The Leatherback Sea Turtle | Breeding and Nesting
The Leatherback sea turtles usually mate at sea. The mating comprises of two stages. The first stage is courtship which lasts around 20 minutes. After the courtship the female accepts the male and the copulation begins. During copulation the male mounts the female and embraces her in his flippers.
The Leatherback nests are located in tropical and subtropical regions. Atlantic, Indian and Pacific Oceans are the most common breeding grounds for the female. Some nesting has also been discovered in the Mediterranean.
The female turtle comes at night to the shores to lay eggs. They generally choose sandy beaches which have a gentle slope and are free of rocks, as rocks can hurt the soft-skinned Leatherbacks. Leatherbacks are quick in the water but are extremely slow on land. So it can actually take quite a while before she has found a perfect spot. The female climbs ashore at night. The turtle slowly drags herself up the beach using her front flippers. It selects an area which is beyond the reach of high tide and free from any sort of vegetation. While laying eggs the female Leatherback turtle becomes oblivious to its surrounding. That is why the turtle chooses night time for laying eggs as it provides protections from predators.
When she finds a suitable place for a nest she uses her back flippers to dig the nest. The nesting hole is just over 1 meter deep. It goes deep so that its body sits inside the pit. Then she carves out a chamber separately for the eggs so that the nest is shaped like a boot. While carving out the chamber for the eggs the turtle makes sure that the sand will not cave in. When the chamber is dug deep enough the turtle starts to lay the eggs on it.
The turtle lays around 110 to 120 eggs out of which 80 per cent are fertile and the rest are infertile. The function of the infertile eggs is still unknown. However they might be a very poor decoy, as once the nest is found the predators are unlikely to leave any eggs behind. Some scientists think they allow oxygen to continue circulating around the fertile eggs by helping to prevent sand from falling between them.
The Leatherback’s eggs are unlike regular poultry eggs. Instead of the hard outer shell they are made from a leathery substance which has a rather thick shell. The eggs weigh just under 50g and are around 10 centimeters.
Once the eggs are laid she uses her body and flippers to cover the nest with sand. Then it proceeds to leave a large area of disturbed sand. This camouflages the nest from predators and egg poachers. She then uses her front flippers to throw sand around to help disguise the body cavity and the nest before heading back to the ocean. She then heads back to the sea on a low tide when the sea is calmest. Although her efforts to disguise the nest may be successful, she leaves an unmistakable trail leading from the nesting site with her body and front flippers as she returns to sea. The process of laying eggs and returning to the sea takes around 2 hours after which the female Leatherback takes no further part in the protection or care of its hatchlings.
After approximately 60-65 days the Leatherbacks hatch. With enough oxygen in the nest, the hatchlings stay in the nest a while after they’re broken out of the eggs. The hatchlings are tiny, measuring around 5 to 6.5 centimeter and weigh around 40 to 51 grams. The hatchlings have white ridges along their carapace. The edges of their flippers, which are as long as their bodies, are also white.
The gender of the hatchlings depends on the temperature of the nest. At 85 degrees Fahrenheit the nest would produce a mixture of female and male turtles. Temperature cooler than this produces male offspring and warmer produces female offspring.
When they starts moving around the ceiling and walls starts to fall to the bottom of the nest, slowly raising the turtle to the surface of the beach. The Leatherback hatchlings typically have a carapace length of 5.1 cm to 6.8 cm. They are black, and the ridges along their carapace are clearly outlined in white.
The hatchlings look for the brightest spot on the horizon when they emerge from the nest. This s normally the sea reflecting whatever light there is in the sky. Now a dangerous trip starts as they head for the sea. As long as they stay on the beach they’re prey for gulls, hawks, ghost crabs, vultures etc. Once they are in the ocean, the turtles become potential prey for octopi, sharks, and other large fish.
The few who find their way across to the sea have the difficult task of getting to the open waters. It takes them around two days of constant swimming to reach the areas which contain their favorite food, the jellyfish, in abundance. They must eat a lot of jellyfish to support their rapid growth. The juvenile sea turtles have similar mouth structure as the adult. The inward points on the upper lip allow them to easily puncture jellyfishes and swallow it.
In the open sees the turtles are hunted by sharks and other sea predators. Juvenile Leatherback sea turtles spend most of their time in more tropical waters, whereas adults might migrate to temperate regions of the ocean.
During the first week in the ocean the internal guidance system becomes active and imprints the place where they were born.
It takes the turtle around 10 years to reach the sexual maturity. During this period the turtle has grown into one of the largest reptiles known to mankind. It is now around an impressive 2 meter long and weighs around 680kg.
Every 3-5 years the Leatherback females return to the beach they were hatched on to lay eggs. To ensure better distribution of the genes and increase the survival of the species they mate with a different mate each nesting season.
Even though nesting beaches are limited, the Leatherback has the longest migration of all the sea turtles. Some of the large and critical nesting beaches can be found in Indonesia and Mexico. Other nesting places can be found in Costa Rica, Trinidad, USA, French Guiana, Suriname and a few other places.