From egg to hatchling

By Kim Seidl

Before sea turtle hatchlings embark on their incredible ocean adventure, they must first survive the delicate process of development.

Before the Egg:

Mature, female sea turtles vary in frequency of reproduction. Some species will return to their nesting beach once every two years, while others may take as long as nine years to reproduce again. These patterns are influenced by the sea turtle’s species, potential human interaction, migration patterns and climate events.

Finding the Perfect Spot:

The nesting process begins with an intentional stranding and testing of the sand. If the beach does not meet the specifics of an ideal nesting site, the marine turtle will conduct a false crawl, or an abandoned attempt to nest. Once she has found the perfect place to nest on her home beach, the female will ascend the dune to select and clear a nest site. Once the nesting hole is dug, and the eggs have been deposited, the sea turtle will refill and pack the site before traveling back into the ocean.

By the time sea turtles find the ideal nesting site, the embryos will be near halfway developed; evolving their shells beyond seven days of ovulation. The eggs will suspend development while being deposited; then resume the process within a few hours. This time period is crucial, as any disturbance of the nest will result in a cease of growth.

Developing:

As the eggshell hardens, a white dot will form near the top, slowly spreading until the entire case is solid in both color and rigidity. During the six to 13 weeks of incubation, lots of factors impact hatchling success. Extreme temperatures (below 73.4℉ or above 91.4℉) will result in a failed nest. In the ideal range of 78.8℉ to 89.6℉, a single degree change can determine the length of time a nest will need to fully incubate. Temperature also plays a key role in gender determination; cooler temperatures will produce males while warmer beaches will yield females.

When ready to emerge, hatchlings will use their caruncle, a special egg tooth, to help them get through the tough shell; this special adaptation will disappear in time as it is no longer needed. After breaking out of the shell and into the nest cavern the young hatchlings will flatten into the familiar turtle shape while absorbing the remaining yolk from their eggs. The fevered emergence process is known as “social facilitation,” where the upward digging activity of the hatchlings near the bottom will stimulate the hatching and ascent by those near the top (Musick & Lutz). The hatchlings work together to crawl through the compacted sand and emerge onto the dune. Digging through a foot of heavy sand may result in a period of rest once above the nest where the hatchlings will pause to allow their bodies’ natural oxygen intake to normalize before their next hurdle.

The Great Migration:

The great migration of hatchlings typically occurs after the sun goes down. If a nest accidentally hatches during the day, the hatchlings face the dangers of abundant diurnal, or day-feeding, predators and scorching sands. The gradient of sand temperature which occurs in the evening alerts the tiny reptiles that it is now cool enough to scurry toward the water. The mass of hatchlings will go through a period of frenzy in which their tiny bodies will function in overdrive to reach the moderately safe surf. This overpopulation of tiny turtles allows for the highest chance of survival, known as the dilution effect — with so many of them scampering to the water, predators have no chance to consume them all. The hatchlings will venture out into open ocean until they reach the mass of floating seaweed, the Sargasso Sea, roughly a 24- to 48-hour journey.

In ideal conditions, the hatching success rating will near 80 percent. During incubation, sea turtle nests will face several dangerous factors, including predation, weather events, human impact, and environmental conditions. Beaches where sea turtle nests are frequently found need to be kept dark, flat, and free of obstructions. If you come across a hatchling who has not completed their journey to the ocean, please contact your local turtle conservation organization.

In Brevard County: Sea Turtle Preservation Society: (321) 206-0646

Statewide: Florida Fish & Wildlife Conservation Commission: (888) 404-3922

References:

Musick, John A, and Lutz, Peter L. The Biology of Sea Turtles. 2017. CRC Press. Available at: https://books.google.com/books?hl=en&lr=&id=QNRBDwAAQBAJ&oi=fnd&pg=PT75&dq=sea+turtle+reproduction&ots=yC06RHzCJZ&sig=VgeaX35zBN8dCWkvgKUw1AsUBlM#v=onepage&q=sea%20turtle%20reproduction&f=false