August 28, 2019

Sea Turtles: A Reason for Shell-abration Pt. 2

Posted by: Nate Ramey

Sea Turtles: A Reason for Shell-abration Pt. 2
    above:  A “lost years” hatchling blown in by Tropical Storm Hermine 2016 


       Well, more “egg”-citing news here on Little Saint Simons Island. As of July 24th we have officially broken our previous island nesting record for sea turtles of 223 nests, and as I write this blog the island has a total of 238 nests. A true conservation success story for Georgia’s coast thanks to the tireless effort of so many dedicated people.

       Last month you all joined me on a journey through the eyes of a hatchling female loggerhead sea turtle. We began the story in the nest with 100 of your siblings eventually braving the first week of life against countless obstacles, from human light sources to hungry predators.  We ended the story having finally reached the Sargasso Sea in the Atlantic, with only 20 of your siblings. Here you have started a chapter of your life that will take approximately 10 years to complete. We now find you floating along with a patch of Sargassum in the “Big Blue”

       This time of your life is the most unknown life stage of sea turtles to researchers, due to the challenges of studying such small creatures in such a large environment. But as the years go by researchers are uncovering more and more and starting to piece together the “lost” years of a loggerhead sea turtle’s life. Going back to our journey as a hatchling, we find ourselves adrift in the open ocean. It’s hard to believe that at only a week old you are now expected to navigate the vastness of the open ocean. As you bob up and down near the surface and look around, other than the small patch of yellow brown vegetation you are floating in, you are surrounded by miles upon miles of blue water. The open sea is the ocean’s equivalent of a desert, and the sargassum an oasis. Here amongst the small fronds of the sargassum weed you find numerous small invertebrates such as crabs and the like to feed on. Starting on such a small diet, it’s hard to believe that one day you might weigh 300 lbs. or more, but you begin to grow none the less.

       As the days and months pass you continue to drift along in the currents of the open ocean. Absorbing the warmth of the sun from the mat of sargassum you are drifting on helps keep your ectothermic body warm, and you continue to feed on the small creatures living amongst the fronds of sargassum. Unfortunately, you see some small colorful items floating amongst the sargassum. You attempt to take a bite but find the item inedible, so you spit it out. You have just had your first run-in with marine debris. An ever-growing human caused problem; marine debris might be one of the biggest issues currently facing our ocean habitats. The biggest culprit is plastic. The easily molded, inexpensive material has made its way into all the world's oceans in the form of bottles, fishing gear, bags, cups, balloons, and so much more. Even a recent dive to the bottom of a deep-sea trench, several miles below the surface, revealed that plastic marine debris had found its way to even these hard to reach habitats. The problem plastic poses for sea turtles, mainly has to do with fact that sea turtles will often attempt to eat anything that looks slightly edible. Often this is a case of mistaken identity as a floating plastic bag or balloon looks like a jellyfish, a staple in many sea turtles' diets. If not passed, the plastic will usually block the gastro-intestinal tract leading to the demise of the turtle. Luckily, you have avoided this fate and you swim on.

       Sometimes you get the urge to swim to new areas rather than drift and due to new research done by Dr. Kate Mansfield of the University of Central Florida, it is being found that the juvenile sea turtles are far more mobile in the open ocean than what was previous thought. Using solar powered trackers attached to the shells of young sea turtles Dr. Mansfield, and her team have found that turtles do sometimes actively move against the currents or leave them to spend time in the middle of the Atlantic gyre, or Sargasso Sea. All in all, you are at the whim of the open ocean and you continue to float, swim, and grow in this habitat for up to ten years. Possibly circumnavigating the north Atlantic once or twice, until you have reached a size that can no longer be supported by the tiny creatures hidden amongst the sargassum weed, slightly larger than a dinner plate. Your next phase of life has started, and you begin a journey back to the coastal region of the Southeast U.S, using the internal GPS point you imprinted on as a hatchling. At this point it’s likely that you are the lone survivor of your nestmates. A testament of just how hard it is to grow a sea turtle, but you’ve made it this far and its likely you’ll continue to live and grow as you head back to the coast from which you were born.

       Sometime later in the coastal waters off Georgia you find plentiful food for an ever-growing turtle. Whelk, crabs, and other hard-shelled prey have little defense against your powerful beak and jaws. In fact, Loggerhead refers to the above average head size of the turtle owed to large jaw muscles for crunching tough prey. Being larger now has afforded you protection from most coastal predators. Only bigger sharks remain a threat, luckily you have become a proficient swimmer and can often outmaneuver most things after you. One day you find yourself within 20 miles of land. Feeding on a whelk down at the bottom 20 feet down, you notice a wide object coming at you, and unfortunately you are unable to react fast enough before it overtakes you almost like being swallowed by a huge beast. You find your world spinning as you bounce off the insides of the object and the sides begin to press in, when suddenly you hit a hard surface and begin to slide up and suddenly, you're free again and swim off. Your turtle brain doesn’t know what to make of what just happened. What has happened is that you have been fortunate enough to live through the experience of going through a shrimp trawl net. In years past this would have been a death sentence as most turtles would drown in the nets but luckily for you, a TED or Turtle Excluder Device was installed in the net allowing animals bigger than a shrimp to escape through a hatch in the top of the net. These devices have been instrumental in helping the sea turtle populations recover in Georgia, and as of this year Georgia is seeing record breaking sea turtle nesting up and down it’s coast.

       It’s likely that this won’t be your last run in with a shrimp trawl and in fact there are many human related dangers still out there for you as you spend the next 20 years maturing into an adult female. Boat collisions, fishing gear/net entanglement, and plastic ingestion are some of the hazards out there awaiting you, but if you manage to avoid all of that you’ll reach maturity at around 30 years of age weighing in at 250 lbs. and measuring over 3 feet long. A far cry from the hatchling that you once were, but with luck you’ll find a mate and begin the cycle all over again and lay your first nest on a beach not too far from where you hatched.

       Well, that completes our journey through the eyes of a sea turtle. Hopefully, I’ve been able to shed some light on the challenges that a sea turtle faces into making it to adulthood. They truly are fascinating creatures, and we are still learning so much about their lives through research every year. It’s exciting that an animal that is almost universally recognized could still have so much of its life still a mystery.

Learn more about our friend Dr. Kate Mansfield and her work directing the Marine Turtle Research Group at the University of Central Florida.


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