Along the narrow strip of sand and coco palm separating the river from the sea at Tortuguero, Costa Rica, thousands of newborn turtles are digging their way out of the beach every night and heading for the open Caribbean. Two months before, fleets of ponderous female green turtles (Chelonia mydas) buried some two million eggs on this 22-mile-long beach. Eggs from a two-mile section are dug up and transferred to a wire enclosure where dogs, raccoons, and crabs cannot get at them. Artificially hatched, these babies make up an unusual cargo that U. S. Navy planes from the Caribbean Sea Frontier fly all over Latin America every year.
Between 10,000 and 30,000 baby turtles, each about two inches long, are fed fish and packed in wooden boxes with sea-soaked plastic foam in the bottom. Two to three hundred hatchlings go into each box. Water is poured over them; the lids are nailed shut and the boxes loaded on board the plane. In September and October 1965, four flights ferried 13,300 baby turtles to 22 locations on the shores and islands of the Caribbean and Gulf of Mexico.
There are the inevitable expressions of amusement by foreign customs officials when a U. S. Navy plane loaded with baby turtles lands in their country. After a minimum of paper work, the young travelers are quickly trucked to the coast and released on the beach or, if predators are numerous, a half-mile or so offshore. Last year, the Navy turned turtles loose in Florida, the Bahamas, Jamaica, Grand Cayman, Puerto Rico including Roosevelt Roads Naval Air Station, Mexico, British Honduras, Colombia, Trinidad, Grenada, Barbados, and Antigua.
The purpose of these turtle sorties, known as Operation Green Turtle, is to help prevent the extinction of an important food source and to restore it to its former abundance. The U. S. Navy is a partner in this venture with scientists and citizens from Latin America, the Caribbean Conservation Corporation (CCC), the University of Florida, and the informal Brotherhood of the Green Turtle. This unlikely alliance is engaged in a complex plot to trick the reptile into believing it was born somewhere that it was not.
When hatchling turtles dig themselves out of the sand they head straight for the surf and, in a frenzy of swimming, disappear out to sea. They do not return to land again until they have become mature enough to mate and nest—some five or more years later. The turtle alliance hopes the hatchlings they have displaced will return to the locations where they were released rather than to Tortuguero. If the turtles do this, new breeding colonies will be established all over the Caribbean, providing a much needed source of protein to many overpopulated, undernourished areas.
Is the plot working? It appears that it is, but no one is quite sure yet. The Navy has been in the turtle transport business since 1961, but this may not be long enough. Professor Archie Carr, the University of Florida zoologist who manages Operation Green Turtle, says:
There is the possibility that the project has not been underway long enough for the hatchlings of the first season to have matured. Perhaps it takes five to eight years for the turtles to mature, instead of four or five as we once thought. Then again, they might all be going back to Tortuguero, or maybe predators eat most of them before they reach mating age. While we have no clear evidence of the successful establishment of nesting activity at any of the reintroduction sites, there is no doubt that some of the hatchlings are remaining in the vicinity of the places where they have been released. It can be hoped that some of these will eventually establish resident breeding populations.
Off Belize, British Honduras, two groups— yearlings and two-year-olds—live where no turtles lived before Operation Green Turtle. Three new groups inhabit waters near Bimini and three colonies have taken up residence on the north side of Cayman.
There are other results, too, to keep the turtle alliance from becoming discouraged. Archie Carr states that:
... as understanding of the disinterested, non-political character of the project spreads, there is growing good will both toward the United States and Costa Rica. This psychological by-product may ultimately outweigh all other considerations. All along the Caribbean coast people are approvingly aware that an airplane of the U. S. Navy came to their locality for no other reason than to improve local living standards. Latins are giving gringos the only warm smile they ever got in this part of the world. Such favorable reaction among our Caribbean neighbors must be reckoned an asset to our country.
In Costa Rica, assistance by the U. S. Navy has helped the CCC to get laws passed and enforced to prevent the killing of pregnant females. As they lumber up the beach, the 150- to 350-pound mothers are easy prey for hunters who are after calipee, meat, skin, and shell. Back in 1954, not a single female made it back to the sea from the nesting beach at Tortuguero, except by accident. In some seasons no mother got to lay her eggs. Now egg-carrying females are fully protected.
The ten to 30 thousand eggs taken by Carr and the CCC for their hatchery is an inconsequential withdrawal from the bank of two million or more eggs buried in the beach. The Costa Rican people do not object to this because they realize there is no personal or commercial gain involved. Hatchlings that do not fly with the Navy are released on Costa Rican beaches.
Archie Carr wrote in his 1965 report to the Office of Naval Research:
An awareness of conservation problems is increasing among people who have thought little of such matters in the past. Concern over the plight of marine turtles has risen markedly in areas in which it never existed before, and in some of these, the governments have initiated sea turtle projects of their own.
In Mexico there is strong interest in this field. Off the Yucatan Peninsula, on the Island of Women, Operation Green Turtle has stocked a turtle ranch, and two young biologists are trying to raise the reptiles like sea-going cattle.
Four private projects have been started in Florida—one at Naples on the southwest coast, one at Islamorada in the Keys, and two at Key West. Senator John M. Spottswood operates one of the latter ranches. “All of these are small, experimental operations,” observes Carr, “really just tests of growth potential under various pen and feeding conditions. There is as yet nowhere in the world a real commercial venture in turtle culture.” The oldest and largest turtle ranch is a collaborative venture of the CCC and the Bahamas National Trust at Great Inagua, Bahamas. As in other experimental operations, hatchlings are hand fed on meat during their first six to eight months. Then when they switch to a vegetable diet the youths are released into enclosed pastures of turtle grass.
On Inagua, Audubon Society wardens Sammy and Jimmy Nixon feed their youngest charges a gourmet diet of ground-up conch and fish. Big Sammy or his brother wade into the chicken wire pens chanting “come for conch,” and immediately hundreds of little heads pop out of the water. Even after they have moved to the coral-enclosed seaweed pastures outside the pens, many turtles come back to answer the feeding call.
Hatchlings have been flown into Inagua every year since 1963 and something over a thousand green and hawksbill turtles live on the ranch now. In nature, only about one baby in a thousand survives to maturity. On the ranches where they are protected from predators and poachers virtually all the hatchlings should reach adulthood. Some turtles will be released and CCC expects them to establish breeding colonies on open beaches in the vicinity. Others will be kept to breed in the enclosures. Together with the two groups they should supply enough hatchling to stock other ranches.
Archie Carr comments that, “Despite two severe reverses—a hurricane in 1963 and flooding the following year—the Bahamas ranch project can be counted a success. The good condition of the herbivorous older animals is strong indication that green turtles can be raised to maturity in numbers at Inagua.” The 57-year-old naturalist believes that commercial turtle ranches offer the only hope of saving the green turtle and its close relatives. Although progress has been made in conservation, increasing commercial exploitation threatens to make Caribbean sea turtles extinct.
In England and on the European continent turtle soup is in constant demand. The finest turtle soup is a clear, savory broth, laced with Madeira and having a consistency that makes your lips stick together. (The dark, vealy gravy that masquerades under the name in many U. S. restaurants is a fraud.) Calipee supplies the sought-after consistency and forms the body and soul of good potage á la tortue. Filling the space between the bones of the shell, this yellowish cartilage has the texture of hard jello. A man living near the coast can make a week’s wages by slicing out three or four pounds of turtle calipee and selling it to the soup market.
Bakers have known for hundreds of years that cakes made with turtle eggs are superior in taste and stay fresh longer on their shelves. An insatiable new market exists for turtle skins, which turn up in the form of ladies shoes in places like England. There is also a resurging demand for objects made of natural tortoise shell instead of the plastic imitations that once monopolized the market. These economic facts of life are very hard on Chelonia.
Carr feels that successful commercial ranches would take the pressure off wild stocks. They could also provide a new source of food and income in underdeveloped areas bordering on tropical seacoasts. Coupled with sensible and well enforced conservation practices and the success of Operation Green Turtle, ranches would not only save Chelonia mydas but would go a long way toward restoring it to its former abundance.
To appreciate fully these goals of the turtle alliance you need to know something about the history of the green turtle. Carr tells it best in his book, The Windward Road:
For three hundred years after the arrival of Columbus vast fleets of green turtles were a prime factor in the growth of the Caribbean. . . While there were other sources of food from which to replace exhausted ships stores, none was as good, abundant, and sure as turtle; and no other edible creature could be carried away and kept so long alive. ... It was only the green turtle that could take the place of spoiled kegs of beef and send a ship on for a second year of wandering or marauding. All early activity in the New World tropics—exploration, colonization, buccaneering, and even the maneuvering of naval squadrons—was in some way or degree dependent on turtle.
The green turtle had all the qualities needed for a role in history. It was big, abundant, available, succulent, sustaining and remarkably tenacious of life. Like the buffalo on the western plains, it stayed in one place and grazed on rich pastures of submarine grass, turning them into good savory meat... . Each June it came ashore wherever there was sand, and you had only to walk the beach and turn on their backs as many as you could use. Fat, numerous, and delicious, the green turtle was a blessing in every way.
It was too great a blessing to last.
Just as buffalo vanished from the plains so, one by one, under pressure of unrelenting exploitation, the nesting haunts of the green turtle became deserted. First it was Bermuda, next the shores of the Greater Antilles, then the Bahamas and Florida. In the latter place turtle crawls were once more common than hen houses and vast herds grazed in the estuaries and marshes along both coasts. In 1886, Charles Peak caught 2,500 greens around Sebastian, Florida; in 1895 he could find only 60.
In the days of galleons, turtle herds flippered to the Cayman Islands from hundreds of miles around to mate in the clear, green waters of the Cayman Sea and lay their eggs in the honey-colored sand. But in 1954, Archie Carr walked the beaches of Grand Cayman until he was tired and saw the tracks of only one sea turtle. This sparked him to write:
The history of the turtle fishery—its burgeoning and exhaustion, the heedless killing of females bearing eggs, the plight of the people who had no other way to live and their tenacity in following the declining schools from one remote shore to another— is as extraordinary from the standpoint of human ecology as from that of resource depletion.
The Navy is not interested in Chelonia mydas solely as a source of soup and good will: the Office of Naval Research wants very much to learn more about the travels of the green turtle. In going between their nesting and feeding grounds, these supposedly stupid creatures demonstrate an ability to navigate that would make any line officer green with envy. They can find their way from one remote spot to another without landmarks, sextants, chronometers, radar or a college education. To find out how they do it, the Navy is trying to learn all it can about the routes and schedules of migrating turtles. Such basic information is of value to conservationists, too. As Carr points out: “To protect an animal you have got to know where it is— not just once in a while but all the time.” The biggest remaining mystery in the life history of the green turtle is where it spends its early years. In the days of journeys to the moon and billion-electron-volt atom smashers, you would think scientists could tell you where a green turtle goes after it leaves the nesting beach, but they cannot. No one—not even the grizzled turtle catchers of Cayman —ever sees green turtles during their first year of life. After reaching the sea, they disappear completely from the ken of man until their return as adults. Archie Carr affirms that “The total disappearance of young turtles during their first year of life is one of the most important remaining gaps in the natural history of the green turtle and one hindering the piecing together of the routes and schedules of their migrations.”
To help fill this gap, U. S. Navy turtle planes drop drift bottles into the sea off Tortuguero and search the area for rafts of Sargassum or gulfweed. The bottles should reveal the trends of local currents off the beach when hatchling are entering the sea in maximum numbers. Carr feels that the youths may simply move offshore into the currents and drift as plankton. If so, their only source of food would be other creatures of the plankton. The clumps of golden Sargassum weed would provide lodging for the youths and shelter from predators. Thus far, however, seaweed searches have not turned up enough weed to support the number of turtles known to reach the sea each season.
The drift bottles contain notices that promise a small reward if the finder fills out and returns a form giving the time and location of the recovery. It would be better, of course, to attach such a notice to the hatchlings. Then scientists would learn where the turtles go instead of where currents would have carried them. Such tags would provide a means of determining whether or not Operation Green Turtle is a success. Hatchlings ferried to various places could be marked with tags, the color and shape of which would reveal the location and year of release. If these tagged turtles were later found on Tortuguero, the turtle alliance would know their attempts to repopulate some of the breeding grounds had failed. Every time a marked turtle was found, scientists would have another piece in the jigsaw puzzle of Chelonia's life and travels.
So far no one has been able to come up with a tag that will remain in place and be easily recognizable after the turtle’s five years of rapid growth from a two-inch baby to a 200- pound adult. Archie Carr says he knows of no paint that would survive such growth and wave wash that long. Notches cut into the flippers and shell disappear by the time the turtle reaches adulthood. Plastic or metal tags are shed or overgrown, and tattoos disappear. Radioactive tags offer some help but no one is sure how radiation will affect young turtles, the animals that eat them, or local opinions. If you can think of a good way to tag a baby turtle, Archie Carr and his colleagues at the University of Florida would like to hear from you.
From the day they hatch, green turtles exhibit an amazing ability to find their way in the world. As soon as the tiny newborns thrash their way to the surface of the sand, they nearly always set a straight course for the sea, even though they have never seen water before and it may be out of sight behind dunes or brush. Archie Carr flew some Tortuguero turtles across Costa Rica and allowed them to emerge from artificial nests in a beach fronting the Pacific. Even though the sea lay in the opposite direction these turtles reached it as easily as their cousins on the home beach. From this Carr concluded that no direction sense is involved. Rather, he believes, “the sea finding mechanism seems to be an innate response to the uncluttered appearance of the horizon and the quality of the brighter, paler sky above water.”
The signs are there even on a cloudy or rainy day. When hatchlings move out from behind a dune or stand of sea oats, and sky and horizon become clearer, they immediately increase their pace. A wave breaking in the moonlight or a fiery display of luminescence brings the same response. At the first feel of a spent wave sliding under their flippers, the babies break into excited, unco-ordinated swimming motions. After some awkward flapping and flipping, they get the hang of it and head out to sea with smooth, hurried strokes.
The hatchlings continue to swim with frantic energy until they are out of sight. Carr believes that “either their sea-finding drive gives way to other orienting mechanisms or they simply keep swimming until whatever difference they perceive between sea light and land light becomes too slight to provide a guiding stimulus.” But green turtles never loose their sea-finding sense. Hatchlings kept away from water for a year after birth head directly for the sea when released. Undoubtedly, mature females rely on this inborn sense to guide them back to the ocean after nesting—especially when the nest is located out of sight of the sea.
When Archie Carr was poking about the Caribbean in the early 1950s, he heard recurring rumors of marvelous feats of homing by green turtles. The rumors drew him to the Cayman Islands and the bronzed turtlemen who have, for generations, made a living fishing off the coast of Nicaragua. “Sure, mon,” they said, “turtles can go home from anywhere—just like a pigeon.” Turtle-boat captains told Carr about the black beach at Turtle Bogue (Tortuguero) where greens and hawksbills from all around the western Caribbean go to give birth. They told him of captured turtles that escaped when schooners were wrecked on reefs or soup-factory crawls were flooded by storms. After making their way across hundreds of miles of unmarked water and skirting unfamiliar coasts, these animals arrived back at the same feeding area from which they were taken.
The story that impressed Archie Carr most was one told by Captain Charlie Bush. Captain Charlie netted a curious-looking 300- pound male green on a rock at Mosquito Cay off Nicaragua. Curious because he had a striking set of scars or notches spread with odd regularity around the after edges of all four fins, Charlie put his brand on the belly shell of this green and shipped him off to Norberg Thompson’s soup factory at Key West.
Eight months later, Charlie and his crew put down a net on the same rock where they caught the notch-fin turtle. When a green was snagged, the crewmen heaved and grappled him over the side of the boat. As the big reptile lay there on his back, hissing and blinking and slapping his chest with long front flippers, Captain Charlie could see it was the same turtle he had caught on that rock the eight months before. The sight of the extraordinary scars on the turtle’s fins was all he needed, but to make sure Charlie rubbed the crusted belly shell and traced out the brand cut into it. There was no doubt that he had cut that brand himself.
Hurricane-churned seas had slammed into Thompson’s crawls and washed the old turtle to his freedom. Somehow he managed to swim over 800 miles in a relatively short time and find his way back to the one rock in all the Caribbean that he called home. “To appreciate what that turtle accomplished,” remarks Carr, “you have to understand what he was up against. When the storm freed him he was in strange water 800 miles from home by air line, and a good deal farther by any route accessible to a sea turtle. He had come by schooner, on his back, the whole way out of touch with whatever landmarks cruising turtles might see and use. His home was only ... a dim reptilian memory of somewhere beyond untracked space; a goal to be sought, you would think, by random wandering if it were sought at all.”
The tale of that turtle’s argosy—the route he took, the adventures he had, the signs that guided him—would truly be one of the greatest nature stories of all time.
The most extraordinary outcome of the journey of the notch-fin turtle was to involve Archie Carr in the mysteries of Chelonia's migrations. He set out to use the methods of science to prove the folklore of the turtle captains. But trying to convince scientists that a reptile with a reputation for being sluggish and stupid possesses uncanny powers of navigation is not easy.
For nine years Carr and his students walked the black beach at Turtle Bogue turning females on their backs and clipping metal identification tags to their flippers. (You can do this with adults; they grow very slowly, if at all. Last summer I helped four college students and a handful of men from the village of Tortuguero tag some 300 greens. This brought the number of individuals tagged to over 3,600, 134 of which have been found again in other parts of the Caribbean.
Turtle fishermen working off Nicaragua recovered most of the tags and mailed them to the University of Florida. Some individuals traveled as much as 1,500 miles from Tortuguero and were picked up in the Florida Keys, off northern Cuba and the Yucatan Peninsula, and in the Gulf of Maracaibo, Venezuela. Fidel Castro’s government allowed a Cuban fisherman to return the tag he found but would not let him accept the small reward.
Turtles tagged at Tortuguero have never been recovered there after nesting season and have never been found nesting anywhere else. Also, no correlation exists between distance traveled and the time elapsed from tagging to recovery. “This,” explains Carr, “strongly suggests that turtles are not random wanderers but migrants following a fixed schedule between nesting beaches and home pastures. Otherwise, the reptiles would tend to cover the same distance in the same time.”
But does this travel involve anything more than piloting by landmarks? Many kinds of animals are accomplished pilots. Green turtles could simply leave their home pastures and follow the coast until things look, smell or taste in ways that mean the ancestral breeding ground has been reached.
In searching for an instance of turtle travel that clearly involves an ability to make long, oriented sea journeys in the absence of landmarks. Carr thought of the colony of green turtles that nest on Ascension Island. Every February large numbers of turtles begin to arrive at this remote spire of rock lost in the vastness of the South Atlantic Ocean. Males either travel with the females or make precisely timed rendezvous off the beaches of the island. At once, the strenuous business of courting, mating and often fighting begins.
You would not think so by looking at them but turtle males are passionate lovers. If a turtleman strikes an attended female, her swain may try to follow her into the boat. Since male greens weigh up to 500 pounds, this could prove troublesome. Foiled in his boarding attempts, Carr notes that “the loving male, a-slosh with hormones and crackling with short circuits in his vagus nerve, may thrash about your boat for an embraceable substitute. He flaps, scraps and bites at the plankings; he chews your paddle blade or hugs your oars until they snap. Fall over yourself and you’re out of luck.”
These violent encounters serve to fertilize eggs to be laid during the following nesting season—two or three years hence. The females, often scratched and lacerated from the male’s attentions, lumber ashore and nearly always stop in the backwash to press their snouts against the sand. A turtle may get on with her nesting or turn around and go back. Once satisfied that she has made the right selection, a female will make three to seven trips to the same small stretch of beach. Each time she uses her hind flippers to dig a pit about two feet deep. Each time she straddles the hole and lays about 100 golf- ball-sized eggs. She then carefully covers the eggs and disturbs the sand over a wide area to obscure the exact location of the nest.
There are no lush pastures of turtle or eel grass around lonely Ascension, so by June all the males and females have gone somewhere else to feed. But where? The African mainland is a thousand miles away and 1,400 miles of open ocean separate Ascension from the Brazilian coast.
Although longer, the route to Brazil would be easier for both the spent adults and young hatchlings. The South Equatorial Current flows westward from the African coast to the shores of South America and a tired or weak turtle could get a free ride, or at least a welcome push.
If you search around the Brazilian coast you find plenty of seaweed and green turtles. When Carr searched the coast of Brazil and Argentina in 1957, however, he failed to find any nesting beaches. If these turtles did, indeed, swim all the way to Ascension to nest, their journeys would conform to the classical migration pattern of aquatic animals. The strong, capable adults swim upstream or against the currents to reach their spawning grounds, then the weak, inexperienced young ride the currents downstream.
To see if this is what really happens, Harold Hirth, then a graduate student at the University of Florida, went to Ascension in 1960. From February to April he tagged 206 females at six nesting beaches on the volcanic island. Since that time nine of these tagged turtles have been found off the Brazilian coast by turtle fishermen. In 1963, when the group that nests every three years was due back at Ascension, a tag patrol was set up on the beaches. They came across three of Hirth’s turtles. In 1964, when the two-year nesting group was due to return a second time, two more tagged animals were discovered. Four of these five females landed on the same short section of beach where Hirth first labelled them. The fifth came ashore on a recently formed beach next to her old nesting site.
As Carr indicates: “This does not prove beyond all possible doubt that turtles regularly cross the open ocean between Brazil and Ascension, but I think it does so beyond all reasonable doubt.”
When changes in temperature or the length of day stimulate glands and send hormones coursing through their bodies, the turtles feel an instinctive, irresistible urge to travel to the natal beaches. It is likely that they refer to the sun and stars, to determine the correct course to set out on from Brazil. Then it is “uphill” all the way to Ascension. The turtles must swim against the currents for two months to cover the 1,400-mile distance. With miles of cold, dark ocean under their bellies, they find little, if any, food during the trek. The beasts most not sleep much either, for as soon as they stop beating their flippers the Equatorial Current pushes them away from their destination. Without benefit of charts, sextant sights or loran, the turtles must hold their course and compensate for any drift. They must avoid the tooth-filled jaws of sharks and the playful, curious pushes of dolphins without losing orientation. “The difficulties facing such voyages would seem insurmountable,” observes Carr, “were it not so clear that the turtles are somehow surmounting them.”
How do they do it? How did the journey originate and what natural guideposts do turtles use to find their way?
Archie Carr thinks Ascension Island may have been originally colonized by pregnant turtles accidently carried from West Africa by the South Equatorial Current. As he points out: “Another kind of sea turtle—the West African ridley—appears to have colonized the Guiana coast north of Brazil in just this fashion.” The young of any turtles nesting on the island would be carried on westward to Brazil by the same current. These youths could carry imprinted in their “memory,” the information necessary for them to retrace their journey. When reaching maturity, the turtles might travel north or south along the Brazilian coast until they smell, see or otherwise recognize the vicinity of their first landfall. This would put the reptilian navigators at or near the latitude of Ascension. From here an innate sense of direction—a biological compass—might guide them due east to a point where they would pick up odors, tastes or sights peculiar to Ascension.
Many animals possess an inborn compass sense which enables them to determine direction by the sun and stars. Honeybees on a search for nectar keep track of their course by taking bearings on the sun. After finding food, they fly a beeline back to their hive and relay the correct course to their hive mates by means of a complex dance. Since the sun moves across the sky while the search and dance are in progress, these animals must also possess a time sense in order to compensate for this movement and hold a fixed course. Pigeons, night-flying warblers and other birds can do this, so it is not far-fetched to attribute the same abilities to turtles.
But greens crossing hundreds of miles of open ocean run into a problem that cannot be solved with only a biological compass and clock. Even if a turtle maintains a fixed course, any drifting due to wind and current could push him many miles off a direct path between Brazil and Ascension. The island is only seven miles wide, so even a slight drift during the 1,400-mile swim could cause a reptilian mariner to miss his destination completely. Since they do not miss it, turtles must have some way to compensate for the vagrancies of wind and water.
Human navigators do this by determining latitude and longitude. Calculating longitude requires measurement of the azimuth or bearing of a celestial body, that is determining the horizontal component of its movement. A turtle in the open sea probably cannot make such measurements against a featureless horizon. In a way, the reptile’s position is the same as that of human navigators before precise chronometers were available. In those days, mariners found an island by sailing north or south until the altitude of the sun at noon showed they had reached the latitude of their destination. They then turned east or west and held the same latitude until the island was raised.
Archie Carr thinks turtles may navigate in much the same way. To do this they would have to determine the angular height of the sun above the horizon at noon. This angle is equal to latitude and is what deck officers measure when they squint through a sextant at midday. If turtles can do this, it would be an astounding adaptation to their surroundings and would answer the question of how they find their way.
A pregnant turtle could cruise along the coast of Brazil until her noon sights revealed she was at the same latitude as Ascension (7°55' S.) She could then use her compass sense to set an eastward course and strike out across the open sea. If the sun’s height at noon began to decrease, the turtle would know she was drifting southward. She could apply a little right flipper and reshape her course a few points northward. If the sun’s height increased she would correct her course with left flipper. In this manner, the mother- to-be would make a zig-zag track across the Atlantic until she picked up whatever beacon turtles use to home-in on Ascension.
It might be the sight of Green Mountain, which reaches an altitude of 5,000 feet and is often crowned with clouds that rise much higher. Or Ascension Island might exude a characteristic scent that is wafted westward on the Equatorial Current. It takes only two molecules of earth-scented fresh water in its nasal sacs to turn a young eel from the sea and cause it to head for the bays and backwaters of the land. Such aromas would become stronger and stronger as the turtle approached her island and would provide an excellent guide. Carr suggests that “turtles may be able to detect an Ascension effusion in the westbound current far downstream and follow it until they make a landfall.”
To determine if turtles actually find their way by sun, stars, and smell requires tracking them throughout an entire migratory journey. A start has been made in this direction. Shrimp boat crews working off the Florida Keys have been startled to see turtles towing rafts with brightly colored balloons attached. Carr and his colleagues attempted to track the movements of the turtle-borne balloons with transits, alidades, and optical range finders. They ran into “gross procedural troubles” such as leaking, bursting balloons; curious fishermen, and rafts being dragged under when the turtles spotted attractive foraging spots. Nevertheless, Carr feels this method is promising for short runs.
With support from the Office of Naval Research, University of Florida trackers are trying to monitor longer trips by mounting transmitters on turtle shells, on towed floats or, for greater range, on the balloons. Carr has suggested putting a tracking antenna atop Green Mountain to pick up signals from such transmitters. But what he would really like is a satellite. “Tracking Ascension-bound turtles by satellite could easily prove to be the most efficient way of learning the route they follow,” he says. “The green turtle could without inconvenience tow a raft, bearing a radio transmitter and power source, for long distances.” Signals from the turtle transmitters would be picked up as the satellite came within range, then rebroadcast to a central station where the reptiles’ plodding paths would be precisely plotted.
Animals probably get different kinds of travel information from their surroundings, just as they obtain different kinds of food. Migrating turtles must combine information they get from the heavens with cues from the land and sea. What signs in the sky they use is unknown, but use them they must. “It is unthinkable,” avers Carr, “that the struggling races of Earth should have missed the opportunity for survival offered by the stars.” By following nature’s signposts, creatures reach places where food is plentiful or where conditions are ideal for the development of the young. In other words, migrations increase an animal’s chance of survival.
For millions of generations turtles have followed these subtle signposts. They have drawn information from an environment that extends out to the stars. Now man’s desire for soup and shell threatens them with extinction before we learn what this information is and how it is used. Perhaps every man who tries to find his way by sea, land or air may Profit from this knowledge.
The green turtle’s ability to make successful migrations and the impregnable armor of its shell has assured the survival of the species for hundreds of millions of years. Turtles and dinosaurs share a common ancestor, and Chelonia has adapted to its surroundings so well its appearance has changed little in 200 million years. Today’s greens are too big and hard for most predators and too fast and Wary for others. Only unreasonable acts of man can end their long history and send them the way of their ancient cousins, the dinosaurs. Indeed, Chelonia has already started down the road to extinction. Perhaps the efforts of Archie Carr, the Caribbean Conservation Corporation, and the U. S. Navy can turn them back.
With the help of turtle ranches and the protection of local governments, green turtles may be restored to their former abundance. Then not only gourmets will delight in their savory substance but children bloated with disease caused by protein deficiency may fill their weakened frames with turtle. Millions of babies cry themselves to sleep at night from hunger, yet many of their undernourished parents live close to potential turtle Caches. It is not too much to say that the green turtles could make a large contribution toward loosening the cruel grip hunger holds on over half the world’s population.
Perhaps Operation Green Turtle may help man have his turtle and eat it, too.