Learning how many horseshoe crabs inhabit Delaware's coastal waters is key to ensuring these ancient creatures survive into the future.

Kitts Hummock beach at night. You can see the lights burning on the distant Jersey shore and the stars peeking brightly through the blackness of space, their pinpricks of light undimmed by an absent moon.

The sounds are equally mesmerizing: the rush of the water as it swells onto the beach at high tide and the gurgling as it recedes into the Delaware Bay.

And, if you listen carefully, you’ll hear the sound of male horseshoe crabs answering nature’s oldest call: the search for a mate.

But there is no screeching or howling, just the noise of thousands of rounded shells clacking as they clamber all over each other, sometimes ganging up by the dozen on the much larger and rarer females. No soft music and candlelight for one of nature’s oldest species: they’ve got only one thing on their minds.

All of this makes DNREC’s Drexel Siok a very happy environmental scientist. He is running the Horseshoe Crab Spawning Survey, the state’s annual effort to gauge the Delaware Bay’s population of these 300-million-year-old creatures, ones that still are vital to 21st century medical science and the environment.

“It all went very well,” Siok said after a May 8 midnight expedition. “We saw quite a few crabs, more than expected for this early in the year.”

The Sunday night team included about a dozen University of Delaware students who were doing part of their environmental science coursework. There are nine survey nights left this season, Siok said, but no more open volunteer slots.

The teams will take the numbers they gather and turn them in to a data processing center that will come up with final figures. These numbers are used to determine how many male crabs may be harvested -- females are off limits -- in the coming season.

As many know, horseshoe crab eggs are a primary food source for migrating birds, including the red knot, as they pass through Delmarva each year. The crabs’ blood, which normally is extracted without killing the animal, has numerous medical uses.

“This is a part of a baywide effort using standard methods and protocols,” said Kim Cole, environmental program manager for DNREC’s Delaware National Estuarine Research Reserve. Other projects include tagging crabs and then tracking their movements in the bay, she said.

The St. Jones Reserve, off Route 9 south of Dover Air Force Base, provides research opportunities for natural coastal habitat areas.

Last Sunday night -- just before midnight -- the UD volunteers were bused to Kitts Hummock to begin their work. Starting at the public beach access, they headed south for about one kilometer.

With the waters of the Delaware Bay on the left and homes on their right, they stepped over driftwood and beach detritus, including dozens of freshly- and long-dead horseshoe crabs.

Split into two teams, they carried one-meter square constructions of PVC pipe, which they would place in the surf at predetermined points. The group would gather around and count the crabs in each square, sometimes finding only one or two. Sometimes each would contain one or two large females, each swarmed by much smaller males.

The students carefully flipped over some crabs stranded on their backs, their vulnerable underbellies exposed to predators.

The St. Jones Reserve has volunteers who come back year to year, but it’s always interesting to watch those who never have seen a horseshoe crab before, Siok said. With their hard carapace and long, deadly-looking telson, or tail, these living fossils look fearsome. Actually, the crabs are quite docile, he said.

“I think that saying people are taken aback is a good way to put it,” Siok said. “It’s like they’re seeing dinosaurs. They see pictures during their training, but it’s a whole new experience to see them firsthand.”

The scientists rely on volunteers to help gather data to monitor the crab population, he said.

“We have a very small staff and we could not do the survey without our volunteers,” Siok said. “Last year we had more than 200 volunteers and this year we’ll have more than that. They’re critical, to say the least.” Volunteers drive from as far away as Massachusetts each year just to spend a night counting the horseshoe crabs.

“That’s astonishing to me, but I think the opportunity to help science make better decisions about the horseshoe crab is important,” he said. “It’s one thing to walk on the beach and just look at them. It’s another to be there and be part of something like this.”

To learn more and to sign up for the 2017 season, visit horseshoecrabsurvey.com.