Like clockwork, the urge to procreate calls Maryland terrapins to shore and into harm's way

DIAMONDBACK DILEMMA

September 04, 1994|By TOM HORTON

Patuxent River, June 24, 8 a.m. No heads in sight.

The stage is set: the water tranquil, beach empty, sands beginning to bake in humid heat, already nearing 90; the steamy anomie of the bordering marsh is punctuated only by the piping of ospreys, wren songs and the flitting of swallows.

We are concealed in a cramped, makeshift blind along this Southern Maryland tributary of the Chesapeake Bay. But so far, since sunup, no heads; no sign of what we're prepared to spend the day -- or days -- to witness. It is a courtship between an animal and the river's edge, an evolutionary ritual whose astounding complexity is only beginning to emerge from eight years of unique study.

The animal is the diamondback terrapin.

This deep summer dance of the diamondbacks is teasing and secretive. Though it goes on for months, scattered throughout the estimated 9,000 miles of land-water edge around the Chesapeake and its 40-odd tidal rivers, you may live your life in such regions and never observe it.

9:45 a.m.

A head pops up, just off a little point the beach makes, about 200 feet from us, before it angles out of our line of vision behind the spartina grass and high-tide bush of the marsh. Two heads, three heads, four; black as coal against the reflective water. They belong to big female terrapins, all paddling hard now, closing fast on the nesting beach.

Relax, says Greg Bokor, a senior from Hood College who spends seven days a week in the blind on the "first shift," 6 a.m. until 2 p.m. Submerged except for their craning necks, the diamondbacks may flirt with the beach for hours, half-emerging, diving back in, disappearing, reconnoitering. Anything can spook them -- a dog barking, the bang of a distant farmhouse door, the shadow of a heron gliding across the shallows.

Sure enough, all four have disappeared. But wait. A head is moving just off the blind where Greg and I are concealed. The terrapin enters a little creek behind the blind, circling us, arching her neck, peering intently.

Does she know someone is watching? Most likely, Greg says. Female terrapins don't even reach sexual maturity until somewhere between 8 and 13 years, and quite possibly live for half a century or more, he explains. And with a precision rivaling that of spawning salmon, they return every summer to the same small stretch of beach to nest. It is not certain whether they use visual clues or, as salmon are thought to do, employ some exquisitely refined sense of smell; but there is little doubt that the old girl checking us out has a long and complex association with the piece of real estate on which we have intruded.

10 a.m. No heads.

An osprey alights on the point of beach, wades out a few feet and flaps and thrashes in the shallows, soaking itself and luxuriating in the cooling bath for a good five minutes.

10:30 a.m. Five heads.

Two more; here they come!

No heads.

A little green heron takes the osprey's spot, and progues for darting minnows.

Greg is reading "Silent Spring," Rachel Carson's 1962 classic on the perils of pesticides. I'm reading a draft of "Chesapeake Diamondback Terrapin Investigations," Willem Roosenburg's someday-to-be classic on the habits of more than 5,000 Patuxent River terrapins. He is Greg's boss, a young biology professor who began catching and marking terrapins here as a Ph.D. student in 1987. Using a system of notches and small holes drilled into the edges of the turtles' shells, he now can precisely identify and track thousands of the creatures.

He grew up on the Patuxent, son of a researcher at the University of Maryland's bay laboratory at Solomons; but it was not until the early 1980s that he caught "turtle fever" as a graduate student, working in Costa Rica with the late Archie Carr, a world authority on sea turtles and an early force for the preservation of the Everglades. Now, regular as the river's diamondbacks, Dr. Roosenburg returns to the Patuxent nesting beaches every summer.

10:40 a.m.

Some 200 feet away, a terrapin is wanting badly now to come ashore and lay down her burden of eggs. She crawls out, ducks back, re-emerges. Her thick dark neck is stretched to the limit, straining to see as much as possible. Down on the beach goes her head, as if smelling the sand. I have never seen a deer, or a fox, or a rabbit any more alert, soaking in every nuance of its surroundings, than this old, slow turtle.

What a terrible and lovely moment in nature this is, the beach powerfully beckoning -- also repelling -- the terrapin. What sights and scents of the land must draw her; and what urges within must propel her to be about her business -- nothing less powerful than the perpetuation of her species.

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