by Dr. Richard Reina, expedition scientist
The nest labeled 'H001' looks just the same from the outside as it did 66 days ago on October 10. This first clutch that we relocated to the hatchery includes 48 yolked eggs and 50 yolkless eggs. One of the expedition volunteers took ten of the eggs to put in the lab incubator. These eggs are all developing and getting close to hatching.
The turtle who laid these first eggs, PIT Tag Number 005-259-532, has since come up to nest four more times since October, the last time was December 8.
Although the nest looks the same, we know from the monitoring of the temperatures and gases inside the nest cavity, that the eggs are about to hatch. The temperatures have risen to about 32 degrees Celsius. The gas levels inside the nest have also changed. The carbon dioxide has increased while the amount of oxygen has decreased. Less than three feet underneath the sand, the turtle embryos are probably almost fully developed. A few hatchlings may have already started breaking open their shells. On the nose of each unborn turtle there is a sharp bump called an "egg tooth." This helps the hatchling break open the shell. The egg tooth falls off after birth.
How do hatchlings dig their way up to the surface? Dr. Archie Carr, world known for his study of turtles, replaced one side of a nest wall with a glass pane to observe green turtles. He saw that the first turtles to break from their shells lay still until nest mates had begun wiggling and squirming free. The turtles at the top scratched the sand above. The turtles on the sides undercut the walls, while the turtles on the bottom packed down the falling sand. By continued thrashing, the turtles on top eventually emerged on the surface like a little eruption.
At Playa Grande we have found that most hatchlings emerge at night when it is cooler. The digging out of the nest may take two or three days. This season the incubation period of about 60 days is taking longer. It is likely that Hurricane Mitch is the reason. The prolonged rain in October caused colder sand temperatures, which will have slowed down the development of the eggs. The heavy rains may also have compacted the sand, making it more difficult for the hatchlings to dig themselves out. We are waiting impatiently and with excitement!