Frequently Asked Questions

Note: Answers based on information from works of Dr. Archie Carr and/or Dr. Carl Safina.

A. Natoli - May 2010
rev. -  July 2011

How does the female turtle find her nesting beach?
"Many animals possess abilities that let them know where in the world they are. They can orient, act appropriately, and navigate to a target thousands of miles distant. There is evidence that various animals are able to align themselves with the magnetic field of the earth. The sensory structures involved are not well known but the Earths magnetic field "inclination" varies with latitude, meaning that magnetic-field lines intersect the planet's surface at reliable, consistent angles, ranging from zero degrees at the equator to ninety degrees at the magnetic poles. Magnetic field intensity also varies in a consistent way over the surface of the planet so the information is there for the turtles to use to find their way back home."
Where does the turtle dig her nest?
Generally, She digs her nest at the edge of the first vegetation or beside the rise of a dune or log. The turtle makes trial swipes with her long front flippers and if the sand is to her liking she starts to excavate her nest. If she is disturbed or encounters any obstacles she will abandon the site and either try a different site or return to the sea without nesting and try again, if not somewhere else that night then on the following night.
How many eggs does she lay?
There is some variation depending on the species. The mature Loggerhead, averaging about 120 at a time will lay almost 600 eggs in a season. This is the way she overwhelms the predators that would otherwise eat all of her eggs if she laid any less than this. Any more than this number and the eggs would be too heavy to carry in the turtles belly and to costly to fill with the right amount of yolk.
How deep are the eggs?
After scraping away all the loose sand (which may be as much as a foot or more) she digs the nest to the depth that her rear flippers which, for a mature Loggerhead turtle, will reach about 18 inches. She then drops her eggs into this chamber.
Do the eggs look like chickens eggs?
No, sea turtle eggs are not hard like bird eggs but are leathery and pliable. They are a bit larger than a ping pong ball and have a dimple on the surface to allow for expansion. "It's smooth shell shuts in the white and yolk. It keeps the embryo alive in its shell. Supported, fed, un-poisoned, and un-asphyxiated."

"The shelled egg, laid on land, is a kind of private sequestered pool in which a tender, beginning reptile can go through its perishable stages in much the same environment its ancestors lived in. The egg itself is a terrestrial adaption, but the animal it harbors is still aquatic."

What's the shape of the nest chamber?
"The nest a sea turtle digs is an elegantly designed, flask shaped, slightly lopsided, spherical chamber that communicates with the surface by a narrow neck. Even if the turtle could carry more eggs to the beach she would have trouble housing the bigger clutch in a proper nest. A proper nest means one with the right conditions of temperature and humidity, as well as one with a roof thick enough to hide the eggs."
How many times does she nest in one season?
The turtle will nest anywhere from 3 to 6 times in one season. The individual clutches are stored inside her body and, in succession, are fertilized and moved into the oviduct to develop internally for about 12 -13 days, forming the shell, before she can come ashore and nest again. It is thought that the dropping of the formed egg into the nest chamber starts the incubation process.
Does the same turtle nest every year?
Sea turtles do not nest every year. The normal period between nesting for the loggerhead is thought to be every other year but every two or three years is common. The abundance of resources that have been available for the turtle to restore herself from her last nesting season plays an important role in determining the nesting cycle. This pattern of nesting  is called modulated reproductive periodicity.
Do animals dig up the eggs and eat them?
"By chance or adaptive arrangement, a turtle nest is safe from most natural enemies during the greater part of the ~50 to ~60 day incubation period. The egg eaters are a menace while the eggs are being laid and for a day or two afterwards. After that however there follows a peaceful period when no animal seems to be able to locate turtle eggs in the nest."

Note: If this had not been the case then various animals, some long ago extinct, would have extirpated the sea turtle more than 100 million years ago along with all the other egg laying reptiles.
How long does it take for the eggs to hatch?
Incubation time is directly proportional to the temperature of the sand at the depth where the eggs have been ensconced. At 18 inches or more the sand acts as a huge heat sink moderating any abrupt temperature changes. Incubation cannot begin until that temperature reaches 77°(f). The faster that temperature increase the faster the eggs develop and, in general, hatching can be expected anywhere from 45 to 65 days thereafter.
What determines the sex of the hatchling?
The sex of the hatchling is determined by the incubation temperature at the critical 2nd third of the ~60 days incubation period. Those eggs incubating at or below 83°(f) produce male hatchlings. Those eggs incubating at or above 84°(f) produce female hatchlings. Above 95°the eggs are no longer viable
How do the hatchlings dig out of the nest?
"The first young that hatch do not start digging at once but lie still until some of their nest mates are free of the egg. Each new hatchling adds to the working space, because the spherical eggs and the spaces between them make a volume greater than that of the young and the crumpled shells. The vertical displacement that will carry the turtles to the surface is the upward migration of this chamber, brought about by a witless collaboration that is really a loose sort of division of labor. Although the movements involved are only a generalized thrashing, similar to those that free the hatchling from the egg, they accomplish four different and indispensable things, depending on the position of the turtle in the mass. Turtles of the top layer scratch down the ceiling. Those around the sides undercut the walls. Those on the bottom have two roles, one mechanical and the other psychological: they trample and compact the sand that Filters down from above, and they serve as a sort of nervous system for the hatchling super-organism, stirring it out of recurrent spells of lassitude. Lying passively for a time under the weight of its fellows, one of them will suddenly burst into a spasm of squirming that triggers a new pandemic of work in the mass. Thus, by fits and starts, the ceiling falls, the floor rises, and the roomful of collaborating hatchlings is carried toward the surface."
How do the hatchlings find the water?
"The trip of little turtles to the water begins when they break out of the nest. This may be located on unobstructed beach sloping evenly toward a sea that lies in full view. More likely, however, the location of the nest gives the hatchlings a first view of nothing but sand and sky. In either case the little turtles have got to find the water, and unless they are eaten they nearly always do. After a few short false starts they begin to crawl, and almost at once swing into the general direction of the sea. They move around, through, or over obstacles, and go up or down slopes with unswerving “confidence” in whatever sign it is that marks the ocean for them. They can find it by daylight or at night, in all weather except heavy rain, with the sun or moon hidden, or shining brightly in any part of the sky. The main guiding cue is not yet wholly understood. Although sea finding quite evidently involves light, it is certainly not a simple tendency to move toward light. Otherwise the hatchlings would be expected to go directly toward the sun or moon, which they only rarely do. On the other hand, they sometimes do get distracted by an artificial light source, or even by some especially intense patch of natural light such as a hole in cloud cover provides. Most often, however, they move confidently toward the water, no matter what the condition of the sky may be. After the soft dune sand is left behind and the turtles reach the hard tidal flat, the main guidepost can be supplemented by local signs. Besides the fundamental light-response, a chain of other signs and responses may affect the course or speed of the progress to water. White breakers in strong moonlight and fiery surf on phosphorescent nights both bring accelerated effort."
"When sand wet by the highest waves is reached by the hatchling, a surge of speed and confidence is often shown, and some of the turtles may even break prematurely into short bursts of swimming strokes. The touch of the wet sand may be the cue that brings on this premature change of gait. When a wave slides up the flat and lifts the turtles, the flying swim-stroke is instantly taken up by all the hatchlings; and during the time that they are alternately lifted and stranded by the coming and going of the sheet-flow, some confusion is evident among them. As each wave-wash comes back, however, they begin swimming forward a little toward the surf."

How do the hatchlings learn to swim?
"This sudden “learning” to swim, seems to illustrate what students of animal behavior call the releaser effect. It appears to require no practice period at all. The capacity may develop in the end of a single wave, and along with it there appears to come a current sense too, that causes the turtles to align themselves with the swash and backwash. This response allows them to continue on a seaward course in spite of the changing direction of flow of the surf. It must be their occasional bumping on the bottom that indicates to the hatchlings that the water is in motion, and that it goes first one way and then the other."

Where do the hatchlings swim away to?
The hatchlings should have absorbed and stored up enough energy from their yolk sack to swim for up to 72 hours. They swim almost non-stop until they reach the gulf stream which is approximately sixty miles off the shore of Fripp Island, SC. The gulf stream transports them north and west until it spins them out into the Sargasso sea.

Where is the Sargasso Sea?
"Whirling them slowly towards the Azores, off Portugal, then down past the Canary and Cape Verde Islands, slipping by the unseen coast of West Africa. By the time they are headed west again, back toward North America elapsed time spans years, sometimes a decade."

"A lot of plants get caught in the Gulf Stream and are swirled into the central North Atlantic Gyre, where they accumulate in the quiet center of the current system that circles that part of the globe. This is the place known as the Sargasso Sea. It is a region of little rain and wind, a high-evaporation rate, and very clear, salty water, which stands at a higher level than that of the surrounding ocean."

"It is estimated that some ten million tons of sargassum float in that tranquil sea. The weed accumulates there, partly because more of it drifts in on the Gulf Stream than drifts out the other side on the Equatorial Current, and partly by vegetative reproduction. Algae were pioneers in the art of sexual reproduction. The sargassum algae, however, are for some reason unable to procreate sexually. 'They simply grow and reproduce by breaking off branches of themselves. The individual plants probably never die, unless they are smashed by waves. Rachel Carson suggested that some of the Sargasso weeds out there in the Sargasso Sea today might have been seen by Columbus. In his time the place was feared by mariners as a trap for ships."

How long do the turtles stay at sea?
Sea turtles spend their entire life at sea. It may take as long as 10 years for the hatchlings to circumvent the Atlantic ocean before returning to their home waters where they then spend their entire life.
Only the females venture back to dry land when it is their time to nest. It is thought that it takes loggerhead turtles 25 years or more to attain sexual maturity before they can mate and  successfully nest.