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Morning Beauty
It is five thirty in the morning. The sun is rising rapidly over the
Caribbean. The sea is calm as always during the dry season. Distant
thunder is rolling in over the water from a storm at the horizon. I'm trying
to shake off the tiredness of the early hour and start heading south on the
beach.
Every morning we have two teams checking on the nests that we have marked
previously during the nesting season. We look for hatched out nests and also
try to determine if the nests have been tampered with by natural
or unnatural predators,, or by other nesting turtles. The nest patrols are carried
out in the early morning before the tropical sun is high enough to make the
walk unbearable and when the hatchling tracks from the previous night are
still fresh and visible in the sand.
This morning I was checking the nests on my own and decided to start the
walk half an hour earlier than normal. I checked the few nests that we have
marked in front of the village, all of which seemed fine and with no
evidence of hatching. There was already activity on the beach. Many
villagers get up with the sun to try their luck fishing. They fish for
mackerel and jack with hand held lines and hooks baited with pieces of
sardine. Jose Antonio, the weekend night guard at the station, as well as
several school children were casting their lines, hoping for a
big catch.
I continued walking into the Tortuguero National Park, south of the village. Nesting
has been so dense there this year that the beach is covered with eggshells that nesting turtles have dug up from older nests. This time of year the beach is also
full of the remains of green turtle hatchlings. Many of them have been eaten
by vultures or ghost crabs and others have succumbed to the glowing mid-day
heat of the sand.
Ahead of me, I could see a group of vultures running around, picking in the
sand, no doubt finishing off a group of hatchlings unfortunate enough to try
the dangerous run from the nest to the sea in daylight. It is natural
predation, but it is difficult to let nature have its way in this game
of cat and mouse. To give the hatchlings a bit more of a chance, I waved a
stick in the air which is enough to get the vultures into a flurry of
feathers and fly away. At the same time, a coatimundi that had been hidden in
the bottom of a large body pit, virtually shoot out of the
hole and into the safety of the vegetation behind the beach.
The coatimundi, or coatis, is a relatively large mammal that can measure over
a meter in length. It is dark brown, has a large tail and a long
snout to smell out prey such as green turtle nests. The sexually mature
males are solitary for most of the year and only join the females and their
offspring during the mating season. We have encountered many of them
predating green turtle nests this year, both solitary males and groups of
females with lots of young in various sizes.
This particular nest that the coatimundi had feasted upon in unison with the
turkey and black vultures, was close to hatching. Opened eggs, with almost fully
developed hatchlings inside, were spread all around the nest. Only the
large yolk sacs outside their body cavities told me that they were not quite ready to hatch. Some hatchlings had been partly eaten by the large birds.Vultures tend to eat the front flippers of hatchlings and then stick
their beaks into the body cavity to finish off what food there is in a
turtle hatchling. Often they leave the remains of the hatchlings --
rear flippers still attached to the carapace -- for a grizzly find on the
beach.
Nothing could be done for the hatchlings, so I continued the walk. I looked
back over my shoulder and could see the coatimundi sneaking down to the nest
again. It dug into the nest with its front paws, picked up an egg in its
mouth and ran back for cover in the cocoplum. I left the coatimundi to its
breakfast eggs and walked on down the beach.
Green turtles fill an important ecological role in that they transport vast
quantities of energy from sea grass beds to sandy beaches. Tropical sea
grass beds are among the most productive habitats, catching and
transforming the energy of sun rays with an ability similar to that of
rainforests. In contrast, the sandy beaches where the green turtles deposit their eggs, are
very energy poor (what have you seen living or growing on a
sandy beach?). Tortuguero beach is given an injection of energy every
nesting season in the form of turtle eggs. Even animals from habitats
adjoining the beach, such as the rainforest, benefit from the turtle eggs.
Coatimundis, vultures, night herons and racoons feed on the turtle eggs and
the vulnerable hatchlings. These animals may in turn become prey to snakes
or other predators in the forest, passing the energy of the turtle eggs,
higher and higher up the food chain. Where green turtle populations have
become eradicated, the important energy transfer provided by the turtles has
been lost forever. This affects animal populations and habitats far away from
the sea grass beds where green turtles used to swim in abundance.
I reflected on the importance of turtles during my walk. The vegetation
behind the beach, the sea grapes, the cocoplum and the palms trees, and
farther back, the large trees of the lowland rainforest, were almost shining
green in the morning sunlight. Eighteen miles to the south, I could see the
trees in front of the village of Parismina. Even further south, the Talamanca mountain chain was visible in the clear
morning. If I turned around I could see the northern spit of the beach, by
the Tortuguero river mouth and the silhouette of Cerro Tortuguero, the remains
of an old volcano, north of the river mouth. The beach was full of tracks
left by nesting turtles. The old faded tracks from nights earlier in the
week were covered by the fresh tracks from the previous night. The chelonid
tractors had been driving up and down the beach as far as I could see in
both directions. Ahead of me I saw a late crawler, a straggling
turtle, returning to the sea in broad daylight after finally depositing its
eggs in the sand. Disappointed vultures waited in vain for our carapaced
friend to keel over in the sand. She reached the water's edge and was back
in the sea where she is a much more agile creature.
The lack of rain had left hatchling tracks from several nights ago
to mix with the tracks from last night. I came upon nest number 51 and
measured the distance from the two pieces of flagging tape in the vegetation out onto the beach and marked the spot where the two lines intersected. X marked the spot of the nest and there was a characteristic depression. Out of the dent in the sand came hatchling tracks, a hundred of them stretching down the beach to the water's edge. Our
nest had hatched out the night before with what looked like good success. I
marked the nests with a couple of sticks to make it easier for the afternoon
excavation team to find the right spot to start digging. I also took the
bearing of the tracks with a compass to determine the hatchling orientation
and then noted the distance from the nest to the high tide line.
The earlier storm had come ashore but seemed to have lost most of
its power while at sea, only a slight sprinkle fell on the beach. A million
black spots showed where the raindrops hit the sand. The drizzle cooled
down the surface of the beach, and in front of me I could see a nest hatching
out in response to the lowered temperature. The hatchlings scrambled to the
sea in a hurry not to be swept up by vultures or other predators that make a
nice morning snack out of a little turtle. The rain covered their tracks and
the sand stuck to their bodies making them look dirty as they alternated
their flippers in the run for the water. The first wave washed them clean
and they changed into swimming motion as they disappeared into the
surf. Hatchlings reaching the water during daylight probably stand little
chance of surviving, as they have to run the gauntlet through the coastal
waters where many predatory fish are active during the day. Further out at
sea, the national park guards passed by in their patrol boat on the lookout
for poachers. I waved at them to let them know I did not have stealing
turtle eggs in mind and they continued the journey northwards, close to the
beach.
At the end of my beach section, I turned around after having checked the
last one of the 75 nests and started heading back to the station. The breeze
and the rain cooled me down nicely. The clear green of the forest behind the
beach, the dark brown sand, the clouds over the mountains in the distance
and the tiredness in my eyes made for a picture more beautiful than any
painting that I have ever seen.
Pura vida,
Sebastian Troëng
Research Coordinator
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