The Relativity of Hatchling Fitness

Among the many en-vogue areas of sea turtle research, many individuals have become interested in studying hatchling 'fitness'. That is. based upon an array of various biotic and abiotic factors experienced by multiple nests over the course of a summer, how do these conditions affect the morphology and physiology of emerging hatchlings.

The term 'fitness' implies that we as researchers already know what makes a 'super-hatchling' - a hatchling capable of successfully making it to post-hatchling and juvenile nursery areas. Obviously, we do not. Some research suggests that nests incubated in drier areas produce hatchlings different from nests incubated in moist environments. Some of these hatchlings are larger and swim relatively slow whereas other hatchlings are smaller but swim faster. But what kind of hatchling is best suited for life away from the nest? Again, we do not know.

My opinion is that this type of research is all relative, as are nest hatch rates. To understand my view we must first journey away from the long, expansive beaches of Florida and move northward to where turtles nest on Barrier Islands.

Barrier Islands are seperated from one another and from the mainland by large tidal rivers, whose beaches on the north and south ends of islands are frequented by loggerhead turtles. Radio tracking studies in Georgia have shown that if hatchlings enter these areas during an in-coming tide, they are swept up the rivers and into the marsh rather than making it to the open ocean. Chances are these hatchlings use up valuable energy trying to fight the tide or they are eaten by the plethora of estuarine residents before the tide shifts and an out-going tide carries them out to sea. Nonetheless, these hatchlings are not immediately embarking on a journey to the southeastern North Atlantic nursery grounds and probably never will.

Additionally, we must think of the moon. I have seen nests with over 90% hatch rates where none of the hatchlings have crawled to the ocean. Instead and because the moon is over the western side of the island, the hatchlings follow the natural light into the woods.

We must also think of wind. I have seen hatchlings enter the surf at 3:00 in the morning only to be in the surf still at 6:00 am becasue off-shore winds have made it impossible for the turtles to venture past the breakers and to the open ocean. In these instances, diurnal predators like birds find these little ones easy pickings.

I'm sure there are many more examples that can be used; but from the above observations one really has no choice but to think that we really do not have a good grasp on what factors are truly responsible for determining which hatchlings will make it to their nursery areas. If a turtle doesn't emerge from a nest under certain conditions, (low wind, moonlight that doesn't confuse the turtles, out-going tide in some areas) then it doesn't really matter how 'fit' a turtle is, the couch potato turtle gets sucked up into the marsh along with the athletic turtle.