All is calm on the shores of a great bay. Light waves propelled by a warm summer breeze gently caress the sandy beach. The sun hangs over the horizon, ablaze in red as it awaits its final plunge into darkness. Nothing stirs save for the wind, waves, and tide.

Suddenly, armored shapes appear in the rolling surf, moving slowly, inexorably, toward shore. By the thousands they come, grotesque and hideous soldiers at the van of a great invasion. They swarm the idyllic beach, overcoming everything in their path, their steely will focused on one single task.

An alien invasion? A scene from some prehistoric feeding frenzy? No, it’s the annual Atlantic horseshoe crab spawn, one of the most amazing wildlife events on the planet! Every year, tens of thousands of horseshoe crabs come ashore on the beaches of the Delaware Bay to spawn, and if you are fortunate enough to be at the right place at the right time, you will witness crabs literally covering the entire shore for miles in all directions. It is an incredible event to see, certainly one of the most unique – if not creepy – wildlife experiences the mid-Atlantic area has to offer.

There are many places to see the crabs in Delaware and New Jersey. Cape May on the New Jersey shore has many remote beaches for crab viewing, but unfortunately many of the New Jersey beaches are closed during prime crab spawning season to protect migrating birds. Most of the Delaware beaches, on the other hand, are easy to access and open year round. Arguably the best place to watch crabs is Slaughter Beach in Delaware. One more consideration: shooting on the New Jersey side of the Bay offers opportunities to shoot into the sunset, whereas the Delaware beaches face away from the setting sun.

Timing is critical if you wish to see a peak spawning event. Crab numbers peak during full and new moons between mid-May and late June. This month there are two peak spawning times: the new moon on June 3rd, and the full moon on June 18th. The four or five days surrounding each moon event (that is, two days prior through two days after) offer the best chances of seeing peak crab activity. Make sure to be there a little before sunset, and be prepared to hang around for a few hours if the crabs don't come ashore until after dark. Bring a flashlight, and keep your fingers crossed!

The crabs come ashore with the high tide, often just before sunset, to engage in their . . . ahem, activity . . . throughout the night. By morning they are gone, with just a small percentage of crabs left stranded on the beach (because they got flipped on their backs during all of the excitement and were unable to right themselves). Of course, a small percentage of crabs, when you are dealing with tens of thousands, means that you can see hundreds of crabs stranded on the beach, or trying to make it back into the water, the day after their nocturnal revels.

The crabs are not actually mating, they are spawning, which means that females lay eggs and then the males subsequently fertilize the eggs. But it sure doesn’t look that way! A male will grasp a female’s abdomen and hold on waiting for the female to lay her eggs, while “satellite” males follow the conjoined pair, so any single female usually has several males in tow. The result is that the crabs appear to be rolling all over each other, making it look like a scene out of some mythic ancient Roman orgy, but in reality the whole affair is somewhat less kinky in nature.

As the crabs often peak at sunset, during twilight, or at night, exposures can be long and often tricky. Don't be too worried by long exposures, however, since the crabs usually move very slow, and a little bit of motion blur to convey a sense of the "action" can be a nice touch. Flash is useful, if not necessary, for night-time exposures.

Large waves often flip the crabs upside down. Most are able to flip back; those that do not get stranded when the tide recedes. The next morning the shore will be littered with hundreds of stranded crabs. Those that manage to get off their backs (either by themselves or with a little help from a kind-hearted photographer) will wander about looking for water, carving deep furrows in the sand, which can be very photogenic. Most of the stranded crabs, however, do not survive the night, and instead become food for migrating birds.

This is definitely a wide-angle shoot. You will want to get low and close to the crabs, and use a wide perspective to show the grand scale of the spawning event. Be prepared to get a little wet from incoming waves, but be careful with your gear if the wave action is rough. If you drop a camera bag on the shore while shooting, make sure it is well above the high tide line!

A final word of warning is in order: Sometimes, in the heat of the moment, an over-stimulated crab may mistake you for a prospective mate. Under no circumstances should you accept the crab's . . err, proposal . . . as it will likely leave both you and the crab less than satisfied. Unless you're into that sort of thing.

Comments on NPN nature photography articles? Send them to the editor.

Ian Plant lives in the Washington, D.C. area and has been photographing the natural world for fifteen years. His work has appeared in a number of books and calendars, as well as national and regional magazines, including Outdoor Phtoographer, National Parks, Blue Ridge Country, Adirondack Life, Wonderful West Virginia, and Chesapeake Life, among others. His sixth and most recent book is the critically acclaimed Chesapeake: Bay of Light. An Exploration of the Chesapeake Bay's Wild and Forgotten Places. Ian’s work has also appeared in five other books of the Wonder and Light series.

Ian is co-owner of Mountain Trail Press and leads workshops through Mountain Trail Photography Workshops. To see more of Ian's work, visit him online at www.ipphotography.com.