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Double White
Rare things always seem to happen in Tortuguero. We see so many green
turtles that some of them are bound to differ from the norm. A normal green
turtle hatchling, for example, has a dark carapace and a white plastron on
the underside. It may be that they are therefore more difficult to spot and
hence they can better avoid predators. Sea birds cannot see the dark little
dot that is a hatchling swimming in a frenzy toward the distant ocean
currents. Likewise, predatory fish looking up against the sea surface can
not see the white underside of a green turtle hatchling striving for the
open ocean.
However, sometimes a rare genetic combination occurs that results in albino
hatchlings. These are double-white, both underneath and on top. Nature has
its own way of dealing with these rare turtles and limits their numbers as
they are easily found by predators, sticking out as bright points in the
dark sea. Dr. Carr wrote in "So excellente a fishe" that only one of 30,000
Tortuguero green turtle hatchlings are albinos. Well, this week Richard, one
of the research assistants, hit it lucky. He was excavating one of the nests
that we had marked earlier in the season. The hatchlings had already emerged
a couple of days earlier and Richard was digging up the nest to count the
empty eggshells and to estimate the hatching success. A large majority of
the eggs had hatched, but several eggs were still in the bottom of the nest
that for various reasons had not developed and hatched.
After counting the empty eggshells, Richard started opening up the
non-hatched eggs to determine at what stage they had stopped developing. He
opened up the first egg and found an almost fully developed albino hatchling
that had died during the late stages of development. In the next egg there
was also a fully developed albino hatchling, but this one was still alive.
The hatchling had not yet absorbed the yolksack and would no doubt had died
had Richard not found it and released it. Normally, green turtle hatchlings
absorb the yolksack during their travel up toward the sand surface. However,
our albino hatchling had missed the emergence of his/hers brothers and
sisters.
Richard brought back the albino hatchling to the field station and put it
inside a plastic bag with wet sand, hoping that the yolksac would be
absorbed. After a couple of days in the bag the double-white hatchling
started crawling towards the sand surface. Its yolksac was still not even
close to being absorbed so we had to keep the hatchling for a little while longer.
One night, a week after the hatchling was found at the bottom of the nest,
the yolksac was sufficiently absorbed for the hatchling to be released. We
brought it out to the dark beach and made sure it made it down the beach
without being eaten by any predators. The white little hatchling made it to
the sea and started to swim out against the breaking waves in a swimming
frenzy. Its chances of survival are even smaller than that of a normal green
turtle hatchling, but its chances are better in the sea than if it was left
behind at the bottom of the nest chamber.
Less rare and variable than the color of the hatchlings is our work
schedule. Although the number of nesting turtles has started to drop off, we
are still out every night and every morning in pursuit of turtles and their
nests. This week we were joined in our efforts by eight program
participants. They walked the beach at night, dodging driftwood and old
bodypits to find the nesting turtles. With no moon, their work was hard and
difficult but they all left with a feeling of having contributed to the
conservation of the amazing animals that are the sea turtles. Rarity makes
for an exciting time but it is the daily, hard work by dedicated and
concerned conservationists that will make a difference in the survival
outlook of our intriguing friends from the sea.
Pura vida,
Sebastian Troëng
Research Coordinator
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