We had our first boil yesterday, August 10th, and I'm happy to report that the day before the boil, I sent an e-mail to the National Park Service saying that I thought something might be happening in the nest. Given this, it might actually be possible to predict when a nest will hatch!
After the boil, I spent a few hours looking at all the data to see what I could find, and the results were not quite what I had expected. In fact, I have a new hypothesis about how to predict when a boil is about to occur.
Previously, I had heard that the activity from the turtles moving around in their eggs and then from hatching stimulated the other turtles to hatch, and that somehow they coordinated the boil from all this motion. From looking at the data, I think what might be happening is that the motion ramps up gradually until they start hatching. Then, as they hatch, the motion becomes erratic. Finally, after they all have hatched and are waiting for the boil, everything quiets down. It is this quieting down that might be the clue to the turtles that all their siblings have hatched and it is time for a boil. It makes sense, since as each turtle hatches, there is no need for it to move any more. All it needs to do is wait for everyone else to finish their wiggling. If there is no wiggling, all the eggs have hatched, and it is time to go.
From looking at the orientation of the sensor, it appears to have rotated a little between 2 PM and 7 PM on August 7th, which appears to be the period when there were the largest jolts. This makes sense if this movement was from the collapse of the nest as the turtles hatched. The sensor would get lower, and its orientation would rotate about as much as can be seen in the data.
It will be interesting to see what the data looks like from some more hatching nests and whether they all look similar. Who knows? Another nest might be boiling as I write this . . .
The data was also quite surprising in another respect. The boil itself is hardly noticeable. In fact, I'm not exactly sure what time it occurred from looking at the data. There were no dramatically large motions. I thought for sure that we would get very high readings when the baby turtles moved past the sensor egg. It looks like the sand might have absorbed much of the energy. It might also be that when the nest collapsed, the sensor did not sink with it as much, and very few of the turtles had any contact with the sensor. It will be useful to know the orientation of the sensor relative to the egg shells when nests are excavated.