Sea turtle species

They might look similar from a distance, but there are great variations between sea turtle species, as our guide explains. Sadly, however, something that they all have in common is that their populations are struggling. Six out of seven sea turtle species are classified as threatened, and hawksbills, prized for their beautiful shells, are critically endangered. Read on to learn about the types of turtles you’ll encounter on our sea turtle conservation trips, and how you can tell them apart.
Hawksbill turtles are named after their birdlike, pointed beaks - but it is their distinctive shells that they are most known for.


The beautiful patterns on hawksbill shells, made up of overlapping scales – or scutes – are extremely desirable, and expensive. Sadly, this means the turtles have been hunted for thousands of years, their shells sold as ornamental tortoiseshell. This is illegal, although there are thriving black markets, particularly in East Asia, and the hawksbill turtle is classed as critically endangered. Some nest in the Seychelles, making this a particularly important turtle volunteering destination.

Adult hawksbills are around a metre long, and you can spot their tracks in the sand as they are asymmetrical, unlike those of the leatherback and green turtles with whom they share nesting beaches. Incredibly, scientists have only just discovered that hawksbills are biofluorescent – meaning their shells glow shades of green, red and orange when a light is shone on them at night. This is the only reptile which is known to have this trait.

Olive ridley

Olive ridleys are the world’s smallest sea turtles, but they are responsible for one of the most impressive turtle sights – the arribada in Costa Rica. In the last week before the new moon, over the course of four or five days, thousands – sometimes hundreds of thousands – of olive ridley turtles crawl ashore simultaneously to lay their eggs on the Pacific beach at Ostional.

This eggs-travaganza takes place during the rainy months of August to December, when this remote region is at its least accessible; though that hasn’t stopped it becoming a huge tourist attraction in the last couple of years. People arrive literally by the busload, crowding the beaches, leaving little space for the turtles, trampling over nests and causing huge problems. The most responsible way to support the turtles in Ostional is, sadly, by not going. But we think that witnessing a turtle nesting on an empty beach elsewhere in Costa Rica is a far more magical experience anyway.
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As the name suggests, the leatherback does not have a shell, but is protected by a leathery carapace which is more flexible than a regular turtle shell.


These marine giants are the world’s largest, reaching an impressive two metres in length and weighing up to 900kg. But size isn’t the only leatherback superlative; they have the widest range of any sea turtle, being found everywhere in the world except the Arctic and Antarctic. This is partly due to their ability to generate and maintain body heat, unlike most other reptiles. The leatherback swims further than any other sea turtle during its annual migrations between its feeding and breeding grounds – on average around 6,000km. They also dive deeper, reaching depths of up to 1,280m and staying beneath the surface for up to 85 minutes.

The lack of valuable shell does not deter poachers, however. Leatherback meat is still in demand – as are their eggs. They frequently get caught in fishing nets and coastal development has destroyed many nesting grounds – as every female returns to the beach she was born on to lay her own eggs, losing a beach can mean that dozens of females are no longer able to nest. In addition, plastic waste can resemble jellyfish – the leatherback’s favourite food. Ingesting large amounts of this (some dead turtles have been found with close to 5kg in their stomachs) will kill them. As a result, leatherback turtles are classified endangered.

Green Turtle

The green turtle is, appropriately, a herbivore, living entirely off sea grass and algae. Yet despite being the only turtle to have a veggie diet, it is the second largest species after the mighty leatherback, reaching lengths of around 1.5m and weighing up to 190kg. Their smooth shells are dark brown, olive or black in colour, though their name comes from the greenish tinge of their body fat. Green turtles nest throughout the tropics, and even reach the Mediterranean, with a nesting ground in Turkey – although this small population is classified as critically endangered.
Written by Vicki Brown
Photo credits: Isabella Jusková [Hawksbill: Kris-Mikael Krister] [Olive ridley: Pawar Pooja] [Leatherback: Rabon David, USFWS] [Green Turtle: Bernard DUPONT]