Episode 20
Copyright © John Page Williams Jr. All rights reserved.
This is John Page Williams with another reading from Chesapeake Almanac. The month is August and the title of this chapter is "Sea Turtles in the Bay."
It just didn't look right. The shape was too small to be a boat out in the middle of Tangier Sound, but it was too big to be anything else. We had to go look at it.
Four students and I were fishing for dinner out of the Chesapeake Bay Foundation's lodge on Great Fox Island. We picked up our lines and ran a half mile south to investigate.
It was an immense dead sea turtle. A ship must have run over it, for its head had been cut off cleanly, as had the aft quarter of its shell. Even so, the neck was about 12 inches in diameter, and the remaining shell was over six feet long. Its flippers were intact. None of us knew much about sea turtles, so we looked it over carefully for characteristics for identification back at the lodge. Besides its size, its most striking feature was a series of lengthwise ridges along its shell.
At the lodge, the task of identifying a turtle from a field guide was easy. It was an Atlantic leatherback, the world's largest living reptile. This was a big one, probably weighing over a thousand pounds.
These animals are completely pelagic--creatures of open waters—and streamlining is more important than hardness of shell. Despite their great size, they swim very well. They breed in the tropics but migrate north as far as Nova Scotia in the summer, thriving in water temperatures much too cold for other turtles to stay active. Their bodies are well insulated with fats and oils, and they can maintain their body temperatures as much as 30 degrees higher than the water around them. The fuel that sustains these huge active animals is surprising—it's jellyfish! They feed on all sorts including the Portuguese man-of-war and our Bay's own stinging nettle. What draws them to Canada is the gigantic lion's mane jellyfish, three feet or more in diameter at the head with tentacles hanging down 70 feet.
As much as we would like to have an army of leather backs in the Chesapeake to keep down the summertime sea nettle population, they are uncommon here. Our turtle corpse appeared in August of 1977, a summer when scientists observed several other leatherbacks feeding at the mouth of the Bay. According to Dr J.A. Musick of the Virginia Institute of Marine Science, a large eddy formed at the Virginia Capes that summer, collecting quantities of everything that drifted in, including jellyfish.
The leatherback story illustrates the essential mystery of sea turtles. They are all long-range, open-water migrants, but they must nest on beaches, and their behavior is best known there, where they congregate. None nest in the Chesapeake, so early studies have ignored the Bay's roles in their life cycles. They do, however, use our estuary especially the Atlantic loggerhead, the Atlantic green, and the Atlantic ridley.
Loggerheads are almost common in the lower Bay through the spring, summer, and early fall. These turtles generally weigh over a hundred pounds and are colored a reddish brown. They, too, eat jellyfish but they also include sponges, crabs, clams, fish, and even eelgrass in their diet. They appear to be comfortable feeding on the bottom. Before the days of sonar, commercial fishermen in the Gulf of Mexico used to look for surfacing loggerheads to mark reefs where they set their lines. In the Bay, loggerheads will sometimes take up stations on oyster shell humps and bars, and even charter boat captains looking for trout will see them there every day.
Like the wandering leatherbacks, the loggerheads have an air of mystery about them. They lay their eggs on undeveloped ocean beaches from Virginia's Eastern Shore barrier islands south to the Caribbean and Central America. The tiny hatchlings are particularly difficult to trace. They crawl across the beaches from their nests and disappear from human contact for several years. Adults, on the other hand, can be marked with tags on their flippers, and extensive programs have been in operation along the coast for years.
Some particularly interesting work is being done now by VIMS researchers tracking radio-tagged loggerheads with a satellite. Early indications are that at least some of the turtles summer in the Chesapeake, migrate south close to shore as the water cools in the fall, and then swim out to the warm Gulf Stream, which carries them back up to the waters off the Virginia coast in the winter. The work continues, so more pieces of the loggerhead puzzle should turn up in the future.
Although once hunted extensively for meat and eggs, all species of sea turtles are now protected by federal law as endangered. They may not be molested, and there are stiff penalties for collecting shells and other parts of dead ones. There is a better reward for studying them, anyway. Begin by reading the book Time of the Turtle by Jack Rudlow. Report any dead or stranded turtles immediately to VIMS. You can do so online by going to www.vims.edu.
Sea turtles have been roaming the world's oceans for millions of years. It's got to give us a chuckle to find it being tracked by satellites. If we're ingenious enough to work out these ways to study them, maybe we're wise enough to coexist with them for years to come.
For more happenings around the Bay in August see our other Chesapeake Almanac podcasts and read our blog post "Late Summer Glory in Tidal Fresh Marshes."
