Born Free Foundation - Keep Wildlife in the Wild

Sea Turtle Facts

Green Turtle (c) Peter Richardson / MCS
© Sea Sense

There are seven species of sea turtle, the largest of which is the leatherback which can grow up to 3m in length and weigh up to 900kg, the smallest are the olive ridley and Kemp's ridley at just 65cm and 40kg. 

How are turtles classified?

Living things can be organised into different groups.  Species that are alike are grouped together.  This is called classification.  


Class:           Reptiles 

Order:           Testudines 

Family:         Dermochelyidae (leatherbacks) / Cheloniidae (all others) 

Species:       Chelonia mydas (green) 

Dermochelys coriacea (leatherback) 

Eretmochelys imbricata (hawksbill) 

Caretta caretta (loggerhead) 

Lepidochelys olivacea (olive ridley) 

Lepidochelys kempii (Kemp's ridley)

Natator depressus (flatback)


The seven species are found around the globe mainly in tropical and subtropical waters.  The leatherback, which can regulate its own body temperature, is the most widespread of all the turtles and can venture into colder waters including around the UK.  The hawksbill is the most tropical of the species and prefers warmer waters.  All species of turtle migrate large distance between feeding and nesting sites each season. 


Perfectly adapted for the marine environment, the males spend their entire lives at sea, while the females return to shore only to lay eggs. 


Green turtles are the only vegetarian turtle with the adults eating seagrass and marine algae while leatherbacks for example prefer jellyfish. The diet of each of the subspecies of sea turtle varies and can include crabs, mollusks and sponges to name a few.


Although slow and cumbersome on land, in the water turtles are fast and agile swimmers, propelled by muscular front flippers.  Like all reptiles turtles are cold-blooded and rely on their environment to regulate their body temperature. 

Adaptations for life in the sea include a streamlined body and long wing-like flippers for swimming.  The hard shell carapace provides protection against potential predators.  Air-breathing lungs are adapted for long, deep dives while excess salt is excreted from a special gland in the eye as ‘turtle tears’. 

Ecology and Behaviour

Turtles have a life span of up to 80 years and are generally solitary creatures, rarely encountering other turtles apart from courtship and mating.  Even when turtles come together at feeding grounds there is little apparent interaction. 

After mating the females lay up to 150 eggs in each clutch, sometimes laying as many as 3 clutches per season.  She nests at night, coming up onto the beach and carefully digging a nest with her hind flippers.  Incubation takes around 60 days and the hatchlings emerge, predominantly in the evening or at night, and swim out to sea.

Although the behaviour of nesting females and hatchlings is much documented, much is still unknown about turtle life cycles and migration patterns. Young juvenile turtles are often seen close to shore, but after that they ‘disappear’ and little is known about their behaviour until they reappear as mature adults ready to mate and reproduce. 


Over the last century sea turtle numbers have plummeted for a number of reasons, including: exploitation for their meat and other products, disturbance of nesting beaches associated with the tourism industry, light pollution, egg raiding by humans and predators, bycatch in the fishing industry, rising sea levels leading to a loss of nesting habitat, disease and marine pollution. 

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