turtles in the ocean almost lack natural enemies. Intensive fishing poses a major threat. Sea Turtles are endangered by diseases to which they are more easily subject due to weakened immunity caused by marine pollution.
Predators and Disease Most Sea Turtle mortality occurs early in life. Sea Turtles usually lay approx. 100 eggs at a time, but on average only a fraction of the nest will survive. Raccoons, foxes, and seabirds may raid nests, or hatchlings may be eaten within minutes of hatching as they make their initial run for the ocean. Once in the water, they are susceptible to seabirds, large fish and even other Sea Turtles.
Bycatch While many dangers to Sea Turtles are natural predators, there is an increase in man-made threats to their lives. There is also a black-market demand for tortoiseshell for both decoration and supposed health benefits.
One of the most significant and contemporary threats to Sea Turtles comes from bycatch due to imprecise fishing methods. Sea Turtles must surface to breathe. Caught in a fishing net, they are unable to surface and thus drown.
Beach Development Coastal development, degradation of nesting beaches, dredging of the ocean floor, vessel traffic, construction, alteration of vegetation all damage Sea Turtle habitats. Light pollution disrupts the nesting behavior of Sea Turtles and leads hatchlings away from the sea, causing their death, as they can head into traffic instead of the ocean.
Poaching Sea Turtles and their eggs are killed by people throughout the world for food, and for by-products, including oil, leather and tortoiseshell. Black-market trade in Sea Turtle eggs and meat is a global problem, particularly in China, the Philippines, India, Indonesia and Latin America. Poachers in Baja California kill over 35 000 Sea Turtles each year, to meet the demand for turtle meat in Mexico and the United States.
Marine Debris Sea Turtles are injured or killed by plastics, discarded fishing gear, petroleum by-products and other debris. Marine debris, especially plastic waste which may be mistaken for jellyfish, and abandoned fishing nets in which sea creatures can become entangled, are major threats to Sea Turtles. Plastic bags which can be mistaken for jellyfish and other components of their natural diet, clog their intestines and cause internal bleeding which eventually kills them. The chemicals in the digested plastic are also dangerous - more in the Cause: Cleanse Oceans of Plastic Waste.
Climate Change Climate change increases the frequency of extreme weather events, resulting in the loss of nesting beaches for Sea Turtles. Sand temperature on nesting beaches defines the sex of a Sea Turtle while developing in the egg; rising temperatures may produce too many females.
Similarly, rising ocean temperatures impact their diet, particularly the food found on coral reefs. With the reefs dying, the marine life dependent on them also dies.
Read the Solution section on how to assist in the survival of the Sea Turtles.
The situation is better in the Atlantic Ocean, where protection is often already taking place on beaches. The situation in the Pacific Ocean is bad, where populations are declining exponentially. The worst situation is that of the Indian Ocean, where Sea Turtle populations have completely disappeared in many places.
We can all contribute to saving the Sea Turtles.
How can YOU help? **Reduce the amount of trash and plastic you produce. **This will reduce marine debris, which can entangle them or be accidentally eaten by Sea Turtles. Use reusable water bottles and shopping bags. Do not release balloons, as they can eventually end up in the ocean, where Sea Turtles mistake them for prey and consume them. Sea Turtles can become entangled in plastic and other trash in the water as well as on shore. Sea Turtles can not distinguish a plastic bag from a jellyfish! As a result, they eat plastic bags, which can injure or kill them.
Consume seafood responsibly. Avoid eating turtle meat and turtle eggs. Choose seafood caught in ways that do not harm or kill turtles. Demand food labeling with all the information.
Increase awareness about what can be done to save Sea Turtles. Use your voice on social media to inspire your friends.
Volunteer. Participate in coastal clean-ups to keep the beaches and oceans clean. Give a presentation to your local community or school on things they can do to save Sea Turtles.
Turn off, shield, or redirect lights visible from the beach. Lights discourage nesting females from coming on to the beach to lay their eggs. Sea Turtle hatchlings instinctively head toward the light of stars reflected on the ocean. Artificial sources of light can confuse hatchlings, who head in the wrong direction to become prey to predators.
Do not disturb nesting turtles, nests, or hatchlings.
Do not buy any turtle/ tortoise products.
Support organizations doing the work on the ground, providing anti-poaching patrols, cleaning beaches and oceans, and protecting natural reserves where Sea Turtles can hatch.