Born Free Foundation - Keep Wildlife in the Wild

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)

Five species of turtles are found in the waters off Tanzania and are focussed on here.

Turtles are special

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 body temperature.

Distribution

The five 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 the UK.  The hawksbill is the most tropical of the species and the olive ridley also prefers warmer waters.  The green is found in tropical and temperate climates, but prefers hallow coastal waters, while the loggerhead prefers cooler temperate regions.  

Habitat

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

Diet

Greens are the only vegetarian turtle with the adults eating seagrass and marine algae.  Leatherbacks prefer jellyfish, loggerheads shellfish, hawksbills sea sponges while the olive ridley probably eats small sea creatures such as crabs and fish.

Adaptations

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.  Excess salt is excreted from a special gland in the eye, the source of ‘turtle tears’.

Behaviour

Although the behaviour of nesting females and hatching infants 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.

Society

Turtles are generally solitary creatures and rarely encounter other turtles apart from courtship and mating.  Even when turtles come together at feeding grounds there is little interaction.

Reproduction

Turtles have a 70 year life span and mature around 30 years.  After mating the female lays several nests of around 100 eggs.  She nests at night, returning to the same sandy beach each time and carefully digging a nest with her hind flippers.  Incubation takes around 60 days and the hatchlings emerge, also at night, heading for the brightest horizon and swimming out to sea.