GREEN TURTLES

                                         A Great Experience

In Costa Rica we learned that Green Turtles are the largest of all hard-shell sea turtles, but have a small head. Hatchlings are just 2 inches long, while adults grow to three feet and weigh 300-350 pounds.  They are unique among sea turtles because they are herbivores, feeding primarily on sea grasses and algae. This diet is thought to give their body fat a greenish color, hence their name. The top shell (carapace) is smooth and can be shades of black, grey, green, brown, and yellow. Their bottom shell (plastron) is yellowish-white. The green turtle cannot crawl into its shell so its head and legs are always exposed. At the Conservation Center we viewed a very interesting video about the green turtle.

            Sexual maturity is reached between ages 20-50. At that time the turtle returns to her natal beach every 2-4 years to lay eggs. The nesting season depends on location. At Tortuguero National Park they nest March-October, with August being the most active time, and they have been doing so since 1592.   Up to 3000 turtles come ashore several times, with 15 days between laying times during the nesting season. The turtle saves some sperm so she can have multiple layings. The turtle goes into a trance during the actual laying process.

With their flipper they make the nest in the sand near or in vegetation areas. The nest ranges 4-5 feet in diameter, and is three feet deep, with eggs actually being buried even deeper. If roots are encountered while building the nest, the turtle will abandon it and make another nest nearby. Up to 100-120 perfectly round, soft, pliable eggs can be laid at a time. Eggs incubate 2 months; then hatchlings scramble to sea at night in the dark. About half will make it, but less than 1% grow to become breeding adults. Between breeding years the turtles migrate to fertile feeding grounds. The hatchings do not eat for nine days after hatching.

Green turtles have three types of habitat: beaches for nesting, convergence zones in open ocean, and benthic feeding grounds in coastal areas. Foraging areas may be hundreds or thousands of kilometers from nesting areas.  Hatchlings swim to offshore areas where they remain for several years feeding close to the surface. On the ground their predators are pumas, a raccoon-family animal who uncovers the nest, and humans. In the water the predators are sharks, large fish, plus debris and fishing nets.

The two largest nesting areas for green turtles are Tortuguero, Costa Rica with 22,500 acres on the Caribbean coast and Raine Island, with 18,000 acres on the Great Barrier Reef in Australia. At Tortuguero 22 miles of beach is protected, but only five miles is actually monitored.

The principal cause of worldwide decline in the green turtle population has been the long term harvesting of the eggs and adults on the nesting beaches. Endangered in the early 1900s, they were killed for meat, shell and skin. Incidental capture in fishing gear has also been a contributing factor. In some areas the turtles are threatened by disease.           

We went on an evening turtle walk where our guide, Johnny, who is a member of one of the nine original families left in Tortuguero. His grandfather and father both worked with Dr. Carr in the very early days of research. It was the most awesome experience to see the eggs drop into the nest. I was amazed at how big the hole was. We all were given night vision lights as flashlights are not allowed. Everyone was extremely quiet so not to disturb the turtle, but we were simply in awe of the experience and the trance–like condition of the turtle while expelling her eggs.  Wow!