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My first Green Sea Turtle Experience
In this story I would like to share my first experience with sea turtles that has left a deep impression l will never forget. It is wonderful that I also involved my wife and both of my kids and had them take part as active volunteers in the project. I think by reading this, many of you that had the privilege of being part of this, will recall fond memories.
It has been six years ago, literally to the day, but I remember that evening as if it has been a few of nights ago. It was my first night out on the beach of Cancun as a Volunteer with the Sea Turtle Protection Program accompanied by my wife and an "old dog" (our instructor).
The water was calm, and the moonlight was mirroring on the surface. The noise of the shallow waves breaking was the only noise to fill the evening. As we watch the shore, a silvery shiny shape becomes visible. The object, or the part that is visible, is smooth and somewhat rounded. Suddenly the object moves with three sudden, jerky movements and as the gentle swell recedes, the shape of a turtle is unmistakable. It remains stationary for several minutes, the water lapping against its shell. It appears exceptionally large. Periodically it raises its head, then moves up the beach. The movement is labored, and the animal has some difficulty in hauling its weight across the soft sand. Soon it stops to rest.
After about a minute the head is raised and the creature makes several throaty noises, then movement up the beach recommences. The reptile progresses by advancing both its front flippers together and literally dragging itself forward. Later we see that by acting in union with the front limbs, the rear flippers also help to push it forward. Hence the body is never raised clear of the ground but moved forward a few inches at a time by simultaneous pulling and pushing off both pairs of limbs. The turtle makes a series of these movements and then rests. As it progresses farther up the beach, we notice that the rest periods decrease until they average under a minute's duration.
Now the turtle is almost upon us. She, for the turtle is a female which has come ashore to lay her eggs, had emerged from the water only a few meters to our left. Initially we were sitting, but as the turtle closes in, we are now flat on our bellies - motionless as instructed. The turtle is now only two turtle lengths from our heads and for a moment it appears that it will walk over us. When it first dragged itself out of the water it appeared enormous and beside us in the shadows we are again impressed by its size. It must measure at least 1.2 meters in shell length and about 1 meter in width. The head is small, and the front flippers, now so close to our heads, are large and powerful.
As we lay down, scarcely daring to breathe, it raises its head and we learn that the noise we heard on the beach at the end of rests was made by it exhaling air from its lungs. It takes a breath and then laboriously pull-pushes its significant weight alongside of us, stops, and then moves just past us. The incline has increased as it is nearing the edge of a naturally formed bank of sand which runs along the beach. The increased slope together with a change in the sand's resistance causes it to make extraordinarily little progress with each forward movement. It rests.
This is our first turtle and now that it is safely up the beach, we feel we can relax a little. Looking down the beach we can count several other tracks and see four other turtles making their way across the sand and one returning to the water. Being so focused on our turtle, we did not even realize what was going on around us.
The turtle has now moved about 20 meters over the sandbank. As we watch her, she makes several sweeping movements with her front flippers rather like swimming into the sand, and then moves forward. Further up she stops again and makes a similar series of front flipper movements after which she rests. It continues the front flipper movements with increasing force. The flippers are angled slightly so they dig into the sand and each backward stroke showers sand vigorously behind the turtle. After a few minutes, the rear flippers move. The front flipper action has resulted in piles of sand collecting at each side of the turtle where the front flipper stroke ceases.
As the turtle moves slightly forward by digging into the sand, the rear flippers can reach this sand. Working independently, they push it backwards. By now there is quite a depression around the turtle. The head is just below the level of the sand surface and the turtle is digging vigorously with the front flippers. Interruptions by rest periods are frequent. The digging continues for about twenty minutes when suddenly the action of the rear flipper's changes. Instead of pushing sand backwards by a lateral action, the flippers dig downwards, curve and become almost like hands. They seem to scoop sand. The body of the turtle, which has been resting stationary on the sand throughout the preceding twenty minutes, now moves slightly at the rear so that each scooping flipper is in turn positioned over the same spot.
The depression in which the turtle is resting is approximately oval but somewhat larger than the turtle. The bottom is almost horizontal, and the turtle is angled slightly downwards at the back. The depth of the depression, which is known as the body pit, is about 40 centimeters.
The rear flippers continue to work away in the soft sand. They seem to make little progress. As each "handful" of sand is removed, surrounding sand falls in almost negating the digging effort. However, after a further five minutes a definite depression forms. The flippers go through a scooping process which culminates in a rear flipper full of sand being lifted out of the hole and deposited on the ground beside the hole. The flippers are now decidedly hand-like in their action and are seen to be remarkably flexible.
A definite and regular series of actions takes place between which the turtle rests. The left rear flipper hangs down the hole. The right rear flipper is resting flat on the sand next to the hole. The turtle breathes, then the left flipper reaches down the hole and scoops sand. The sand is deposited on the left side of the hole and then the right rear flipper flicks sand laterally. By pressing down firmly with the left rear flipper, it raises the body clear of the hole. It is then rotated to position the right flipper directly above the hole. It then curves the flipper to enter the hole without damaging the walls and scoops sand which is deposited on the right of the hole. The left rear flipper flicks sand away, the body is rotated once more, and the left flipper positioned over the hole. This flipper is curved and enters the hole. It reaches down and activity ceases.
Each rest period is terminated by the turtle elevating its head and exhaling noisily. It then gulps air into its lungs by a pumping action of the throat. When on land, turtles have considerable difficulty in breathing. At sea, the water provides support for their bodies but when ashore their weight presses down on their lungs making inhalation difficult. In turtles the problem is overcome during the several hours involved in nesting by elevating the head as described above.
The hole dug by the rear flippers, called the egg chamber, is now almost as deep as their reach. As digging progresses, the turtle achieves greater digging depth by raising the front of the body slightly with the front flippers and so angling the rear downwards. During the next ten minutes, it makes little progress. Sand slipping into the hole, particularly when the rear of the turtle is moved to position the next digging flipper, seems to just keep pace with that removed by the digging action. As we watch, a small avalanche of sand enters the hole from a cave-in of the wall at the left of the egg chamber. Digging action ceases. To our shock, after several minutes, the turtle moves forwards and then clambers out of the body pit. Because of the sand slippage it has abandoned the hole and will move off to try again somewhere else. The whole laborious process has to be carried out again from the commencement of digging the body pit.
Sand moisture is the major factor in determining success or failure in digging the egg chamber. After prolonged periods without rain, when the sand is very dry even at the level of the floor of the body pit, digging the egg chamber is difficult. When the sand is very dry few turtles are successful at their first attempt. In fact, much fail even after digging for the greater part of a night during which they may attempt five or more egg chambers. These turtles, and others which give up after two or three attempts, return to try again the following night and/or the night thereafter. We have records of several turtles which have tried for up to five nights before succeeding.
Our turtle has now moved another 10 meters further inland and has commenced digging a new body pit. The area next to the site, and between the first nesting attempt and the present location, is popular with turtles as the sand is "cratered" with old diggings. The second location selected is a crater. As is often the case, the head down posture, resulting from entering the old pit, released the digging urge, and front flipper digging activity started.
After about fifteen minutes, front flipper activity ceased, and the rear flippers changed their action to dig instead of pushing sand away. Finally, the egg chamber has now reached the full depth to the maximum reach of the rear flippers, even with the added assistance given by angling the rear of the shell downwards. The turtle is engaged in widening the foot of the chamber. Enlarging the foot of the egg chamber by sideways scooping movements of the flippers occupies about ten minutes. The digging action has altered. Each flipper makes several scooping movements before being withdrawn with its load of sand. This results from the difficulty in obtaining sand now that the chamber is nearing completion.
Shortly thereafter, the left flipper is placed half-way into the hole but instead of digging is positioned against the posterior surface of the hole diagonally from left to right. The egg chamber is now complete and ready to receive the eggs. In shape it is rather like a pear with a definite neck-region and a much wider chamber below, which will house most of the eggs. The egg chamber is about 50-60 centimeters deep, and since the body pit has a depth of 40 centimeters, the foot of the chamber is approximately one meter below the level of the surrounding sand.
The right rear flipper is brought backwards to cover part of the hole and the cloacal region, which opens on the underside of the short thick tail, contracts several times. This is followed by the secretion of some viscous mucus which falls into the egg chamber. After a couple of minutes an egg is extruded and falls into the hole, soon to be followed by another and then another. The eggs are white, almost circular, slightly larger than a ping-pong ball and covered with mucus. The shell is soft and parchment-like, similar to that of most snakes and lizards. The shell can be dented as the egg is not turgid. There are now eight or nine eggs in the egg chamber and this time the turtle expels two eggs together. As egg laying progresses, eggs come out in twos, occasionally in threes or even fours. Between each laying there are contractions of the cloacal region, and preceding laying muscular contraction in which intra-abdominal pressure is increased by slight limb retraction. This probably helps to eject the eggs.
The turtle has now laid 134 eggs and the rate of egg laying has decreased markedly. Eggs are being laid singly or in twos. After expelling its 140th egg, the turtle rests. The mucus which dripped from the cloaca periodically during laying, and which coated each egg, is still extruded each time the cloaca contracts but now no further eggs are laid. After a couple of minutes, the rear flipper in the neck of the egg chamber is removed and reaching out to one side drags sand across to the edge of the egg chamber. The flipper stops just short of the egg chamber. The right rear flipper then performs a similar action. These movements show a remarkable sensitivity, unexpected in a heavy animal which appears clumsy on land. At no time do the flippers touch the eggs, nor do they make any strong sweeping action close to the eggs until these have been covered by a substantial layer of sand. After a few minutes, a pile of sand builds up over the site of the egg chamber because of the action of the rear flippers which is now more vigorous and involves a vertical patting action and horizontal movement of sand.
Digging the egg chamber and covering the eggs is one of the remarkable feats of turtle behavior since it is carried out so precisely with no visual cues. Without warning, the front flippers now make several sweeping movements, sending a shower of sand backwards. The rear flippers then continue to pile sand on the mound. The tail seems to serve as a location point in this behavior as it drags sand in by the rear flipper until the flipper or the sand it is guiding touches the tail. Periodically, the rear flippers consolidate the sand on top of the eggs by a kneading process using the sides of the curved flippers. The front flippers move again and gradually their action becomes more vigorous. At the same time, rear flipper activity decreases and eventually ceases altogether. The front flippers may act in unison or individually. The action of the rear flippers during the covering action, as when excavating, is always an alternate movement.
After half an hour the turtle does not appear to have filled in the body pit to any extent. The powerful action of the front flippers has been directed at the low wall of sand in front of the head and as this caved in the turtle has slowly moved forwards. The result of its activity, therefore, has been to dig out in front and fill in behind. Its tail is now almost a meter in front of the position where we think it lay the eggs. I say "think" since it is impossible to be certain about this as the entire area has been disturbed by the filling-in activity and the front flipper action has spread sand to both sides.
The action continues with the front flippers now often acting together and performing such a vigorous breaststroke that at the end of each stroke both flippers strike the shell making a loud noise. We can hear similar noises coming from several areas down the beach, so presumably several other turtles have also reached this stage of the filling-in process.
After a further half hour, the turtle has moved at least three meters farther forward and we notice that the body pit is becoming shallower. The "wall" of sand in front of the head is now noticeably lower. In the last hour, the turtle appears to have moved a substantial amount of sand in the filling-in process - we estimate about a ton. The turtle has stopped and raises its head to breathe. Without warning, it then climbs out of the egg chamber and turns to face the sea. It rests again, before moving on. On reaching the bank it makes one strong series of flipper movements and slides down the bank.
The limb action is the same as when it came up the beach; however, the downward slope makes movement easier than when it was ascending, and a greater number of limb movements occur between rests. Soon the turtle is on the area of wet sand. Progress across this is slow with frequent lengthy stops. It takes a few more minutes to cross this region and eventually reaches the sea where it rests with its head just at the water's edge. Soon it crawls into the water. Because of the air in its lungs it is buoyant and can swim despite the shallowness of the water. It heads directly towards the deep sea. There is still a mound of sand on the carapace. However, this is soon washed off as it reaches deeper water and exhales. The last we see of it is when it comes up for air about 50 meters from the water's edge. We had spent several hours watching our first turtle and did not even realize how the time passed by.
Even though we have since then closely watched many hundreds of nesting sea turtles, we will never forget the experience from this evening…