A Look at the ‘Lord Mayor’s Turtle’
By “Awake!” correspondent in Costa Rica
WHAT do you know of the ‘Lord Mayor’s Turtle’? Actually, there is no species of turtle officially called that. But in England the Lord Mayor’s banquet traditionally began with a bowl of green-turtle soup, so that name was applied to the Caribbean green turtle.
Perhaps you have tasted turtle soup, made with the gelatinous calipee found under the shell of green sea turtles. In West Germany, the United States and other affluent parts of the world it is considered a delicacy. But being the source of a delicacy as well as offering a supply of meat rich in protein has led to the green turtle’s being threatened with extinction. Come along and consider close up the interesting lives of these creatures. Here in Costa Rica you have an unusual opportunity to do so.
For centuries the green turtle’s eggs and succulent flesh were sought as food. But with the arrival of the Spanish in the Americas the hunting by man of this large amphibious reptile began on a wide scale. According to an authority on sea turtles, zoologist Archie Carr, “more than any other dietary factor, the green turtle supported the opening up of the Caribbean.” It is said that during the first century after the invasion of the Spanish more than 75 percent of the breeding colonies were destroyed. Now Costa Rica possesses the only large remaining spawning site in the Caribbean.
Until recently in Costa Rica the turtles were hunted indiscriminately. Then the government, aware of the dangers of extinction, passed laws prohibiting the hunting of turtles or their eggs on the beaches. This was not the first attempt to stop their wanton destruction. As far back as 1620 the Bermuda Assembly passed a law to protect “so excellent a fische.” This law prohibited the killing of small turtles on or near the shores of those islands. Offenders were punished by a fine of fifteen pounds (5.8 kilos) of tobacco, half of which was for public use and the other half for the informer.
Visiting Tortuguero
The green turtle (Chelonia mydas) uses as its breeding and nesting ground a twenty-mile (32-kilometer) stretch of beach on the Atlantic coast of Costa Rica, called Tortuguero. During the months of July to October, green turtles from all over the Caribbean converge on this lonely stretch of beach to go through their mating rites. The actual mating is done offshore and is very seldom witnessed by man. After that the females are obliged to risk their lives in order to deposit their eggs in the warm sand, which serves as an incubator. At two-week intervals a female may go through this dangerous mission up to seven times during the mating season.
I decided that I could best describe the scene if I went to see it for myself. I arrived at Tortuguero beach by launch just as it was getting dark. With the aid of a flashlight I was able to pick my way through the branches of trees and other obstacles that were strewn about by the surf. After walking for about fifteen minutes I came across two parallel tracks about two feet (.6 meter) apart. My heart leaped. Could this be the trail of a turtle in search of a nesting place? I decided to follow the tracks and, sure enough, they led to a turtle half hidden in the sand. She certainly was large, but I should have anticipated that, for a mature green turtle can weigh up to 250 pounds (113 kilos).
I found, though, that we had company. Three policemen armed with rifles were standing guard against poachers. When I told them that I only wanted to take pictures, they were very cooperative. The sound of voices and the light from the flashlights and the camera did not interrupt the turtle as she silently occupied herself with digging a suitable hole. Alternately she sank her flippers into the sand, curled them up and with a swift movement threw the sand clear of the hole.
When unable to reach any deeper she began to deposit her eggs. They fell like ping-pong balls, two or three at a time, into the nest. After laying about a hundred eggs she went about the task of filling in the hole and covering up her tracks with different movements of her flippers. We observers certainly were intrigued.
By this time some small boys from the village had arrived on the scene. They aid the authorities in their conservation program, being paid three colones (about 35 cents) for every turtle they turn upside down. This does not harm the turtles and in the morning they are marked with a metal tag before being released into the sea. These tags help to trace the turtles’ migratory routes and feeding grounds. That night I saw about eight turtles in different stages of the egg-laying process.
Dangers Ahead
A hundred eggs may seem quite a lot for one sitting. But probably fewer than one in a thousand young turtles survive. If the sand happens to be too wet or too dry, the eggs may be attacked by fungi or bacteria. Egg poachers are also a constant menace, as the eggs are a favorite boca or appetizer and are served with the drinks in the local bars.
The incubation period lasts about two months. Then the tiny creatures begin using their sharp beaks to break free from their shells. The next task is to reach the surface. This calls for much teamwork. So those that hatch first wait until all their brothers and sisters are hatched and their shells have hardened. In an experiment twenty-two eggs were buried separately. Of these only six baby turtles made it to the surface.
But how do groups of a hundred or more manage to reach the surface? As the young turtles emerge from their eggs the available space in the nest increases. The space occupied by the hatchlings and the crumpled egg shells is less than that filled by the eggs themselves. When all have hatched and conditions are just right, the young turtles begin thrashing with their tiny flippers. Those on the top break down the ceiling, those on the sides undercut the walls and those underneath compact the fallen sand onto the floor. In this way they all rise to the surface en masse. The small creatures, weighing only about three ounces (85 grams), must now make a dash for the sea. Instinctively their tiny legs begin to carry them as fast as possible toward the ocean that they have never seen. Overhead, black vultures may be waiting to swoop down and gobble them up. Dogs and other animals also take their toll. Thus, even though the surf may be just a few minutes away, not all the turtles reach it. If a baby turtle can survive this dangerous period, it may live more than one hundred years.
Very little is known about what happens to the baby turtles after they enter the ocean. When young hatchlings are released into tanks in captivity they usually swim for about ten days without even stopping to eat. So in the ocean they could be hundreds of miles from the shore by that time. After about six years of ocean life the females will return to the same beach to reenact the egg-laying scene performed by their mothers.
Their Navigational Ability
Although we know little about what happens to the baby turtles after their entering the water, we can be pretty sure that they do not get lost. According to naturalists, they have a homing and navigational ability that rivals that of pigeons, bees and salmon. Female turtles have been tagged on Costa Rican beaches and in a little more than a year have shown up about 1,400 miles away. Nevertheless, studies have proved that they will always return to the same beach to lay their eggs, perhaps a couple hundred yards (183 meters) from where they themselves were hatched. According to A Natural History of Sea Turtles, no turtle tagged at Tortuguero has ever been found nesting at another place.
How does the turtle manage to find its way back to this beach after having traveled thousands of miles in the ocean? Many theories have been proposed, but so far no satisfactory answer has been forthcoming. Consider some of the possible answers to this marvelous mystery.
A native legend says that the turtles are guided by Cerro Tortuguero. That is a mount of volcanic rock at the northern end of the nesting beach. It is five hundred feet (152 meters) high and covered with tropical vegetation. But sea turtles cannot see well above water, and many turtles return to parts of the twenty-mile (32-kilometer) nesting beach that are out of sight of the mountain.
Another theory is that green turtles use celestial navigation, orienting themselves by observing the stars. Celestial position-finding would require a fantastically complicated map sense. Yet, their poor eyesight when their heads are out of the water presents a problem as to this possible explanation.
A professor of zoology who has studied our Costa Rican green turtles for many years speculates that the turtles “smell” their way back to the same beach. Imagine that! But how? Is there something about the chemical characteristics of the sand or groundwater in this area that the turtles can recognize? Then how do they guide themselves back and forth over the years to ocean “pasture grounds” many hundreds of miles away? This specialist on green turtles concludes: “We really have made very little progress in accounting for either the long-range navigation of turtles, or their ability to recognize their hatching place.”
Future of Our Turtles
In spite of the laws prohibiting the wanton destruction of these delightful creatures, their numbers continue to diminish. The species is threatened with extinction. Some hunters still defy the law, for it is difficult to patrol long stretches of isolated beach. Often poachers do not bother to carry off the whole animal but cut away the calipee and abandon the rest. When dry, this calipee may weigh less than five pounds (2.2 kilos). Still, because of the great demand for it in making soup, the poachers can earn easy money rather than doing honest work.
Historical evidence found in ships’ logs indicates that other breeding grounds existed in the past. Operation “Green Turtle” was organized by the Caribbean Conservation Corporation for the purpose of increasing the turtle population and with the hope of reopening some of these former breeding grounds. Hundreds of thousands of green turtles were hatched in captivity, transported and released near former nesting sites with the hope that the females would return there to lay their eggs. However, the project was abandoned, as there seemed to be no increase in the turtle population and no new breeding grounds were established.
Furthermore, some nations in whose waters the turtles pasture have not cooperated with efforts to preserve this diminishing resource. The turtles are relentlessly hunted in the water near their feeding areas, being harpooned or taken in nets as they rise for air. Will men continue to exploit these interesting creatures until they, like the dodo bird and the passenger pigeon, are driven to extinction? Let us hope not, for the green turtles add to the truthfulness of this statement of praise about their Creator:
“How many your works are, O Jehovah! All of them in wisdom you have made. . . . As for this sea so great and wide, there there are moving things without number, living creatures, small as well as great. . . . Jehovah will rejoice in his works.”—Ps. 104:24, 25, 31.