Digging for Answers

What turtle nests in the Dry Tortugas reveal about sea turtle survival

09-29-2010 // Bob Serata
Digging up Sea Turtle nests

It's a Tuesday morning and I'm at Dry Tortugas National Park in the Florida Keys. The sun is shining, the beach is empty, and I am staring at a two-inch wide tunnel going straight down into a green sea turtle nest. I'm told this is not a good sign.

"Ghost crabs," frowns Dr. Kristen Hart, U.S. Geological Survey (USGS) scientist in charge of a multi-year research project examining the migration and nesting habits of endangered sea turtles in the park.

The crabs, whitish, pale-bodied relatives of fiddler crabs, feed on turtle eggs and hatchings. "I know we're not supposed to choose sides but I hate to see it," says Hart. "It is nature's way, though."

Dr. Hart pulls a three-foot length of white PVC pipe out of the sand, reads the location, date and species data written on the pipe and then jabs it back into the sand. "We should dig up this nest,” says Hart. “The hatchlings should be gone.”

The nest looks like a five-foot-wide volcano rising a foot above the beach. The usual surface evidence of hatchings is not easily seen. There are no flipper tracks or clearly defined exits holes. Only the crab burrows are easy to see.

Along with Capt. Keith Ludwig, also of USGS, and Dr. Nicholas Whitney, of Mote Marine Laboratory in Sarasota, FL, Hart begins scooping, gently, softly removing sand. It's slow work but it's all about making sure no harm comes to turtle hatchlings or eggs.

Two feet down, Ludwig points to one side of the large dig. He sees another ghost crab tunnel. "Looks like it goes that way," he says. The digging continues.

Sea Turtle Hatchling

"Wait!" calls Dr. Hart. There's a dark smudge on the side wall of the hole. She carefully flicks away some sand. A tiny shell appears. It's an inch and a half long. A few more flicks and a green turtle hatchling drops into her hand, its flippers racing through the air.

Hart smiles. "He's late but he's a great shape," she says. With careful delicacy she hands the hatchling to Ludwig. He puts the hatchling into a bucket that contains a few inches of sand from the nest, gently covers the hatchling with sand, and resumes digging.

Within a minute, they find another smudge. Then another. Altogether, seven hatchlings are found making their way to the surface. Three show signs of predation -- bloody necks, a missing rear flipper, a damaged left flipper.

After all the hatchlings are transferred to the bucket, Hart continues to dig. Finally, she finds what she’s been looking for: the hatched eggs.

Handful by handful they come out. Twisted and white, soft and leather-like, the sand-covered egg shells pile up. A few show predation, again caused by crabs. Dr. Hart separates and categorizes all of the eggs. In all, this green turtle laid 125 eggs. One hundred twenty of these made it out of the nest, plus the seven late comers who will be released and given a shot at life in the Dry Tortugas.

"Nature is hard," says Hart. "Used to be, we thought about one turtle in a hundred made it to adulthood. Now, we guess it's more like one in a thousand."

I'm hoping it will be one from this nest.

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