Do you know how many species of sea turtles inhabit our seas and oceans? How do they feed, where do they live, what is their role in the ecosystems or conservation status? In this post you will learn more about the 7 species of sea turtles that live with us.
Green sea turtle in Tenerife. Image courtesy of ©Joaquín Gutiérrez Fernández
Green sea turtles are herbivorous when they reach adulthood, taking a key role as "gardeners" of the ocean, cutting seagrass and helping to maintain the health of seagrass meadows that are home to many species of fish, mollusks and crustaceans.
In our oceans live two types of green turtles: Atlantic green turtle, which occupies waters of Europe and North America, and the East Pacific green turtle, which can be found in the western Pacific coast, from Alaska to Chile. These turtles can live up to 80 years and migrate long distances from their feeding grounds to nesting areas, usually in the same sandy beaches that their mothers chose to lay their eggs.
Legend tell us that during the Age of Discovery, the sailing ships that were lost in the Caribbean could find their way to the Cayman Islands guided by the sounds that green turtles produced during their migration to the islands. When Columbus discovered the islands in 1503, he named them "Las Tortugas" due to the large amount of green turtles that they could find around. Today, green turtles are listed as endangered species, having decreased in 500 years from estimates of over 100 million specimens to around 200,000 that we have today. Green turtles are caught for their meat and eggs but are also being decimated by the propellers of boats that they collide with and also because of fishing nets that suffocate them.
Hawksbill sea turtle (Eretmochelys imbricata)
Hawksbill sea turtle, image courtesy of ©Francois Parot
The hawksbill sea turtle is a small turtle that can grow up to 90 centimeters and weigh up to 80 Kilos. One of the most notable features of this turtle is its beak-shaped mouth used to make way through the coral to get to the sponges, their primary food source. By feeding on the sponges, it clears space for the growth of coral. Also, thanks to the way these turtles feed, they provide food for other species that cannot access them due to the chemical defenses of sponges. Hawksbill females return every 2 or 3 years to the same beaches where they were born in, between April and November, to lay their eggs.
These turtles live in different habitats during different stages of their life cycle, occupying coral reefs when adults. Hawksbill turtles can be found in almost all oceans and seas, especially in the Caribbean and western Atlantic Ocean, in the Coral Triangle and in the Red Sea. The degradation of coral reefs by global warming and ocean acidification is affecting them directly, as coral reefs are their home and source of food. In addition to the disappearance of their habitat, hawksbill turtles face other threats such as hunting of their eggs and their meat and by-catch in nets, placing the hawksbill turtles in a critical situation.
Leatherback sea turtle. Image courtesy of ©Lazaro Ruda www.thelivingsea.com
The leatherback sea turtle is the largest sea turtle in the world and can weigh up to 600 kilos. It is a mystery that a turtle that feeds almost exclusively on jellyfish can grow to such an incredible size. Leatherback turtles, which have a preference for the biggest jellyfish species, as the lion's mane jellyfish, can get to eat two of these jellyfish every minute being the best natural remedy against plagues of jellyfish. The mere existence of this turtle, along with other fish such as the sunfish, can keep these plagues at bay.
Leatherback turtles are pelagic creatures that can migrate 20,000 km in a period of 647 days but usually travel around 7,000 kilometers during several months. In the past 30 years, the population of western Pacific leatherback turtles has declined by 78%, seriously threatening the survival of this species. Among the dangers facing the adult leatherback turtles are fishing nets, fishing lines or hunting in their nesting places for their meat.
Loggerhead sea turtle (Caretta caretta)
Loggerhead sea turtle in Sardinia. Image courtesy of ©OCEANA / Juan Cuetos
The loggerhead sea turtle is a pelagic marine turtle that inhabits oceans around the world. The adults, like the one pictured, can carry across the ocean more than 100 animal species and 37 types of algae attached to its shell, creating a small and safe ecosystem that also provides food. The way this turtle feeds plays a very important role for the benthic system: by breaking the shells of crustaceans it provides the bottom of the sea a large amount of food and sediments and by swimming in the sandy bottoms it oxygenates it and fertilizes it.
The Mediterranean Sea is a nursery for the loggerhead turtle, being a common place for adults in the spring and summer and for egg laying. Almost half of the young population has migrated to the Mediterranean from the Atlantic and is on the shores of Greece where the most popular nesting sites are along the Mediterranean, with more than 3,000 nests per year.
The loggerhead turtle is considered an endangered species and, like other turtles, has its main threats in driftnets and trawls (that lead them to suffocation), the disappearance of their nesting beaches and the introduction of exotic predators.
Olive ridley sea turtle (Lepidochelys olivacea)
Olive ridley turtles nesting in Costa Rica. Image courtesy of ©Olivier Blaise http://www.fontainebleau-photo.com/
The olive ridley turtle, also known as Kemp's ridley turtle is considered the most abundant of the sea turtles, however it is vulnerable due to the few remaining nesting sites in the world, having dramatically reduced its population by 30% in the last 20 years.
The olive ridley turtle lives in warm tropical waters in the Pacific and Indian oceans, but can also be found in the Atlantic Ocean, off the west coast of Africa and off the coast of northern Brazil.
Olive ridley turtles are known for their synchronized nesting in groups of thousands of specimens in just a few days. In the Indian Ocean most turtles nest in groups in the Bay of Bengal, India, having registered in 1991 over 600,000 turtles nesting in a single week.
Turtle eggs produce many benefits to the beaches and the ecosystem. They provide nutrients through the shells and fluids to beaches helping plants grow and their roots avoid beach sand erosion. Also the predators that arrive to the beach to feed on the eggs and babies leave stool on the beaches and in its surroundings allowing the growth of vegetation.
Precisely the deterioration of nesting sites is the main problem that olive ridley turtles are facing. Their synchronized nesting behavior makes them need large beaches which, due to the actions of human beings, are getting smaller.
Flatback sea turtle (Natator depressus)
Flatback sea turtle. Image by Guy Harvey Marazine
The flatback turtle lives in shallow bays, coral reefs, estuaries and lagoons by the northern coast of Australia and Papua New Guinea and although it can enter in Indonesian waters in search of food, nests only in Australia. This turtle has a very varied diet, from seagrass to mollusks, jellyfish, shrimps, fish, soft corals and sea cucumbers. Although it is classified as a vulnerable species it still has enough population to not endanger their existence, with more than 20,000 nesting females registered.
Kemp's Ridley sea turtle (Lepidochelys kempii)
Kemp's Ridley sea turtle. Image by Terry Ross
The Kemp's ridley is the second smallest of the sea turtles with a maximum size of one meter in length and weighing just 45 kilograms. 95% of these turtles nest in just one beach at Rancho Nuevo, in the Mexican state of Tamaulipas. No one knows exactly what causes that thousands of Kemp's Ridley nests almost in unison on this beach and theories exist ranging from wind to lunar cycles or the release of pheromones from females.
Accidental capture in fishing nets, primarily in shrimp trawls and in gillnets, longlines, and dredges are the main threats for Kemp's Ridley turtles, the most endangered sea turtle species. Capturing their eggs also been historically the greatest threat until 1973 when, under the Act Endangered Species, the collection of their eggs was prohibited.
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