Sea Turtle Life Cycle
(illustration adapted from Lanyon & Limpus)
The sea turtle life cycle is typical for all 7 of the world’s species.
Coastal water feeding area
Sea turtles become sexually mature between about 11 and 40 years old. Much of their juvenile and adult lives are spent in coastal feeding areas.
Once sexually mature adult males and females migrate towards the area where they hatched. This migration can be thousands of kilometres.
Mating mainly occurs offshore from nesting beaches and females mate with a number of different males. Females store the sperm and use it to fertilise several clutches of eggs that they will lay in the course of the nesting season.
Males return to feeding area
Males return to their feeding areas once the females begin to nest.
Females usually nest at night to avoid the sun’s heat. They crawl out of the water and seek a suitable location to dig a nest in the sand and lay their eggs.
They dig a body pit with their fore flippers then excavate an egg chamber with their rear flippers. They may repeat this process several times until they are satisfied that the nesting conditions are correct, at which point they will lay a clutch of eggs.
They then fill in the nest with sand and return to the water where they begin the fertilisation process again with sperm that they have previously stored. This process is repeated about every 2 weeks.
Depending on the species, a female may lay between 50 and 130 eggs, and as many as 7 clutches of eggs each nesting season.
Females return to feeding area
Females return to their foraging grounds once the nesting season is over. They may not breed again for several years though this is dependant on the availability of food.
Eggs hatch after about 7-12 weeks, depending on the species and environmental conditions. Sand temperature determines the sex of the turtle: cooler sands produce more males, warmer sands produce more females.
Hatchlings emerge from their eggs and make their way upwards where they wait just under the sand surface. A drop in temperature is the trigger for them all to emerge together and make their way to the sea. This usually happens at night and they orientate themselves by looking for the lowest light horizon.
Once in the water they swim for several days, but are also taken by ocean currents towards deeper offshore waters.
Open-ocean feeding area ‘the lost years’
Hatchlings enter a phase known as ‘the lost years’ where little is known about their movements. They are thought to spend time feeding in oceanic areas where flotsam attracts a plentiful food supply.
Enter coastal feeding area
Older hatchlings join the juveniles and adults at the coastal feeding areas when they are about 5-10 years old and have reached about 30 centimetres in length.
Find out more about individual species of sea turtles.