Today is World Sea Turtle Day, named in honor of the birthday of Dr. Archie Carr who was the father of modern sea turtle biology. Tonight, I am hopefully going to head down to the beach after work, around 10pm to sit, relax, hear the waves, spend some quality time with hubby and watch for turtles. It seems like such a better idea instead if heading home and sitting in front of the TV. There are five main types of turtles that nest in Florida, in my area (Cape Canaveral) the loggerhead is most prevalent.
With that said, I wanted to talk about a day in the life of a nesting sea turtle. I know many of you reading this may not be divers and are just curious about these magnificent sea creatures. As a scuba diver I can’t tell you how much joy I get when I see one of these marvelous dinosaurs.
Sea Turtle nesting season will vary depending on species but the main times are May thru to October hatching. When you think about it the water temps are warmer but also this is during our stormy hurricane season. I point this out as I find it incredible that their natural instincts to mate and lay eggs endures even through the tropical storms they may have to endure. Imagine the little babies struggling in rough waters.
For the most part turtles are loners. Sea turtles for them most part are generally solitary creatures that remain submerged for much of the time they are at sea, which makes them extremely difficult to study. They rarely interact with one another outside of courtship and mating. The exception is Ridleys which do come together in massive groups during nesting. But even when large numbers of turtles gather on feeding grounds or during migration, there is little behavioral exchange among individuals. No touchy feeling, no social dinner parties, no family gatherings.
So, what do they do, and how do they do “it”?
All the sea turtles I see are feeding during the day with occasional nap periods. When diving, occasionally you come across one just hanging out near a rocky interval. In LDBS we have seen turtles napping down in the rubble reef areas in the holes during the day. Many types of turtles, loggerheads included will follow the same old routes between the beach they will nest on and the offshore reef structures or other rocky intervals. Scientists believe that the actual mating takes place in these areas. Sea turtles can also sleep at the surface while in deep water. Little baby hatchlings once born will typically sleep floating on the surface, and they usually have their front flippers folded back over the top of their backs.
The courting dance and the actual mating for most sea turtles are believed to occur during a limited period prior to the female’s first nesting emergence. After mating, only the female comes ashore to lay her eggs. Male sea turtles almost never return to land once they leave the sand of their natal beach. They spend their life at sea. During the mating ritual, the male sea turtle may court a female by nuzzling her head or by gently biting the back of her neck and rear flippers. If he does not scare her away and she stays around, the male attaches himself to the back of the female’s shell by gripping her top shell with claws in his front flippers. He then folds his long tail under her shell to copulate.
Beach goers and scientists have observed female sea turtles on the nesting beach after recently mating with scratched shells and minor bleeding from where the males’ were hooked to their shells. “The act” can take place either on the surface or under water. Sometimes several males will compete for females and may even fight each other. Observers of sea turtle mating have reported very aggressive behavior by both the males and females. Females may mate with several males just prior to nesting season and store the sperm for several months. When she finally lays her eggs, they will have been fertilized by a variety of males. This behavior may help keep genetic diversity high in the population. I wonder if it means all the babies have one proud papa, several or does one hatchling have one dad while his brother has a different one?
Not much is known about why some turtles pick certain beaches. It is believed that the females return to the same beach they were born on to lay their eggs. Major nesting season is May to October as I stated previously. It makes me wonder why? What will all the coastal building we are doing, do to the future nesting behaviors. Are we messing with landmarks they identify with or perhaps it has something to do with what they sense be it smell or tastes along the way.
Once, the female turtle has arrived, she slowly makes her way up. We know that during full moons, they are very active. Also, she takes her time up the beach. She may even decide not to lay and head back to the ocean to wait. This is a “false crawl,” and it can happen naturally or be caused by artificial lighting or the presence of people on the beach. Now some may think, why go to the beach at night like I am planning to do. We generally sit up on the beach a ways and if we come across a sea turtle, we stay away and watch from afar. No flashlights, no poking, no touching. LEAVE HER ALONE!
Most females nest at least twice during the nesting season, although individuals of some species may nest only once and others more than ten times. Sea turtles are generally slow and awkward on land, and nesting is exhausting work. She will lay several nests during nesting season. It takes each female hours to lay dig her nest and deposit the eggs. Keep in mind that these dinosaurs are massive and she has to drag herself up the beach with her flippers. She will then use her back flippers to dig the hole. She then constructs a “body pit” by digging with her flippers and rotating her body. After the body pit is complete, she digs an egg cavity using her cupped rear flippers as shovels. The egg cavity is shaped roughly like a tear drop and is usually tilted slightly. She will then lay a “clutch” of about 80-120 ping pong shaped slimy eggs. Usually the top eggs are blanks. Many people believe that while laying her eggs a sea turtles goes into a trance from which she can not be disturbed. Again, LEAVE HER ALONE! She may abort if harassed.
Last she disguises the nest by covering it with sand. Then she abandons the eggs, they are on their own.
The interesting thing is these females return faithfully to the same beach each time they are ready to nest. Not only do they appear on the same beach, they often emerge within a few hundred yards of where they last nested.
Incubation takes about 60 days, but since the temperature of the sand governs the speed at which the embryos develop, the hatching period can cover a broad range. Basically the hotter the sand is surrounding the nest, the faster the embryos will develop. Cooler sand has a tendency to produce more males, with warmer sand producing a higher ratio of females.
To break open their shells, hatchlings use a temporary, sharp egg-tooth, called a “caruncle.” The caruncle is an extension of the upper jaw that falls off soon after birth. Digging out of the nest is a group effort that can take several days. Next the little baby turtles thrash about together causing the walls of the nest to collapse and the bottom of the hole to rise. Once near the surface, the hatchelings wait until the sand temperature cools to emerge. This is why they tend to hatch at night. or when it is raining. Then it is a mad dash for the shoreline. Once they decide to burst out, they erupt from the nest cavity as a group. The little turtles orient themselves to the brightest horizon, (think full moon) and then dash toward the sea.
The dangers the hatchlings have now are immense. Crabs, birds, dehydration from the sun, then hit the water and you have sharks big fish and circling birds all eat baby turtles or they die after accidentally eating tar balls and plastic garbage. The obstacles are so numerous for baby turtles that only about one in 1,000 survives to adulthood.
So, here I go, getting up on my soap box….do you part, pick up the trash, don’t litter and LEAVE NESTING TURTLES ALONE!
If you encounter a nesting sea turtle on the beach stay clear. Do not shine lights or take flash photographs. When frightened the nesting turtle will return to the water where she will drop her eggs. If you see an injured, nesting or dead sea turtle, call the Florida Marine Patrol at 1-800-DIAL FMP