By Carol Vinzant
Special to The Washington Post
Wednesday, May 22, 2002
At first I had several eager partners for my little horseshoe crab adventure. When I proposed driving to see the annual spectacle of masses of the prehistoric critters mating on the beaches of Delaware Bay, a few friends were enthusiastic. After all, anyone with an old pair of shoes and a flashlight is invited to come out and play biologist for a night at a ritual that a National Geographic guidebook has dubbed "one of the great marine spectacles on the planet." The bay's population of horseshoe crabs which have been around in some form for hundreds of millions of years has plummeted by perhaps 90 percent in the past decade. Worried scientists are out counting crabs on many nights of this late spring mating frenzy, and they're looking for help.
But as the event got closer and the realities involved sank in particularly driving to a remote beach in Delaware around midnight in possibly stormy weather excuses were made.
Hangovers, weekend work, medical dramas I heard it all. And so I set out on a recent Sunday night, alone and dubious. Anyone who has ever tried to make an appointment to see wildlife knows that it is notorious for standing people up, and I was pretty sure I was on a fool's errand. The moon was new (dark) and therefore perfect for horseshoe crab love. But the forecast called for severe storms, which neither the crabs nor the scientists care for. Nor I, for that matter.
So I imagined driving for hours to find myself alone on a beach with two or three amorous crabs. I was heading out early in the late spring mating season to a supposedly mediocre beach to join a crew led by Bill Hall, a marine education specialist at the University of Delaware, whom some volunteers call the god of horseshoe crabs.
Sure enough, as soon as I crossed into Delaware, the lightning began. I drove on. Finally I saw the tiny sign for South Bowers Beach. To get there I had to suppress everything I had learned from horror movies about driving solo on stormy rural roads at night. I thought of the "X-Files" drinking game that requires a shot each time Agent Scully pushes on into a dark place by herself. This drive, during which deer materialized in front of my car out of the mist and which took me miles past an ominous "NO OUTLET" sign, would have required many drinks.
But when I arrived, volunteer Bret Ritchie was there to greet me. "Did you see them yet?" the 28-year-old asked, with the kind of ebullience people get from seeing a freakish natural wonder. "There are thousands."
If you had managed, however improbably, to stumble upon this scene by accident, you would never imagine horseshoe crabs were in any danger. It seemed more like they were invading the beach. An arthropod orgy stretched as far as I could see by flashlight. From the high tide line down into the shallows, thousands and thousands of crabs were enmeshed in every conceivable angle and position. Some seemed to form a conga line. Tails spiked out of the water. The overzealous overturned, a potential death sentence.
The male crabs are always the first on the scene, Hall explained when I caught up to him. They lurk in the dark, waiting for an opportunity to spray their sperm on the thousands of tiny green eggs the females bury. Some males will even attach themselves to a female as early as the fall, waiting for her to lay her eggs.
"His anatomy is designed so that he can just clasp onto her and just ride," said David Smith, a biological statistician with the U.S. Geological Survey who has been running the horseshoe crab study the past several years. "He's got a long wait, kind of a typical freeloading male."
We got to work. Since the crabs line up for roughly 30 miles along the Delaware shore, an actual count is out of the question. Instead, volunteers "sample" the population by counting how many males and females lie within a one-square-meter frame placed every 10 meters along the beach, then extrapolate the total. The highest count on South Bowers was 18 males and five females in a space the size of a welcome mat!
At our beach, Hall performed the counting, calling out the numbers to Ritchie's brother, Andrew, an aspiring biologist who had trekked from West Virginia to see the phenomenon.
This is the 12th year volunteers have counted crabs. The survey was prompted by suspicions that conch and eel fishermen were catching more and more horseshoe crabs to use as bait.
The concern is not just for the horseshoe crab itself but also for what it supplies to other species. Migrating red knots, turnstones, sanderlings and sandpipers depend on the eggs as road food. Atlantic loggerhead turtles a threatened species eat adult horseshoe crabs. Researchers also use an extract of horseshoe crab blood to test for bacterial toxins in prescription drugs.
So far, the surveys show that the crab population has declined but that the decline has leveled off. To track the trend, researchers need lots of data, from lots of volunteers. Anyone can sign up (see box), but because it takes a night of training, Hall particularly wants people who can come out for more than one night.
If you want to see the crabs without counting over the next several weeks, you don't necessarily have to go out in the middle of the night. (But it's much more spectacular if you do. They like the full and new moons.) For the less ambitious watcher, horseshoe crabs also show up at high tide during the day.
But midnight it was as we walked along the beach. I spent most of my time turning upended crabs back over. Hall directed some back toward the water. "C'mon, lady of the night, you'll find your way," he coached them. "When you see them try to right themselves, you wonder how they survived 300 million years."
Horseshoe crabs are the same phylum, arthropoda, as the true crabs, but they belong to a different subphylum and are actually more related to spiders, scorpions and mites. As militaristic as they look in their spiked armor, the crabs are no risk to handle. They don't bite or pinch. About the only way you could get hurt by a horseshoe crab is if someone threw one at you.
In fact, I realized as I got ready for my drive back along that dark road, the horseshoe crab is the least scary thing out here.
The greatest crab activity tends to be at high tide on nights of either full or new moons. Upcoming dates include: May 24, 26 (full moon), June 8, 10 (new moon), 12, 22, 24 (full moon), 26. To sign up, visit www. aegis.er.usgs.gov/groups/stats/Limulus. You can specify your date and choice of Delaware or New Jersey sides, but researchers will assign you to a specific beach, with directions.