For more than 100 million years, sea turtles have been roaming the seas, covering vast distances across the world’s oceans, and filling a vital role in the balance of marine habitats.
Today, seven species of sea turtles are recognised and can be found in every ocean around the world – six of which are listed under the Endangered Species Act. Keep reading to find out more about these sea turtle species and what sets them apart from each other.
What are Sea Turtles?
Sea turtles are large, air-breathing marine reptiles that are perfectly built for life in the ocean. They are most commonly found in tropical and subtropical seas worldwide, where warm waters support their feeding and migration routes. Over millions of years of evolution, they have developed streamlined shells that reduce drag in the water, along with powerful flipper-like limbs that make them strong and efficient swimmers. This allows them to travel incredible distances, with some species moving thousands of miles between feeding grounds and nesting beaches as part of their life cycle.
How many species of sea turtles are there?
There are seven recognised species of sea turtles found across the world’s oceans, and they vary quite a lot in size, shape and diet. From the small Kemp’s ridley to the enormous leatherback, each species has its own unique features and adaptations.
Below, we take a closer look at each of these seven sea turtle species and explore what makes them so fascinating.
Leatherback Turtle
The leatherback is the largest of all sea turtles and one of the biggest reptiles on Earth, growing between 1.2 and 2.4 metres in length and weighing anywhere from 225 to 900 kg. They are also the oldest living sea turtle species, having existed for more than 150 million years!
Unlike other sea turtles, leatherbacks have dark skin covered in white or pink spots and a unique shell marked by five distinct ridges, rather than the hard plates you may see on other turtles. Their shell is made mostly of cartilage with small pieces of bone and is covered by a tough, leathery skin, giving the species its name. This flexible shell helps them withstand the intense pressure of deep dives, which can reach depths of almost 1,000 metres.
Their diet consists mainly of jellyfish, and although they are solitary animals, they sometimes gather in groups in areas where jellyfish are plentiful.
Green Turtle
The green turtle is the second-largest sea turtle species after the leatherback, growing up to 1.2 metres in length and weighing as much as 225 kg.
Green turtles are unique because they are the only fully herbivorous sea turtle species. Their diet mainly consists of seaweed and algae, which they graze using their sharp, finely serrated beaks. These specialised beaks are perfectly designed for scraping algae from rocks and feeding in seagrass beds. Interestingly, this plant-based diet gives their body a greenish colour, which is where the species gets its name.
Unlike most sea turtles, green turtles are known to come ashore to bask in the sun. This behaviour can often be seen in places such as Hawaii and parts of Australia.
Loggerhead Turtle
The loggerhead turtle is one of the larger sea turtle species and can be found in temperate and tropical regions of the Pacific, Indian and Atlantic Oceans. They are easily recognised by their reddish-brown shell and their large, powerful head.
Loggerheads can grow up to 1.2 metres in length and weigh as much as 180 kg – around 4 washing machines! They also have the strongest jaws of any sea turtle species, with an impressive bite force that helps them crush hard-shelled prey such as crabs, conchs and whelks. Alongside these tougher foods, loggerheads also feed on molluscs and jellyfish.
Flatback Turtle
The flatback turtle gets its name from its distinctive flattened shell, which is pale greyish-green in colour and much flatter than the curved shells seen in other sea turtle species.
Adult flatbacks grow to around 0.9 metres in length and weigh about 90 kg. They are omnivores, although their diet is mostly carnivorous, with vegetation making up only a small part of what they eat.
Flatback turtles also have the smallest distribution of all seven sea turtle species. They are found only in the coastal waters of Australia, where they breed and nest. Because much of their habitat is remote and difficult to access, flatback turtles remain one of the least studied sea turtle species.
Hawksbill Turtle
Often considered the most beautiful of all sea turtles, the hawksbill turtle is famous for the colourful tortoiseshell pattern on its shell and its narrow, pointed beak, which resembles the beak of a hawk, giving this species its name.
Hawksbill turtles grow to around 0.9 metres in length and weigh up to 90 kg. They are commonly found in coral reefs, lagoons, mangroves, rocky coastlines and shallow coastal waters, where they spend much of their time searching for food. Their diet mainly consists of sea sponges, including species with sharp, needle-like skeletons. Their specially adapted beak allows them to reach into small cracks and crevices in coral reefs to find food that other animals cannot access.
Olive Ridley Turtle
The olive ridley turtle is the second smallest of all sea turtle species, typically weighing between 34 and 45 kg and growing to around 0.8 metres in length. It gets its name from its olive-green shell and is thought to be the most abundant sea turtle species in the world, living in tropical waters across the globe.
Olive ridleys are best known for their incredible mass nesting events, called arribadas, where thousands of females gather on the same beach at once to lay their eggs. Their diet mainly consists of invertebrates such as crabs, shrimp, jellyfish and rock lobsters, although some also feed on algae.
Kemp’s Ridley Turtle
The Kemp’s ridley turtle is the smallest of all sea turtle species, growing to around 0.6 to 0.75 metres and weighing up to 45 kg. Named after Florida fisherman Richard Kemp, who first described the species in 1880, these turtles are recognised by their rounded grey-green shell and relatively short, broad head.
Kemp’s ridleys are mainly found in the temperate and subtropical coastal waters of the western Atlantic Ocean and the Gulf of Mexico. They prefer shallow habitats with sandy or muddy sea floors, where they can easily hunt for prey such as crabs and other shellfish.
During the 1960s, the Kemp’s ridley was pushed to the brink of extinction. However, thanks to conservation efforts (including protecting nesting beaches in Mexico and reducing accidental capture in fishing gear), their population has slowly begun to recover, increasing from only around 200 nesting females in the 1980s to thousands today.
Are Sea Turtles Endangered?
Despite surviving for millions of years, sea turtles are now considered vulnerable, with all seven species classed as threatened or endangered due to human and environmental pressures.
One of the biggest challenges they face is survival from egg to adulthood. Hatchlings must make a dangerous journey from nest to sea, avoiding predators such as birds and crabs, with very few making it to maturity. Once in the ocean, sea turtles face further threats from fishing activity, including accidental capture and “ghost fishing”, as well as plastic pollution, which is often mistaken for food.
However, there is hope. Thanks to ongoing conservation efforts such as protecting nesting beaches and reducing fishing-related threats, some populations are beginning to recover. Green sea turtles in particular, are showing encouraging signs of improvement in certain areas.
Learn More about Loggerhead Sea Turtles at Blue Reef Newquay
Want to see a sea turtle for yourself? Visit Blue Reef Aquarium and come face-to-face with our very own loggerhead sea turtle in the Ocean Tunnel exhibit.
Book your tickets online today!