This afternoon a few of us went down to the beach to excavate a couple of nests. To refresh your memory from an earlier post, a nest is excavated two days after its first batch of hatchlings appear. During the excavation, the nest is dug into, and whatever is left in the nest is sorted, counted, and recorded.
The excavation of the first nest was straight-forward: we found three hatchlings still alive, and the rest of what was left in the nest -- a couple of dead hatchlings; fully hatched eggs; unhatched eggs; SAGs (shelled albumen globules) -- was there in its usual numbers.
The excavation of the second nest, only 3-4 yards away from the first, was a different story. As Kim, the excavator, dug into the nest, we noticed several hatchling heads sticking up. We immediately became excited: it's always a goosebump moment finding live hatchlings in the nest. And find some we did -- six, to be exact. But then the findings started to turn grim: ten dead hatchlings. Sad, but, according to Kim, not too out of the ordinary.
Next, Kim began pulling out the unhatched eggs and the fully hatched eggs. It gradually became apparent to those of us watching that Kim was concerned about the unhatched eggs she was finding. Once Kim had finished the excavation, the team sorted. Out of approximately 88 eggs laid in the nest, only 20 -- less than a quarter -- had hatched. We had pulled out 6 live hatchlings and 10 dead hatchlings, so only 4 had made it all the way out of the nest on their own -- a low number.
Kim then opened the 68 unhatched eggs: 4 were unfertilized (stage 0), and the entirely of the remaining 64 were in the final stage of development (stage 3 -- there were no stage 1 or 2 eggs). What that means is, there were 64 embryos that were 'this close' to being hatchlings, and yet, for some reason (or combination of reasons) they didn't complete the final stage of their development. Kim has been at her job for awhile, and she assured us she had never seen that large a number of stage 3 unhatched eggs. Because she has to break into the shells of the unhatched eggs to determine specifically what's inside, it was enormously disappointing to see these 64 little leatherback turtle almost-hatchlings laid out on the sand. It's a sight I won't soon forget.
Though she can never know for certain what caused such a high number of stage 3's in this nest, Kim is pretty sure two main factors contributed to the arrested development: first, the nest was too shallow, so, second, the nest could never cool sufficiently at night to let the eggs develop fully.
Once we had finished sorting, counting, and recording, we swept back into the hole all of what Kim had dug out. We then filled the hole with large handfuls of sand and tamped the sand down. Kim was clearly shaken by what she had just witnessed, but she assured us that, though rare, such findings are a fact of life for leatherback turtles.
The silver lining to this story? The six surviving members of the ill-fated nest, along with the three from the first nest, that some of our group coaxed into the water tonight. The people who released the nine hatchlings told me it was an exhilarating sight to see those little buggers paddle their way through thesand down to the surf and then ride the waves out to sea. That, too,thank goodness, is also a fact of life for leatherback turtles.