Wildlife Spotlight: Leatherback Sea Turtles

May 30, 2013
Blog Image

Having grandchildren and watching the movie Finding Nemo more times than I have counted, always brings to mind the numerous animated sea turtles riding the Gulf Stream, at a tremendous rate of speed.  In watching this, I can’t help but think of the tremendous distances that some species of sea turtles travel in the course of a year — even more astounding the distance traveled over their life time. 

For example, a number of leatherback sea turtles that have been fitted with satellite transmitters while laying eggs on the beach at Tortuguero, Costa Rica. This is on the Caribbean coast near the border with Nicaragua. Amazingly, some of these turtles have been tracked across the width of the Caribbean, where they catch the Gulf Stream and proceed North with the warm water flow. Once a turtle has reached New Foundland, it continues with the Gulf Stream, crossing the North Atlantic and reaching the European coast near Scotland or Ireland. The turtle continues its migration southward, eventually reaching Portugal, where the turtle then does something absolutely incredible — crossing the Atlantic at its widest point!

The leatherback turtle eventually returns into the Caribbean Sea where it once again mates, and may lay as many as seven clutches of eggs in a nesting season.  A turtle may lay on a beach in Trinidad, then up to lay a clutch or two in Panama and finally its last clutches of the nesting season once again on the beach in Tortuguero.  Leatherback sea turtles, the largest of turtles and debatably the largest reptile in the world, are indeed world travelers, and one that IE’s Costa Rica tour guests can see nesting in Tortuguero, as well as beaches on the North Pacific coast of Costa Rica.

I’ll never forget my first observation of a massive female leatherback as she was just leaving the ocean beginning her crawl up the beach at Tortuguero. This was probably 20 years ago, but the memories are just as vivid today as they were that night so long ago. The turtle looked like a small car coming out of the water. She was a large female, almost maximum size for her species. About six feet in carapace (shell) length and her front flippers had a span of almost eight feet. She was enormous! As a few International Expeditions guests and I sat in the sand watching this huge turtle, she gradually crawled up to the edge of the very low dune line and began digging her body pit. These turtles dig a large hole that allows the entire turtle to lay below the surface of the sand.  She then began digging the nest hole using only her hind flippers, digging a flask shaped hole. Due to the length of her hind flippers, the nest hole eventually becomes quite deep. She then began depositing eggs. We used a red light to observe the process, and at first just a few eggs at a time would be deposited. Then the egss began to come in large clusters as she got into a rhythm of laying and then relaxing briefly before the next cluster of eggs were deposited. 

Once egg deposition was completely, the females sea turtle filled in the hole, then filled in the body pit and did a number of gyrations over the sand. When she was finally finished, it was difficult to tell where her eggs had been deposited. The band on this turtle indicated that she had laid eggs only a couple of weeks earlier in Panama and this would most likely be her last clutch for this year.  (This info was provided on the spot, via computer and satellite link that a Caribbean Conservation Corp (CCC) turtle researcher had in his back pack).  After laying, the turtle returned to the very dark ocean and would once again be off on her Atlantic migration, entering cold water up north and off of the coast of Northwestern Europe, down to Portugal and then all the way back across the Atlantic. 

Amazingly, these massive turtles feed almost entirely on jellyfish, thus they are able to cross mid-ocean as they can eat along the way.  Leatherbacks are also very deep diving turtles with dive depths of 1,200 meters being recorded. Their leathery shell allows for compression as water pressure is quite severe during these incredibly deep dives. Even their skull is quite unusual as it is made up of many small pieces, and between the pieces of the skull is material that allows for the skull to compress and expand. Also of interest in regards to this species is the leatherback’s ability to maintain a body temperature well above ambient sea water temperatures. At times as much as 18° C above ambient. This is accomplished with a unique vascular system as well as a nonvascular carapace.

So, the question is:  are all reptiles cold blooded or poikiliothermic? Not the leatherback! These turtles truly are marvels of the reptilian world and they can be observed nesting on both coasts of Costa Rica. Typically from February through July on the Caribbean coast and October to March on the Pacific coast. 

 
Naturalist Greg Greer is a favorite among IE travelers, and has gained a reputation for his friendliness and good humor, along with his incomparable knowledge of natural history, photos and articles have been widely published in books and magazines, including Georgia Outdoor News, Bird Watcher’s Digest, Alabama Outdoor News, Riversedge and Southern Wildlife.