The Life Cycle of Marine Turtles

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The Ningaloo Region has been identified as having significant beaches for the life cycle of marine turtles nesting. Three main species of marine turtles nest on the Ningaloo Coast:

• Green Turtle (Chelonia mydas)

• Loggerhead Turtle (Caretta caretta)

• Hawksbill Turtle (Eretmochelys imbricata)

Young marine turtles drift and feed in the open ocean. When they are about dinner plate size, turtles settle near inshore feeding grounds.

Marine turtles grow slowly and take between 30 and 50 years to reach sexual maturity. They live for years in the one place before they are ready to make the long breeding migration of up to 3,000 kilometres from the feeding grounds to nesting beaches.

During the breeding season, between November and February, you can book a tour to see the Green, Loggerhead and Hawksbill turtles (three of the world's seven marine turtle species) come ashore to lay their eggs or to see the hatchlings rushing back to the sea.

After reaching sexual maturity, the life cycle of marine turtles breed for several decades, although there may be intervals between breeding of several years.

When breeding, nesting females return to the same area, thought to be in the area of where they were born.

Courtship and mating take place in shallow waters near the nesting beach. Females often mate with more than one male and after mating, the males return to their feeding grounds.

When ready to lay eggs, the female turtle crawls out of the sea to above the high water mark, usually about one hour before, to about two hours after, the night high tide.

In preparation for nesting, the female turtle scrapes away loose sand with all four flippers to form a body pit. She then excavates a vertical pear-shaped egg chamber with the hind flippers. Often, the sand is unsuitable for nesting, especially if it is too dry, and the turtle moves on to another site. For most turtle species, digging the nest takes about 45 minutes. It then takes another 10 to 20 minutes to lay the clutch of leathery shelled eggs. Each clutch contains about 100 white, spherical, "ping-pong" ball sized eggs.

After laying, the turtle fills the egg chamber with sand using the hind flippers, and then fills the body pit using all her four flippers. The nests can be covered to a depth of more than a metre by sand blown over it during the incubation of the eggs. The turtle finally crawls back to sea, entering the water about one to two hours after leaving it. Green turtles may take longer to nest.

While on the beach, fluid hangs from the turtle's eyes. This is a concentrated salt solution which helps to remove excess salt ingested by the turtle from drinking sea water. This solution also washes the eyes free of sand.

A female green turtle usually lays six clutches of eggs at two weekly intervals. Between nesting efforts, female turtles gather adjacent to the nesting beaches. They return to the same beach to lay consecutive clutches as part of the life cycle of marine turtles.

Incubation time and sex of the hatchlings depend on the temperature of the sand. Warm, dark sand produces mostly females and the eggs hatch in seven to eight weeks. Eggs laid in cool, white sand mostly result in males and the eggs take longer to hatch.

After hatching, the babies take a few days to dig their way through the sand to the surface. 
When leaving the nest, usually at night, hatchlings head for the ocean. Hatchlings can be easily disoriented and attracted to bright lights such as street and house lights - this contributes to many hatchling deaths.

Most hatchlings reach the sea although crabs and sea birds attack them on the beach. During their first few hours in the water, these young turtles face heavy predation by sharks and other fishes. 
In February and early March, turtles hatch and venture into the sea.

Then the life cycle of marine turtles continue with the next generation.

This page not only has a lot of information about marine turtles, but have a look at my other related topics including:

• Marine Turtles at Coral Bay, Ningaloo Reef

• Green Turtles 

• Loggerhead Turtles

• Hawksbill Turtles

Ian Molloy is the owner of Crikey Adventure Tours. Visit his website for more information about this article and other related topics. His site is full of very helpful travel information including tips on motorcycle travel, driving cross-country, travelling with a caravan and other camping and travel information.

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