NAVIGATION
Sea Turtles
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Sea turtles have survived for over 120 million years. Their unique life cycle, body shape, strength and tenacity have enabled them to adapt to a constantly changing environment over a period in which many other animals – including the dinosaurs – became extinct.
In the past the world’s oceans were home to vast numbers of sea turtles. Although the chances of survival were slim for an individual sea turtle hatchling due to many and varied natural threats, as a population they were incredibly successful.
But today human impacts have seriously depleted sea turtle populations to the point where we are in danger of losing some species forever. Today the long term future of sea turtles is uncertain.
These pages explore the fascinating sea turtle life cycle. The text below contains sea turtle life cycle information that is common to all 7 of the world’s species. Click on the links at the bottom or to the left of this page for sea turtle life cycle information that is species specific.
- Sea turtles are perfectly adapted to their environment. Their shells are strong, light and streamlined and provide protection, buoyancy and the ability to slip through the water with minimum effort.
- The back or top shell is called the carapace and the bottom is called the plastron.
- The shell is made of flattened bones covered in horny plates called scutes, with the exception of leatherback turtles that have a shell made from many small bones embedded in a leathery skin.
- Unlike most land turtles, sea turtles cannot retract their heads into their shell for safety. They have exchanged this feature for powerful fore flipper muscles that propel them at great speed through the water. Their muscles take up so much room inside their shell that there is no room for their heads.
- Their strong, paddle shaped fore flippers power them through the water whilst the smaller rear flippers are used for steering and digging nest chambers.
- The ‘tears’ often seen around a sea turtle’s eyes when it is on land come from special glands located near the tear ducts that excrete excess salt ingested while feeding underwater.
- Sea turtles have no teeth. Their mouths have evolved to either shear food such as sponges and sea grass in the case of hawksbill and green turtles, or to crush food such as crustaceans and gastropods in the case of loggerheads and olive ridley turtles.
- Although much is known of their activities when they come ashore to nest, little is known of their ocean activities.
- The young of most sea turtle species drift and feed in the open ocean until they reach about 5-10 years old and about 30 centimetres in length when they settle at inshore feeding grounds.
- Sea Turtles grow slowly and – depending on species – take between 11 – 40 years to reach sexual maturity.
- They can live for years in the one place, often returning to the same location to sleep.
- They make long migrations, which can be hundreds and even thousands of kilometres, from feeding grounds to nesting beaches. Males mate with females along the route and close to nesting beaches.
- Females return to nest on the same beach, or beaches nearby, on which they hatched. How they achieve this remarkable feat of navigation is poorly understood, however it is thought they use a combination of clues such as reading the earth’s magnetic pull and reading ocean currents and even judging the angle of the sun.
- Most female sea turtles breed only every 2 to 3 years as an annual breeding pattern would be too exhausting due to long migrations and the energy required to produce and lay many hundreds of eggs.
- Hatchling gender is dependant on sand temperature. Cooler sands produce more males, warmer sands produce more females.
For species specific sea turtle life cycle information click on the links below (recommended further reading Sea Turtles: A complete guide to their biology, behaviour and conservation by James R. Spotila):
